Here are definitions for some of the medical terms that you may encounter while you're reading about your heart or meeting with your cardiologist or cardiac surgeon.
Ablation: A procedure used to treat an abnormality in the heart's rhythm. Either high-frequency radio waves (radiofrequency ablation) or extreme cold (cryoablation) are used to destroy the damaged portion of your heart's electrical system. "Ablation" comes from Latin words meaning "take away from" or "remove," and "cryo" comes from a Greek word meaning "frost." See also "Cardiac conduction system."
Aneurysm: A bulge in the wall of a blood vessel. "Aneurysm" comes from a Greek word meaning "to widen out."
Angina: Chest pain—or a sensation of discomfort in the chest—due to an insufficient supply of blood to the heart. Officially known as "angina pectoris," from Latin words meaning "strangle the chest," it is most often the result of a narrowing of the arteries that supply the heart with blood (a condition known as coronary artery disease or coronary heart disease). Regardless of its cause, the presence of angina indicates that your heart's demand for oxygen isn't being fulfilled by your arteries' ability to supply it with oxygenated blood. See also "Coronary artery" and "Coronary artery disease."
Angiography: A diagnostic test that uses opaque dye and X-rays to create an image of your cardiovascular system; also called "cardiac catheterization."
Anticoagulant: Any of several cardiac medications used to retard the formation of blood clots (clotting is known as "coagulation"). Anticoagulants are sometimes popularly referred to as "blood thinners," but they don't actually thin the blood. They may be used to help prevent a heart attack, stroke or pulmonary embolism. See also "Embolism."
Antiplatelet: Any of several cardiac medications that keep platelets from sticking together, thus retarding the formation of blood clots. They may be used to help prevent a heart attack, stroke or pulmonary embolism. See also "Embolism" and "Platelet."
Aorta: The body's main artery, which supplies oxygen-rich blood from your heart to every part of your circulatory system. The aorta is about three feet long and an inch in diameter and has three parts: the ascending aorta, which extends upward from your heart's left ventricle to the aortic arch; the arch, which curves up and over the top of your heart; and the descending aorta, which extends from your aortic arch down through your chest and abdomen. The aorta is also classified into the thoracic aorta (the parts in your chest—the ascending aorta, the aortic arch, and the part of the descending aorta above your diaphragm) and the abdominal aorta (the part of the descending aorta below your diaphragm).
Aortic valve: One of your heart's four valves. A valve is several little flaps of tissue that open and close each time your heart beats, ensuring that the blood flows in the correct direction. The aortic valve, which controls the flow of blood from your heart's left ventricle into your aorta, normally has three triangular-shaped flaps.
Arrhythmia: A disturbance of the heart's rhythm due to an abnormality in the heart's electrical system. There are various kinds of arrhythmias; some make your heart beat too fast, some make it beat too slow, and some make it beat in an irregular rhythm.
Artery: A vessel that transports blood away from your heart, either to your lungs, where it's reoxygenated, or out to your body, where it supplies your cells' need for oxygen and other nutrients. Arteries range in size from your aorta, which is an inch in diameter, down to your capillaries, which are finer than a human hair (see also "Aorta" and "Capillary").
Atherosclerosis: A progressive buildup of plaque—or deposits of cholesterol, inflammatory cells and other substances—on the inner walls of your arteries. The buildup occurs over a period of years or even decades and results in a narrowing of the arteries, reducing their ability to carry blood. Atherosclerosis also leads to a loss of the arteries' ability to dilate, or expand, in response to exercise; this process is sometimes called "hardening of the arteries."
Atrial fibrillation: One of the most common disturbances of the heart's rhythm (see also "Arrhythmia"). Often referred to as AFib, it's an irregular rhythm; the term "fibrillation" means rapid, quivering, uncoordinated movement.
