Subacute coronary care units (SCCUs), also called progressive care units (PCUs), intermediate coronary care units (ICCUs), or stepdown units,  provide a level of care intermediate to that of the intensive care unit and that of the general medical floor. These units typically serve patients who require cardiac telemetry, such as those with  unstable angina .


Coronary care units developed in the 1960s when it became clear that close monitoring by specially trained staff,  cardiopulmonary resuscitation  and medical measures could reduce the mortality from complications of cardiovascular disease. The first description of a CCU was given in 1961 to the  British Thoracic Society  by  Desmond Julian , who founded the first CCU at the  Royal Infirmary of Edinburgh  in 1964. [ 2 ]  Early CCUs were also located in  Sydney ,  Kansas City ,  Toronto  and  Philadelphia . The first coronary care unit in the US was opened at Bethany Medical Center in  Kansas City, Kansas  by Hughes Day, and he coined the term. [ 3 ] [ 4 ]  Bethany Medical Center is also where the first "crash carts" were developed. [ 5 ]  Studies published in 1967 revealed that those observed in a coronary care setting had consistently better outcomes. [ 6 ]


DF Beck performed the first successful resuscitation of a physician with myocardial infarction in 1953, and pioneered the use of open-chest defibrillation. Zoll introduced external defibrillation in Boston in 1956, and Kouwenhoven and colleagues at Johns Hopkins highlighted the effectiveness of a combo of mouth-to-mouth, sternal compression, and closed chest defibrillation in restoring cardiac function in ventricular fibrillation patients. The first diagnostic angiogram was discovered by Mason Sones in 1958, due to an accidental injection of dye directly into the coronary artery rather than into the entire circulation - something that was previously believed to be fatal. [ citation needed ]


These developments led to an interest in intensive care for myocardial infarction. In 1967, Thomas Killip and John Kimball published a report of 250 patients with acute MI's, who had experienced significantly better survival rates in CCUs compared to other institutions. This, along with other reports, led to an increase in coronary care units. Now catheterization units are commonplace in large cities. [ citation needed ]


Coronary circulation  is the  circulation of blood  in the  arteries  and  veins  that supply the  heart muscle  (myocardium).
 Coronary arteries  supply  oxygenated  blood to the heart muscle.  Cardiac veins  then drain away the blood after it has been deoxygenated.
Because the rest of the body, and most especially the  brain , needs a steady supply of oxygenated blood that is free of all but the slightest interruptions, the heart is required to function continuously. Therefore its circulation is of major importance not only to its own tissues but to the entire body and even the  level of consciousness  of the brain from moment to moment.
Interruptions of coronary circulation quickly cause heart attacks ( myocardial infarctions ), in which the heart muscle is damaged by  oxygen starvation . Such interruptions are usually caused by  coronary ischemia  linked to  coronary artery disease , and sometimes to  embolism  from other causes like obstruction in blood flow through vessels.


Coronary arteries  supply blood to the myocardium and other components of the heart. Two coronary arteries originate from the left side of the heart at the beginning (root)  left ventricle . There are three  aortic sinuses  (dilations) in the wall of the aorta just superior to the aortic semilunar valve. Two of these, the  left posterior aortic sinus  and  anterior aortic sinus , give rise to the  left  and  right coronary arteries , respectively. The third sinus, the  right posterior aortic sinus , typically does not give rise to a vessel. Coronary vessel branches that remain on the surface of the heart and follow the sulci of the heart are called  epicardial  coronary arteries. [ 1 ]


The left coronary artery distributes blood to the left side of the heart, the left atrium and ventricle, and the interventricular septum. The  circumflex artery  arises from the left coronary artery and follows the  coronary sulcus  to the left. Eventually, it will fuse with the small branches of the right coronary artery. The larger  left anterior descending artery  (LAD), is the second major branch arising from the left coronary artery. It follows the anterior interventricular sulcus around the pulmonary trunk. Along the way it gives rise to numerous smaller branches that interconnect with the branches of the  posterior interventricular artery , forming  anastomoses . An anastomosis is an area where vessels unite to form interconnections that normally allow blood to circulate to a region even if there may be partial blockage in another branch. The anastomoses in the heart are very small. Therefore, this ability is somewhat restricted in the heart so a  coronary artery blockage  often results in  myocardial infarction  causing  death of the cells  supplied by the particular vessel. [ 1 ]


The right coronary artery proceeds along the coronary sulcus and distributes blood to the right atrium, portions of both ventricles, and the  heart conduction system . Normally, one or more  marginal arteries  arise from the right coronary artery inferior to the right atrium. The marginal arteries supply blood to the superficial portions of the right ventricle. On the posterior surface of the heart, the right coronary artery gives rise to the posterior interventricular artery, also known as the posterior descending artery. It runs along the posterior portion of the interventricular sulcus toward the apex of the heart, giving rise to branches that supply the interventricular septum and portions of both ventricles. [ 1 ]


The  vessels  that remove the deoxygenated  blood  from the  heart  muscle are the cardiac  veins . These include the  great cardiac vein , the  middle cardiac vein , the  small cardiac vein , the  smallest cardiac veins , and the  anterior cardiac veins . Cardiac veins carry blood with a poor level of  oxygen , from the  myocardium  to the  right atrium . Most of the blood of the coronary veins returns through the  coronary sinus . The  anatomy  of the veins of the heart is very variable, but generally it is formed by the following veins: heart veins that go into the coronary sinus: the  great cardiac vein , the  middle cardiac vein , the  small cardiac vein , the posterior vein of the  left ventricle , and the  oblique vein of Marshall . Heart veins that go directly to the right atrium: the anterior cardiac veins, the  smallest cardiac veins  (Thebesian veins). [ 2 ]


There are some anastomoses between branches of the two coronary arteries.  However the coronary arteries are functionally end arteries and so these meetings are referred to as potential  anastomoses , which lack function, as opposed to true anastomoses like that in the palm of the hand. This is because blockage of one coronary artery generally results in death of the heart tissue due to lack of sufficient blood supply from the other branch. When two arteries or their branches join, the area of the myocardium receives dual blood supply. These junctions are called anastomoses. If one coronary artery is obstructed by an  atheroma , the second artery is still able to supply oxygenated blood to the myocardium. However, this can only occur if the atheroma progresses slowly, giving the anastomoses a chance to proliferate. [ citation needed ]


Under the most common configuration of coronary arteries, there are three areas of anastomoses. Small branches of the LAD (left anterior descending/anterior interventricular) branch of the left coronary join with branches of the posterior interventricular branch of the right coronary in the interventricular sulcus (groove). More superiorly, there is an anastomosis between the circumflex artery (a branch of the left coronary artery) and the right coronary artery in the atrioventricular groove. There is also an anastomosis between the septal branches of the two coronary arteries in the interventricular septum. The photograph shows area of heart supplied by the right and the left coronary arteries. [ citation needed ]


The left and right coronary arteries occasionally arise by a common trunk, or their number may be increased to three; the additional branch being the posterior coronary artery (which is smaller in size). In rare cases, a person will have the third coronary artery run around the root of the aorta. [ citation needed ]


Occasionally, a coronary artery will exist as a double structure (i.e. there are two arteries, parallel to each other, where ordinarily there would be one). [ citation needed ]


The artery that supplies the posterior third of the  interventricular septum  – the  posterior descending artery  (PDA) [ 3 ]  determines the coronary dominance. [ 4 ]


Approximately 70% of the general population are right-dominant, 20% are co-dominant, and 10% are left-dominant. [ 4 ]
A precise anatomic definition of dominance would be the artery which gives off supply to the AV node i.e. the AV nodal artery. Most of the time this is the right coronary artery. [ citation needed ]


The  papillary muscles  attach the  mitral valve  (the valve between the  left atrium  and the  left ventricle ) and the  tricuspid valve  (the valve between the  right atrium  and the  right ventricle ) to the wall of the heart.  If the papillary muscles are not functioning properly, the mitral valve may leak during contraction of the left ventricle.  This causes some of the blood to travel "in reverse", from the left ventricle to the left atrium, instead of forward to the aorta and the rest of the body.  This leaking of blood to the left atrium is known as  mitral regurgitation .  Similarly, the leaking of blood from the right ventricle through the tricuspid valve and into the right atrium can also occur, and this is described as  tricuspid insufficiency  or tricuspid regurgitation. [ citation needed ]


The anterolateral papillary muscle more frequently receives two blood supplies:  left anterior descending  (LAD) artery and the  left circumflex artery  (LCX). [ 5 ]
It is therefore more frequently resistant to  coronary ischemia  (insufficiency of oxygen-rich blood).  On the other hand, the posteromedial papillary muscle is usually supplied only by the PDA. [ 5 ]   This makes the posteromedial papillary muscle significantly more susceptible to  ischemia .  The clinical significance of this is that a  myocardial infarction  involving the PDA is more likely to cause mitral regurgitation. [ citation needed ]


During contraction of the  ventricular  myocardium ( systole ), the subendocardial coronary vessels (the vessels that enter the myocardium) are compressed due to the high ventricular pressures.
This compression results in momentary retrograde blood flow (i.e., blood flows backward toward the aorta) which further inhibits perfusion of myocardium during systole.
However, the epicardial coronary vessels (the vessels that run along the outer surface of the heart) remain open.
Because of this, blood flow in the subendocardium stops during ventricular contraction.
As a result, most myocardial perfusion occurs during heart relaxation ( diastole ) when the subendocardial coronary vessels are open and under lower pressure.
Flow never comes to zero in the right coronary artery, since the right ventricular pressure is less than the diastolic blood pressure. [ 6 ]


The heart regulates the amount of  vasodilation  or vasoconstriction of the coronary arteries based upon the oxygen requirements of the heart. This contributes to the filling difficulties of the coronary arteries.
Compression remains the same. Failure of oxygen delivery caused by a decrease in blood flow in front of increased oxygen demand of the heart results in tissue  ischemia , a condition of oxygen deficiency. Brief ischemia is associated with intense chest pain, known as  angina . Severe ischemia can cause the heart muscle to die from hypoxia, such as during a  myocardial infarction .  Chronic moderate ischemia causes contraction of the heart to weaken, known as myocardial hibernation. [ citation needed ]


In addition to metabolism, the coronary circulation possesses unique pharmacologic characteristics. Prominent among these is its reactivity to adrenergic stimulation. [ citation needed ]


The following are the named branches of the coronary circulation in a right-dominant heart: [ citation needed ]


The  vessels  that deliver  oxygen -rich  blood  to the  myocardium  are the  coronary arteries . When the  arteries  are healthy, they are capable of autoregulating themselves to maintain the coronary blood flow at levels appropriate to the needs of the  heart muscle .


