All cardiologists in the branch of medicine study the disorders of the heart, but the study of adult and child heart disorders each require different training pathways. Therefore, an adult cardiologist (often simply called "cardiologist") is inadequately trained to take care of children, and pediatric cardiologists are not trained to treat adult heart disease. Surgical aspects outside of cardiac rhythm device implant are not included in cardiology and are in the domain ofcardiothoracic surgery. For example,coronary artery bypass surgery (CABG),cardiopulmonary bypass andvalve replacement are surgical procedures performed by surgeons, not cardiologists. Typically a cardiologist would first identify who is in need of cardiac surgery and refer them to a cardiac surgeon for the procedure. However, some invasive procedures such ascardiac catheterization andpacemaker implantation are performed by cardiologists.
In India, a three-year residency in General Medicine or Pediatrics afterM.B.B.S. and then three years of residency in cardiology are needed to be a D.M. (holder of a Doctorate of Medicine [D.M.])/Diplomate of National Board (DNB) in Cardiology.[citation needed]
PerDoximity, adult cardiologists earn an average of $436,849 per year in the U.S.[5]
Cardiac electrophysiology is the science of elucidating, diagnosing, and treating the electrical activities of the heart. The term is usually used to describe studies of such phenomena by invasive (intracardiac)catheter recording of spontaneous activity as well as of cardiac responses toprogrammed electrical stimulation (PES). These studies are performed to assess complexarrhythmias, elucidate symptoms, evaluate abnormalelectrocardiograms, assess risk of developing arrhythmias in the future, and design treatment. These procedures increasingly include therapeutic methods (typicallyradiofrequency ablation, orcryoablation) in addition to diagnostic and prognostic procedures.
The cardiacelectrophysiology study typically measures the response of the injured or cardiomyopathic myocardium to PES on specific pharmacological regimens in order to assess the likelihood that the regimen will successfully prevent potentially fatal sustainedventricular tachycardia (VT) orventricular fibrillation (VF) in the future. Sometimes aseries of electrophysiology-study drug trials must be conducted to enable the cardiologist to select the one regimen for long-term treatment that best prevents or slows the development of VT or VF following PES. Such studies may also be conducted in the presence of a newly implanted or newly replaced cardiac pacemaker or AICD.[6]
Clinical cardiac electrophysiology is a branch of the medical specialty of cardiology and is concerned with the study and treatment of rhythm disorders of the heart. Cardiologists with expertise in this area are usually referred to as electrophysiologists. Electrophysiologists are trained in the mechanism, function, and performance of the electrical activities of the heart. Electrophysiologists work closely with other cardiologists and cardiac surgeons to assist or guide therapy for heart rhythm disturbances (arrhythmias). They are trained to perform interventional and surgical procedures to treat cardiac arrhythmia.[8]
The training required to become an electrophysiologist is long and requires eight years after medical school (within the U.S.). Three years of internal medicine residency, three years of cardiology fellowship, and two years of clinical cardiac electrophysiology.[9]
Cardiogeriatrics, or geriatric cardiology, is the branch of cardiology and geriatric medicine that deals with the cardiovascular disorders in elderly people.
Cardiac imaging includes echocardiography (echo), cardiac magnetic resonance imaging (CMR), and computed tomography of the heart.Those who specialize in cardiac imaging may undergo more training in all imaging modes or focus on a single imaging modality.
Echocardiography (or "echo") uses standard two-dimensional, three-dimensional, andDoppler ultrasound to create images of the heart. It is used to evaluate and quantify cardiac size and function, valvular function, and can assist with diagnosis and treatment of conditions including heart failure, heart attack, valvular heart disease, congenital heart defects, pericardial disease, and aortic disease. Those who specialize in echo may spend a significant amount of their clinical time reading echos and performing transesophageal echo, in particular using the latter during procedures such as insertion of a left atrial appendage occlusion device. Transesophageal echo provides higher spatial resolution than trans thoracic echocardiography and because the probe is located in the esophagus, it is not limited by attenuation due to anterior chest structures such as the ribs, chest wall, breasts, lungs that can hinder the quality of trans thoracic echocardiography. It is generally indicated for a variety of indications including: when the standard transthoracic echocardiogram is non diagnostic, for detailed evaluation of abnormalities that are typically in the far field, such as the aorta, left atrial appendage, evaluation of native or prosthetic heart valves, evaluation of cardiac masses, evaluation of endocarditis, valvular abscesses, or for the evaluation of cardiac source of embolus. It is frequently used in the setting of atrial fibrillation or atrial flutter to facilitate the clinical decision with regard to anticoagulation, cardioversion and/or radio frequency ablation.[14]
Cardiac MRI utilizes special protocols to image heart structure and function with specific sequences for certain diseases such ashemochromatosis andamyloidosis.
