Multiple causes exist for AI in the setting of ascending AD. The dissection may dilate the annulus of the  aortic valve , preventing the leaflets of the valve from coapting. The dissection may extend into the aortic root and detach the aortic valve leaflets. Alternatively, following an extensive intimal tear, the intimal flap may prolapse into the  left ventricular outflow tract , causing intimal  intussusception  into the aortic valve, thereby preventing proper valve closure. [ 17 ]


Heart attack  occurs in 1–2% of aortic dissections. Infarction is caused by the involvement of the  coronary arteries , which supply the heart with oxygenated blood, in the dissection. The right coronary artery is involved more commonly than the left coronary artery. If the myocardial infarction is treated with  thrombolytic  therapy, the mortality increases to over 70%, mostly due to bleeding into the pericardial sac, causing  cardiac tamponade . [ 18 ]


A  pleural effusion  (fluid collection in the space between the  lungs  and the chest wall or  diaphragm ) can be due to either blood from a transient rupture of the aorta or fluid due to an inflammatory reaction around the aorta. If a pleural effusion were to develop due to AD, it is more common in the left hemithorax rather than the right hemithorax. [ 19 ]


Aortic dissection is associated with  hypertension  (high blood pressure) and many  connective tissue  disorders.  Vasculitis  ( inflammation  of an artery) is rarely associated with aortic dissection. It can also be the result of chest trauma. About 72 to 80% of individuals who present with an aortic dissection have a previous history of hypertension. Illicit drug use with stimulants such as  cocaine  and  methamphetamine  is also a modifiable risk factor for AD. [ 20 ] [ 21 ]  It can also be caused by smoking.


A  bicuspid aortic valve  (a type of  congenital heart disease  involving the  aortic valve ) is found in 7–14% of individuals who have an aortic dissection. These individuals are prone to dissection in the ascending aorta. The risk of dissection in individuals with bicuspid aortic valves is not associated with the degree of  stenosis  of the valve. [ citation needed ]


Connective tissue disorders  such as  Marfan syndrome ,  Ehlers–Danlos syndrome , and  Loeys–Dietz syndrome  increase the risk of aortic dissection. [ 13 ]  Similarly, vasculitides such as  Takayasu's arteritis ,  giant cell arteritis ,  polyarteritis nodosa , and  Behçet's disease  have been associated with a subsequent aortic dissection. [ 13 ] [ 20 ]   Marfan Syndrome is found in 5–9% of individuals who had an aortic dissection. In this subset, the incidence in young individuals is increased. Individuals with Marfan syndrome tend to have aneurysms of the aorta and are more prone to proximal dissections of the aorta. [ 22 ]


Turner syndrome  also increases the risk of aortic dissection, by aortic root dilatation. [ 23 ]


Chest trauma leading to aortic dissection can be divided into two groups based on cause: blunt chest trauma (commonly seen in  car accidents ) and  iatrogenic . Iatrogenic causes include trauma during  cardiac catheterization  or due to an  intra-aortic balloon pump . [ citation needed ]


Aortic dissection may be a late sequela of  heart surgery . About 18% of individuals who present with an acute aortic dissection have a history of open-heart surgery. Individuals who have undergone aortic valve replacement for  aortic insufficiency  are at particularly high risk because aortic regurgitation causes increased blood flow in the ascending aorta. This can cause dilatation and weakening of the walls of the ascending aorta. [ citation needed ]


Syphilis  only potentially causes aortic dissection in its tertiary stage. [ 24 ]


As with all other arteries, the aorta is made up of three layers, the  intima , the  media , and the  adventitia . The intima is in direct contact with the blood inside the vessel, and mainly consists of a layer of  endothelial cells  on a  basement membrane ; the media contains connective and muscle tissue, and the vessel is protected on the outside by the adventitia, comprising connective tissue. [ 25 ]


In an aortic dissection, blood penetrates the intima and enters the media layer. The high pressure rips the  tissue  of the media apart along the laminated plane splitting the inner two-thirds and the outer one-third of the media apart. [ 26 ]  This can propagate along the length of the aorta for a variable distance forward or backward. Dissections that propagate towards the iliac bifurcation (with the flow of blood) are called anterograde dissections and those that propagate towards the aortic root (opposite of the flow of blood) are called retrograde dissections. The initial tear is usually within 100 mm of the  aortic valve , so a retrograde dissection can easily compromise the pericardium leading to a hemopericardium. Anterograde dissections may propagate all the way to the iliac bifurcation of the aorta, rupture the aortic wall, or recanalize into the intravascular lumen leading to a double-barrel aorta. The double-barrel aorta relieves the pressure of blood flow and reduces the risk of rupture. Rupture leads to hemorrhaging into a body cavity, and prognosis depends on the area of rupture. Retroperitoneal and pericardial ruptures are both possible. [ 27 ]


The initiating event in aortic dissection is a tear in the intimal lining of the aorta. Due to the high pressures in the aorta, blood enters the media at the point of the tear.  The force of the blood entering the media causes the tear to extend. It may extend proximally (closer to the heart) or distally (away from the heart) or both. The blood travels through the media, creating a  false lumen  (the true lumen is the normal conduit of blood in the aorta). Separating the false lumen from the true lumen is a layer of intimal tissue known as the intimal flap. [ citation needed ]


The vast majority of aortic dissections originate with an intimal tear in either the  ascending aorta  (65%), the  aortic arch  (10%), or just distal to the  ligamentum arteriosum  in the  descending thoracic aorta  (20%). [ clarification needed ]


As blood flows down the false lumen, it may cause secondary tears in the intima. Through these secondary tears, the blood can re-enter the true lumen. [ citation needed ]


While it is not always clear why an intimal tear may occur, quite often it involves degeneration of the  collagen  and  elastin  that make up the media. This is known as  cystic medial necrosis  and is most commonly associated with Marfan syndrome and is also associated with Ehlers-Danlos syndrome. [ 28 ] [ 29 ]


In about 13% of aortic dissections, no evidence of an intimal tear is found. In these cases, the inciting event is thought to be an intramural  hematoma  (caused by bleeding within the media). Since no direct connection exists between the true lumen and the false lumen in these cases, diagnosing an aortic dissection by  aortography  is difficult if the cause is an intramural hematoma. An aortic dissection secondary to an intramural hematoma should be treated the same as one caused by an intimal tear. [ 28 ] [ 29 ]


Because of the varying symptoms of aortic dissection, the diagnosis is sometimes difficult to make. Concern should be increased in those with low blood pressure, neurological problems, and an unequal pulses. [ 30 ]


While taking a good history from the individual may be strongly suggestive of an aortic dissection, the diagnosis cannot always be made by history and physical signs alone.  Often, the diagnosis is made by visualization of the intimal flap on a diagnostic imaging test. Common tests used to diagnose an aortic dissection include a  CT scan  of the chest with iodinated contrast material and a  transesophageal echocardiogram . The proximity of the aorta to the  esophagus  allows the use of  higher-frequency ultrasound  for better anatomical images. Other tests that may be used include an aortogram or magnetic resonance angiogram of the aorta.  Each of these tests has pros and cons, and they do not have equal sensitivities and specificities in the diagnosis of aortic dissection. [ citation needed ]


In general, the imaging technique chosen is based on the pretest likelihood of the diagnosis, availability of the testing modality, patient stability, and the sensitivity and specificity of the test. [ citation needed ]


A measurement of blood  D-dimer  level may be useful in diagnostic evaluation. A level less than 500 ng/ml may be considered evidence against a diagnosis of aortic dissection, [ 1 ] [ 31 ]  although this guideline is only applicable in cases deemed "low risk" [ 32 ]  and within 24 hours of symptom onset. [ 33 ]  The  American Heart Association  does not advise using this test in making the diagnosis, as evidence is still tentative. [ 34 ]


Chest radiography  may although demonstrate a change in the morphology of the thoracic aorta which can be seen in aortic dissection. Classically, new widening of the  mediastinum  on radiograph is of moderate  sensitivity  for detecting an ascending aortic dissection; however, this finding is of low  specificity , as many other conditions can cause apparent widening of the mediastinum. [ citation needed ]


There are several other associated radiographic findings: [ citation needed ]


Importantly, about 12 to 20% of aortic dissections are not detectable by chest radiograph; therefore, a "normal" chest radiograph does not rule out aortic dissection. If there is high clinical suspicion, a more sensitive imaging test ( CT angiogram ,  MR angiography , or  transesophageal echo ) may be warranted. [ citation needed ]


Computed tomography angiography  is a fast, non-invasive test that gives an accurate three-dimensional view of the aorta. These images are produced by taking rapid, thin-cut slices of the chest and abdomen, and combining them in the computer to create cross-sectional slices. To delineate the aorta to the accuracy necessary to make the proper diagnosis, an iodinated contrast material is injected into a peripheral vein. Contrast is injected and the scan performed using a  bolus tracking  method. This type of scan is timed to injection to capture the contrast as it enters the aorta. The scan then follows the contrast as it flows through the vessel. It has a sensitivity of 96 to 100% and a specificity of 96 to 100%. Disadvantages include the need for iodinated contrast material and the inability to diagnose the site of the intimal tear. [ citation needed ]


Magnetic resonance imaging  (MRI) is also used for the detection and assessment of aortic dissection, with a sensitivity of 98% and a specificity of 98%. An MRI examination of the aorta produces a three-dimensional reconstruction of the aorta, allowing the physician to determine the location of the intimal tear and the involvement of branch vessels, and to locate any secondary tears. It is a noninvasive test, does not require the use of iodinated contrast material, and can detect and quantitate the degree of aortic insufficiency. [ citation needed ]


The disadvantage of the MRI scan in the face of aortic dissection is that it may be available only in larger hospitals, and the scan is relatively time-consuming, which could be dangerous in people who are already very unwell. Due to the high-intensity magnetic fields used during MRI, it cannot be used on individuals with metallic implants. In addition, some individuals experience  claustrophobia  while surrounded by the MRI magnet. [ citation needed ]


The  transesophageal echocardiogram  (TEE) is a good test in the diagnosis of aortic dissection, with a sensitivity up to 98% and a specificity up to 97%. It has become the preferred imaging modality for suspected aortic dissection. It is a relatively noninvasive test, requiring the individual to swallow the echocardiography probe. It is especially good in the evaluation of AI in the setting of ascending aortic dissection and to determine whether the ostia (origins) of the coronary arteries are involved. While many institutions give sedation during transesophageal echocardiography for added patient comfort, it can be performed in cooperative individuals without the use of sedation. Disadvantages of TEE include the inability to visualize the distal ascending aorta (the beginning of the  aortic arch ), and the descending abdominal aorta that lies below the  stomach . A TEE may be technically difficult to perform in individuals with esophageal strictures or  varices . [ citation needed ]