Atrium: One of your heart's two upper chambers (also known as an "auricle"), a hollow space through which blood flows. "Atrium" comes from a Latin word meaning "entryway"—just like the atrium of a hotel; this is a reference to the fact that on each circuit through your body, your blood enters your heart via the atriums. (The plural of atrium can be spelled either "atriums," following English rules, or "atria," following Latin rules.)
Auricle: See "Atrium."
Beta blocker: Any of several cardiac medications that block receptors associated with increasing the heart's activity. They may be used to control the heart's rhythm or treat angina or hypertension; see also "Arrhythmia," "Angina" and "Hypertension."
Bicuspid: A term applied to heart valves that means the valve has two cusps, or flaps. The term is used in two distinct ways: Most commonly, it describes a congenital heart condition known as "bicuspid aortic valve," meaning the aortic valve, which normally has three flaps, has only two (see also "Congenital heart condition" and "Aortic valve"). Less often, it may be used as an alternate way of referring to the mitral valve, since that valve normally has only two flaps (see also "Mitral valve").
Blood pressure: A determination of the force with which your blood pushes against the walls of your blood vessels—measured in a unit known as millimeters of mercury, abbreviated as mmHg. Blood pressure is measured during both the systolic and the diastolic phases of a heartbeat (see also "Systole" and "Diastole"); this is why your blood pressure is given as two numbers—systolic pressure (the higher number, during the pumping phase) over diastolic pressure (the lower number, during the relaxation phase). A normal resting blood pressure for a healthy adult should be below 120/80 mmHg.
Blood thinner: See "Anticoagulant."
Calcification: A process your body uses to repair damaged tissue in your cardiovascular system. The process results in hardening of the tissue, such as a heart valve or a blood vessel, due to the abnormal deposit of calcium salts.
Capillary: One of the body's tiniest blood vessels. "Capillary" comes from a Latin word meaning "hair," but in fact the smallest capillaries are even finer than a human hair. Capillaries have very thin walls so the oxygen and nutrients in arterial blood can pass into the other cells of your body; at the same time, carbon dioxide and other waste products pass from the cells into the capillaries, so they can be returned to your lungs via your body's veins and exhaled. It is within the capillaries where your arteries connect to your veins.
Cardiac: Having to do with the heart; the term comes from a Greek word meaning "heart or upper opening of the stomach."
Cardiac catheterization: See "Angiography."
Cardiac conduction system: The heart's electrical system, which transmits the electrical impulses that control the complicated and coordinated series of actions that make up each heartbeat.
Cardiomyopathy: A disease of the heart muscle that causes it to either fail to contract during the systole phase or to relax during the diastole phase. The result is abnormal thickening or thinning, and often enlargement, of the heart muscle. See also "Systole" and "Diastole."
Cardiovascular system: The bodily system responsible for circulating blood and lymph (a fluid containing white blood cells) throughout your body. It encompasses your heart, blood vessels, and blood, as well as your lymphatic system.
CAT scan: Computerized axial tomography, a diagnostic test that uses computer processing to combine numerous x-ray images, each of them a "slice" taken from a slightly different angle, in order to create a virtual three-dimensional image of an internal organ; also referred to as a "CT scan."
Catheter: A long, thin tube that is inserted into a bodily cavity, such as a blood vessel. In cardiac medicine, catheters may be used for diagnostic purposes—such as in cardiac catheterization, also known as "angiography" (see also "Angiography")—or to perform minimally invasive procedures—such as transcatheter aortic valve replacement (TAVR).
Circulatory system: See "Cardiovascular system."
Coagulation: The process by which blood clots, or changes from a fluid to a solid state. Clotting is beneficial, indeed essential, when it occurs in an external wound. But when it occurs inside the body's cardiovascular system, often as a result of atherosclerosis, it can be highly detrimental and may result in a heart attack, stroke, or pulmonary embolism. See also "Atherosclerosis," "Cardiovascular system" and "Embolism."
Congenital heart defect: A structural abnormality in the heart that has been present since birth.