Cardiac CT utilizes special protocols to image heart structure and function with particular emphasis on coronary arteries.
Interventional cardiology is a branch of cardiology that deals specifically with thecatheter based treatment of structural heart diseases.[15] A large number of procedures can be performed on the heart by catheterization, including angiogram, angioplasty, atherectomy, and stent implantation. These procedures all involve insertion of a sheath into thefemoral artery or radial artery (but, in practice, any large peripheral artery or vein) andcannulating the heart underX-ray visualization (most commonlyfluoroscopy). This cannulation allows indirect access to the heart, bypassing the trauma caused by surgical opening of the chest.
The main advantages of using the interventional cardiology or radiology approach are the avoidance of the scars and pain, and long post-operative recovery. Additionally, interventional cardiology procedure of primaryangioplasty is now the gold standard of care for an acute myocardial infarction. This procedure can also be done proactively, when areas of the vascular system become occluded fromatherosclerosis. The Cardiologist will thread this sheath through the vascular system to access the heart. This sheath has a balloon and a tiny wire mesh tube wrapped around it, and if the cardiologist finds a blockage orstenosis, they can inflate the balloon at the occlusion site in the vascular system to flatten or compress the plaque against the vascular wall. Once that is complete astent is placed as a type of scaffold to hold the vasculature open permanently.
A relatively newer specialization of cardiology is in the field of heart failure and heart transplant. Cardiomyopathy is a disease of the heart muscle that make it larger or stiffer, sometimes making the heart worse at pumping blood.[16] Specialization of general cardiology to just that of thecardiomyopathies leads to also specializing inheart transplant andpulmonary hypertension.
A recent specialization of cardiology is that of cardiooncology.This area specializes in the cardiac management in those with cancer and in particular those with plans forchemotherapy or those who have experienced cardiac complications of chemotherapy.
In recent times, the focus is gradually shifting to preventive cardiology due to increasedcardiovascular disease burden at an early age. According to the WHO, 37% of all premature deaths are due to cardiovascular diseases and out of this, 82% are in low and middle income countries.[17] Clinical cardiology is the sub specialty of cardiology which looks after preventive cardiology and cardiac rehabilitation. Preventive cardiology also deals with routine preventive checkup though noninvasive tests, specifically electrocardiography,fasegraphy, stress tests,lipid profile and general physical examination to detect any cardiovascular diseases at an early age, while cardiac rehabilitation is the upcoming branch of cardiology which helps a person regain their overall strength and live a normal life after a cardiovascular event. A subspecialty of preventive cardiology issports cardiology. Because heart disease is the leading cause of death in the world including United States (cdc.gov), national health campaigns and randomized control research has developed to improve heart health.
Helen B. Taussig is known as the founder of pediatric cardiology. She became famous through her work withTetralogy congenital heart defect in whichoxygenated and deoxygenated blood enters the circulatory system resulting from aventricular septal defect (VSD) right beneath the aorta. This condition causes newborns to have a bluish-tint,cyanosis, and have a deficiency of oxygen to their tissues,hypoxemia. She worked withAlfred Blalock andVivien Thomas at theJohns Hopkins Hospital where they experimented with dogs to look at how they would attempt to surgically cure these "blue babies". They eventually figured out how to do just that by theanastomosis of the systemic artery to the pulmonary artery and called this theBlalock-Taussig Shunt.[18]
As more children with congenital heart disease are surviving into adulthood, a hybrid of adult and pediatric cardiology has emerged called adult congenital heart disease (ACHD).This field can be entered as either adult or pediatric cardiology.ACHD specializes in congenital diseases in the setting of adult diseases (e.g., coronary artery disease, COPD, diabetes) that is, otherwise, atypical for adult or pediatric cardiology.
As the center focus of cardiology, the heart has numerous anatomical features (e.g.,atria,ventricles,heart valves) and numerous physiological features (e.g.,systole,heart sounds,afterload) that have been encyclopedically documented for many centuries. The heart is located in the middle of the abdomen with its tip slightly towards the left side of the abdomen.