The relatively narrow coronary arteries are commonly affected by  atherosclerosis  and can become blocked, causing  angina  or a  heart attack . The coronary arteries are classified as "terminal circulation", since they represent the only source of blood supply to the myocardium; there is very little redundant blood supply, that is why blockage of these vessels can be so critical. [ citation needed ]


This article incorporates text from the  CC BY  book:  OpenStax College,  Anatomy & Physiology. OpenStax CNX. 30 July 2014.


A  coronary CT calcium scan  is a  computed tomography (CT) scan  of the heart for the assessment of severity of  coronary artery disease . Specifically, it looks for calcium deposits in atherosclerotic plaques in the coronary arteries that can narrow arteries and increase the risk of heart attack. [ 1 ]  These plaques are the cause of most heart attacks, and become calcified as they develop.


These calcifications can be detected by CT imaging because of their opacity to x-rays. This severity can be presented as an Agatston score or coronary artery calcium (CAC) score. The CAC score is an independent marker of risk for cardiac events, cardiac mortality, and all-cause mortality. [ 2 ]  In addition, it provides additional prognostic information to other cardiovascular risk markers. [ 2 ]


Obstructions may be present even with an Agatston score of zero, especially in younger patients. [ 3 ]  A typical coronary CT calcium scan is done without the use of  radiocontrast  agent but it can also be performed using contrast-enhanced images as well, such as in  coronary CT angiography . [ 4 ]  The exam is best performed with cardiac gating to eliminate motion but can also be estimated in the presence of motion.


The well-established indications for the use of the CAC score include stratification of global cardiovascular risk for asymptomatic patients: intermediate risk based on the Framingham risk score (class I); low risk based on a family history of early coronary artery disease (CAD) (class IIa); and low-risk patients with diabetes (class IIa). [ 2 ]


In symptomatic patients, the pre-test probability should always be given weight in the interpretation of the CAC score as a filter or tool to indicate the best method to facilitate the diagnosis. Therefore, the use of the CAC score alone is limited in symptomatic patients. [ 2 ]


In patients with diabetes, the CAC score helps identify the individuals most at risk, who could benefit from screening for silent ischemia and from more aggressive clinical treatment. [ 2 ]


However,  coronary CT angiography  (CTA) is superior to coronary CT calcium scanning in determining the risk of Major Adverse Cardiac Events (MACE). [ 5 ]


There is potential to measure CAC on chest radiographs taken for other indications, possibly allowing some primary screening for  coronary artery disease  without adding to radiation exposure and with minimal marginal cost. [ 6 ]


The  Agatston score , named after its developer  Arthur Agatston , is a measure of calcium on a coronary CT calcium scan. [ 7 ]  The original work, published in 1990, [ 8 ]  was based on  electron beam computed tomography  (also known as ultrafast CT or EBCT). The score is calculated using a weighted value assigned to the highest density of calcification in a given coronary artery.


The density is measured in  Hounsfield units , and score of 1 for 130–199 HU, 2 for 200–299 HU, 3 for 300–399 HU, and 4 for 400 HU and greater. This weighted score is then multiplied by the area (in square millimeters) of the coronary calcification. For example, a "speck" of coronary calcification in the left anterior descending artery measures 4 square millimeters and has a peak density of 270 HU. The score is therefore 8 (4 square millimeters × weighted score of 2).


The tomographic slices of the heart are 3 millimeters thick and average about 50–60 slices from the coronary artery ostia to the inferior wall of the heart. The calcium score of every calcification in each coronary artery for all of the tomographic slices is then summed up to give the total coronary artery calcium score (CAC score). [ 9 ]


The Agatston score is frequently used today because of its long history of clinical validation. Several variations of the Agatston score have been described, including mass-based calcium scoring, volume-based calcium scoring, or lesion-specific calcium-scoring have been developed. [ 10 ]


A lesion-specific calcium score has been developed. [ 11 ]  Each individual calcified lesion is characterized and measured using parameters including the width, length, density, and distance from the entrance of the major coronary arteries. [ 12 ]  Research has shown that the lesion-specific calcium scoring method is superior to the traditional  Agatston score  for the prediction of significant blockages in the heart. [ 10 ]


On average, a single scan will expose a patient to about 2.3 millisieverts of radiation, equivalent to 23 chest x-rays (front and side views). [ 13 ] [ 14 ]  That average covers a wide range of doses depending on equipment type and scanning protocol. Using modern equipment and protocols, a 1 millisievert exposure is possible. [ 15 ]  Because the exact radiation exposure for a specific patient depends on the equipment type in use, the patients build and a variety of scanning options (such as retrospective vs prospective gating) it is difficult for a patient to know what their radiation exposure will be.


A 2009 study indicated that for every 100,000 people screened with CAC testing every 5 years between ages 45 to 75 years (men) or 55 to 75 years (women), there would be 42 (men) or 62 (women) additional radiation induced cancer cases. [ 13 ]


Coronary flow reserve  ( CFR ) is the maximum increase in blood flow through the  coronary arteries  above the normal resting volume. [ 1 ]  Its measurement is often used in medicine to assist in the treatment of conditions affecting the coronary arteries and to determine the efficacy of treatments used.


When demand for oxygen in the  myocardium  is increased, the  vascular resistance  of the coronary arteries has the ability to reduce, and this can increase the volume of blood passing through the blood vessels.  This reduction occurs because the arteries  dilate , which causes an increase in the diameter of the  lumen . [ 2 ] [ 3 ]  The greatest potential for this change is normally in the branches ( arterioles ) of the coronary artery that penetrate the myocardium, rather than those on the surface of the heart.
 [ 1 ]


Coronary flow reserve can be measured through a variety of methods, including digital subtraction  cineangiography  with  coronary catheterization , [ 4 ]   doppler echocardiography , [ 5 ]  and  positron emission tomography  (PET). [ 6 ]


Coronary flow reserve is used in diagnostics and treatment of patients with conditions such as  coronary artery disease  and  syndrome X . [ 7 ]  In the treatment of these conditions,  vasodilators  are used to allow sufficient blood to flow past a  stenosis , for example, and the measurement of CFR enables the efficacy of such interventions to be measured.
 [ 3 ]   In patients with  Anderson-Fabry disease , there is evidence to suggest that CFR can be reduced. [ 5 ]
When coronary flow reserve is used in medicine, it is often expressed with a numerical value, which is formed by dividing the maximal coronary blood flow by resting blood flow.  This allows for an objective view, which can aid diagnosis and treatment. [ 8 ]


Coronary reflex  is the change of coronary diameter in response to chemical, neurological or mechanical stimulation of the  coronary arteries .
The coronary reflexes are stimulated differently from the rest of the  vascular system . [ citation needed ]


Cocaine abuse  frequently can cause a coronary spasm, resulting in a spontaneous  myocardial infarction . [ citation needed ]


Cough  CPR  is the subject of a hoax email that began circulating in 1999. [ citation needed ]  It is described as a "resuscitation technique" in which through prolonged  coughing  and deep breathing every 2 seconds, a person suffering a  cardiac dysrhythmia  immediately before  cardiac arrest  can keep conscious until help arrives (or until the person can get to the nearest hospital). Neither the  American Heart Association  nor the  American Red Cross  endorses cough CPR during a heart attack. [1]


This confusion appears to revolve primarily over the public's failure to discriminate between a  heart attack ,  cardiac arrest , and cardiac dysrhythmias. A heart attack occurs when an occlusion (e.g. blood clot) of an artery in the heart slowly causes tissue to die. This can result in chest pain and discomfort, and requires immediate medical attention to resolve the occlusion by emergency surgery or  cardiac clot-busting drugs . A cardiac dysrhythmia is primarily an electrical problem within the heart, and is sometimes treated with electrolytes, vagal maneuver, or electrical cardioversion.  Many dysrhythmias may herald an impending heart attack. [ medical citation needed ]


Cough CPR has been the subject of a series of  chain email  campaigns. These emails are typically of the following format: [ citation needed ]   (See Snopes for this and other citation issues.)  [2]


HOW TO SURVIVE A HEART ATTACK WHEN ALONE


Since many people are alone when they suffer a heart attack, this article seemed in order. Without help the person whose heart stops beating properly and who begins to feel Faint, has only about 10 seconds left before losing consciousness. However, these victims can help themselves by coughing repeatedly and very vigorously. A deep breath should be taken before each cough, and the cough must be deep and prolonged, as when producing sputum from deep inside the chest. A breath and a cough must be repeated about every two seconds without let up until help arrives, or until the heart is felt to be beating normally again. Deep breaths get oxygen into the lungs and coughing movements squeeze the heart and keep the blood circulating.


Coxsackie B  is a group of six  serotypes  of  coxsackievirus  (CVB1-CVB6), a  pathogenic   enterovirus , that trigger illnesses ranging from a mild febrile rash to full-fledged  pericarditis  and  myocarditis  ( coxsackievirus-induced cardiomyopathy ). [ 1 ] [ 2 ]


The genome of Coxsackie B virus consists of approximately 7,400 base pairs. [ 3 ]


The various members of the Coxsackie B group were discovered almost entirely in the United States, appearing originally in  Connecticut ,  Ohio ,  New York , and  Kentucky , although a sixth member of the group has been found in the  Philippines . [ 1 ]   However, all six serotypes have a global distribution and are a relatively common cause of gastrointestinal upset. The name reflects  the first isolation from Coxsackie, New York . [ citation needed ]


Infections are most commonly spread by the  Fecal-oral route , emphasizing the importance of good hygiene, especially hand-washing. [ 2 ]  Oral-oral and  respiratory droplets  can also be means of transmission. [ 4 ]


Coxsackie B infections have been reported to account for nearly a quarter of all  enterovirus  infections. [ 5 ]  Nearly half of all reported cases of Coxsackie B infections occur before the age of five. [ 5 ]  For the CBV1 serotype, two-thirds of  Centers for Disease Control and Prevention  reported infections in the United States were for children under one year of age. [ 4 ]


Symptoms of infection with viruses in the Coxsackie B grouping include  fever ,  headache ,  sore throat , gastrointestinal distress, extreme  fatigue  as well as  chest  and  muscle pain . It can also lead to  spasms  in arms and legs.  This presentation is known as pleurodynia or  Bornholm disease  in many areas.  Patients with chest pain should see a doctor immediately—in some cases, viruses in the Coxsackie B family progress to myocarditis or pericarditis, which can result in permanent heart damage or death.  Coxsackie B virus infection may also induce  aseptic meningitis .  As a group, they are the most common cause of unexpected  sudden death , and may account for up to 50% of such cases. [ 6 ]   The incubation period for the Coxsackie B viruses ranges from 2 to 6 days, and illness may last for up to 6 months in extreme cases, but may resolve as quickly as two days.  Infection usually occurs between the months of May and June, but do not show symptoms until October in temperate Northern Hemisphere regions. People should ideally spend 1 month resting during the height of infection.  Another cause of this virus is from a dirty wound from an accident. [ 1 ]