An aortogram involves the placement of a catheter in the aorta and injection of contrast material while taking X-rays of the aorta. The procedure is known as  aortography . Previously thought to be the diagnostic  gold standard , it has been supplanted by other, less-invasive imaging modalities. [ citation needed ]


Several different classification systems have been used to describe aortic dissections. One such classification is based on chronicity and labels aortic dissections as hyperacute (<24 hours duration), acute (2–7 days), subacute (8–30 days), and chronic (>30 days). [ 20 ]  The systems commonly in use are based on either the anatomy of the dissection or the duration of onset of symptoms before the presentation. The Stanford system is used more commonly now, as it is more attuned to the management of the patient. [ 37 ]


The DeBakey system, named after cardiothoracic surgeon  Michael E. DeBakey , is an anatomical description of the aortic dissection. It categorizes the dissection based on where the original intimal tear is located and the extent of the dissection (localized to either the ascending aorta or descending aorta or involving both the ascending and descending aorta). [ 38 ]


The Stanford classification is divided into two groups, A and B, depending on whether the ascending aorta is involved. [ 39 ]


The Stanford classification is useful as it follows clinical practice, as type A ascending aortic dissections generally require primary surgical treatment, whereas type B dissections generally are treated medically as initial treatment with surgery reserved for any complications. [ 40 ]


The main indication for surgical repair of type A dissections is the prevention of acute hemorrhagic pericardial tamponade due to leakage of blood through the dissected layers of the intrapericardial proximal aorta. A secondary indication is acute aortic valve insufficiency (regurgitation): ascending aortic dissections often involve the aortic valve, which, having lost its suspensory support, telescopes down into the aortic root, resulting in aortic incompetence. The valve must be resuspended to be reseated, as well as to repair or prevent coronary artery injury. Also, the area of dissection is removed and replaced with a Dacron graft to prevent further dissection from occurring. However, type B dissections are not improved, from a mortality point of view, by the operation, unless leaking, rupture, or compromise to other organs, e.g. kidneys, occurs. [ 40 ]


Among the recognized risk factors for aortic dissection, hypertension,  abnormally high levels of lipids (such as cholesterol) in the blood , and smoking tobacco are considered preventable risk factors. [ 1 ]


Repair of an enlargement of the ascending aorta from an aneurysm or previously unrecognized and untreated aortic dissections is recommended when greater than 5.5 cm (2.2 in) in size to decrease the risk of dissection. Repair may be recommended when greater than 4.5 cm (1.8 in) in size if the person has one of the several connective-tissue disorders or a family history of a ruptured aorta. [ 41 ]


In an acute dissection, treatment choice depends on its location. For Stanford type A (ascending aortic) dissection, surgical management is superior to medical management. [ 4 ]  For uncomplicated Stanford type B (distal aortic) dissections (including abdominal aortic dissections), medical management is preferred over surgery. [ 42 ]  Complicated Stanford type B aortic dissections require surgical intervention after initiation of medical therapy, with endovascular stent-grafting (TEVAR) available as a less invasive alternative to surgery. [ 42 ]


The risk of death due to aortic dissection is highest in the first few hours after the dissection begins, and decreases afterward. [ 42 ]  Because of this, the therapeutic strategies differ for the treatment of an acute dissection compared to a chronic dissection. An acute dissection is one in which the individual presents within the first two weeks. If the individual has managed to survive this window period, their prognosis is improved. [ 42 ]  About 66% of all dissections present in the acute phase. Individuals who present two weeks after the onset of the dissection are said to have chronic aortic dissections. [ 42 ]   These individuals have been self-selected as survivors of the acute episode and can be treated with medical therapy as long as they are stable. [ citation needed ]


Aortic dissection generally presents as a hypertensive emergency, and the prime consideration of medical management is to decrease the  shear stress  in the aortic wall (dP/dt (force of ejection of blood from the  left ventricle )) by decreasing blood pressure and the heart rate. The target blood pressure should be a  mean arterial pressure  (MAP) of 60 to 75  mmHg , or the lowest blood pressure tolerated. Initial decreases should be by about 20%. [ 2 ]  The target heart rate is less than 65 beats per minute. Long-term blood pressure control is required for every person who has experienced aortic dissection. [ 42 ]   [ 43 ]


Beta blockers  are the first-line treatment for patients with acute and chronic aortic dissection. In acute dissection, fast-acting agents can be given intravenously and have doses that are easier to adjust (such as  esmolol ,  propranolol , or  labetalol ) is preferred. Vasodilators such as  sodium nitroprusside  can be considered for people with ongoing high blood pressure, but they should never be used alone, as they often stimulate a  reflexive increase in the heart rate . [ citation needed ]


Calcium channel blockers  can be used in the treatment of aortic dissection, particularly if a contraindication to the use of beta-blockers exists.  The calcium channel blockers typically used are  verapamil  and  diltiazem , because of their combined vasodilator and negative  inotropic  effects. [ citation needed ]


If the individual has refractory hypertension (persistent hypertension on the maximum doses of three different classes of antihypertensive agents), involvement of the renal arteries in the aortic dissection plane should be considered. [ citation needed ]


Indications for the surgical treatment of aortic dissection include an acute proximal aortic dissection and an acute distal aortic dissection with one or more complications.  Complications include compromise of a vital organ, rupture or impending rupture of the aorta, retrograde dissection into the ascending aorta. These are more common with a history of Marfan syndrome or Ehlers-Danlos syndrome. [ citation needed ]


The objective in the surgical management of aortic dissection is to resect (remove) the most severely damaged segments of the aorta and to obliterate the entry of blood into the false lumen (both at the initial intimal tear and any secondary tears along the vessel). While excision of the intimal tear may be performed, it does not significantly change mortality. [ citation needed ]


The particular treatment used depends on the segment or segments of the aorta involved. Some treatments are: [ citation needed ]


A number of comorbid conditions increase the surgical risk of repair of an aortic dissection.  These conditions include the following: [ citation needed ]


Patients who have suffered aortic dissection are at risk of  Aortic aneurysm  formation at the site of the dissection, thought to be due to weakening of the aortic wall.  [ 43 ]  The risk of this aneurysm degeneration is 10 times higher in individuals who have uncontrolled hypertension, compared to individuals with a systolic pressure below 130 mmHg.


The risk of death is highest in the first two years after the acute event, and individuals should be followed closely during this time period. About 29% of late deaths following surgery are due to rupture of either a dissecting aneurysm or another aneurysm. In addition, a 17% to 25% incidence exists of new aneurysm formation, typically due to dilatation of the residual false lumen. These new aneurysms are more likely to rupture, due to their thinner walls. [ 43 ]


Serial imaging of the aorta is recommended, although guidelines on modality (CT vs MRI vs ultrasound) and interval (timing of imaging tests) do not exist. [ 43 ]


Of all people with aortic dissection, 40% die immediately and do not reach a hospital in time. Of the remainder, 1% die every hour, making prompt diagnosis and treatment a priority. Even after diagnosis, 5–20% die during surgery or in the immediate postoperative period. [ 25 ]  In ascending aortic dissection, if surgery is decided to be not appropriate, 75% die within 2 weeks. With aggressive treatment, 30-day survival for thoracic dissections may be as high as 90%. [ 45 ]


Establishing the incidence of aortic dissection has been difficult because many cases are only diagnosed after death (which may have been attributed to another cause), and is often initially misdiagnosed. Aortic dissection affects an estimated 2.0–3.5 people per every 100,000 every year. Studies from Sweden suggest that the incidence of aortic dissection may be rising. [ 46 ]  Men are more commonly affected than women: 65% of all people with aortic dissection are male. The mean age at diagnosis is 63 years. [ 25 ]  In females before the age of 40, half of all aortic dissections occur during  pregnancy  (typically in the third trimester or early  postpartum  period). [ 47 ]  Dissection occurs in about 0.6% of pregnancies. [ 48 ]


The earliest fully documented case of aortic dissection is attributed to  Frank Nicholls  in his  autopsy  report of  King George II of Great Britain , who had been found dead on 25 October 1760; the report describes a dissection of the aortic arch and into the pericardium. [ 3 ] [ 49 ]  The term "aortic dissection" was introduced by the French physician J. P. Maunoir in 1802, and  René Laennec  labeled the condition "dissecting aneurysm". [ 3 ] [ 50 ]  London cardiologist  Thomas Bevill Peacock  contributed to the understanding of the condition by publishing two series of the cases described in the literature so far: 19 cases in an 1843 review, and 80 in 1863. [ 50 ]  The characteristic symptom of tearing pain in the chest was recognized in 1855 when a case was diagnosed in life. [ 50 ]


Surgery for aortic dissection was first introduced and developed by  Michael E. DeBakey ,  Denton Cooley , and Oscar Creech, cardiac surgeons associated with the  Baylor College of Medicine , Houston, Texas, in 1954. DeBakey developed aortic dissection himself at age 97 in 2005, [ 3 ]  and underwent surgery in 2006. [ 51 ]  Endovascular treatment of aortic dissection was developed in the 1990s. [ 3 ]


Aortopexy  is a surgical procedure in which the  aortic arch  is fixated to the  sternum . It results in the  tracheal  lumen being pulled open. It is used to treat severe  tracheomalacia  or tracheal compression.


The procedure was originally proposed as a treatment for tracheomalacia Filler et al. [ 1 ]  in 1976.


Arteriotomy  (or  arterotomy ) is a medical term for an opening or cut of an  artery  wall. [ 1 ]  It is a common step in many  vascular surgical  procedures and operations. The corresponding term for an incision into a vein is a  venotomy .


Either a transverse or a longitudinal incision can be made (with respect to the direction of the artery), depending on the situation. The incision is typically made with a  scalpel  and extended with surgical  scissors . [ 2 ]


Atherectomy  is a  minimally invasive  technique for removing  atherosclerosis  from blood vessels within the body. It is an alternative to  angioplasty  for the treatment of  peripheral artery disease , but the studies that exist are not adequate to determine whether it is superior to angioplasty. [ 1 ]  It has also been used to treat  coronary artery disease , albeit without evidence of superiority to angioplasty. [ 2 ]


Atherectomy is used to treat  narrowing  in  arteries  caused by  peripheral artery disease  and  coronary artery disease . [ 1 ] [ 2 ]


The use of atherectomy instead of or in addition to angioplasty remains an area of controversy, as atherectomy typically involves the use of more costly disposable devices, and clear evidence to justify its use is lacking. [ 1 ]  Atherectomy has high physician reimbursement relative to angioplasty alone. [ 3 ]  According to the New York Times, ‘Medical device makers have bankrolled a cottage industry of doctors and clinics that perform artery-clearing procedures that can lead to amputations.’ [ 4 ]


Unlike  angioplasty  and  stents , which push plaque into the vessel wall, atherectomy cuts plaque from the wall of the artery. While atherectomy is usually employed to treat  arteries  it can be used in  veins  and  vascular bypass  grafts as well.