Congestive heart failure: A condition (also called just "heart failure") in which your heart is unable to pump enough blood to supply your body's needs. It means your heart is working harder than it should but is still not keeping up with your body's demands. The reason it's called congestive heart failure is that it often results in a buildup of fluid—or congestion—in your lungs and other bodily tissues.
Coronary artery: An artery that supplies blood to the heart itself. The left coronary artery and right coronary artery branch off the aorta and run along the surface of the heart, then branch out further into smaller arteries that penetrate the heart to supply it with oxygen and nutrients.
Coronary artery bypass graft: Surgery to establish a new pathway so blood can flow around a blockage in one or more of the coronary arteries. The procedure is also referred to as a CABG, pronounced like "cabbage," or simply as bypass surgery. See also "Coronary artery" and "Graft."
Coronary artery disease: A condition in which the arteries that supply your heart itself with blood have become narrowed due to atherosclerosis and so are unable to keep up with the heart's demands; also referred to as "coronary heart disease." (See also "Atherosclerosis.")
Coumadin: The brand-name version of an anticoagulant known generically as "warfarin"; see "Anticoagulant" and "Warfarin."
Cryoablation: See "Ablation."
CT scan: See "CAT scan."
Cusp: One of the little flaps of tissue that make up your heart's valves ("cusp" comes from a Latin word meaning "point," since most of the valves have triangular-shaped flaps), also sometimes referred to as a "leaflet." See also "Valve."
Cyanosis: A bluish tinge to the skin, lips and fingernails caused by incomplete oxygenation of the blood.
Diaphragm: The wall of muscular tissue that separates your thorax, or chest, from your abdomen.
Diastole: One of two primary phases in your heart's pumping action. The diastolic phase is when the muscle of your heart relaxes and the atriums fill with blood ("diastole" comes from Greek words meaning "to place apart"). See also "Systole."
Dissection: A split, tear, or weakened area in the lining of a blood vessel. ("Dissection" comes from a Latin word meaning "to cut apart.")
Diuretic: Any of several medications that increase the body's output of urine. They may be used to treat edema. See also "Edema."
Dyspnea: Shortness of breath or difficulty breathing.
Echocardiography: A diagnostic test that uses ultrasound waves to record the action of your heart.
Edema: A buildup of excess fluid in the body's tissues and cavities.
Electrical system: See "Cardiac conduction system."
Electrocardiography: A diagnostic test that measures and records your heart's electrical activity; often referred to as either EKG or ECG.
Embolism: An obstruction in an artery or vein, typically caused by a mobile blood clot that has become stuck at a particular point in the cardiovascular system.
Endocarditis: An infection of the valves of the heart.
Endocardium: The innermost of the three layers of tissue that make up the heart. It is a thin, smooth membrane that lines all four chambers of the heart and the surfaces of the valves between the chambers ("endo" comes from a Latin word meaning "within," and "cardium" comes from a Greek word meaning "heart").
Endoscope: A flexible device with a camera on its tip that is inserted into the body through a tiny incision, allowing a surgeon to operate using long, thin surgical instruments inserted through another tiny incision.
Endovascular surgery: A minimally invasive procedure that involves making a couple of tiny incisions in blood vessels in your groin; inserting long, thin tubes known as a catheters through the vessels; and then using X-ray guidance and long, thin instruments threaded through the catheters to perform the procedure. (The term "endovascular" comes from Greek and Latin words meaning "within a vessel.")
Epicardium: The outermost of the three layers of tissue that make up the heart. It is a smooth, transparent membrane ("epi" comes from a Latin word meaning "above").
Graft: The transplantation of living tissue from one place to another—in the case of a coronary artery bypass graft, of blood vessels from another part of your body to your coronary arteries. See also "Coronary artery bypass graft."
Great vessels: A term that encompasses the body's largest veins and arteries, which connect the heart to the rest of your circulatory system, including the aorta and the vena cavae (see also "Aorta" and "Vena cava").
Holter monitor: A portable device that records your heart's electrical activity over the course of 24 to 48 hours.