Enterovirus infection is diagnosed mainly via  serological  tests such as  ELISA [ 7 ]  and from  cell culture . [ 1 ]   Because the same level and type of care is given regardless of type of Coxsackie B infection, it is mostly unnecessary for treatment purposes to diagnose which virus is causing the symptoms in question, though it may be epidemiologically useful. [ citation needed ]


Coxsackie B infections usually do not cause serious disease, although for newborns in the first 1–2 weeks of life, Coxsackie B infections can easily be fatal. [ 2 ]  The pancreas is a frequent target, which can cause  pancreatitis . [ 2 ]


Coxsackie B3 (CB3) infections are the most common enterovirus cause of  myocarditis  and  sudden cardiac death . [ 8 ]  CB3 infection causes  ion channel  pathology in the heart, leading to  ventricular arrhythmia . [ 8 ]  Studies in mice suggest that CB3 enters cells by means of  toll-like receptor 4 . [ 9 ]  Both CB3 and CB4 exploit cellular  autophagy  to promote  replication . [ 9 ]


The B4 Coxsackie viruses (CB4) serotype was suggested to be a possible cause of  diabetes mellitus type 1  (T1D). [ 10 ]  An  autoimmune  response to Coxsackie virus B infection upon the  islets of Langerhans  may be a cause of T1D. [ 2 ]


Other research implicates strains B1, A4, A2 and A16 in the destruction of  beta cells , [ 11 ] [ 12 ]  with some suggestion that strains B3 and B6 may have protective effects via immunological cross-protection.


As of 2008 [update] , there is no well-accepted treatment for the Coxsackie B group of viruses. [ 1 ]   Palliative care  is available, however, and patients with chest pain or  stiffness of the neck  should be examined for signs of cardiac or  central nervous system  involvement, respectively.  Some measure of prevention can usually be achieved by basic sanitation on the part of food-service workers, though the viruses are highly contagious.  Care should be taken in washing ones hands and in cleaning the body after swimming.  In the event of Coxsackie-induced myocarditis or pericarditis,  anti-inflammatories  can be given to reduce damage to the heart muscle. [ citation needed ]


Enteroviruses are usually only capable of acute infections that are rapidly cleared by the adaptive immune response. [ 13 ] [ 14 ]  However, mutations which enterovirus B serotypes such as coxsackievirus B and  echovirus  acquire in the host during the acute phase can transform these viruses into the non-cytolytic form (also known as non-cytopathic or defective enterovirus). [ 15 ]  This form is a mutated  quasispecies [ 13 ]  of enterovirus which is capable of causing persistent infection in human tissues, and such infections have been found in the pancreas in type 1 diabetes, [ 16 ] [ 17 ]  in chronic myocarditis and  dilated cardiomyopathy , [ 18 ] [ 13 ] [ 19 ]  in valvular heart disease, [ 20 ]  in  myalgic encephalomyelitis , [ 21 ] [ 22 ]  and in Sjögren's syndrome. [ 23 ]   In these persistent infections, viral RNA is present at very low levels, and some researchers believe it is just a fading remnant of the acute infection [ 14 ]  although others scientists believe this persistent viral RNA may have pathological effects and cause disease. [ 24 ]


The  CPK-MB test  (creatine phosphokinase-MB), also known as  CK-MB test , is a  cardiac marker [ 3 ]  used to assist diagnoses of an  acute myocardial infarction ,  myocardial ischemia , or  myocarditis . It measures the blood level of CK-MB (creatine kinase myocardial band), the bound combination of two variants (isoenzymes  CKM  and  CKB ) of the enzyme  phosphocreatine kinase . [ citation needed ]


In some locations, the test has been superseded by the  troponin test . However, recently, there have been improvements to the test that involve measuring the ratio of the CK-MB1 and CK-MB2 isoforms. [ 4 ]


The newer test detects different  isoforms  of the B subunit specific to the myocardium whereas the older test detected the presence of cardiac-related  isoenzyme  dimers. [ citation needed ]


Many cases of CK-MB levels exceeding the blood level of total CK have been reported, especially in newborns with cardiac malformations, especially ventricular septal defects. This reversal of ratios is in favor of pulmonary emboli or vasculitis. An autoimmune reaction creating a complex molecule of CK and IgG should be taken into consideration. [ 5 ]


Das Reizleitungssystem des Säugetierherzens  (English: " The Conduction System of the Mammalian Heart ") is a scientific  monograph  published in 1906 by  Sunao Tawara . It has been recognized by cardiologists as a monumental discovery, [ 1 ]  and a milestone in  cardiac electrophysiology ". [ 2 ]


The monograph revealed the existence of the  atrioventricular node  and the function of  Purkinje cells . It was used by  Arthur Keith  and  Martin Flack  as a detailed guide in their attempts to verify the existence of the  Bundle of His , which subsequently led to their discovery of the  sinoatrial node . Throughout the beginning of the 20th century, Tawara's monograph influenced the work of many cardiologists and it was later cited by  Willem Einthoven  in his anatomical interpretation of the  electrocardiogram . [ 3 ]


Prior to Tawara's discoveries, it was assumed that electrical conduction through the  Bundle of His  was slow, because of the long interval between  atrial  and  ventricular  contractions. The Swiss cardiologist  Wilhelm His, Jr.  assumed that the heart bundle was connected directly to the base of the ventricle, and physiologists incorrectly taught that the base of the ventricle contracted first, followed by the apex. [ 1 ]


However, Tawara postulated that ventricular contraction occurs in the opposite manner, with the apex contracting earlier than the base. He also believed that the heart's electrical conduction was not slow but rapid. Working under the guidance of his mentor,  Ludwig Aschoff , Tawara performed a histological examination of 150 hearts with  myocarditis  (which led to the discovery of  Aschoff bodies ), and he began examining the atrioventricular bundle before embarking on a comprehensive study of the anatomy and histology of the heart's conduction system. [ 1 ]


The implications of his work were immediately recognized by Aschoff, who arranged for it to be published in the form of a  monograph . [ 1 ]


Tawara's monograph, titled " Das Reizleitungssystem des Säugetierherzens " (English: " The Conduction System of the Mammalian Heart ") was published in 1906. The most important discoveries are listed below:


Tawara commented that the system represents a transporting or conducting pathway, and "because the pathway is not a ductal, but a continuously related protoplasmic cord, conduction of excitation impulses surely must take place there." [ 1 ]


On 26 September 1905, shortly before the monograph was due to be published,  Ludwig Aschoff  wrote an article about Tawara's work. It was subsequently read by the Scottish cardiologist  James Mackenzie  and forwarded to anatomist  Arthur Keith , who was attempting to confirm the existence of the  Bundle of His . Despite putting in his best efforts, he failed to locate the structure. On 15 January 1906, Keith wrote a letter to Mackenzie and acknowledged his skepticism about its existence: " I have given up the search for His' bundle—having come to the conclusion that there is not and never was any such thing. ” [ 4 ]


In response to Arthur Keith's skepticism, Mackenzie forwarded Aschoff's article about Tawara's findings, which stimulated Keith's renewal of his studies on the cardiac conduction system. [ 5 ]  Despite having written a letter to  The Lancet  about his failure to locate the  Bundle of His  and his increasing doubts about its existence, Keith (with his student  Martin Flack ) later reported that they had succeeded in locating the structure by following the detailed descriptions and figures in Tawara's monograph. [ 6 ]  In a paper published in  The Lancet  on 11 August 1906, they acknowledged the monograph's high degree of accuracy:


Encouraged by their initial success and inspired by Tawara's discovery of the  atrioventricular node , Keith and Flack extended their studies and eventually discovered the  sinoatrial node  in 1907. [ 4 ]  They wrote that they were examining other regions of the heart for "peculiar musculature" similar to the one discovered by Tawara. [ 8 ]


In 1908, the Dutch physiologist  Willem Einthoven  referred to Tawara’s monograph as the anatomical basis for interpreting the electrocardiogram. [ 3 ]  In his monograph, Tawara theorized about the velocity of the excitatory process in the conduction system and the mode of ventricular contraction. Together with his anatomic findings and physiological assumptions, it contributed to the rapid popularization of  electrocardiography . [ 9 ]


In 1909, the American pathologist  Lydia DeWitt  created the first 3D wax model of the conduction system, using Tawara’s description as a guide. [ 10 ]  In 1911, the British cardiologist  Thomas Lewis  reviewed the auriculo-ventricular connection system and described Tawara's discoveries in  Das Reizleitungssystem des Saugetierherzens  as the "main advance" in knowledge about the system:


In his autobiography published in 1950,  Arthur Keith  explained how he had systematically searched for Tawara's system to verify its components:


Acknowledging the significance and implications of these discoveries, Keith commented: "With the discovery of the conducting system of Tawara, heart research entered a new epoch." [ 12 ]


Shortly before his death,  Wilhelm His, Jr.  published a personal account about the discovery of the  Bundle of His . He noted that it took ten years before anatomists began to pay attention to the bundle, starting with the studies of Retzer and Brauning in 1903, followed by the "important work of Tawara" in 1906, and the subsequent discovery of the sinus node which completed the system. He credited Tawara for connecting the bundle with the  Purkinje fibers  and for declaring it the heart's conduction system. [ 13 ]


In clinical  cardiology  the term  "diastolic function"  is most commonly referred as how the  heart  fills. [ 1 ]  Parallel to "diastolic function", the term " systolic  function" is usually referenced in terms of the left ventricular  ejection fraction  (LVEF), which is the ratio of  stroke volume  and  end-diastolic volume . [ 2 ]  Due to the epidemic of  heart failure , [ 3 ]  particularly the cases determined as  diastolic heart failure , it is increasingly urgent and crucial to understand the meaning of “diastolic function”. Unlike "systolic function", which can be simply evaluated by LVEF, there are no established dimensionless parameters for "diastolic function" assessment. [ 4 ]  Hence to further study "diastolic function" the complicated and speculative physiology must be taken into consideration.


How the heart works during its filling period still has many misconceptions remaining. To better understand diastolic function, it is crucial to realize that the left  ventricle  is a mechanical  suction pump  at, and for a little while after, the  mitral valve  opening. [ 5 ]  In other words, when mitral valve opens, the  atrium  does not push  blood  into the ventricle, instead, it is the ventricle that mechanically "sucks" in blood from the  atrium . [ 6 ] [ 7 ]  The energy that drives the suction process is generated from phase of  systole . During systole, to overcome the peripheral arterial load at ejection, ventricle contracts, which also compresses elastic tissues internal to and external to the  myocardium . Then, when  cardiac muscle  relaxes, the energy captured by compressed elements releases, driving the recoil of ventricular wall until a new balanced equilibrium state is reached. [ 8 ]


During  diastole , the ventricle of heart must remain elastic or compliant enough and have capacity to hold incoming blood to guarantee effectiveness of the filling phase. Hence stiffness and relaxation are ventricle's intrinsic feature parameters that are practical in evaluating and quantifying diastolic function. [ 9 ]  In addition,  volumetric load [ 10 ]  serves as an extrinsic indicating parameter that modulates diastolic function.