Atherectomy falls under the general category of  percutaneous   revascularization , which implies re-canalizing blocked vasculature via a needle puncture in the skin. The most common access point is near the groin through the  common femoral artery  (CFA). Other common places are the  brachial artery ,  radial artery ,  popliteal artery ,  dorsalis pedis , and others.


There are four types of atherectomy devices: orbital, rotational, laser, and directional.


The decision to use which type of device is made by the interventionist, based on a number of factors. They include the type of lesion being treated, the physician's experience with each device, and interpretation of the devices' risks and effectiveness, based on a review of the medical literature.


Directional atherectomy is an intravascular procedure guided by  optical coherence tomography  termed as  lumivascular atherectomy . [ 5 ]


Autoamputation  is the spontaneous detachment ( amputation ) of an  appendage  or organ from the body. [ 1 ]  This is not to be confused with  self-amputation . It is usually due to destruction of the blood vessels feeding an extremity such as the finger tips. Once the vessels are destroyed, the tissue is  starved of oxygen  and  dies , which is often followed by  gangrene .
Autoamputation is a feature of  ainhum ,  cryoglobulinemia [ 2 ]  and  thromboangiitis obliterans . In 1881, Thornton made the case of autoamputation. [ 3 ]   Autoamputation could be the result of severe cases of certain chronic wounds, such as  frostbite . These chronic wounds might be due to some vascular and pathogenic conditions [ 4 ]  like  Buerger disease  or  Reynaud's phenomenon . Also, uncontrolled  diabetes  can predispose one to autoamputation. [ 4 ]  However, autoamputation has been described as spontaneous. [ 5 ]  Autoamputation has often been associated with fingers and toes but other parts of the body can suffer this condition as well. There have been reported cases of ovarian autoamputation in a newborn [ 6 ]  and also in a mature ovary of adults. [ 3 ]  Autoamputation has been reported to affect the tip of fingers. [ 7 ]  Though autoamputation is often regarded as an acquired ailment, it could also be congenital. [ 3 ]  Chronic torsion or a delay in the diagnosis of acute adnexal torsion has been attributed as causes of acquired autoamputation [ 3 ]


Though its facts are being unraveled and analyzed, autoamputation can be categorized as acute, subacute or chronic. [ 3 ]  Acute autoamputation is characterized by tumor necrosis. This is accompanied by inadequate supply of blood to the heart and other body parts (ischemia) leading to the degeneration of the cells, a condition known as atropy. [ 3 ]  Chronic or subacute autoamputation is evident in the attachment of the tumor to other cells surrounding it. [ 3 ]  There is a rare possibility of the tumor detaching itself from the  pedicle . When this happens, it could be parasitic.


Balloon-occluded retrograde transvenous obliteration  ( BRTO ) is an  endovascular procedure  used for the treatment of  gastric varices . When performing the procedure, an  interventional radiologist  accesses blood vessels using a catheter, inflates a balloon (e.g. balloon occlusion) and injects a substance into the variceal blood vessels that causes blockage of those vessels. To prevent the flow of the agent out of the intended site (variceal blood vessels), a balloon is inflated during the procedure, which occludes.


BRTO is used for the treatment of bleeding from gastric varices. In addition to  transjugular intrahepatic portosystemic shunt  (TIPS), BRTO is a first line treatment for the prevention of recurrent bleeding from gastric varices (GOV2 or IGV1). [ 1 ]  BRTO may be used for the treatment of ectopic varices. [ 1 ]


As BRTO results in a blockage of a portosystemic shunt, the procedure may result in increased portal hypertension, which may worsen esophageal varices or ascites. [ 2 ] [ 1 ]


BRTO was developed as a procedure in the early 1990s. [ 2 ]  Initially, the procedure was performed using  ethanolamine oleate  as a sclerosant. [ 2 ] [ 3 ]  Between 2006 and 2007, American physicians began using  sodium tetradecyl sulfate  (3% STS) as an alternative sclerosing agent. [ 2 ] [ 3 ]


A  vascular bypass  is a  surgical procedure  performed to redirect  blood flow  from one area to another by reconnecting blood vessels. Often, this is done to bypass around a diseased artery, from an area of normal blood flow to another relatively normal area. It is commonly performed due to inadequate blood flow ( ischemia ) caused by  atherosclerosis , as a part of  organ transplantation , or for  vascular access  in  hemodialysis . In general, someone's own  vein  (autograft) is the preferred graft material (or conduit) for a vascular bypass, but other types of grafts such as  polytetrafluoroethylene  (Teflon),  polyethylene terephthalate  (Dacron), or a different person's vein ( allograft ) are also commonly used.  Arteries  can also serve as vascular grafts. A surgeon sews the graft to the source and target vessels by hand using  surgical suture , creating a  surgical anastomosis .


Common bypass sites include the  heart  ( coronary artery bypass surgery ) to treat coronary artery disease, and the legs, where  lower extremity bypass surgery  is used to treat  peripheral vascular disease .


Cardiac bypass is performed when the arteries that bring  blood  to the  heart muscle  (coronary arteries) become clogged by  plaque . [ 1 ] [ 2 ]  Such a condition may cause chest pain from  angina pectoris  or a heart attack. Dimensional aspects, material selection, and manufacturing methods influence mechanistic behaviours of artificial grafts and chosen to receive artery-like behaviour  [ 3 ]


In the legs, bypass grafting is used to treat  peripheral vascular disease ,  acute limb ischemia ,  aneurysms  and  trauma . While there are many anatomical arrangements for vascular bypass grafts in the lower extremities depending on the location of the disease, the principle is the same: to restore blood flow to an area without normal flow.  [ citation needed ]


For example, a femoral-popliteal bypass ( "fem-pop" ) might be used if the  femoral artery  is occluded. A fem-pop bypass may refer to the above- or below-knee popliteal artery. Other anatomic descriptions of lower extremity bypasses include:


A vascular bypass is often created to serve as an access point to the  circulatory system  for  hemodialysis . Such a bypass is referred to as an  arteriovenous fistula  if it directly connects a  vein  to an  artery  without using synthetic material. [ citation needed ]


In the skull, when blood flow is blocked or a damaged  cerebral artery  prevents adequate blood flow to the  brain , a cerebral artery bypass may be performed to improve or restore flow to an oxygen-deprived (ischemic) area of the brain. [ 5 ]


There are two main types of cerebral artery bypass: direct and indirect. Direct revascularization is also known as EC-IC bypass because it involves directly connecting an extracranial artery outside the brain to an intracranial artery inside the brain. This is also sometimes called STA-MCA bypass because the superficial temporal artery and the middle cerebral artery are the most commonly used arteries for the surgery. [ 6 ]  STA-MCA bypass surgery has been shown to be ineffective in reducing the risk of ischemic stroke in an international, randomized clinical trial [ 7 ]  led by   clinical scientist    Dr. Henry Barnett . Indirect revascularization involves placing part of an artery, in the case of EDAS (encephaloduroarteriosynangiosis), or part of a muscle, in the case of EMS (encephalomyosynangiosis), on the surface of the brain and allowing it to revascularize the brain through new vessel growth. Both types of indirect revascularization typically take 3-6 months to see effects. [ 8 ]


When several arteries are blocked and several bypasses are needed, the procedure is called multiple bypass. The number of bypasses needed does not always increase the risk of surgery, which depend more on the patient's overall health.


Prior to constructing a bypass, most surgeons will obtain or perform an imaging study to determine the severity and location of the diseased blood vessels. For cardiac and lower extremity disease, this is usually in the form of an  angiogram . For hemodialysis access, this can be done with ultrasound. Occasionally, a  CT angiogram  will take the place of a formal angiogram. [ citation needed ]


The lack of an adequate venous conduit is a relative contraindication to bypass surgery, and depending on the area of disease, alternatives may be used. Medical conditions such as  ischemic heart disease  or  chronic obstructive pulmonary disease  that increase the risk of surgery are also relative contraindications. For coronary and peripheral vascular disease, lack of "runoff" to the distal area is also a contraindication because a vascular bypass around one diseased artery to another diseased area does not solve the vascular problem. [ citation needed ]


If a patient is deemed to be too high-risk to undergo a bypass, he or she may be a candidate for  angioplasty  or  stenting  of the relevant vessel. [ citation needed ]


Dogma in vascular bypass technique says to obtain  proximal  and  distal  control. This means that in a vessel with flow through it, a surgeon must have exposure of the furthest and nearest extents of the blood vessel in which the bypass is being created, so that when the vessel is opened, blood loss is minimized. After the necessary exposure, clamps are usually used on both the proximal and distal end of the segment. Exceptions exist where there is no blood flow through the target vessel at the area of proposed entry, as is the case with an intervening occlusion. [ citation needed ]


If the organ perfused by an artery is sensitive to even temporary occlusion of blood flow, such as in the brain, various other measures are taken. [ citation needed ]


In  neurosurgery , excimer laser assisted non-occlusive anastomosis (ELANA) is a technique use to create a bypass without interrupting the blood supply in the recipient blood vessels. This reduces the risk of stroke or a rupture of an  aneurysm .


Several complications can arise after vascular bypass. [ 9 ]


Risks of the bypass: [ citation needed ]


General risks of surgery: [ citation needed ]


Immediately following coronary artery or neurosurgical vascular bypass surgery, patients recover in an  intensive care unit  or  coronary care unit  for one to two days. Provided that recovery is normal and without  complications , they can move to a less intensively monitored unit such as a  step-down unit  or a  ward bed . Depending on the extent of the surgery, recovery from a leg bypass may start from a step-down or ward bed.  Monitoring  immediately after bypass surgery focuses on signs and  symptoms  of bleeding and graft occlusion. If bleeding is detected, treatment can range from  transfusion  to  reoperation . Later on in the hospital course, common complications include  wound infections ,  pneumonia ,  urinary tract infection , and graft occlusion. [ 10 ]


At discharge, patients are often prescribed oral painkillers, and should be prescribed a  statin  and an  anti-platelet medication  if not contraindicated and their bypass was performed for  atherosclerosis , (e.g.,  peripheral vascular disease  or  coronary artery disease ). Some patients start feeling normal after one month, while others may still experience problems several months after the procedure. [ 10 ]


During the first twelve weeks after most bypass operations, patients are advised to avoid heavy lifting, house work, and strenuous recreation like  golf ,  tennis , or  swimming  while their surgical wounds heal, particularly the sternum after coronary bypass. [ 10 ] [ 11 ]


Part of the recovery after any bypass surgery includes regular visits to a physician to monitor the patient's recovery. Normally a follow-up visit with a surgeon is scheduled for two to four weeks after surgery. The frequency of these visits gradually lessens as the patient's health improves. [ 10 ]


For vascular bypass operations performed for atherosclerosis, the operation does not cure the metabolic problem that led to the vascular disease. Lifestyle changes that include  quitting smoking , making  diet  changes, and getting regular exercise are required to cure the underlying condition. [ 10 ] [ 12 ]


Carotid endarterectomy  is a  surgical  procedure used to reduce the risk of stroke from  carotid artery stenosis  (narrowing the  internal carotid artery ). In  endarterectomy , the surgeon opens the artery and removes the plaque. The plaque forms and thickens the inner layer of the artery, or  intima , hence the name of the procedure which simply means removal of part of the internal layers of the artery.