Disorders of the heart lead toheart disease and cardiovascular disease and can lead to a significant number of deaths: cardiovascular disease is the leadingcause of death in the U.S. and caused 24.95% of total deaths in 2008.[19]
The primary responsibility of the heart is to pump blood throughout the body.It pumps blood from the body — called thesystemic circulation — through thelungs — called thepulmonary circulation — and then back out to the body. This means that the heart is connected to and affects the entirety of the body. Simplified, the heart is a circuit of thecirculation.[20] While plenty is known about the healthy heart, the bulk of study in cardiology is in disorders of the heart and restoration, and where possible, of function.
The heart is a muscle that squeezes blood and functions like a pump. The heart's systems can be classified as either electrical or mechanical, and both of these systems are susceptible to failure or dysfunction.
The mechanical system of the heart is centered on thefluidic movement of blood and the functionality of the heart as apump.The mechanical part is ultimately the purpose of the heart and many of the disorders of the heart disrupt the ability to move blood.Heart failure is one condition in which the mechanical properties of the heart have failed or are failing, which means insufficient blood is being circulated. Failure to move a sufficient amount of blood through the body can cause damage or failure of other organs and may result in death if severe.[22]
Coronary circulation is the circulation of blood in theblood vessels of theheart muscle (the myocardium). The vessels that deliver oxygen-rich blood to the myocardium are known as coronary arteries. The vessels that remove the deoxygenated blood from the heart muscle are known as cardiac veins. These include thegreat cardiac vein, themiddle cardiac vein, thesmall cardiac vein and theanterior cardiac veins.
As the left and right coronary arteries run on the surface of the heart, they can be called epicardial coronary arteries. These arteries, when healthy, are capable of autoregulation to maintain coronary blood flow at levels appropriate to the needs of the heart muscle. These relatively narrow vessels are commonly affected byatherosclerosis and can become blocked, causingangina or myocardial infarction (a.k.a., a heart attack). The coronary arteries that run deep within the myocardium are referred to as subendocardial.
The coronary arteries are classified as "end circulation", since they represent the only source of blood supply to the myocardium; there is very little redundant blood supply, which is why blockage of these vessels can be so critical.
The cardiac examination (also called the "precordial exam"), is performed as part of aphysical examination, or when a patient presents withchest pain suggestive of a cardiovascularpathology. It would typically be modified depending on theindication and integrated with other examinations especially therespiratory examination.[23]
Like all medical examinations, the cardiac examination follows the standard structure of inspection, palpation and auscultation.[24][25]
Cardiology is concerned with the normal functionality of the heart and the deviation from a healthy heart. Many disorders involve the heart itself, but some are outside of the heart and in the vascular system. Collectively, the two are jointly termed the cardiovascular system, and diseases of one part tend to affect the other.
Coronary artery disease, also known as "ischemic heart disease",[26] is a group of diseases that includes:stable angina,unstable angina, myocardial infarction, and is one of the causes ofsudden cardiac death.[27] It is within the group of cardiovascular diseases of which it is the most common type.[28] A common symptom ischest pain or discomfort which may travel into the shoulder, arm, back, neck, or jaw.[29] Occasionally it may feel likeheartburn. Usually symptoms occur with exercise or emotionalstress, last less than a few minutes, and get better with rest.[29]Shortness of breath may also occur and sometimes no symptoms are present.[29] The first sign is occasionally a heart attack.[30] Other complications includeheart failure or anirregular heartbeat.[30]
Prevention is by eating a healthy diet, regular exercise, maintaining a healthy weight and not smoking.[35] Sometimes medication for diabetes, high cholesterol, or high blood pressure are also used.[35] There is limited evidence for screening people who are at low risk and do not have symptoms.[36] Treatment involves the same measures as prevention.[37][38] Additional medications such asantiplatelets includingaspirin,beta blockers, ornitroglycerin may be recommended.[38] Procedures such aspercutaneous coronary intervention (PCI) orcoronary artery bypass surgery (CABG) may be used in severe disease.[38][39] In those with stable CAD it is unclear if PCI or CABG in addition to the other treatments improvelife expectancy or decreases heart attack risk.[40]
In 2013 CAD was themost common cause of death globally, resulting in 8.14 million deaths (16.8%) up from 5.74 million deaths (12%) in 1990.[28] The risk of death from CAD for a given age has decreased between 1980 and 2010 especially indeveloped countries.[41] The number of cases of CAD for a given age has also decreased between 1990 and 2010.[42] In the U.S. in 2010 about 20% of those over 65 had CAD, while it was present in 7% of those 45 to 64, and 1.3% of those 18 to 45.[43] Rates are higher among men than women of a given age.[43]
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Heart failure, or formally cardiomyopathy, is the impaired function of the heart, and there are numerous causes and forms of heart failure.
