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. coronary circulation main article: coronary circulation coronary circulation is the circulation of blood in the blood vessels of the heart 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 the great cardiac vein, the middle cardiac vein, the small cardiac vein and the anterior 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 by atherosclerosis and can become blocked, causing angina 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. cardiac examination main article: cardiac examination the cardiac examination (also called the "precordial exam"), is performed as part of a physical examination, or when a patient presents with chest pain suggestive of a cardiovascular pathology. it would typically be modified depending on the indication and integrated with other examinations especially the respiratory examination. like all medical examinations, the cardiac examination follows the standard structure of inspection, palpation and auscultation. heart disorders main article: list of heart disorders 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 main article: coronary artery disease coronary artery disease, also known as "ischemic heart disease", is a group of diseases that includes: stable angina, unstable angina, myocardial infarction, and is one of the causes of sudden cardiac death. it is within the group of cardiovascular diseases of which it is the most common type. a common symptom is chest pain or discomfort which may travel into the shoulder, arm, back, neck, or jaw. occasionally it may feel like heartburn. usually symptoms occur with exercise or emotional stress, last less than a few minutes, and get better with rest. shortness of breath may also occur and sometimes no symptoms are present. the first sign is occasionally a heart attack. other complications include heart failure or an irregular heartbeat. risk factors include: high blood pressure, smoking, diabetes, lack of exercise, obesity, high blood cholesterol, poor diet, and excessive alcohol, among others. other risks include depression. the underlying mechanism involves atherosclerosis of the arteries of the heart. a number of tests may help with diagnoses including: electrocardiogram, cardiac stress testing, coronary computed tomographic angiography, and coronary angiogram, among others. prevention is by eating a healthy diet, regular exercise, maintaining a healthy weight and not smoking. sometimes medication for diabetes, high cholesterol, or high blood pressure are also used. there is limited evidence for screening people who are at low risk and do not have symptoms. treatment involves the same measures as prevention. additional medications such as antiplatelets including aspirin, beta blockers, or nitroglycerin may be recommended. procedures such as percutaneous coronary intervention (pci) or coronary artery bypass surgery (cabg) may be used in severe disease. in those with stable cad it is unclear if pci or cabg in addition to the other treatments improve life expectancy or decreases heart attack risk. in 2013 cad was the most common cause of death globally, resulting in 8.14 million deaths (16.8%) up from 5.74 million deaths (12%) in 1990. the risk of death from cad for a given age has decreased between 1980 and 2010 especially in developed countries. the number of cases of cad for a given age has also decreased between 1990 and 2010. 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. rates are higher among men than women of a given age. cardiomyopathy main article: cardiomyopathy heart failure or formally cardiomyopathy, is the impaired function of the heart and there are numerous causes and forms of heart failure. cardiac arrhythmia main article: arrhythmia cardiac arrhythmia, also known as "cardiac dysrhythmia" or "irregular heartbeat", is a group of conditions in which the heartbeat is too fast, too slow, or irregular in its rhythm. a heart rate that is too fast – above 100 beats per minute in adults – is called tachycardia. a heart rate that is too slow – below 60 beats per minute – is called bradycardia. many types of arrhythmia present no symptoms. when symptoms are present, they may include palpitations, or feeling a pause between heartbeats. more serious symptoms may include lightheadedness, passing out, shortness of breath, or chest pain. while most types of arrhythmia are not serious, some predispose a person to complications such as stroke or heart failure. others may result in cardiac arrest. there are four main types of arrhythmia: extra beats, supraventricular tachycardias, ventricular arrhythmias, and bradyarrhythmias. extra beats include premature atrial contractions, premature ventricular contractions, and premature junctional contractions. supraventricular tachycardias include atrial fibrillation, atrial flutter, and paroxysmal supraventricular tachycardia. ventricular arrhythmias include ventricular fibrillation and ventricular tachycardia. arrhythmias are due to problems with the electrical conduction system of the heart. arrhythmias may occur in children; however, the normal range for the heart rate is different and depends on age. a number of tests can help diagnose arrhythmia, including an electrocardiogram and holter monitor. most arrhythmias can be effectively treated. treatments may include medications, medical procedures such as a pacemaker, and surgery. medications for a fast heart rate may include beta blockers or agents that attempt to restore a normal heart rhythm such as procainamide. 