An alternative procedure is  carotid stenting , which can also reduce the risk of stroke for some patients.


Carotid endarterectomy is used to reduce the risk of strokes caused by  carotid artery stenosis  over time. Carotid stenosis can either have symptoms (i.e., be symptomatic), or be found by a doctor in the absence of symptoms (asymptomatic) - and the risk-reduction from endarterectomy is greater for symptomatic than asymptomatic patients.


Carotid endarterectomy itself can cause strokes, so to be of benefit in preventing strokes over time, the risks for combined 30-day mortality and stroke risk following surgery should be < 3% for asymptomatic people and ≤ 6% for symptomatic people. [ 1 ]


Carotid endarterectomy does not treat symptoms of prior strokes. It is controversial if carotid endarterectomy can improve cognitive function in some patients. [ 2 ]


Symptomatic people have had either a stroke or  transient ischemic attack  or amaurosis fugax.


In symptomatic patients with a 70–99% stenosis, for every six people treated, one major stroke would be prevented at two years (i.e., a  number needed to treat  of six). [ 3 ]


Unlike asymptomatic patients, symptomatic people with moderate carotid stenosis (50–69%) still benefit from endarterectomy, albeit to a lesser degree, with a number needed to treat of 22 at five years. Recent evidence demonstrated that unstable carotid atherosclerotic plaques are responsible for cerebral ischemic events and symptoms (stroke or  transient ischemic attack ) in these patients. [ 4 ] [ 5 ]  In addition, co-morbidity adversely affects the outcome: people with multiple medical problems have a higher post-operative  mortality rate  and hence benefit less from the procedure. For maximum benefit people should be operated on soon after a stroke or transient ischemic attack, preferably within the first 2 weeks. [ 3 ]


Asymptomatic people have narrowing of their carotid arteries, but have not experienced a transient ischemic attack or stroke. The annual risk of stroke in patients with asymptomatic carotid disease is between 1% and 2%, although some patients are considered to be at higher risk, such as those with ulcerated plaques. This low rate of stroke means that there is less potential stroke risk-reduction from endarterectomy for asymptomatic patients relative to symptomatic patients. However, for asymptomatic patients with severe carotid stenosis (80-99%), carotid endarterectomy plus treatment with a  statin  medicine and  anti-platelet therapy  does reduces stroke risk further than medication alone in the five years following surgery. [ 6 ]


The most feared complication of carotid endarterectomy is stroke. Risks of stroke at the time of surgery are higher for symptomatic (3–5%) than asymptomatic patients (1–3%). [ 7 ]


Bleeding, infection, and  cranial nerve  injury are also risks at the time of surgery. Following surgery, a rare early complication is  cerebral hyperperfusion syndrome , also known as reperfusion syndrome, which is associated with headache and high blood pressure following surgery.


Long term complications include restenosis of the endarterectomy bed, although the clinical significance of this is controversial in asymptomatic patients.


The procedure should be avoided when:


High risk criteria for carotid endarterectomy include the following:


Carotid artery stenting  is an alternative to carotid endarterectomy in cases where endarterectomy is considered too risky.


An incision is made on the midline side of the  sternocleidomastoid muscle . The incision is between 5 and 10 cm (2.0 and 3.9 in) in length. The internal, common and external carotid arteries are carefully identified, controlled with vessel loops, and clamped. The lumen of the internal carotid artery is opened, and the atheromatous plaque substance removed.  The artery is closed using  suture  with or without a patch to increase the size of the  lumen .  Hemostasis  is achieved, and the overlying layers closed with suture. The skin can be closed with suture which may be visible or invisible (absorbable). Many surgeons place a temporary  shunt  to ensure blood supply to the brain during the procedure.  The procedure may be performed under general or local  anaesthesia . The latter allows for direct monitoring of neurological status by intra-operative verbal contact and neurological assessment. [ 8 ]   With general anaesthesia, indirect methods of assessing cerebral perfusion must be used.  Electroencephalography  (EEG), transcranial doppler analysis, cerebral oximetry, or carotid artery stump pressure monitoring can guide the placement of a shunt,  or a shunt may be routinely used.  At present there is still ongoing debate related to difference in outcome between local and general anaesthesia, and methods of determining the need for a shunt. [ 3 ]  However, excellent outcomes can be achieved by performing carotid endarterectomy under local  anaesthesia . [ 9 ]


The endarterectomy procedure was developed and first done by the Portuguese surgeon Joao Cid dos Santos in 1946, when he operated an occluded subsartorial artery, at the  University of Lisbon . In 1951 an Argentinian surgeon repaired a carotid artery occlusion using a bypass procedure. The first endarterectomy was successfully performed by  Michael DeBakey  around 1953, at the  Methodist Hospital  in Houston, TX, although the technique was not reported in the medical literature until 1975. [ 10 ]  The first case to be recorded in the medical literature was in The Lancet in 1954; [ 10 ] [ 11 ]  the surgeon was Felix Eastcott, a consultant surgeon and deputy director of the surgical unit at  St Mary's Hospital, London , UK. [ 12 ]  Eastcott's procedure was not strictly an endarterectomy as we now understand it; he excised the diseased part of the artery and then resutured the healthy ends together. [ citation needed ]  Carotid endarterectomy was finally shown to be effective in stroke prevention after a landmark clinical trial [ 13 ]  spearheaded by the Canadian clinical scientist  Dr. Henry Barnett . Since then, evidence for its effectiveness in different patient groups has accumulated. In 2003 nearly 140,000 carotid endarterectomies were performed in the US, however, the number of procedures has continued to decrease over time. [ 14 ]


Carotid artery stenting  is an  endovascular procedure  where a  stent  is deployed within the  lumen  of the  carotid artery  to treat  narrowing of the carotid artery  and decrease the risk of  stroke . It is used to treat narrowing of the carotid artery in high-risk patients, when  carotid endarterectomy  is considered too risky.


Carotid stenting is used to reduce the risk of stroke associated with  carotid artery stenosis . Carotid stenosis can have no symptoms, or have symptoms such as  transient ischemic attacks  (TIAs) or  strokes .


While historically  endarterectomy  has been the treatment for  carotid stenosis , stenting is an alternative intervention for patients who are not candidates for surgery.  High risk factors for endarterectomy, which would favor stenting instead, include medical comorbidities (severe heart disease,  heart failure , severe lung disease) and anatomic features (contralateral carotid occlusion, radiation therapy to the neck, prior ipsilateral carotid artery surgery, intra-thoracic or intracranial carotid disease) that would make surgery difficult and risky. [ 1 ]


While rates of stroke and death after both surgery and stenting are low, rates of stroke and death after stenting may be higher than with endartererectomy, particularly for transfemoral stenting in patients over age 70. [ 2 ]


Carotid stenting involves the placement of a  stent  across the  stenosis  in the carotid artery. It can be performed under general or local  anesthesia .


The stent may be placed from the  femoral artery ,  radial artery , or from the  common carotid artery  at the base of the neck. Critical steps in both approaches are vascular access, crossing the stenosis with a wire, deploying a stent across the lesion, and removing the  vascular access . A number of other steps may or may not be performed, including the use of a cerebral protection device, pre- or post-stent  balloon angioplasty  and cerebral angiography.


The trans-femoral route is the traditional approach to carotid stenting. The vast majority of these procedures are performed under local anesthesia. In this technique, puncture of the  common femoral artery  is used to gain access to the arterial system. Wire and sheath are advanced through the  aorta  to the  common carotid artery  on the side to be treated. Flow reversal or filter cerebral protection may be used. The procedure is typically performed  percutaneously . [ 3 ]


Trans-carotid artery stenting involves a surgical incision at the base of the neck over the  common carotid artery . It is performed under either local or general anesthesia. Wire access is obtained at that location and used to deliver the stent to the  internal carotid artery . Cerebral protection is usually obtained by flow reversal - the common carotid artery is clamped, and arterial blood from the internal carotid is run through a filter and returned to a  femoral vein  during the highest risk portions of the procedure. [ 4 ]


The trans-radial route has been introduced as an alternative in the past few years. The vast majority of these procedures are performed under local anesthesia. In this technique, puncture of the radial artery is used to gain access to the arterial system. Wire and sheath are advanced through the  aorta  to the  common carotid artery  on the side to be treated. Flow reversal or filter cerebral protection may be used. The procedure is typically performed  percutaneously . [ 5 ]


Recovery after carotid artery stenting depends not only on the presence of complications during the procedure, but also on the presence of symptoms at the time of arrival to the hospital. Asymptomatic patients typically leave the hospital in 0–1 days. The blood pressure is kept at a goal below 140 mmHg systolic. Elevated blood pressure in the 2–10 days post-operatively may lead to  reperfusion syndrome .


The most feared short-term complication of any stroke prevention procedure on the carotid artery is stroke itself.  Patients must still be carefully selected for surgery or stenting in order to reduce the risks related to the procedure and ensure the long-term benefit after such intervention. Other short-term complications might include bleeding, infection and heart problems such as  myocardial infarction  related to anesthesia.


Late complications such as recurrent stenosis may occur, and surveillance with  duplex ultrasound  or  CT-Angiography  may be performed.


The risk-reduction from intervention for carotid stenosis (stenting or endarterectomy) is greatest when the indication for intervention is symptoms (i.e., the patient is symptomatic) - typically  stroke  or  TIA . [ 6 ]
A new generation of double-layer stents is currently being developed to reduce the risk of stroke during or after the procedure.  [ 7 ]  There is insufficient evidence to say that stenting or endarterectomy is better for symptomatic patients.