The causes of cardiomyopathy can begenetic, viral, or lifestyle-related. Key symptoms of cardiomyopathy include shortness of breath, fatigue, and irregular heartbeats. Understanding the specific function of cardiac muscle is crucial, as the heart muscle's main role is to pump blood throughout the body efficiently.[44]
Cardiac arrhythmia, also known as "cardiac dysrhythmia" or "irregular heartbeat", is a group of conditions in which theheartbeat is too fast, too slow, or irregular in its rhythm. Aheart rate that is too fast – above 100 beats per minute in adults – is calledtachycardia. A heart rate that is too slow – below 60 beats per minute – is calledbradycardia.[45] Many types of arrhythmia present no symptoms. When symptoms are present, they may includepalpitations, or feeling a pause between heartbeats. More serious symptoms may includelightheadedness,passing out,shortness of breath, orchest pain.[46] While most types of arrhythmia are not serious, some predispose a person to complications such asstroke orheart failure.[45][47] Others may result incardiac arrest.[47]
Most arrhythmias can be effectively treated.[45] Treatments may include medications, medical procedures such as apacemaker, and surgery. Medications for a fast heart rate may includebeta blockers oragents that attempt to restore a normal heart rhythm such asprocainamide. This later group may have more significant side effects especially if taken for a long period of time. Pacemakers are often used for slow heart rates. Those with an irregular heartbeat are often treated withblood thinners to reduce the risk of complications. Those who have severe symptoms from an arrhythmia may receive urgent treatment with a jolt of electricity in the form ofcardioversion ordefibrillation.[50]
Arrhythmia affects millions of people.[51] In Europe and North America, as of 2014, atrial fibrillation affects about 2% to 3% of the population.[52] Atrial fibrillation and atrial flutter resulted in 112,000 deaths in 2013, up from 29,000 in 1990.[28]Sudden cardiac death is the cause of about half of deaths due to cardiovascular disease or about 15% of all deaths globally.[53] About 80% of sudden cardiac death is the result of ventricular arrhythmias.[53] Arrhythmias may occur at any age but are more common among older people.[51]
The most common cause of cardiac arrest iscoronary artery disease. Less common causes includemajor blood loss, lack of oxygen,very low potassium,heart failure, and intense physical exercise. A number of inherited disorders may also increase the risk includinglong QT syndrome. The initial heart rhythm is most oftenventricular fibrillation.[57] The diagnosis is confirmed by finding no pulse.[55] While a cardiac arrest may be caused by heart attack or heart failure these are not the same.[54]
In theUnited States, cardiac arrest outside ofhospital occurs in about 13 per 10,000 people per year (326,000 cases). In hospital cardiac arrest occurs in an additional 209,000[61] Cardiac arrest becomes more common with age. It affects males more often than females.[62] The percentage of people who survive with treatment is about 8%. Many who survive have significantdisability. Many U.S. television shows, however, have portrayed unrealistically high survival rates of 67%.[63]
Lifestyle factors can increase the risk of hypertension. These includeexcess salt in the diet,excess body weight,smoking, and alcohol consumption.[65][68] Hypertension can also be caused by other diseases, or occur as a side-effect of drugs.[69]
Blood pressure is expressed by two measurements, thesystolic anddiastolic pressures, which are the maximum and minimum pressures, respectively.[65] Normal blood pressure when at rest is within the range of 100–140millimeters mercury (mmHg) systolic and 60–90 mmHg diastolic.[70] High blood pressure is present if the resting blood pressure is persistently at or above 140/90 mmHg for most adults.[68] Different numbers apply to children.[71] When diagnosing high blood pressure,ambulatory blood pressure monitoring over a 24-hour period appears to be more accurate than "in-office"blood pressure measurement at a physician's office or other blood pressure screening location.[64][68][72]