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 with blood 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 of cardioversion or defibrillation. arrhythmia affects millions of people. in europe and north america, as of 2014, atrial fibrillation affects about 2% to 3% of the population. atrial fibrillation and atrial flutter resulted in 112,000 deaths in 2013, up from 29,000 in 1990. sudden cardiac death is the cause of about half of deaths due to cardiovascular disease or about 15% of all deaths globally. about 80% of sudden cardiac death is the result of ventricular arrhythmias. arrhythmias may occur at any age but are more common among older people. cardiac arrest main article: cardiac arrest cardiac arrest is a sudden stop in effective blood flow due to the failure of the heart to contract effectively. symptoms include loss of consciousness and abnormal or absent breathing. some people may have chest pain, shortness of breath, or nausea before this occurs. if not treated within minutes, death usually occurs. the most common cause of cardiac arrest is coronary artery disease. less common causes include major blood loss, lack of oxygen, very low potassium, heart failure, and intense physical exercise. a number of inherited disorders may also increase the risk including long qt syndrome. the initial heart rhythm is most often ventricular fibrillation. the diagnosis is confirmed by finding no pulse. while a cardiac arrest may be caused by heart attack or heart failure these are not the same. prevention includes not smoking, physical activity, and maintaining a healthy weight. treatment for cardiac arrest is immediate cardiopulmonary resuscitation (cpr) and, if a shockable rhythm is present, defibrillation. among those who survive targeted temperature management may improve outcomes. an implantable cardiac defibrillator may be placed to reduce the chance of death from recurrence. in the united states, cardiac arrest outside of hospital occurs in about 13 per 10,000 people per year (326,000 cases). in hospital cardiac arrest occurs in an additional 209,000 cardiac arrest becomes more common with age. it affects males more often than females. the percentage of people who survive with treatment is about 8%. many who survive have significant disability. many u.s. television shows, however, have portrayed unrealistically high survival rates of 67%. hypertension main article: hypertension hypertension, also known as "high blood pressure", is a long term medical condition in which the blood pressure in the arteries is persistently elevated. high blood pressure usually does not cause symptoms. long term high blood pressure, however, is a major risk factor for coronary artery disease, stroke, heart failure, peripheral vascular disease, vision loss, and chronic kidney disease. lifestyle factors can increase the risk of hypertension. these include excess salt in the diet, excess body weight, smoking, and alcohol consumption. hypertension can also be caused by other diseases, or occur as a side-effect of drugs. blood pressure is expressed by two measurements, the systolic and diastolic pressures, which are the maximum and minimum pressures, respectively. normal blood pressure when at rest is within the range of 100–140 millimeters mercury (mmhg) systolic and 60–90 mmhg diastolic. high blood pressure is present if the resting blood pressure is persistently at or above 140/90 mmhg for most adults. different numbers apply to children. 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. lifestyle changes and medications can lower blood pressure and decrease the risk of health complications. lifestyle changes include weight loss, decreased salt intake, physical exercise, and a healthy diet. if changes in lifestyle are insufficient, blood pressure medications may be used. a regimen of up to three medications effectively controls blood pressure in 90% of people. the treatment of moderate to severe high arterial blood pressure (defined as >160/100 mmhg) with medication is associated with an improved life expectancy and reduced morbidity. the effect of treatment for blood pressure between 140/90 mmhg and 160/100 mmhg is less clear, with some studies finding benefits while others do not. high blood pressure affects between 16% and 37% of the population globally. in 2010, hypertension was believed to have been a factor in 18% (9.4 million) deaths. essential vs secondary hypertension main articles: essential hypertension and secondary hypertension essential hypertension is the form of hypertension that by definition has no identifiable cause. it is the most common type of hypertension, affecting 95% of hypertensive patients, it tends to be familial and is likely to be the consequence of an interaction between environmental and genetic factors. prevalence of essential hypertension increases with age, 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 of cerebral, cardiac, and renal events. secondary hypertension is a type of hypertension which is caused by an identifiable underlying secondary cause. it is much less common than essential hypertension, affecting only 5% of hypertensive patients. it has many different causes including endocrine diseases, kidney diseases, and tumors. it also can be a side effect of many medications. complications of hypertension main complications of persistent high blood pressure main article: complications of hypertension complications of hypertension are clinical outcomes that result from persistent elevation of blood pressure. hypertension is a risk factor for all clinical manifestations of atherosclerosis since it is a risk factor for atherosclerosis itself.it is an independent predisposing factor for heart failure, coronary artery disease, stroke, renal disease, and