The most established index to describe left ventricular diastolic function is Tau, left ventricular diastolic time constant. Measurement of Tau is traditionally delivered in a catheter lab by an invasive method. Recently, non-invasive measurement of Tau is available for mitral regurgitation or aortic regurgitation patients in an Echo lab. [ 11 ]


There have been many attempts intending for extracting both intrinsic and extrinsic properties. Early attempts concentrated on pulse-wave Doppler-echo measured trans-mitral flow velocity contours. [ citation needed ]


In terms of filling, diastolic intervals consist of early rapid filling E-waves followed by  diastasis  and followed by atrial systole-generated A-waves. Empirically, E- and A- wave contours were simplified as triangles. Nowadays, triangle-based indexes, such as the peak velocities of the E- and A-waves and ratio of them, the deceleration time and time duration of the E-wave, and the velocity time integral of both E- and A- waves, are usually measured and evaluated. [ citation needed ]


The triangular approach applies to E-wave shape conveniently, especially in the past when the images rendered by technology back in days are of poor resolution quality. Nevertheless, with rapidly improving temporal resolution and image processing capabilities, the curvature of E-wave contours can be clearly identified with detailed information revealed.


Due to advancement of modern medical imaging technology, the measurement of even smaller (i.e. tissue) velocities are possible to be made, which even leads to capability to measure the longitudinal displacements of the  mitral annulus . The shapes of mitral annular velocity contours used to be approximated to be triangles, whose peak height is label to be E’. E’ proved useful in selected patient populations for estimation of  end-diastolic pressure  (EDP). [ 9 ]


Other innovative imaging modalities consist of techniques such as  speckle tracking . Speckle tracking enables strain and strain-rate measurements. It is a relatively recent instance of technological progress, due to the fact that it relies on the information content inherent in the seemingly random arrangement of bright speckles present in all echocardiographic images. [ 12 ]  Even though a variety of echo-based imaging technologies represent multiple levels of research innovation, much remains to be studied in relation to how to interpret the recorded data embedded in images.


Door-to-balloon  is a time measurement in emergency cardiac care (ECC), specifically in the treatment of  ST segment elevation myocardial infarction  (or STEMI). The interval starts with the patient's arrival in the  emergency department , and ends when a catheter guidewire crosses the culprit lesion in the  cardiac cath lab . Because of the adage that "time is muscle", meaning that delays in treating a myocardial infarction increase the likelihood and amount of  cardiac muscle  damage due to localised  hypoxia , [ 1 ] [ 2 ] [ 3 ] [ 4 ]   ACC / AHA  guidelines recommend a door-to-balloon interval of no more than 90 minutes. [ 5 ]  As of 2006 in the United States, fewer than half of STEMI patients received reperfusion with primary  percutaneous coronary intervention  (PCI) within the guideline-recommended timeframe. [ 6 ]  It has become a core quality measure for the  Joint Commission on Accreditation of Healthcare Organizations  (TJC). [ 7 ] [ 8 ] [ 9 ]


The benefit of prompt, expertly performed primary percutaneous coronary intervention over thrombolytic therapy for acute ST elevation myocardial infarction is now well established. [ 10 ]  Few hospitals can provide PCI within the 90 minute interval, [ 11 ]  which prompted the American College of Cardiology (ACC) to launch a national Door to Balloon (D2B) Initiative in November 2006. The D2B Alliance seeks to "take the extraordinary performance of a few hospitals and make it the ordinary performance of every hospital." [ 12 ]  Over 800 hospitals have joined the D2B Alliance as of March 16, 2007. [ 13 ]


The D2B Alliance advocates six key  evidence-based  strategies and one optional strategy to help reduce door-to-balloon times: [ 12 ] [ 14 ]


On May 30, 2007, the  American Heart Association  launched 'Mission: Lifeline', a "community-based initiative aimed at quickly activating the appropriate chain of events critical to opening a blocked artery to the heart that is causing a heart attack." [ 15 ]  It is seen as complementary to the ACC's D2B Initiative. [ 16 ]  The program will concentrate on patient education to make the public more aware of the signs of a heart attack and the importance of calling  9-1-1  for  emergency medical services  (EMS) for transport to the hospital. [ 15 ]  In addition, the program will attempt to improve the diagnosis of STEMI patients by EMS personnel. [ 15 ]  According to Alice Jacobs, MD, who led the work group that addressed STEMI systems, [ 17 ]  when patients arrive at non-PCI hospitals they will stay on the EMS stretcher with paramedics in attendance while a determination is made as to whether or not the patient will be transferred. [ 17 ]  For walk-in STEMI patients at non-PCI hospitals, EMS calls to transfer the patient to a PCI hospital should be handled with the same urgency as a 9-1-1 call. [ 17 ]


Although incorporating a prehospital 12 lead ECG into critical pathways for STEMI patients is listed as an optional strategy by the D2B Alliance, the fastest median door-to-balloon times have been achieved by hospitals with paramedics who perform 12 lead ECGs in the field. [ 18 ]   EMS  can play a key role in reducing the first-medical-contact-to-balloon time, sometimes referred to as EMS-to-balloon (E2B) time, [ 19 ]  by performing a 12 lead  ECG  in the field and using this information to triage the patient to the most appropriate medical facility. [ 20 ] [ 21 ] [ 22 ] [ 23 ]


Depending on how the prehospital 12 lead ECG program is structured, the 12 lead ECG can be transmitted to the receiving hospital for physician interpretation, interpreted on-site by appropriately trained paramedics, or interpreted on-site by paramedics with the help of computerized interpretive algorithms. [ 24 ]  Some EMS systems utilize a combination of all three methods. [ 19 ]  Prior notification of an inbound STEMI patient enables time saving decisions to be made prior to the patient's arrival. This may include a "cardiac alert" or "STEMI alert" that calls in off duty personnel in areas where the  cardiac cath lab  is not staffed 24 hours a day. [ 19 ]  The 30-30-30 rule takes the goal of achieving a 90-minute door-to-balloon time and divides it into three equal time segments. Each STEMI care provider (EMS, the emergency department, and the cardiac cath lab) has 30 minutes to complete its assigned tasks and seamlessly "hand off" the STEMI patient to the next provider. [ 19 ]  In some locations, the emergency department may be bypassed altogether. [ 25 ]


Bradley et al. (Circulation 2006) performed a qualitative analysis of 11 hospitals in the National Registry of Myocardial Infarction that had median door-to-balloon times = or < 90 minutes. They identified 8 themes that were present in all 11 hospitals: [ 6 ]


Granger et al. (Circulation 2007) identified the following criteria of an ideal primary PCI center. [ 24 ]


Granger et al. (Circulation 2007) identified the following barriers to timely access to primary PCI. [ 24 ]


The  Duke Activity Status Index  ( DASI ) is an assessment tool used to  evaluate the functional capacity  of patients with  cardiovascular disease  (CVD), such as  coronary artery disease ,  myocardial infarction , and  heart failure . [ 1 ]


In  clinical practice , DASI can be used to assess the effects of medical treatments and cardiac rehabilitation as well. [ 2 ]  Positive responses are summed up to get a total score, which ranges from 0 to 58.2. Higher scores would indicate a higher functional capacity. [ citation needed ]


The instrument is copyrighted by one of its authors, Mark Hlatky. [ 3 ] [ 4 ]


Duke Treadmill Score  is one of the tools for predicting the risk of  ischemia  or  infarction  in the  heart muscle . [ 1 ]  The calculation is done based on the information obtained from an  exercise test  by this formula: [ citation needed ]


In which, the exercise duration is written in "minutes" and the ST changes in "millimetres". [ 1 ]  Angina index will be zero if no pain appears during the exercise, one if the pain is limited to the exercise period but the patient can continue the exercise ( typical angina ), and two if a limiting pain occurs which is a reason to stop the exercise test. [ 2 ] [ 3 ]


Duke treadmill scores typically range from -25 (highest risk) to +15 (lowest risk).  One-year  mortality  and five-year survival rates respectively for the results of the Duke treadmill score have been reported as: [ 4 ] [ 5 ]
 [ 6 ]


Echocardiography , also known as  cardiac ultrasound , is the use of  ultrasound  to examine the  heart . It is a type of  medical imaging , using standard ultrasound or  Doppler ultrasound . [ 1 ]  The visual image formed using this technique is called an  echocardiogram , a  cardiac echo , or simply an  echo .


Echocardiography is routinely used in the diagnosis, management, and follow-up of patients with any suspected or known  heart diseases . It is one of the most widely used diagnostic imaging modalities in cardiology. It can provide a wealth of helpful information, including the size and shape of the heart (internal chamber size quantification), pumping capacity, location and extent of any tissue damage, and assessment of valves. An echocardiogram can also give physicians other estimates of heart function, such as a calculation of the  cardiac output ,  ejection fraction , and  diastolic  function (how well the heart relaxes).


Echocardiography is an important tool in assessing wall motion abnormality in patients with suspected cardiac disease. It is a tool which helps in reaching an early diagnosis of  myocardial infarction , showing regional wall motion abnormality. Also, it is important in treatment and follow-up in patients with  heart failure , by assessing  ejection fraction . [ 2 ] [ 3 ]


Echocardiography can help detect  cardiomyopathies , such as  hypertrophic cardiomyopathy , and dilated cardiomyopathy. The use of stress echocardiography may also help determine whether any chest pain or associated symptoms are related to heart disease.


The most important advantages of echocardiography are that it is not invasive (does not involve breaking the skin or entering body cavities) and has no known risks or side effects. [ 4 ]


Not only can an echocardiogram create ultrasound images of heart structures, but it can also produce accurate assessment of the blood flowing through the heart by Doppler echocardiography, using pulsed- or continuous-wave Doppler ultrasound. This allows assessment of both normal and abnormal blood flow through the heart. Color Doppler, as well as spectral Doppler, is used to visualize any abnormal communications between the left and right sides of the heart, as well as any leaking of blood through the valves (valvular regurgitation), and can also estimate how well the valves open (or do not open in the case of valvular stenosis). The Doppler technique can also be used for tissue motion and velocity measurement, by  tissue Doppler echocardiography .


Echocardiography was also the first ultrasound subspecialty to use intravenous contrast. Echocardiography is performed by  cardiac sonographers , cardiac physiologists (UK), or physicians trained in echocardiography.