Lifestyle changes and medications can lower blood pressure and decrease the risk of health complications.[73] Lifestyle changes include weight loss, decreased salt intake, physical exercise, and a healthy diet.[68] If changes in lifestyle are insufficient,blood pressure medications may be used.[73] A regimen of up to three medications effectively controls blood pressure in 90% of people.[68] The treatment of moderate to severe high arterial blood pressure (defined as >160/100 mmHg) with medication is associated with an improvedlife expectancy and reducedmorbidity.[74] The effect of treatment for blood pressure between 140/90 mmHg and 160/100 mmHg is less clear, with some studies finding benefits[75][76] while others do not.[77] High blood pressure affects between 16% and 37% of the population globally.[68] In 2010, hypertension was believed to have been a factor in 18% (9.4 million) deaths.[78]
Essential hypertension is the form ofhypertension that by definition has no identifiable cause. It is the most common type of hypertension, affecting 95% of hypertensive patients,[79][80][81][82] it tends to be familial and is likely to be the consequence of an interaction betweenenvironmental andgenetic factors.Prevalence of essential hypertension increases withage, and individuals with relatively high blood pressure at younger ages are at increased risk for the subsequent development of hypertension.Hypertension can increase the risk ofcerebral,cardiac, andrenal events.[83]
A congenital heart defect, also known as a "congenital heart anomaly" or "congenital heart disease", is a problem in the structure of the heart that is present atbirth.[101] Signs and symptoms depend on the specific type of problem.[102] Symptoms can vary from none to life-threatening.[101] When present they may include rapid breathing,bluish skin, poor weight gain, and feeling tired.[103] It does not cause chest pain.[103] Most congenital heart problems do not occur with other diseases.[102] Complications that can result from heart defects includeheart failure.[103]
The cause of a congenital heart defect is often unknown.[104] Certain cases may be due to infections duringpregnancy such asrubella, use of certain medications or drugs such asalcohol ortobacco, parents being closely related, or poor nutritional status orobesity in the mother.[102][105] Having a parent with a congenital heart defect is also a risk factor.[106] A number of genetic conditions are associated with heart defects includingDown syndrome,Turner syndrome, andMarfan syndrome.[102] Congenital heart defects are divided into two main groups:cyanotic heart defects andnon-cyanotic heart defects, depending on whether the child has the potential to turn bluish in color.[102] The problems may involve the interior walls of the heart, theheart valves, or the large blood vessels that lead to and from the heart.[101]
Heart defects are the most commonbirth defect.[102][108] In 2013 they were present in 34.3 million people globally.[108] They affect between 4 and 75 per 1,000 live births depending upon how they are diagnosed.[102][106] About 6 to 19 per 1,000 cause a moderate to severe degree of problems.[106] Congenital heart defects are the leading cause of birth defect-related deaths.[102] In 2013 they resulted in 323,000 deaths down from 366,000 deaths in 1990.[28]
Tetralogy of Fallot is the most common congenital heart disease arising in 1–3 cases per 1,000 births. The cause of this defect is aventricular septal defect (VSD) and anoverriding aorta. These two defects combined causes deoxygenated blood to bypass the lungs and going right back into the circulatory system. Themodified Blalock-Taussig shunt is usually used to fix the circulation. This procedure is done by placing a graft between the subclavian artery and the ipsilateral pulmonary artery to restore the correct blood flow.
Pulmonary atresia happens in 7–8 per 100,000 births and is characterized by the aorta branching out of the right ventricle. This causes the deoxygenated blood to bypass the lungs and enter the circulatory system. Surgeries can fix this by redirecting the aorta and fixing the right ventricle and pulmonary artery connection.