Angioplasty and carotid stenting in patients with asymptomatic carotid atherosclerotic stenosis should not be performed except in the context of randomized clinical trials. [ 8 ]


Cholesterol embolism  occurs when  cholesterol  is released, usually from an  atherosclerotic plaque , and travels as an  embolus  in the bloodstream to lodge (as an  embolism ) causing an obstruction in  blood vessels  further away. Most commonly this causes skin symptoms (usually  livedo reticularis ),  gangrene  of the extremities and sometimes  kidney failure ; problems with other organs may arise, depending on the site at which the  cholesterol crystals  enter the bloodstream. [ 2 ]  When the  kidneys  are involved, the disease is referred to as  atheroembolic renal disease . [ 3 ]  The diagnosis usually involves  biopsy  (removing a tissue sample) from an affected organ. Cholesterol embolism is treated by removing the cause and giving supportive therapy;  statin  drugs have been found to improve the prognosis. [ 2 ]


The symptoms experienced in cholesterol embolism depend largely on the organ involved.  Non-specific symptoms  often described are  fever ,  muscle ache  and  weight loss . Embolism to the legs causes a mottled appearance and purple discoloration of the  toes , small  infarcts  and areas of  gangrene  due to  tissue death  that usually appear black, and areas of the skin that assume a marbled pattern known as  livedo reticularis . [ 3 ]  The pain is usually severe and requires opiates. If the ulcerated plaque is below the renal arteries the manifestations appear in both lower extremities. Very rarely the ulcerated plaque is below the aortic bifurcation and those cases the changes occur only in one lower extremity. [ citation needed ]


Kidney involvement leads to the symptoms of  kidney failure , which are non-specific but usually cause  nausea , reduced  appetite  ( anorexia ), raised  blood pressure  (hypertension), and occasionally the various symptoms of  electrolyte disturbance  such as an  irregular heartbeat . Some patients report  hematuria  (bloody urine) but this may only be detectable on microscopic examination of the urine. Increased amounts of  protein  in the urine may cause  edema  (swelling) of the skin (a combination of symptoms known as  nephrotic syndrome ). [ 3 ]


If emboli have spread to the  digestive tract , reduced appetite, nausea and vomiting may occur, as well as nonspecific  abdominal pain ,  gastrointestinal hemorrhage  (vomiting blood, or  admixture of blood in the stool ), and occasionally  acute pancreatitis  (inflammation of the  pancreas ). [ 3 ]


Both the  central nervous system  (brain and  spinal cord ) and the  peripheral nervous system  may be involved. Emboli to the brain may cause  stroke -like episodes,  headache  and episodes of loss of vision in one eye (known as  amaurosis fugax ). [ 3 ]  Emboli to the eye can be seen by  ophthalmoscopy  and are known as  plaques of Hollenhorst . [ 4 ]  Emboli to the spinal cord may cause  paraparesis  (decreased power in the legs) or  cauda equina syndrome , a group of symptoms due to loss of function of the distal part of the spinal cord – loss of control over the  bladder ,  rectum  and skin sensation around the anus. [ 3 ]  If the blood supply to a single nerve is interrupted by an embolus, the result is loss of function in the muscles supplied by that nerve; this phenomenon is called a  mononeuropathy . [ 3 ]


It is relatively unusual (25% of the total number of cases) for cholesterol emboli to occur spontaneously; this usually happens in people with severe  atherosclerosis  of the large arteries such as the  aorta . In the other 75% it is a complication of medical procedures involving the blood vessels, such as  vascular surgery  or  angiography . In  coronary catheterization , for instance, the incidence is 1.4%. [ 5 ]  Furthermore, cholesterol embolism may develop after the commencement of  anticoagulants  or  thrombolytic  medication that decrease blood clotting or dissolve blood clots, respectively. They probably lead to cholesterol emboli by removing blood clots that cover up a damaged atherosclerotic plaque; cholesterol-rich debris can then enter the bloodstream. [ 3 ]


Findings on general investigations (such as  blood tests ) are not specific for cholesterol embolism, which makes diagnosis difficult. The main problem is the distinction between cholesterol embolism and  vasculitis  (inflammation of the small blood vessels), which may cause very similar symptoms - especially the skin findings and the kidney dysfunction. [ 3 ]  Worsening kidney function after an angiogram may also be attributed to kidney damage by substances used during the procedure ( contrast nephropathy ). Other causes that may lead to similar symptoms include  ischemic kidney failure  (kidney dysfunction due to an interrupted blood supply), a group of diseases known as  thrombotic microangiopathies  and  endocarditis  (infection of the  heart valves  with small clumps of infected tissue embolizing through the body). [ 3 ]


Tests for  inflammation  ( C-reactive protein  and the  erythrocyte sedimentation rate ) are typically elevated, and abnormal  liver enzymes  may be seen. [ 3 ]  If the kidneys are involved, tests of  kidney function  (such as  urea  and  creatinine ) are elevated. [ 3 ]  The  complete blood count  may show particularly high numbers of a type of  white blood cell  known as  eosinophils  (more than 0.5 billion per liter); this occurs in only 60-80% of cases, so normal eosinophil counts do not rule out the diagnosis. [ 3 ] [ 5 ]  Examination of the urine may show  red blood cells  (occasionally in  casts  as seen under the microscope) and increased levels of protein; in a third of the cases with kidney involvement, eosinophils can also be detected in the urine. [ 3 ]  If vasculitis is suspected,  complement  levels may be determined as reduced levels are often encountered in vasculitis; complement is a group of proteins that forms part of the innate  immune system . Complement levels are frequently reduced in cholesterol embolism, limiting the use of this test in the distinction between vasculitis and cholesterol embolism. [ 6 ]


The microscopic examination of tissue ( histology ) gives the definitive diagnosis.  The diagnostic  histopathologic  finding is intravascular cholesterol crystals, which are seen as cholesterol clefts in routinely processed tissue (embedded in  paraffin wax ). [ 7 ]  The cholesterol crystals may be associated with  macrophages , including  giant cells , and  eosinophils . [ citation needed ]


The  sensitivity  of small core biopsies is modest, due to  sampling error , as the process is often patchy.  Affected organs show the characteristic histologic changes in 50-75% of the clinically diagnosed cases. [ 3 ] [ 5 ]  Non-specific tissue findings suggestive of a cholesterol embolization include  ischemic changes ,  necrosis  and unstable-appearing complex  atherosclerotic plaques  (that are cholesterol-laden and have a thin fibrous cap).  While biopsy findings may not be diagnostic, they have significant value, as they help exclude alternate diagnoses, e.g.  vasculitis , that often cannot be made confidently based on clinical criteria. [ citation needed ]


Treatment of an episode of cholesterol emboli is generally symptomatic, i.e. it deals with the symptoms and complications but cannot reverse the phenomenon itself. [ 5 ]  In kidney failure resulting from cholesterol crystal emboli,  statins  (medication that reduces cholesterol levels) have been shown to halve the risk of requiring  hemodialysis . [ 2 ]


The phenomenon of embolisation of cholesterol was first recognized by the  Danish   pathologist  Dr.  Peter Ludvig Panum  and published in 1862. [ 8 ]  Further evidence that eroded atheroma was the source of emboli came from American  pathologist  Dr. Curtis M. Flory, who in 1945 reported the phenomenon in 3.4% of a large  autopsy  series of older individuals with severe atherosclerosis of the  aorta . [ 3 ] [ 9 ]


A  Cimino fistula , also  Cimino-Brescia fistula ,  surgically created arteriovenous fistula  and (less precisely)  arteriovenous fistula  (often  abbreviated   AV fistula  or  AVF ), is a type of vascular access for  hemodialysis . It is typically a surgically created connection between an  artery  and a  vein  in the arm, although there have been acquired arteriovenous fistulas which do not in fact demonstrate connection to an artery. [ 1 ]


The radiocephalic arteriovenous fistula (RC-AVF) is a shortcut created between  cephalic vein  and  radial artery  at the wrist. It is the recommended first choice for hemodialysis access. However, after a period of usage, failures can occur. Possible causes for failure are stenosis and thrombosis especially in diabetics and those with low blood flow such as due to narrow vessels, arteriosclerosis and advanced age. Reported patency of fistulae after 1 year is about 60%, when primary failures were included. [ 2 ]


Juxa-anastomotic site (venous segment that is between 2 and 5 cm distal to the anastomotic site) is the most common site of stenosis. One of the reasons affecting the rate of stenosis could be the anastomotic angle. [ 3 ] [ 4 ]  In  computational fluid dynamics  study, the ideal anastomotic angle should be less than 30 degrees to ensure  laminar flow  of the blood, thus prolong the  endothelial cell  survival, and prevent smooth muscle proliferation within vessel wall, and clogging the vessel. However, in another study using  angiographic  images of the juxta-anastomotic sites, the ideal anastomotic angle of less than 46.5 degrees was obtained. [ 3 ]


Surgically created AV fistulas work effectively because they:


The procedure was invented by doctors  James Cimino  and M. J. Brescia at the  Bronx Veterans Administration Hospital  in 1966. [ 6 ]  Before the Cimino fistula was invented, access was through a  Scribner shunt , which consisted of a  Teflon  tube with a needle at each end. Between treatments, the needles were left in place and the tube allowed blood flow to reduce clotting. But Scribner shunts lasted only a few days to weeks. Frustrated by this limitation, James E. Cimino recalled his days as a  phlebotomist  (blood drawer) at  New York City 's  Bellevue Hospital  in the 1950s when  Korean War   veterans  showed up with  fistulas  caused by trauma. Cimino recognized that these fistulas did not cause the patients harm and were easy places to get repeated blood samples. He convinced surgeon Kenneth Appell to create some in patients with  chronic kidney failure  and the result was a complete success. Scribner shunts were quickly replaced with Cimino fistulas, and they remain the most effective, longest-lasting method for long-term access to patients' blood for hemodialysis today.


Distal Revascularization and Interval Ligation  (DRIL) is a  surgical  method of treating  vascular access steal syndrome .


DRIL was first proposed by Harry Schanzer and colleagues in 1988. [ 1 ]


A short distal bypass is created and the artery just distal to the AV  anastomosis  is ligated.


In  medicine , a  distal splenorenal shunt procedure  ( DSRS ), also  splenorenal shunt procedure  and  Warren shunt , [ 1 ]  is a  surgical procedure  in which the  distal   splenic vein  (a part of the  portal venous system ) is attached to the left  renal vein  (a part of the  systemic venous system ).  It is used to treat  portal hypertension  and its main complication ( esophageal varices ). [ 2 ]  It was developed by  W. Dean Warren .