Recognized as the "Father of Echocardiography", the Swedish physician  Inge Edler  (1911–2001), a graduate of  Lund University , was the first of his profession to apply ultrasonic pulse echo imaging in diagnosing cardiac disease, which the acoustical physicist  Floyd Firestone  had developed to detect defects in metal castings. In fact, Edler in 1953 produced the first echocardiographs using an industrial Firestone-Sperry Ultrasonic Reflectoscope. In developing echocardiography, Edler worked with the physicist  Carl Hellmuth Hertz , the son of the  Nobel laureate   Gustav Hertz  and grandnephew of  Heinrich Rudolph Hertz . [ 5 ] [ 6 ]


Health societies recommend the use of echocardiography for initial diagnosis when a change in the patient's clinical status occurs and when new data from an echocardiogram would result in the physician changing the patient's care. [ 7 ]  Diagnostic criteria for numerous cardiac diseases are based on echocardiography studies. For example, the differentiation of mild, moderate, and severe valvular disease is based upon measured criteria. Another example is the estimation of heart function by the left ventricular ejection fraction (LVEF) has vast uses including classification of heart failure and cut offs for implantation of  implantable cardioverter-defibrillators .


Health societies do not recommend routine testing when the patient has no change in clinical status or when a physician is unlikely to change care for the patient based on the results of testing. [ 7 ]  A common example of overuse of echocardiography when not indicated is the use of routine testing in response to a patient diagnosis of mild  valvular heart disease . [ 8 ]  In this case, patients are often asymptomatic for years before the onset of deterioration and the results of the echocardiogram would not result in a change in care without other change in clinical status. [ 8 ]


Echocardiography has a vast role in  pediatrics , diagnosing patients with valvular heart disease and other congenital abnormalities. An emerging branch is  fetal echocardiography , which involves echocardiography of an unborn fetus. [ citation needed ]


There are three primary types of echocardiography: transthoracic, transesophageal, and intracardic.
Stress testing utilizes tranthoracic echo in combination with an exercise modality (e.g., a treadmill).
Intravascular ultrasound is included below, but is as the name indicates more "ultrasound" than "echocardiography" as it is imaging the walls of a vessel rather than the heart.


A standard echocardiogram is also known as a transthoracic echocardiogram (TTE) or cardiac ultrasound, and it is used for rapid evaluation of a patient at their bedside. [ 9 ] [ 10 ]  In this case, the echocardiography transducer (or probe) is placed on the chest wall (or  thorax ) of the subject, and images are taken through the chest wall. This is a non-invasive, highly accurate, and quick assessment of the overall function of the heart.


TTE utilizes several "windows" to image the heart from different perspectives. Each window has advantages and disadvantages for viewing specific structures within the heart and, typically, numerous windows are utilized within the same study to fully assess the heart. Parasternal long and parasternal short axis windows are taken next to the sternum, the apical two/three/four chamber windows are taken from the apex of the heart (lower left side), and the subcostal window is taken from underneath the edge of the last rib.


TTE utilizes one- ("M mode"), two-, and three-dimensional ultrasound (time is implicit and not included) from the different windows. These can be combined with pulse wave or continuous wave Doppler to visualize the velocity of blood flow and structure movements. Images can be enhanced with "contrast" that are typically some sort of micro bubble suspension that reflect the ultrasound waves.


A transesophageal echocardiogram is an alternative way to perform an echocardiogram. A specialized probe containing an ultrasound transducer at its tip is passed into the patient's  esophagus  via the mouth, allowing image and Doppler evaluation from a location directly behind the heart. It is most often used when transthoracic images are suboptimal and when a clearer and more precise image is needed for assessment. This test is performed in the presence of a cardiologist, anesthesiologist, registered nurse, and ultrasound technologist. Conscious sedation and/or localized numbing medication may be used to make the patient more comfortable during the procedure.


TEE, unlike TTE, does not have discrete "windows" to view the heart. The entire esophagus and stomach can be utilized, and the probe advanced or removed along this dimension to alter the perspective on the heart. Most probes include the ability to deflect the tip of the probe in one or two dimensions to further refine the perspective of the heart. Additionally, the ultrasound crystal is often a two-dimension crystal and the ultrasound plane being used can be rotated electronically to permit an additional dimension to optimize views of the heart structures. Often, movement in all of these dimensions is needed.


TEE can be used as stand-alone procedures, or incorporated into catheter- or surgical-based procedures. For example, during a  valve replacement  surgery the TEE can be used to assess the valve function immediately before repair/replacement and immediately after. This permits revising the valve mid-surgery, if needed, to improve outcomes of the surgery.


A stress echocardiogram, also known as a stress echo, uses ultrasound imaging of the heart to assess the wall motion in response to physical stress. First, images of the heart are taken "at rest" to acquire a baseline of the patient's wall motion at a resting heart rate. The patient then walks on a treadmill or uses another exercise modality to increase the heart rate to his or her target heart rate, or 85% of the age-predicted maximum heart rate (220 − patient's age). Finally, images of the heart are taken "at stress" to assess wall motion at the peak heart rate. A stress echo assesses wall motion of the heart; it does not, however, create an image of the coronary arteries directly. Ischemia of one or more coronary arteries could cause a wall motion abnormality, which could indicate coronary artery disease. The gold standard test to directly create an image of the coronary arteries and directly assess for stenosis or occlusion is a cardiac catheterization. A stress echo is not invasive and is performed in the presence of a licensed medical professional, such as a cardiologist, and a cardiac sonographer.


Intracardiac echocardiography (ICE) is specialized form of echocardiography that uses catheters to insert the ultrasound probe inside the heart to view structures from within the heart.
ICE is often used as a part of the cardiac procedure of crossing the  interatrial septum  with a transseptal puncture to permit catheter access from the right atrium to the left atrium; alternative access to the left heart would be retrograde through the  aorta  and across the  aortic valve  into the left ventricle.


ICE has the benefit over transthoracic echocardiography in that an operator who is performing a sterile procedure can also operate the ICE catheter and it is not limited to visibility problems that can arise with transthoracic or transesophageal echo. Though, there are image quality limitations due to size constraints of the probe being limited to a catheter.


ICE is often inserted through the femoral vein and into the right atrium.
From the right atrium, visualization of the interatrial septum, all four cardiac chambers, all four valves, and the pericardial space (for an effusion) can be readily visualized.
It can also be advanced across the atrial septum into the left atrium to visualize the left atrial appendage during  left atrial appendage occlusion  device deployment.


Utilization of ICE imagery can be incorporated into the 3-D models built with  electroanatomic mapping  systems.


Intravascular ultrasound (IVUS) is a specialized form of echocardiography that uses a catheter to insert the ultrasound probe inside blood vessels. This is commonly used to measure the size of blood vessels and to measure the internal diameter of the blood vessel. For example, this can be used in a  coronary angiogram  to assess the narrowing of the coronary artery. If the catheter is retraced in a controlled manner, then an internal map can be generated to see the contour of the vessel and its branches.


The various modes describe how the ultrasound crystals are used to obtain information. These modes are common to all types of echocardiography.


A-scan or one dimensional ultrasound represents over half the standard ECHO exam.  For example, it is how aortic stenosis valve area (or any obstruction).  It is also how pressures are calculated in the heart such as right ventricle systolic pressure (RVSP).  It is usually used in the form of Doppler measurements.  There are two forms, pulse and continuous.  Pulsed allows velocities to be calculated in a specific place, but has a limited velocity range is can be used.  Continuous wave allows the velocity to be measured from zero to the fastest blood velocities a diseased heart can generate.  However, it can not tell you where in the A-scan the high velocity is coming from.  Continuous wave would be used to calculate aortic stenosis because you know the high velocity is coming from the stenosis region.  Pulsed would be used to find a ventricular septal defect where there should be no velocity across the septum and the pulsed tells you the location.


Brightness mode is often synonymous with "2D" and is very commonly used in echocardiography.


Motion mode is infrequently used in modern echocardiography. It has specific uses and has the benefit of very high temporal fidelity (e.g., measuring LV size at end diastole).


Strain rate imaging is an ultrasound method for imaging regional differences in contraction (dyssynergy) in for instance  ischemic heart disease  or dyssynchrony due to  Bundle branch block . Strain rate imaging measures either regional systolic deformation (strain) or the rate of regional deformation (strain rate). The methods used are either  tissue Doppler  or  Speckle tracking echocardiography .


Three-dimensional echocardiography (also known as  four-dimensional  echocardiography when the picture is moving) is possible using a matrix array ultrasound probe and an appropriate processing system. It enables detailed anatomical assessment of cardiac pathology, particularly valvular defects, [ 11 ]  and cardiomyopathies. [ 12 ]  The ability to slice the virtual heart in infinite planes in an anatomically appropriate manner and to reconstruct three-dimensional images of anatomic structures make it unique for the understanding of the congenitally malformed heart. [ 13 ]  Real-time three-dimensional echocardiography can be used to guide the location of  bioptomes  during right ventricular endomyocardial biopsies, placement of catheter-delivered valvular devices, and in many other intraoperative assessments. [ 14 ]


Three-dimensional echocardiography technology may feature anatomical intelligence, or the use of organ-modeling technology, to automatically identify anatomy based on generic models.  All generic models refer to a dataset of anatomical information that uniquely adapts to variability in patient anatomy to perform specific tasks. Built on feature recognition and segmentation algorithms, this technology can provide patient-specific three-dimensional modeling of the heart and other aspects of the anatomy, including the brain, lungs, liver, kidneys, rib cage, and vertebral column. [ 15 ]


Contrast echocardiography or contrast-enhanced ultrasound is the addition of an ultrasound contrast medium, or imaging agent, to traditional ultrasonography. The ultrasound contrast is made up of tiny microbubbles filled with a gas core and protein shell. This allows the microbubbles to circulate through the cardiovascular system and return the ultrasound waves, creating a highly reflective image. There are multiple applications in which contrast-enhanced ultrasound can be useful. The most commonly used application is in the enhancement of LV endocardial borders for assessment of global and regional systolic function. Contrast may also be used to enhance visualization of wall thickening during stress echocardiography, for the assessment of LV thrombus, or for the assessment of other masses in the heart. Contrast echocardiography has also been used to assess blood perfusion throughout myocardium in the case of coronary artery disease.


Echocardiography can at many times be subjective, meaning that the person reading the echo may have personal input that affects the interpretation of the findings, leading to so-called "inter-observer variability", where different echocardiographers might produce different reports when examining the same images. [ 16 ] [ 17 ]  It necessitated the development of accreditation programs around the world. The aim of such programs is to standardize the practice of echocardiography and to ensure that practitioners have the proper training prior to practicing echocardiography which will eventually limit inter-observer variability. [ 18 ]


At the European level  [ 19 ]  individual and laboratory accreditation is provided by the European Association of Echocardiography (EAE). There are three subspecialties for individual accreditation: Adult Transthoracic Echocardiography ( TTE ), Adult Transesophageal Echocardiography ( TEE ) and Congenital Heart Disease Echocardiography (CHD).