Hyperlipidemia: Higher than normal levels of fats, also known as lipids or lipoproteins, in your blood. It can lead to the development of atherosclerosis (see also "Atherosclerosis").
Hypertension: Higher than normal blood pressure (see also "Blood pressure").
Hypotension: Lower than normal blood pressure (see also "Blood pressure").
Inflammation: A condition in which a part of the body becomes swollen, red, hot, and often painful, usually as a reaction to infection or injury.
Ischemia: An inadequate supply of blood to a part of the body ("ischemia" comes from a Latin word meaning "stopping blood"). Cardiac ischemia, or a poor supply of blood to the heart, can have effects ranging from angina to sudden cardiac death (see also "Angina" and "Sudden cardiac death").
Leaflet: One of the little flaps of tissue that make up your heart's valves, also sometimes referred to as a "cusp." See also "Valve."
Maze procedure: An operation to treat an abnormality in the heart's rhythm. It involves making tiny cuts known as lesions on the surface of your atriums—in a pattern like a little maze, hence the procedure's name; the lesions disrupt the uncoordinated electrical signals causing the arrhythmia. See also "Atrium" and "Arrhythmia."
Mitral valve: One of your heart's four valves. A valve is several little flaps of tissue that open and close each time your heart beats, ensuring that the blood flows in the correct direction. The mitral valve controls the flow of blood from your left atrium into your left ventricle; it has two flaps—a C-shaped strip, known as the posterior leaflet, and a semicircle that fits into the open side of the C, known as the anterior leaflet.
MRI: Magnetic resonance imaging, a diagnostic test that uses the response of your body's tissues to a strong magnetic field to create an image of your internal organs.
Murmur: A "swooshing" sound in your heart that is perceptible through a stethoscope; congenital heart defects and valvular defects are among the conditions that can cause a murmur.
Myocardial infarction: The medical term for what is commonly called a heart attack, or a blockage in the flow of blood to the heart, caused by a blood clot that lodges in one of the coronary arteries ("myocardial" refers to the "myocardium," the muscular tissue of the heart, and "infarction" means "obstruction"). See also "Myocardium" and "Coronary artery."
Myocarditis: An inflammation of the heart muscle.
Myocardium: The middle layer of the three layers of tissue that make up the heart. The thickest of the layers, it is responsible for the heart's pumping action ("myo" comes from a Latin word meaning "muscle").
Palpitation: A fluttering sensation in your heart.
Pericardium: The tough sac in which your heart is encased ("peri" comes from a Latin word meaning "around"). It also contains a small amount of lubricating fluid.
Plaque: Deposits of cholesterol, inflammatory cells and other substances on the inner walls of your blood vessels; see also "Atherosclerosis."
Platelet: A component of blood that is involved in the clotting process.
Prolapse: Slippage out of place of an internal structure of the body ("prolapse" comes from Latin words meaning "to fall out"). A misalignment in the flaps of the heart's valves may be referred to as a prolapse and can result in regurgitation (see also "Valve" and "Regurgitation").
Pulmonary: Having to do with the lungs; it comes from a Latin word meaning "lung."
Pulmonary valve: One of your heart's four valves. A valve is several little flaps of tissue that open and close each time your heart beats, ensuring that the blood flows in the correct direction. The pulmonary valve, which controls the flow of blood from your right ventricle into your pulmonary artery, toward your lungs, normally has three triangular-shaped flaps.
Pulse: A measure of how fast your heart beats; a normal resting pulse for a healthy adult averages about 72 beats per minute and can range between 60 and 100 beats per minute.
Pulse oximetry: A diagnostic test that measures how well oxygenated your blood is.
Radiofrequency ablation: See "Ablation."
Regurgitation: A flow of fluid in an abnormal direction ("regurgitation" comes from Latin words meaning "to engulf again"). When it affects one of the heart's valves, regurgitation means the flaps of the valve are floppy or won't close completely, so the valve is leaky; this allows some blood to flow backward from its normal course through the heart. It is sometimes also referred to as "insufficiency."