DSRS is typically done with splenopancreatic and gastric disconnection (ligation of the  gastric veins  and  pancreatic veins  (that drain into the  portal vein ) and complete detachment of the  splenic vein  from the  portal venous system ), as it improves the outcome. [ 3 ]


Survival with a  transjugular intrahepatic portosystemic shunt  (TIPS) versus a DSRS is thought to be approximately similar, [ 4 ] [ 5 ]  but still an area of intensive research. [ 6 ] [ 7 ]


Both TIPS and DSRS lead to decreased rates of  variceal bleeding  at the expense of  hepatic encephalopathy ; however, TIPS appears to have more shunt dysfunction and lead to more encephalopathy and bleeds. [ 5 ]  DSRS appears to be more cost effective than TIPS. [ 8 ]


Endovascular aneurysm repair  ( EVAR ) is a type of minimally-invasive  endovascular surgery  used to treat  pathology  of the  aorta , most commonly an  abdominal aortic aneurysm  (AAA). When used to treat  thoracic aortic  disease, the procedure is then specifically termed  TEVAR  for "thoracic endovascular aortic/aneurysm repair." EVAR involves the placement of an expandable  stent graft  within the aorta to treat aortic disease without operating directly on the aorta. In 2003, EVAR surpassed  open aortic surgery  as the most common technique for repair of AAA, [ 1 ]  and in 2010, EVAR accounted for 78% of all intact AAA repair in the United States. [ 2 ]


Standard EVAR is appropriate for aneurysms that begin below the  renal arteries , where there exists an adequate length of normal  aorta  (the  "proximal aortic neck" ) for reliable attachment of the endograft without leakage of blood around the device (" endoleak "). [ 3 ]  If the proximal aortic neck is also involved with the aneurysm, the patient may be a candidate for complex visceral EVAR with a fenestrated or branched EVAR.


Patients with aneurysms require elective repair of their aneurysm when it reaches a diameter large enough (typically greater than 5.5 cm) such that the risk of rupture is greater than the risk of surgery. Repair is also warranted for aneurysms that rapidly enlarge or those that have been the source of  emboli  (debris from the aneurysm that dislodges and travel into other arteries). Lastly, the repair is also indicated for aneurysms that are the source of  pain  and  tenderness , which may indicate impending rupture. The options for repair include traditional  open aortic surgery  or endovascular repair. [ citation needed ]


Endovascular procedures aim to reduce the morbidity and mortality of treating arterial disease in a patient population that is increasingly older and less fit than when major open repairs were developed and popularized. Even in the early days, significant risks were accepted in the understanding that the large open operation was the only option. That is not the case in most patients today. [ citation needed ]


Studies that assign aneurysm patients to treatment with EVAR or traditional open surgery have demonstrated fewer early complications with the minimally invasive approach. Some studies have also observed a lower mortality rate with EVAR. [ 4 ] [ 5 ]  The reduction in death, however, does not persist long-term. After a few years, the survival after repair is similar to EVAR or open surgery. This observation may be the result of durability problems with early endograft, with a corresponding need for additional procedures to repair endoleaks and other device-related issues. Newer, improved technology may reduce the need for such secondary procedures. If so, the results of EVAR may improve to the point where long-term survival benefit becomes evident. [ citation needed ]


EVAR is also used for  rupture  of the abdominal and descending thoracic aorta, and in rare cases used to treat pathology of the  ascending aorta . [ 6 ]


Endografts have been used in patients with  aortic dissection , noting the extremely complex nature of open surgical repair in these patients. In uncomplicated aortic dissections, no benefit has been demonstrated over medical management alone.
In uncomplicated type B aortic dissection, TEVAR does not seem either to improve or compromise 2-year survival and adverse event rates. [ 7 ]  Its use in complicated aortic dissection is under investigation. In the Clinical Practice Guidelines of the European Society for Vascular Surgery, it is recommended that in patients with complicated acute type B aortic dissection, endovascular repair with thoracic endografting should be the first line intervention. [ 8 ]


Before people are deemed to be suitable candidates for this treatment, they have to go through a rigorous set of tests.  These include a CT scan of the complete thorax/abdomen/pelvis and blood tests.  The CT scan gives precise measurements of the aneurysm and the surrounding anatomy. In particular, the calibre/tortuosity of the iliac arteries and the relationship of the neck of the aneurysm to the renal arteries are important determinants of whether the aneurysm is amenable to endoluminal repair. In certain occasions where the renal arteries are too close to the aneurysm, the custom-made fenestrated graft stent is now an accepted alternative to doing open surgery. [ citation needed ]


A patient's anatomy can be unsuitable for EVAR in several ways. Most commonly, in an infrarenal aneurysm, a potential EVAR candidate lacks adequate length of the normal-diameter aorta between the aneurysm and the takeoff of the renal arteries, the "infra-renal neck". Another relative  contraindications  include prohibitively small  iliac arteries , aneurysmal iliac arteries, prohibitively small  femoral arteries , or circumferential calcification of the femoral or iliac arteries. [ citation needed ]


In addition to a short proximal aortic neck, the neck may be angulated, large in diameter, or shaped like a funnel (conical) where the neck diameter at the top is larger than the neck diameter at the bottom. Along with a short proximal aortic neck, necks with any of these characteristics are called "hostile necks" and endovascular repair can be either contraindicated or associated with early-late complications of endoleak, or endograft migration, or both. [ citation needed ]


Many of the advances in EVAR technique aim to adapt EVAR for these situations, and advanced techniques allow EVAR to be employed in patients who previously were not candidates. [ citation needed ]


The procedure is carried out in a sterile environment under  fluoroscopic  guidance.  It is usually carried out by a  vascular surgeon ,  interventional radiologist  or  cardiac surgeon , and occasionally,  general surgeon  or  interventional cardiologist . [ 9 ] [ 10 ] [ 11 ] [ 12 ]  The procedure can be performed under  general ,  regional (spinal or epidural)  or even  local anesthesia . [ 13 ]


Access to the patient's femoral arteries can be with surgical incisions or  percutaneously  in the groin on both sides. Vascular sheaths are introduced into the patient's femoral arteries, through which guidewires, catheters, and the endograft are passed. [ citation needed ]


Diagnostic angiography images are captured of the aorta to determine the location of the patient's renal arteries, so the stent-graft can be deployed without blocking these. Failure to achieve this will cause  kidney failure . With most devices, the "main body" of the endograft is placed first, followed by the "limbs" which join the main body and extend to the iliac arteries, effectively protecting the aneurysm sac from blood pressure. [ citation needed ]


The abdominal aneurysm extends down to the common iliac arteries in about 25%-30% of patients. In such cases, the iliac limbs can be extended into the external iliac artery to bypass a common iliac aneurysm. Alternatively, a specially designed endograft, (an iliac branch device) can be used to preserve flow to the  internal iliac arteries . The preservation of the hypogastric (internal iliac) arteries is important to prevent buttock  claudication  and  impotence , and every effort should be made to preserve flow to at least one hypogastric artery. [ citation needed ]


The endograft acts as an artificial lumen for blood to flow through, protecting the surrounding aneurysm sac. This reduces the pressure in the aneurysm, which itself will usually thrombose and shrink in size over time. [ 14 ]


Staging such procedures is common, particularly to address aortic branch points near the diseased aortic segment. One example in the treatment of thoracic aortic disease is revascularization of the left common carotid artery and/or the left subclavian artery from the innominate artery or the right common carotid artery to allow treatment of a thoracic aortic aneurysm that encroaches proximally into the aortic arch. These "extra-anatomic bypasses" can be performed without an invasive  thoracotomy . Another example in the abdominal aorta is the embolization of the internal iliac artery on one side prior to coverage by an iliac limb device. Continued improvement in stent-graft design, including branched endografts, will reduce but not eliminate multi-stage procedures. [ citation needed ]


Standard EVAR involves a surgical cut-down on either the femoral or iliac arteries, with the creation of a 4–6 cm incision. Like many surgical procedures, EVAR has advanced to a more  minimally invasive  technique, by accessing the femoral arteries  percutaneously  In percutaneous EVAR ( PEVAR ), small, sub-centimeter incisions are made over the femoral artery, and endovascular techniques are used to place the device over a wire. Percutaneous EVAR has been systematically compared to the standard EVAR cut-down femoral artery approach. [ 15 ]  Moderate quality evidence suggests that there are no differences in short-term mortality, aneurysm sealing, long and short-term complications, or infections at the wound site. [ 15 ]  Higher quality evidence suggests that there are no differences in post-repair bleeding complications or haematoma between the two approaches. [ 15 ]  The percutaneous approach may have reduced surgical time. [ 15 ]


Fenestrated endovascular aortic/aneurysm repair (FEVAR) is performed in the cases where the aneurysm extends near or involves the visceral vessels (such as juxta-renal, para-renal, thoraco-abdominal aortic aneurysms). A custom-made graft with fenestrations (holes on the graft body to maintain the patency of the visceral arteries) is used for the procedure. When the aneurysm involves the visceral arteries, standard EVAR is  contraindicated  due to the lack of suitable infra-aortic segment for the endograft attachment; FEVAR achieves seal between the stent graft and para-visceral segment and/or more proximal segment while preserving the flow of the visceral arteries. FEVAR has been in use in the United Kingdom for over a decade and early results were published in Jun 2012.
 [ 16 ]


Thoracoabdominal aortic aneurysms (TAAA) involve the aorta in the chest and abdomen. As such, major branch arteries to the head, arms, spinal cord, intestines, and kidneys may originate from the aneurysm. An endovascular repair of a TAAA is only possible if blood flow to these critical arteries is preserved. Hybrid procedures offer one option, but a more direct approach involves the use of a branched endograft. However, the complex anatomy associated with the supra-aortic vessels is particularly difficult to accommodate with branched endograft devices. [ 17 ]  Dr. Timothy Chuter pioneered this approach, with a completely endovascular solution. After partial deployment of the main body of an endograft, separate endograft limbs are deployed from the main body to each major aortic branch. This procedure is long, technically difficult, and currently only performed in a few centers.
When the aneurysm begins above the renal arteries, neither fenestrated endografts nor "EndoAnchoring" of an infrarenal endograft is useful (an open surgical repair may be necessary). Alternatively, a "branched" endograft may be used. A branched endograft has graft limbs that branch off of the main portion of the device to directly provide blood flow to the kidneys or the visceral arteries. [ 18 ] [ 19 ]


On occasion, there is inadequate length or quality of the proximal or distal aortic neck. In these cases, a fully minimally invasive option is not possible. One solution, however, is a hybrid repair, which combines an open surgical bypass with EVAR or TEVAR. In hybrid procedures, the endograft is positioned over major aortic branches. While such a position would normally cause problems from disruption of blood flow to the covered branches (renal, visceral, or branches to the head or arms), the prior placement of bypass grafts to these critical vessels allowed the deployment of the endograft at a level that would otherwise not be possible. [ citation needed ]


If a patient has calcified or narrow femoral arteries that prohibit the introduction of the endograft transfemorally, an iliac conduit may be used. This is typically a piece of PTFE that is sewn directly to the iliac arteries, which are exposed via an open retroperitoneal approach. The endograft is then introduced into the aorta through the conduit. [ citation needed ]