In the UK, accreditation is regulated by the British Society of Echocardiography. Accredited radiographers, sonographers, or other professionals are required to pass a mandatory exam. [ 20 ]


The "Intersocietal Accreditation Commission for Echocardiography" (IAC) sets standards for echo labs across the US. Cardiologists and sonographers who wish to have their laboratory accredited by IAC must comply with these standards. The purpose of accreditation is to maintain quality and consistency across echocardiography labs in the United States. Accreditation is offered in adult and pediatric transthoracic and transesophageal echocardiography, as well as adult stress and fetal echo. Accreditation is a two-part process. Each facility will conduct a detailed self-evaluation, paying close attention to the IAC Standards and Guidelines. The facility will then complete the application and submit actual case studies to the board of directors for review. Once all requirements have been met, the lab will receive certification. IAC certification is a continual process and must be maintained by the facility: it may include audits or site visits by the IAC. There are several states in which Medicare and/or private insurance carriers require accreditation (credentials) of the laboratory and/or sonographer for reimbursement of echocardiograms.


There are two credentialing bodies in the United States for sonographers, the  Cardiovascular Credentialing International  (CCI), established in 1968, and the  American Registry for Diagnostic Medical Sonography  (ARDMS), established in 1975. Both CCI and ARDMS have earned the prestigious  ANSI-ISO 17024  accreditation for certifying bodies from the International Organization for Standardization ( ISO ). [ citation needed ]  Accreditation is granted through the American National Standards Institute (ANSI). Recognition of ARDMS programs in providing credentials has also earned the ARDMS accreditation with the National Commission for Certifying Agencies (NCCA). The NCCA is the accrediting arm of the National Organization for Competency Assurance (NOCA).


Under both credentialing bodies, sonographers must first document completion of prerequisite requirements, which contain both didactic and hands-on experience in the field of ultrasound. Applicants must then take a comprehensive exam demonstrating knowledge in both the physics of ultrasound and the clinical competency related to their specialty. Credentialed sonographers are then required to maintain competency in their field by obtaining a certain number of Continuing Medical Education credits, or CME's.


In 2009, New Mexico and Oregon became the first two states to require licensure of sonographers. [ citation needed ]


The  American Society of Echocardiography  (ASE) is a professional organization made up of physicians, sonographers, nurses, and scientists involved in the field of echocardiography. One of the most important roles that the ASE plays is providing their recommendations through the ASE Guidelines and Standards, providing resource and educational opportunities for sonographers and physicians in the field.


There have been various institutes who are working on use of  Artificial intelligence  in Echo but they are at a very early stage and still needs full development. [ 21 ]


The most commonly used terminology in echocardiography diagnostics are:


Electrical cardiometry  is a method based on the model of  Electrical Velocimetry , and non-invasively measures  stroke volume  (SV),  cardiac output  (CO), and other  hemodynamic  parameters through the use of 4 surface ECG electrodes.  Electrical cardiometry is a method trademarked by Cardiotronic, Inc., and is U.S. FDA approved for use on adults, children, and neonates. [ 1 ]


The measured bioimpedance over  time  can be expressed as the superposition of three components: [ 3 ]


where Z 0  is the quasi-static portion of the  electrical impedance  (base impedance), ΔZ R  are the changes of impedance due to the  respiratory  cycle, and ΔZ C  are the changes of impedance due to the  cardiac  cycle.  ΔZ R  is considered an artifact akin to the estimation of stroke volume and is therefore suppressed. Exclusion of derived  volumetric  data may diminish the overall product.


The timely measurement of ΔZ C  (dZ(t)) reveals a waveform with shape similar to an arterial pressure waveform.  The calculated first time derivative of dZ(t) is the

 d
 Z
 (
 t
 )

 d
 t

 {\displaystyle {\frac {dZ(t)}{dt}}}

  waveform, which contains landmarks that allow determination of left-ventricular ejection time (LVET) and peak aortic blood acceleration.  The peak aortic blood acceleration occurs at the steepest slope of the dZ(t) waveform, and at the peak of the

 d
 Z
 (
 t
 )

 d
 t

 {\displaystyle {\frac {dZ(t)}{dt}}}

  waveform. [ citation needed ]


Electrical velocimetry  (EV) is the model upon which electrical cardiometry is based.  EV is based on the fact that the conductivity of the blood in the aorta changes during the cardiac cycle.  EV was developed by Dr. Bernstein and Dr. Osypka in 2001, as a new model for interpreting the bioimpedance signals of the thorax. [ 3 ]


Prior to opening of the aortic valve, the red blood cells (erythrocytes) assume a random orientation (there is no blood flow in the aorta).  When the electric current is applied from the outer electrodes, the current must circumference these red blood cells, therefore resulting in a higher voltage measurement, and thus, a lower conductivity.  Shortly after aortic valve opening, the pulsatile blood flow forces the red blood cells to align in parallel with the blood flow.  When the electric current is then applied, it is able to easily pass the red blood cells in the aorta resulting in a lower voltage, and thus, a higher conductivity.  The change from random orientation to alignment of red blood cells upon opening of aortic valve generates a characteristic steep increase of conductivity or dZ(t) (corresponding to a steep decrease of impedance) – beat to beat. [ 3 ]


The model considers the peak amplitude of

 d
 Z
 (
 t
 )

 d
 t

 {\displaystyle {\frac {dZ(t)}{dt}}}

  divided by the base impedance Z 0  as an index for peak aortic acceleration, and as an index of contractility of the heart, or ICON.  The general equation for estimating stroke volume by means of thoracic electrical bioimpedance calculates the product of a patient constant C P  (in ml), the mean blood velocity index

 v
 ¯

 {\displaystyle {\bar {v}}}

 FT  (measured in s −1  during flow time, and FT (flow time measured in s): [ 3 ]


S

 V

 T
 E
 B

 =

 C

 P

 ⋅

 v
 ¯

 F
 T

 ⋅
 F
 T

 {\displaystyle SV_{TEB}=C_{P}\cdot {\bar {v}}_{FT}\cdot FT}


The model of electrical velocimetry derives the mean blood velocity index

 v
 ¯

 {\displaystyle {\bar {v}}}

 FT  from the measured index for peak aortic acceleration ICON. [ 4 ]   The higher the mean blood velocity during flow time, the more SV the left ventricle ejects.  The 'volume of electrically participating tissue' (V EPT ) is used as the patient constant.  The V EPT  is derived primarily from the body mass. [ 3 ]


Impedance cardiography  is a method of non-invasively monitoring hemodynamics, through the use of 4 dual sensors placed on the neck and chest.  Both Impedance cardiography and Electrical Cardiometry derive SV and CO from measurements of TEB, but the underlying model is what differs.  The Impedance Cardiography model contributes the rapid change of bioimpedance which occurs shortly after aortic valve opening to the expansion of the compliant ascending aorta, assuming that more blood volume temporarily stored in the ascending aorta contributes to a decrease in bioimpedance (or an increase in conductity of the thorax).  The underlying model never proved accurate in patients with small cardiac outputs, hence it was never U.S. FDA approved for use in children or neonates. [ citation needed ]


The electrical and impedance signals are processed, and then utilized to measure and calculate hemodynamic parameters such as cardiac output, stroke volume, systemic vascular resistance, thoracic fluid index, ICON (index of contractility), and systolic time ratio.


Endomyocardial biopsy  (EMB) is an  invasive procedure  used routinely to obtain small  samples  of  heart muscle , primarily for detecting  rejection  of a donor  heart  following  heart transplantation . It is also used as a  diagnostic tool  in some  heart diseases . [ 1 ]


A  bioptome  is used to gain access to the heart via a sheath inserted into the  right internal jugular  or less commonly the  femoral vein . [ 1 ]  Monitoring during the procedure consists of performing  ECGs  and blood pressures. [ 1 ]  Guidance and confirmation of correct positioning of the bioptome is made by  echocardiography  or  fluoroscopy . [ 1 ]


The risk of complications is less than 1% when performed by an experienced physician in a specialist centre. [ 1 ]  Serious complications include perforation of the heart with  pericardial tamponade ,  haemopericardium ,  AV block ,  tricuspid regurgitation  and  pneumothorax . [ 2 ]


EMB, sampling  myocardium  was first pioneered in Japan by S. Sakakibra and S. Konno in 1962. [ 1 ] [ 3 ]


The main reason for performing an EMB is to assess  allograft  rejection following heart transplantation and sometimes to evaluate  cardiomyopathy , some  heart disease  research and  ventricular arrhythmias , [ 4 ]  or unexplained  ventricular dysfunction . [ 5 ] [ 6 ]


Visualising the  microscopic appearance  of the heart muscle allows the detection of  cell-mediated  or  antibody-mediated  rejection and is recommended episodically during the first year after heart transplantation. Occasionally, monitoring continues beyond one year. [ 1 ]


The use of EMB in heart transplant rejection surveillance remains the  gold standard test , although the pre-test predictors of rejection  cardiac magnetic resonance imaging  (CMR) and  gene expression profiling , are increasingly used. [ 1 ]


EMB has a role in the diagnosis of viral  myocarditis  and inflammatory myocarditis. [ 1 ]


EMB of the right ventricle via the internal jugular vein is standard after heart transplant.  [ 4 ]  A  bioptome  is used to gain access to the heart via a sheath inserted into the  right internal jugular  or less commonly the  femoral vein . [ 1 ]  Monitoring during the procedure consists of performing ECGs and blood pressures. Guidance and confirmation of correct positioning of the bioptome is made by  echocardiography  or  fluoroscopy [ 1 ]  before the biopsy specimen is taken and in the case of transplants, usually three [ 4 ]  or four or more samples are taken. [ 1 ]


Endomyocardial fibrosis  can occur if biopsies are performed repeatedly. This risk is reduced if the operator is experienced. Unlike for rejection detection, for diagnosing heart disease, different biopsy sites within the heart are targeted. [ 4 ]


It is possible but less common to biopsy the left ventricle via the  femoral arteries . [ 1 ]


The accuracy of diagnosis by EMB depends on whether the correct site is biopsied. There is a risk that a diagnosis can be missed if the biopsy misses the diseased part of heart muscle, particularly with myocardial inflammation or fibrosis. [ 5 ] [ 7 ]


An experienced pathologist trained in biopsy analysis and interpretation also reflects EMB’s reliability. Variability between pathologists has been observed.  [ 4 ]


A frequent concern regarding EMB has been its safety. [ 1 ]  However, it has a low risk of less than 1% when performed by an experienced physician in a specialist centre. [ 1 ] [ 3 ]


Possible complications, which almost all occur at time of procedure, [ 4 ]  include rupture of the  right intraventricular septum , conduction block, arrhythmias,  pneumothorax ,  tricuspid regurgitation ,  atrioventricular fistula , [ 8 ]  and  pulmonary embolism . Death has been reported, but is rare. [ 1 ]


Early heart biopsies, sampling  pericardium , in the latter half of the 1950s were performed through a  cut  in the left  intercostal space  at the  costochondral junction . [ 6 ]  However this method risked lung and  coronary blood vessel  damage,  cardiac tamponade  and  arrhythmias . [ 3 ]


EMB, sampling  myocardium , has evolved since it was first pioneered in Japan by S. Sakakibra and S. Konno in 1962. [ 1 ]  The concept of introducing a biopsy needle through the right internal or external jugular vein to reach the right intraventricular septum for the purpose of sampling the heart muscle was initiated in 1965 by R. T. Bulloch. In 1972, the bioptome and procedure was modified by  Philip Caves . This was to allow access  percutaneously . [ 6 ]


The  ESC Congress  is the annual congress of the  European Society of Cardiology  (ESC), the largest medical congress in Europe. It gathers over 30,000 active participants (mainly cardiologists) and takes place every year in August/September  in a different European city. [ citation needed ]


The first ESC Congress was held in 1950 and from then on every 4 years [ 1 ]  until 1988, when it became an annual event.