Pulmonary atresia with an intact ventricular septum: This type of pulmonary atresia is associated with complete and intactseptum between the ventricles.[110]
Pulmonary atresia with a ventricular septal defect: This type of pulmonary atresia happens when a ventricular septal defect allows blood to flow into and out of the right ventricle.[110]
Double outlet right ventricle (DORV) is when both great arteries, the pulmonary artery and the aorta, are connected to the right ventricle. There is usually a VSD in different particular places depending on the variations of DORV, typically 50% are subaortic and 30%. The surgeries that can be done to fix this defect can vary due to the different physiology and blood flow in the defected heart. One way it can be cured is by a VSD closure and placing conduits to restart the blood flow between the left ventricle and the aorta and between the right ventricle and the pulmonary artery. Another way is systemic-to-pulmonary artery shunt in cases associated withpulmonary stenosis. Also, aballoon atrial septostomy can be done to relieve hypoxemia caused by DORV with the Taussig-Bing anomaly while surgical correction is awaited.[111]
There are two different types oftransposition of the great arteries,Dextro-transposition of the great arteries andLevo-transposition of the great arteries, depending on where the chambers and vessels connect. Dextro-transposition happens in about 1 in 4,000 newborns and is when the right ventricle pumps blood into the aorta and deoxygenated blood enters the bloodstream. The temporary procedure is to create anatrial septal defect. A permanent fix is more complicated and involves redirecting the pulmonary return to the right atrium and the systemic return to the left atrium, which is known as theSenning procedure. TheRastelli procedure can also be done by rerouting the left ventricular outflow, dividing the pulmonary trunk, and placing a conduit in between the right ventricle and pulmonary trunk. Levo-transposition happens in about 1 in 13,000 newborns and is characterized by the left ventricle pumping blood into the lungs and the right ventricle pumping the blood into the aorta. This may not produce problems at the beginning, but will eventually due to the different pressures each ventricle uses to pump blood. Switching the left ventricle to be the systemic ventricle and the right ventricle to pump blood into the pulmonary artery can repair levo-transposition.[citation needed]
Persistent truncus arteriosus is when thetruncus arteriosus fails to split into the aorta and pulmonary trunk. This occurs in about 1 in 11,000 live births and allows both oxygenated and deoxygenated blood into the body. The repair consists of a VSD closure and the Rastelli procedure.[112][113]
Ebstein's anomaly is characterized by a right atrium that is significantly enlarged and a heart that is shaped like a box. This is very rare and happens in less than 1% of congenital heart disease cases. The surgical repair varies depending on the severity of the disease.[114]
Pediatric cardiology is a sub-specialty ofpediatrics. To become a pediatric cardiologist in the U.S., one must complete a three-year residency in pediatrics, followed by a three-year fellowship in pediatric cardiology. Perdoximity, pediatric cardiologists make an average of $303,917 in the U.S.[5]
Cardiology is known forrandomized controlled trials that guide clinical treatment of cardiac diseases. While dozens are published every year, there are landmark trials that shift treatment significantly. Trials often have an acronym of the trial name, and this acronym is used to reference the trial and its results. Some of these landmark trials include:
V-HeFT (1986) — use of vasodilators (hydralazine and isosorbide dinitrate) in heart failure
ISIS-2 (1988) — use of aspirin in myocardial infarction
CASE I (1991) — use ofantiarrhythmic agents after a heart attack increases mortality
Werner Forssmann (1904–1979), who infamously performed the first human catheterization on himself that led to him being let go fromBerliner Charité Hospital, quitting cardiology as a speciality, and then winning the 1956Nobel Prize in Physiology or Medicine ("for their discoveries concerning heart catheterization and pathological changes in the circulatory system")
^According to the University of California, San Francisco, a comprehensive cardiac examination involves these three critical steps: inspection, palpation, and auscultation. This process helps in evaluating the heart's condition by first observing for visible signs, then feeling for abnormalities, and finally listening to the heart sounds.
^Similarly, Chamberlain University outlines that the cardiac examination starts with inspection to identify any visual anomalies, followed by palpation to assess physical findings such as thrills or heaves, and concludes with auscultation to detect any abnormal heart sounds like murmurs or gallops.
^Desai, CS; Blumenthal, RS; Greenland, P (April 2014). "Screening low-risk individuals for coronary artery disease".Current Atherosclerosis Reports.16 (4): 402.doi:10.1007/s11883-014-0402-8.PMID24522859.S2CID39392260.
^Boden, WE; Franklin, B; Berra, K; Haskell, WL; Calfas, KJ; Zimmerman, FH; Wenger, NK (October 2014). "Exercise as a therapeutic intervention in patients with stable ischemic heart disease: an underfilled prescription".The American Journal of Medicine.127 (10):905–11.doi:10.1016/j.amjmed.2014.05.007.PMID24844736.
^abCenters for Disease Control and Prevention, (CDC) (14 October 2011). "Prevalence of coronary heart disease—United States, 2006–2010".MMWR. Morbidity and Mortality Weekly Report.60 (40):1377–81.PMID21993341.
^Schenone AL, Cohen A, Patarroyo G, Harper L, Wang X, Shishehbor MH, Menon V, Duggal A (November 2016). "Therapeutic hypothermia after cardiac arrest: A systematic review/meta-analysis exploring the impact of expanded criteria and targeted temperature".Resuscitation.108:102–110.doi:10.1016/j.resuscitation.2016.07.238.PMID27521472.
^Lackland, DT; Weber, MA (May 2015). "Global burden of cardiovascular disease and stroke: hypertension at the core".The Canadian Journal of Cardiology.31 (5):569–71.doi:10.1016/j.cjca.2015.01.009.PMID25795106.
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