In patients with thoracic aortic disease involving the arch and descending aorta, it is not always possible to perform a completely endovascular repair. This is because head vessels of the aortic arch supplying blood to the brain cannot be covered and for this reason, there is often an inadequate landing zone for stent-graft delivery. A hybrid repair strategy offers a reasonable choice for treating such patients. A commonly used hybrid repair procedure is the "frozen elephant trunk repair". [ 20 ]  This technique involves midline sternotomy. The aortic arch is transected and the stent-graft device is delivered in an ante-grade fashion in the descending aorta. The aortic arch is subsequently reconstructed and the proximal portion of the stent-graft device is then directly sutured into the surgical graft. Patients with anomalies of the arch and some disease extension into the descending aorta are often ideal candidates. Studies have reported successful use of hybrid techniques for treating Kommerell diverticulum [ 21 ]  and descending aneurysms in patients with previous coarctation repairs. [ 22 ] [ 23 ]


In addition, hybrid techniques combining both open and endovascular repair are also used in managing emergency complications in the aortic arch, such as retrograde ascending dissection and endoleaks from previous stent grafting of descending aorta. A "reverse frozen elephant trunk repair" is shown to be particularly effective. [ 24 ]


The complications of EVAR can be divided into those that are related to the repair procedure and those related to the endograft device. For example, a  myocardial infarction  that occurs immediately after the repair is normally related to the procedure and not the device. By contrast, the development of an endoleak from degeneration of endograft fabric would be a device-related complication. [ 19 ]


Durability and problems such as 'endoleaks' may require careful surveillance and adjuvant procedures to ensure the success of the EVAR or EVAR/hybrid procedure. CT angiography (CTA) imaging has, in particular, made a key contribution to planning, success, durability in this complex area of vascular surgery. [ citation needed ]


A major cause of complications in EVAR is the failure of the seal between the proximal, infra-renal aneurysm neck and the endovascular graft. [ 27 ] [ 28 ] [ 29 ]  Risk of this form of failure is especially elevated in adverse or challenging proximal neck anatomies, where this seal could be compromised by unsuitable geometric fit between the graft and vessel wall, as well as instability of the anatomy. [ 30 ] [ 31 ] [ 32 ]  New recent techniques have been introduced to address these risks by utilizing a segment of the supra-renal portion of the aorta to increase the sealing zone, such as with fenestrated EVAR, chimneys and snorkels. [ 33 ]  These techniques may be suitable in certain patients with qualifying factors, e.g., configuration of renal arteries, renal function.  However, these are more complex procedures than standard EVAR and may be subject to further complications. [ 34 ] [ 35 ] [ 36 ]


An approach that directly augments the fixation and sealing between the graft and aorta to mimic the stability of a surgical anastomosis is EndoAnchoring. [ 37 ] [ 38 ]  EndoAnchors are small, helically shaped implants that directly lock the graft to the aortic wall with the goal to prevent complications of the seal, especially in adverse neck anatomies. [ 39 ] [ 40 ]  These EndoAnchors may also be used to treat identified leaks between the graft and proximal neck. [ 41 ] [ 42 ] [ 43 ]


Arterial dissection, contrast-induced kidney failure, thromboembolizaton,  ischemic colitis , groin  hematoma , wound infection, type II endoleaks, myocardial infarction, congestive heart failure, cardiac arrhythmias, respiratory failure. [ citation needed ]


Endograft migration, aneurysm rupture, graft limb stenosis/kinking, type I/III/IV endoleaks, stent graft thrombosis, or infection. [ 44 ]  Device infection occurs in 1-5% of aortic prosthesis placements and is a life-threatening complication. [ 45 ]


An endoleak is a leak into the aneurysm sac after endovascular repair. Five types of endoleaks exist: [ 14 ]


Type I and III leaks are considered high-pressure leaks and are more concerning than other leak types. Depending on the aortic anatomy, they may require further intervention to treat. Type II leaks are common and often can be left untreated unless the aneurysm sac continues to expand after EVAR. [ 46 ]


Spinal cord injury is a devastating complication after aortic surgery, specifically for thoracoabdominal aortic aneurysm repair; severe injury could lead to urine and fecal incontinence, paresthesia and even paraplegia. [ 47 ]  The risk varies between studies with two metanalysis demonstrating a pooled incidence of spinal cord injury 2.2% [ 48 ]  and 11%. [ 49 ]  Predictive factors include increasing extent of coverage, hypogastric artery occlusion, prior aortic repair and perioperative hypotension. [ 50 ]  Spinal cord injury related to aortic repair occurs due to impaired blood flow to the spine after coverage of blood vessels, important to the blood circulation of the spine, namely intercostal- and lumbar arteries. [ 51 ]  Neuromonitoring appears to be effective in detecting perioperative spinal cord injury risk during TEVAR. While the incidence of spinal cord injury remains variable, identification of risk factors may guide clinical decisions, particularly in high-risk procedures. [ 52 ]  A few methods exist for potentially reversing spinal cord injury, if it arises, elevated blood pressure, increased oxygenation, blood transfusion and cerebrospinal fluid drainage.


Cerebrospinal fluid drainage is one of the adjunct methods used to reverse spinal cord injury. With increased drainage of spinal fluid, the intrathecal pressure decreases which allows for increase blood perfusion to the spine, possibly reversing the ischemic injury of the spinal tissue due to lessened blood supply. The benefits of this procedure have been established in open aortic repair [ 53 ]  and suggested in endovascular aortic repair. [ 47 ]


As compared to the traditional aortic repair, standard recovery after EVAR is faster with earlier ambulation. However, there is still risk of spinal cord injury early after the procedure. Patients who have undergone EVAR typically spend one night in the hospital to be monitored, although it has been suggested that EVAR can be performed as a same-day procedure. [ 54 ]


Patients are advised to slowly return to normal activity. There are no specific activity restrictions after EVAR, however, patients typically are seen by their surgeon within one month after EVAR to begin post-EVAR surveillance. [ citation needed ]


There is limited research looking at patients' experience of recovery after more complex and staged EVAR for thoracoabdominal aortic diseases. One qualitative study found that patients with complex aortic diseases struggle with physical and psychological setbacks, continuing years after their operations. [ 55 ]


Dr.  Juan C. Parodi  introduced the minimally-invasive endovascular aneurysm repair (EVAR) to the world and performed the first successful endovascular repair of an abdominal aortic aneurysm on 7 September 1990 in Buenos Aires on a friend of  Carlos Menem , the then President of Argentina. The first device was simple, according to Parodi: "It was a graft I designed with expandable ends, the extra-large Palmaz stent, a Teflon sheath with a valve, a wire, and the valvuloplasty balloon, which I took from the cardiologists." Parodi's first patient lived for nine years after the procedure and died from pancreatic cancer. [ 56 ] [ 57 ]
The first EVAR performed in the United States was in 1992 by Drs.  Frank Veith ,  Michael Marin ,  Juan Parodi  and  Claudio Schonholz  at  Montefiore Medical Center  affiliated with  Albert Einstein College of Medicine . [ citation needed ]


The modern endovascular device used to repair abdominal aortic aneurysms, which is bifurcated and modular, was pioneered and first employed by Dr. Timothy Chuter while a fellow at the  University of Rochester . [ 58 ]  The first clinical series of his device was published from Nottingham in 1994. [ 59 ]  The first endovascular repair of a ruptured abdominal aortic aneurysm was also reported from Nottingham in 1994. [ 60 ]


By 2003, four devices were on the market in the United States. [ 61 ]  Each of these devices has since been either abandoned or further refined to improve its characteristics  in vivo .


Women are known to have smaller aortas on average than men, so are potential candidates for AAA treatment at smaller maximum aneurysm diameters than men. [ citation needed ]


As immunosuppressive medications are known to increase the rate of aneurysm growth, transplant candidates are AAA repair candidates at smaller maximum aneurysm diameters than the general population. [ citation needed ]


Due to the expense associated with EVAR stent-graft devices and their specificity to human aortic anatomy, EVAR is not used in other animals. [ citation needed ]


Endovenous laser treatment  ( ELT ) is a minimally invasive ultrasound-guided technique used for treating  varicose veins  using  laser  energy commonly performed by a  phlebologist ,  interventional radiologist  or  vascular surgeon .


Endovenous laser treatment treats  varicose veins  using an  optical fiber  that is inserted into the vein to be treated, and  laser  light, normally in the  infrared  portion of the  spectrum , [ 1 ]  shines into the interior of the vein. This causes the vein to contract, and the optical fiber is slowly withdrawn. Some minor complications can occur, including  thrombophlebitis ,  pain ,  hematoma ,  edema  and  infection , which can lead to  cellulitis . [ 2 ]


EVLT has the same meaning as ELT, but it is a trademark name owned by Diomed and used as the name for their 910 nm laser treatment unit for ELT.  [ citation needed ] The 810 nm laser is the original laser fiber wavelength as pioneered by Dr. Luis Navarro, Dr. Carlos Bone and Dr. Robert Min, at the Vein Treatment Center in New York, New York.  [ citation needed ] Subsequently, various other fibers with different wavelengths have become available. The varying wavelength each aim to maximize local damage to a component of the varicose vein or the  blood  contained in it while minimizing damage to adjacent tissues.


During the procedure, a  catheter  bearing a laser fiber is inserted under ultrasound guidance into the  great saphenous vein  (GSV) or  small saphenous vein  (SSV) through a small puncture. The catheter is then advanced, also under ultrasound guidance, to the level of the groin or knee crease. Dilute  local anesthesia  is injected around and along the vein (perivascular infiltration) using ultrasound imaging to place the local anesthetic solution around the vein, mostly in a sub-facial location. This technique derives from the tumescent local anesthesia (TLA) method long used and proven safe and effective for some methods of  liposuction . The laser is activated whilst the catheter or laser fiber is slowly withdrawn, resulting in obliteration of the saphenous vein along its entire length. The treatment, which is performed without  sedation , usually takes between 1 and two hours, and the patient walks out under his or her own power. The leg is bandaged and/or placed in a stocking that the patient wears for up to three weeks afterwards.


Foam  sclerotherapy  or  ambulatory phlebectomy  is often performed at the time of the procedure or within the first 1–2 weeks to treat branch varicose veins. However, some physicians do not perform these procedures at the time of the ELT because the varicose veins can improve on their own as a result of reduced reflux from the great saphenous vein.