After the 2017 ESC Congress,  Barcelona    became the city with most congresses since 1988(6), followed by  Stockholm    (5) and then by  Amsterdam    and  Vienna    and  Munich    (4 times each as of 2018).
Some congresses (1994 and 2006) were organised jointly with the World Heart Federation [ 2 ]  under the name of "World Congress of Cardiology".


The  Fick principle  states that blood flow to an organ can be calculated using a marker substance if the following information is known:


Developed by  Adolf Eugen Fick  (1829–1901), the Fick principle has been applied to the measurement of  cardiac output . Its underlying principles may also be applied in a variety of clinical situations.


In Fick's original method, the "organ" was the entire human body and the marker substance was oxygen. The first published mention was in conference proceedings from July 9, 1870 from a lecture he gave at that conference; [ 1 ]  it is this publishing that is most often used by articles to cite Fick's contribution.The principle may be applied in different ways. For example, if the blood flow to an organ is known, together with the arterial and venous concentrations of the marker substance, the uptake of marker substance by the organ may then be calculated. [ citation needed ]


In Fick's original method, the following variables are measured: [ 2 ]


From these values, we know that:


where


This allows us to say


and hence calculate cardiac output.


Note that ( C a  –  C v ) is also known as the  arteriovenous oxygen difference . [ citation needed ]


In reality, this method is rarely used due to the difficulty of collecting and analysing the gas concentrations.  However, by using an assumed value for oxygen consumption, cardiac output can be closely approximated without the cumbersome and time-consuming oxygen consumption measurement.  This is sometimes called an assumed Fick determination. [ citation needed ]


A commonly used value for O 2  consumption at rest is  125  mL  O 2  per minute per square meter of  body surface area . [ citation needed ]


The Fick principle relies on the observation that the total uptake of (or release of) a substance by the peripheral tissues is equal to the product of the blood flow to the peripheral tissues and the arterial-venous concentration difference (gradient) of the substance. In the determination of cardiac output, the substance most commonly measured is the  oxygen  content of  blood  thus giving the arteriovenous oxygen difference, and the flow calculated is the flow across the pulmonary system.  This gives a simple way to calculate the cardiac output: [ citation needed ]


Assuming there is no intracardiac shunt, the pulmonary blood flow equals the systemic blood flow.  Measurement of the arterial and venous oxygen content of blood involves the sampling of blood from the pulmonary artery (low oxygen content) and from the pulmonary vein (high oxygen content).  In practice, sampling of peripheral arterial blood is a surrogate for pulmonary venous blood. Determination of the oxygen consumption of the peripheral tissues is more complex.


The calculation of the arterial and venous oxygen concentration of the blood is a straightforward process.  Almost all oxygen in the blood is bound to  hemoglobin   molecules  in the  red blood cells .  Measuring the content of hemoglobin in the blood and the percentage of saturation of hemoglobin (the oxygen saturation of the blood) is a simple process and is readily available to physicians.  Using the fact that each  gram  of hemoglobin can carry  1.34  mL  of  O 2 , the oxygen content of the blood (either arterial or venous) can be estimated by the following formula:


Assuming a hemoglobin concentration of  15  g/dL  and an oxygen saturation of 99%, the oxygen concentration of arterial blood is approximately  200  mL  of O 2  per L.


The saturation of mixed venous blood is approximately 75% in health. Using this value in the above equation, the oxygen concentration of mixed venous blood is approximately  150  mL  of O 2  per L.


Therefore, using the assumed Fick determination, the approximated cardiac output for an average man (1.9 m3) is:


Cardiac output may also be estimated with the Fick principle using production of  carbon dioxide  as a marker substance. [ 3 ]


The principle can also be used in  renal physiology  to calculate  renal blood flow . [ 4 ]


In this context, it is not oxygen which is measured, but a marker such as  para-aminohippurate . However, the principles are essentially the same.


In the fetal  heart , the  foramen ovale  ( / f ə ˈ r eɪ m ən   oʊ ˈ v æ l i ,   - m ɛ n -,   - ˈ v ɑː -,   - ˈ v eɪ -/ [ 1 ] [ 2 ] [ 3 ] ), also  foramen Botalli  or the  ostium secundum of Born , allows blood to enter the left  atrium  from the right atrium. It is one of two fetal  cardiac shunts , the other being the  ductus arteriosus  (which allows blood that still escapes to the right ventricle to bypass the  pulmonary circulation ). Another similar adaptation in the fetus is the  ductus venosus . In most individuals, the foramen ovale closes at birth. It later forms the  fossa ovalis .


The foramen ovale (from  Latin  'oval hole') forms in the late fourth week of  gestation , as a small passageway between the septum secundum and the ostium secundum. Initially the atria are separated from one another by the  septum primum  except for a small opening below the septum, the  ostium primum . As the septum primum grows, the ostium primum narrows and eventually closes. Before it does so, bloodflow from the  inferior vena cava  wears down a portion of the septum primum, forming the  ostium secundum . Some embryologists postulate that the ostium secundum may be formed through  programmed cell death . [ 4 ]


The ostium secundum provides communication between the atria after the ostium primum closes completely. Subsequently, a second wall of tissue, the  septum secundum , grows over the ostium secundum in the right atrium. Blood then passes from the right to left atrium only by way of a small passageway in the septum secundum and then through the ostium secundum. This passageway is called the foramen ovale . [ citation needed ]


The foramen ovale often closes at birth. At birth, when the lungs become functional, the pulmonary vascular pressure decreases and the left atrial pressure exceeds that of the right. This forces the  septum primum  against the  septum secundum , functionally closing the foramen ovale. In time the septa eventually fuse, leaving a remnant of the foramen ovale, the  fossa ovalis .


A  fetus  receives oxygen not from its lungs, but from the mother's oxygen-rich blood via the  placenta . Oxygenated blood from the placenta travels through the umbilical cord to the right atrium of the fetal heart. As the fetal lungs are non-functional at this time, the blood bypasses them through two cardiac shunts. The first is the foramen ovale (the valve present between them called eustachian valve)  which shunts blood from the right atrium to the left atrium. The second is the  ductus arteriosus  which shunts blood from the pulmonary artery (which, after birth, carries blood from the right side of the heart to the lungs) to the descending aorta. [ citation needed ]


In about 25% of adults the foramen ovale does not close completely, but remains as a small  patent foramen ovale ("PFO") . [ 5 ]  In most of these individuals, the PFO causes no problems and remains undetected throughout life.


PFO has long been studied because of its role in  paradoxical embolism  (an  embolism  that travels from the venous side to the arterial side). This may lead to a  stroke  or  transient ischemic attack .  Transesophageal echocardiography  is considered the most accurate investigation to demonstrate a patent foramen ovale. A patent foramen ovale may also be an incidental finding.


The  fossa ovalis  is a depression in the  right atrium  of the  heart , at the level of the  interatrial septum , the wall between right and  left atrium . The  fossa ovalis  is the remnant of a thin fibrous sheet that covered the  foramen ovale  during  fetal  development.


During fetal development, the foramen ovale allows blood to pass from the right atrium to the  left atrium , bypassing the nonfunctional fetal lungs while the fetus obtains its oxygen from the  placenta . A flap of tissue called the  septum primum  acts as a valve over the foramen ovale during that time. After birth, the introduction of air into the lungs causes the pressure in the  pulmonary circulatory  system to drop. This change in pressure pushes the septum primum against the  atrial septum , closing the foramen. [ 1 ]  The septum primum and atrial septum eventually fuse together to form a complete seal, leaving a depression called the fossa ovalis. By age two, about 75% of people have a completely sealed fossa ovalis. An unfused fossa ovalis is called a  patent foramen ovale . Depending on the circumstances, a patent foramen ovale may be completely asymptomatic, or may require surgery. [ 1 ]  The  limbus of fossa ovalis  ( annulus ovalis ) is the prominent oval margin of the fossa ovalis in the right atrium. It is most distinct above and at the sides of the fossa ovalis; below, it is deficient. A small slit-like valvular opening is occasionally found, at the upper margin of the fossa, leading upward beneath the limbus, into the  left atrium ; it is the remains of the fetal aperture the foramen ovale between the two  atria .


Almost immediately after the infant is born, the foramen ovale and  ductus arteriosus  close. The major changes that are made by the body occur at the first breath (in the case of heart and lung functions) and up to weeks after birth (such as the liver's  enzyme synthesis ). The foramen ovale becomes the fossa ovalis as the foramen closes while edge of the septum secundum in right atrium becomes the anulus ovalis, so the depression beneath it becomes the fossa ovalis. [ 2 ] [ unreliable medical source? ]  This enables respiration and circulation independent from the mother's placenta.


With the child's first breath, the lung sends  oxygenated blood  to the left atrium. As a result, pressure in the left atrium is higher than that of the right, and the increased pressure holds the interatrial flap (which covers the foramen ovale) shut, therefore closing the foramen ovale as well. [ 2 ]  In normal development, the closed foramen ovale fuses with the interatrial wall. During the first breath, vasoconstriction causes the ductus arteriosus to close, and during adult years, tissue occludes what once was the ductus arterious, creating the  ligamentum arteriosum . [ 3 ]


Aneurysms  can occur in adulthood if the foramen ovale is not closed correctly. An aneurysm happens when an artery becomes enlarged in a localized area due to weakening of the arterial wall. [ 4 ]


When this type of aneurysm occurs in the area of the fossa ovalis, an enlarged pouch is formed. This pouch can protrude into the right atrium or the left atrium. The cause of this aneurysm is the result of abnormal, increased pressure within the heart. Even if the foramen ovale does seal shut, an aneurysm may occur, usually on the side of the right atrium. If the aneurysm stretches too far, it can narrow the opening of the  inferior vena cava . [ 5 ]  This type of aneurysm can be a result of  plaque  build-up in the arteries from  coronary heart disease , as well as diseases of the  aortic valve  or  mitral valve . Surgery may be useful in helping to cope with the aneurysm.