Complications of endovenous laser treatment can be categorized as minor, or serious. Minor complications include  bruising  (51%),  hematoma  (2.3%), temporary numbness (3.8%),  phlebitis  (7.4%),  induration  (46.7%), and a sensation of tightness (24.8%). More serious complications include skin  burns  (0.5%),  deep venous thrombosis  (0.4%),  pulmonary embolism  (0.1%), and nerve injury (0.8%). These rates of complications are derived from the Australian MSAC review of all available literature on the procedure. [ 3 ]
 Retinal  damage is a serious but very rare complication (<1%) that can occur during the use of lasers. If the fiber breaks or if the laser is activated when the laser is outside of the body, reflected laser light may cause a focal permanent retinal deficit or "blind spot" or  scotoma . The nominal hazard zone (NHZ) [ 4 ]  or space within which the level of direct, scattered, or reflected laser radiation exceeds the maximum permissible exposure (MPE), varies by the wavelength of the laser and is shorter (17 inches) with the newer 1470 nm laser. Use of appropriate protective eyeware specific to the wavelength laser being used prevents accidental injury. [ 4 ]


A 2005 report from one practice, summarising results of 1,000 limbs treated over a 5-year period with EVLT showed that 98% of the treated vessels at up to 60 months follow-up remained closed, with complications and side effects such as temporary paresthesia and DVTs below 0.5%. [ 5 ]


The Australian Medical Services Advisory Committee (MSAC) in 2008 has determined that endovenous laser treatment for varicose veins "appears to be more effective in the short term, and at least as effective overall, as the comparative procedure of junction ligation and vein stripping for the treatment of varicose veins." [ 3 ]  It also found in its assessment of available literature, that "occurrence rates of more severe complications such as DVT,  nerve injury  and  paresthesia , post-operative infections and hematomas, appears to be greater after ligation and stripping than after EVLT". A study of 516 treated veins over 69 months by Elmore and Lackey reported a success rate of 98.1%. [ 6 ]


Endovenous thermal ablation (EVTA) by radiofrequency or laser is a safe and effective treatment of refluxing great saphenous veins  [ 7 ]  (GSVs) and has replaced traditional high ligation and stripping in official recommendations of various leading Vascular Societies in the United States and the United Kingdom.


Patients are usually fitted with Class 3 (30-40mmHg) graduated compression stockings and/or bandages for up to 12 hours weeks. Duplex ultrasound is used during follow-up to assess the success of treatment, if there is a need for additional sclerotherapy or any deep vein thrombosis that has formed as an EHIT secondary to procedure.


In  cardiac surgery  and  vascular surgery ,  external support  (or  external stent ) is a type of scaffold made of metal or plastic material that is inserted over the outside of the  vein   graft  in order to decrease the intermediate and late  vein graft failure  after  bypass surgery  (e.g.  CABG ).


An external support (external stent) should be differentiated from a  stent . An external support is placed on the outside of the  vessel  whereas a stent is inserted into the  lumen  of a vessel. [ citation needed ]


Veins are adapted to an environment of low pressure and low flow. In order to bypass the coronary obstruction and restore blood flow, veins are transferred and integrated into the  arterial circulation , where they exposed to high pressure and flow. These new  hemodynamic  conditions cause  intimal hyperplasia  and  atherosclerosis  that cause intermediate and late  vein graft failure . [ 1 ] [ 2 ]  The idea of placing an external support on the vein graft was first suggested in 1963. [ 3 ]  The rational being that it will diminish the circumferential strain of the graft wall, therefore inhibiting intimal hyperplasia and later superimposed atherosclerosis, aiding with the adaptation of the vein toward the arterial environment.


The external scaffold provides a mechanical support for the vein graft, absorbs the high arterial pressure, constrict the vein graft dilatation, reduces lumen irregularities and mitigates intimal hyperplasia formation. As shown both in human  tissue cultures  and  experimental models . [ 4 ] [ 5 ] [ 6 ] [ 7 ] [ 8 ]  However, until recently there were a limited number of  clinical studies  that showed less positive results. [ 9 ] [ 10 ] [ 11 ]  It was hypothesized that graft patency rates were lower with external support, because of aggressive over constriction of the vein graft, unsuitable material of the devices and the use of  fibrin glue  that has shown to cause tissue damage,  fibrosis  and intimal hyperplasia. [ 12 ] [ 13 ] [ 14 ]  Lately, more promising results with second generation devices showed that external support can mitigate intimal hyperplasia development, improve vein graft lumen uniformity and improve the flow pattern inside the graft. [ 15 ] [ 16 ] [ 17 ] [ 18 ]
These benefits shown to remain for up to five years follow up. [ 19 ]
In addition to improving the vein graft failure rates in bypass surgeries, other research studies showed that external support might allow the use of conduits that previously have been considered to be unsuitable for surgery. [ 20 ] [ 21 ]


To date the technique is practiced in several cardiac centers in Europe, Israel and South Africa. Further clinical studies are ongoing in Europe and the US on a larger number of patients. [ 22 ] [ 23 ] [ 24 ]


Isolated superior mesenteric artery dissection (ISMAD)  is a rare but potentially life-threatening condition that causes acute abdominal pain. It refers to a dissection that occurs solely in the  superior mesenteric artery  (SMA), typically spontaneously, and does not involve the  aorta . [ 1 ]
Although  aortic dissection  can frequently extend into its peripheral territories, it is rare for these branches to have dissection without main aortic trunk involvement. The SMA is the most common site of dissection among visceral arteries compared to other gastrointestinal arteries. [ 2 ]


ISMAD primarily manifests through a sudden onset of pain, which can vary in location and intensity. [ 2 ]   The nature of the pain and its location can provide clues to the diagnosis of ISMAD. [ 2 ]  The types of pain reported in ISMAD cases include:


ISMAD is more common in males, accounting for 80.6% of cases, and typically occurs in individuals in their fifth decade of life, with a mean age of 55.7 years. [ 2 ]  Other risk factors include smoking and hypertension. [ 4 ]


ISMAD can be associated with isolated arterial dissections and aneurysms, such as those in the celiac and renal arteries, suggesting a systemic component. [ 5 ]  It has been linked to certain vascular diseases like  fibromuscular dysplasia , medial degeneration, and  atherosclerosis . [ 5 ]


The structure of the SMA itself can contribute to ISMAD. Certain anatomical variants are more susceptible to shear stress, leading to dissection. This stress occurs when the SMA, lacking mechanical support from the pancreas, bends within the mesenteric root. The anterior wall, the most common site of ISMAD, faces increased stress due to the SMA's convexity after bending. [ 5 ]


Genetics also plays a role in ISMAD. It has been hypothesized that a genetic component exists, as most reported cases are from East Asia. This hypothesis is supported by a familial case of ISMAD from China linked to a chromosomal locus of 5q13–14. [ 5 ]


In terms of the diagnosis of ISMAD, the following is done: [ 5 ]


The management of isolated superior mesenteric artery dissection (ISMAD) often involves conservative treatment, which includes blood pressure lowering therapy,  analgesics , and initial bowel rest. [ 4 ]  Periodic follow-ups with  CT angiography  are a part of the conservative treatment approach. Over time, many patients show improvement or no change in their condition as observed through these follow-ups. A small percentage of patients reported mild abdominal discomfort during the follow-up period, but no patient developed recurrent abdominal pain following conservative treatment. Importantly, there was no mortality related to SISMAD. These observations suggest that conservative treatment can be an effective approach for managing patients with SISMAD. [ 6 ]


In cases where conservative treatment is not sufficient, endovascular procedures may be considered. These include stenting/stent-grafting of the true lumen, (coil) embolization of the false lumen/aneurysm, catheter-directed local thrombolysis, percutaneous transluminal angioplasty, and catheter-directed local papaverine infusion at 30 mg/h. [ 4 ]


In related surgical procedures such as Minimally Invasive Pancreaticoduodenectomy (MIPD), various approaches for dissection around the SMA have been reported, including anterior, posterior, right, and left approaches. [ 7 ] While these methods are not specifically used for ISMAD, understanding these surgical techniques could potentially inform future treatment strategies for ISMAD. [ 7 ]


The prognosis for patients with ISMAD who undergo conservative treatment is generally positive. Follow-up studies show that the majority of patients either improve or do not show progression of the condition. This is evidenced by CT angiograms, which often show a decrease in the size of the false lumen, a decrease in the length of the dissection, or complete remodeling of the dissection. [ 6 ]


During the follow-up period, some patients reported mild, nonspecific abdominal discomfort. However, no patient developed recurrent abdominal pain following conservative treatment, and there was no mortality related to ISMAD. These findings further support the effectiveness of conservative treatment for managing patients with ISMAD. [ 6 ]


In cases where conservative treatment is not sufficient, endovascular procedures may be considered. These include stenting/ stent -grafting of the true lumen, (coil) embolization of the false lumen/aneurysm, catheter-directed local thrombolysis, percutaneous transluminal angioplasty, and catheter-directed local papaverine infusion at 30 mg/h. [ 6 ]


MIRA ( Minimally Invasive  Reconstructive  Angiography ) is a  multidisciplinary  and  complementary  method for treating many  chronic diseases . It basically consists in  medically grafting  live rejuvenated  tissue  in the form of  autologous   adipose   adult stem cells  to a damaged organ in order to restore it and improve its function. This method is currently approved by the U.S.  Food and Drug Administration  (FDA).


The MIRA Procedure is a result of combining efforts from different medical fields developed in the  University of Chicago  in 1992.


The MIRA Procedure originated as a result of combining medical innovations and was developed as a multidisciplinary technique for applications in a wide range of medical fields. In other words, this procedure was not developed for a specific application, it is a compilation from data and experience retrieved through years of research as well as practice that have been put together to create a new alternative to treat many diseases and other applications.


In 1989 Dr.  Christoph Broelsch  performed the first successful  living donor liver transplantation  in the University of Chicago. [ 1 ]  Nearly two years old Alyssa Smith was the first to receive part of a living’s person liver donated in this case by her mother. [ 2 ]  The remarkable results improved current  prognosis  on patients who required a  liver transplant  but even then there were far from meeting the demand and many hundreds to this date die waiting for a donor. This procedure has also sparked some controversial and legal issues for enticing  organ trafficking  and its practice is currently restricted in some countries.


In 1992, at the University of Chicago Dr.  Fushih Pan  is amongst the first to attempt repairing damaged organ tissue by  tissue grafting , but with little success due to technological limitations for keeping the grafted tissue live and functional. Dr. Fushih Pan later becomes much more involved in the steps that followed in order to develop the MIRA procedure.


In 1995, the  University of Pennsylvania  caught the first glimpse of  regenerative medicine  after successfully regenerating  cranial bone . [ 3 ]  During the same year these results led to determination pressure of adequate tissue growth in cases with  anophthalmia . [ 4 ]


In 1998 Dr. J. Peter Rubin from the  University of Pittsburgh  developed a basic science research program in the biology of adipose derived stem cells and serves as co-director of the Adipose  Stem Cell  Center at the University of Pittsburgh. [ 5 ]  More recently he has determined the safety on fat derived  stem cells  for breast reconstruction after  mastectomy  as long as there is no evidence of  cancer . [ 6 ] [ 7 ]


In the year 2002 the  UCLA  under direction of Dr. Marc H. Hedrick M.D. [ 8 ]  started research on possible applications of  adult stem cells  generating positive results. [ 9 ]