If the atrial septum does not close properly, it leads to a patent foramen ovale (PFO). This type of defect generally works like a flap valve, opening during certain conditions of increased pressure in the chest, such as during strain while having a bowel movement, cough, or sneeze. With enough pressure, blood may travel from the right atrium to the left. If there is a  clot  in the right side of the heart, it can cross the PFO, enter the left atrium, and travel out of the heart and to the brain, causing a  stroke . If the clot travels into a  coronary artery  it can cause a  heart attack . [ 6 ]


The  fourth heart sound  or  S 4  is an extra  heart sound  that occurs during late diastole, immediately before the normal two "lub-dub" heart sounds (S 1  and S 2 ). It occurs just after atrial contraction and immediately before the  systolic  S 1  and is caused by the atria contracting forcefully in an effort to overcome an abnormally stiff or hypertrophic ventricle.


This produces a rhythm classically compared to the cadence of the word " Tennessee ." [ 1 ] [ full citation needed ] [ 2 ]  One can also use the phrase " A -stiff-wall" to help with the cadence (a S 4 , stiff S 1 , wall S 2 ), as well as the pathology of the S 4  sound. [ 3 ]


The normal heart sounds, S 1  and S 2 , are produced during the closing of the  atrioventricular valves  and  semilunar valves , respectively.  The closing of these valves produces a brief period of turbulent flow, which produces sound. [ 4 ]


The S 4  sound occurs, by definition, immediately before S 1 , while the atria of the heart are vigorously contracting. [ 5 ]   It is manifest as a vibration of 20 to 30 Hz within the ventricle. [ 5 ]   While the mechanism is not absolutely certain, it is generally accepted that S 4  is caused by stiffening of the walls of the ventricles (usually the left), which produces abnormally turbulent flow as the atria contract to force blood into the ventricle. [ 5 ] [ 4 ]  This for example occurs in conditions that decrease ventricular compliance like  left ventricular hypertrophy . [ 4 ]


S 4  is sometimes audible in the elderly due to a more rigid ventricle. When loud, it is a sign of a pathologic state, [ 6 ]  usually a failing left ventricle. If the problem lies with the left ventricle, the gallop rhythm will be heard best at the cardiac apex.  It will become more apparent with exercise, with the patient lying on the left-hand side, or with the patient holding  expiration .  If the problem is in the right ventricle, the abnormal sound will be most evident on the lower left hand side of the  sternum  and will get louder with exercise and quick, deep  inspiration . [ 7 ]


S 4  has also been termed an  atrial gallop  or a  presystolic gallop  because of its occurrence late in the heart cycle. It is a type of  gallop rhythm  by virtue of having an extra sound; the other gallop rhythm is called  S 3 . The two are quite different, but they may sometimes occur together forming a  quadruple gallop . If the  heart rate  is also very fast ( tachycardia ), it can become difficult to distinguish between S 3  and S 4  thus producing a single sound called a  summation gallop .


The S4 heart sound itself does not require treatment; rather plans should be laid to stop the progression of whatever causes the underlying ventricular dysfunction. The S4 heart sound is a secondary manifestation of a primary disease process and treatment should be focused on treating the underlying, primary disease.


Fractional flow reserve  (FFR) is a diagnostic technique used in  coronary catheterization . FFR measures pressure differences across a  coronary artery   stenosis  (narrowing, usually due to  atherosclerosis ) to determine the likelihood that the stenosis impedes oxygen delivery to the heart muscle ( myocardial   ischemia ). [ 1 ]


Fractional flow reserve is defined as the pressure after (distal to) a stenosis relative to the pressure before the stenosis. [ 2 ]  The result is an absolute number; an FFR of 0.80 means that a given stenosis causes a 20% drop in  blood pressure . In other words, FFR expresses the maximal flow down a vessel in the presence of a stenosis compared to the maximal flow in the hypothetical absence of the stenosis.


During coronary catheterization, a  catheter  is inserted into the  femoral  (groin) or  radial arteries  (wrist) using a sheath and guidewire. FFR uses a small sensor on the tip of the wire (commonly a  transducer ) to measure pressure, temperature and flow to determine the exact severity of the  lesion . This is done during maximal blood flow ( hyperemia ), which can be induced by injecting products such as  adenosine  or  papaverine . A pullback of the pressure wire is performed, and pressures are recorded across the vessel. [ 3 ]


When interpreting FFR measurements, higher values indicate a non-significant stenosis, whereas lower values indicate a significant lesion. There is no absolute cut-off point at which an FFR measurement is considered abnormal. However, reviews of clinical trials show a cut-off range between 0.75 and 0.80 has been used when determining significance. [ 4 ]


Fractional flow reserve (FFR) is the ratio of maximum blood flow distal to a stenotic lesion to normal maximum flow in the same vessel. It is calculated using the pressure ratio


F
 F
 R
 =

 p

 d

 p

 a

 {\displaystyle FFR={\frac {p_{d}}{p_{a}}}}


where

 p

 d

 {\displaystyle p_{d}}

  is the pressure distal to the lesion, and

 p

 a

 {\displaystyle p_{a}}

  is the pressure proximal to the lesion.


The decision to perform a  percutaneous coronary intervention  (PCI) is usually based on angiographic results alone.  Angiography  can be used for the visual evaluation of the inner diameter of a vessel. In ischemic heart disease, deciding which narrowing is the culprit lesion is not always clear-cut. Fractional flow reserve can provide a functional evaluation by measuring the pressure decline caused by a vessel narrowing. [ 4 ]


FFR has certain advantages over other techniques to evaluate narrowed coronary arteries, such as coronary angiography,  intravascular ultrasound  or  CT coronary angiography . For example, FFR takes into account collateral flow, which can render an anatomical blockage functionally unimportant. Also, standard angiography can underestimate or overestimate narrowing, because it only visualizes contrast inside a vessel. [ 5 ]  Finally, when compared to other indices of vessel narrowing, FFR seems to be less vulnerable to variability between patients. [ 6 ]


Other techniques can also provide information which FFR cannot. Intravascular ultrasound, for example, can provide information on  plaque vulnerability , whereas FFR measures are only determined by plaque thickness. There are newly developed technologies that can assess both plaque vulnerability and FFR from CT by measuring the vasodilitative capacity of the arterial wall.  [ citation needed ]


FFR allows real-time estimation of the effects of a narrowed vessel, and allows for simultaneous treatment with balloon dilatation and stenting. On the other hand, FFR is an  invasive  procedure for which non-invasive (less drastic) alternatives exist, such as  cardiac stress testing . In this test, physical exercise or intravenous medication (adenosine/dobutamine) is used to increase the workload and oxygen demand of the heart muscle, and ischemia is detected using  ECG  changes or  nuclear imaging .


In the DEFER study, fractional flow reserve was used to determine the need for stenting in patients with intermediate single vessel disease. In stenosis patients with an FFR of less than 0.75, outcomes were significantly worse. In patients with an FFR of 0.75 or more however, stenting did not influence outcomes. [ 7 ]


The  Fractional Flow Reserve versus Angiography for Multivessel Evaluation  (FAME) study evaluated the role of FFR in patients with multivessel coronary artery disease. [ 8 ]  In 20 centers in Europe and the United States, 1005 patients undergoing  percutaneous coronary intervention  with  drug eluting stent  implantation were randomized to intervention based on angiography or based on fractional flow reserve in addition to angiography. In the angiography arm of the study, all suspicious-looking lesions were stented. In the FFR arm, only angiographically suspicious lesions with an FFR of 0.80 or less were stented. [ citation needed ]


In the patients whose care was guided by FFR, fewer stents were used (2.7±1.2 and 1.9±1.3, respectively). After one year, the primary endpoint of death, nonfatal  myocardial infarction , and repeat  revascularization  were lower in the FFR group (13.2% versus 18.3%), largely attributable to fewer stenting procedures and their associated complications. There also was a non-significant higher number of patients with residual  angina   (81% versus 78%). In the FFR group, hospital stay was slightly shorter (3.4 vs 3.7 days) and procedural costs were less ($5,332 vs $6,007). FFR did not prolong procedure (around 70 minutes in both groups).


A  fusion beat  occurs when electrical impulses from different sources act upon the same region of the heart at the same time. [ 1 ]  If it acts upon the  ventricular  chambers it is called a  ventricular fusion beat , whereas colliding currents in the  atrial chambers  produce  atrial fusion beats .


Ventricular fusion beats can occur when the heart's natural rhythm and the impulse from a  pacemaker  coincide to activate the same part of a ventricle at the same time, causing visible variation in configuration and height of the  QRS complex  of an  electrocardiogram  reading of the heart's activity. [ 2 ]  This contrasts with the pseudofusion beat wherein the pacemaker impulse does not affect the complex of the natural beat of the heart. Pseudofusion beats are normal. Rare or isolated fusion beats caused by pacemakers are normal as well, but if they occur too frequently may reduce cardiac output and so can require adjustment of the pacemaker. [ 3 ]


A  gallop rhythm  refers to a (usually abnormal) rhythm of the heart on  auscultation . [ 1 ]  It includes three or four sounds, thus resembling the sounds of a  gallop .


The normal heart rhythm contains two audible  heart sounds  called S 1  and S 2  that give the well-known "lub-dub" rhythm; they are caused by the closing of  valves  in the heart. The  first heart sound  (S1) is closure of the valve at the end of ventricular filling (the tricuspid and mitral valves); the  second heart sound  (S2), is closure of the aortic and/or the pulmonary valves as the ventricles relax. Extra sounds, ( third  and/or  fourth heart sound , can be normal, especially in children, or with severe exercise, but are generally heard (on the left side) when ventricular function is impaired, e.g., in case of acute infarction or severe cardiac failure.  The sounds are thought to be caused by the atrium, facing back-pressure, forcing volume into an incompletely emptied ventricle. Then, given tachycardia, a "gallop" is produced. With right-sided back pressure after pulmonary embolism, and therefore an incompletely emptied right ventricle, a right-sided gallop can occur.


Gallop rhythms may be heard in young or athletic people, but may also be a sign of serious cardiac problems like  heart failure  as well as  pulmonary edema .
Gallop rhythms may be associated with the following: [ citation needed ]