Resection: The surgical removal of tissue.
Revascularization: Re-establishment of an adequate flow of blood to a part of the body that has suffered from a poor blood supply.
Septal defect: A kind of congenital heart defect characterized by a hole in the wall that separates the left side of your heart from the right side. See also "Congenital heart defect" and "Septum."
Septum: The wall of tissue that divides the atrium and ventricle on your heart's left side from the atrium and ventricle on the right side. "Septum" comes from a Latin word meaning "enclosure."
Sign: An indication of a disease that can be detected by a doctor, such as the results of a blood test or an X-ray.
Statin: Any of several cardiac medications that reduce the levels of fats in the blood. They may be used to treat hyperlipidemia (see also "Hyperlipidemia").
Stenosis: A narrowing of a passageway in the body ("stenosis" comes from a Greek word meaning "narrow"). When it affects one of the heart's valves, stenosis means the flaps of the valve are thickened, stiff or stuck together and are thus unable to open completely; this partially blocks the flow of blood.
Stent: A little mesh tube placed in a blood vessel to reopen a vessel blocked by atherosclerosis (see also "Atherosclerosis").
Sudden cardiac arrest: Sudden cessation of the heart's function, usually caused by ischemia in the coronary arteries and often resulting in sudden cardiac death. See also "Sudden cardiac death," "Coronary artery" and "Ischemia."
Sudden cardiac death: Sudden death due to cessation of the heart's function (which is known as "sudden cardiac arrest"), usually caused by ischemia in the coronary arteries. See also "Sudden cardiac arrest," "Coronary artery" and "Ischemia."
Symptom: An indication of a disease that can be detected by the patient, such as pain or fatigue.
Systole: One of two primary phases in your heart's pumping action. The systolic phase is when the heart contracts and pumps ("systole" comes from Greek words meaning "to place pressure" or "to contract"). See also "Diastole."
Thoracic: Having to do with the thorax, the part of your body between your neck and your abdomen (often referred to as the chest).
Transesophageal echocardiogram: An ultrasound image of your heart that is obtained by passing a thin tube down your throat and into your esophagus (see also "Echocardiogram").
Tricuspid valve: One of your heart's four valves. A valve is several little flaps of tissue that open and close each time your heart beats, ensuring that the blood flows in the correct direction. The tricuspid valve, which controls the flow of blood from your right atrium into your right ventricle, normally has three triangular-shaped flaps.
Valve: Several little flaps of tissue that open and close each time your heart beats, ensuring that the blood flows in the correct direction. The flaps may also be referred to as "cusps" or "leaflets." Your heart has four valves: aortic, mitral, pulmonary and tricuspid.
Valvular: Having to do with your heart's valves (see "Valve").
Vasodilator: Any of several cardiac medications that relax the blood vessels, thus improving the flow of blood. They may be used to treat angina or atherosclerosis (see also "Angina" and "Atherosclerosis").
Vascular: Having to do with your blood vessels (see "Vessel").
Vein: A vessel that transports blood back to your heart, either from your lungs, where it's been reoxygenated, or from your body, where it has supplied your cells' need for oxygen and other nutrients. Veins range in size from the vena cavae, which return oxygen-depleted blood to your heart's right atrium, down to your capillaries, which are finer than a human hair (see also "Capillary" and "Vena cava").
Vena cava: One of your body's two largest veins ("vena cava" comes from Latin words meaning "hollow vein"); the plural form of the term is "vena cavae," following Latin rules. The vena cavae return oxygen-depleted blood back to your heart's right atrium—the superior vena cava from the upper part of your body, and the inferior vena cava from the lower part of your body.
Ventricle: One of your heart's two lower chambers, a hollow space through which blood flows. "Ventricle" comes from a Latin word meaning "belly," a reference to the fact that it's the lower chamber on each side.
Vessel: A hollow, tubular structure—such as the tubes through which blood flows. Blood vessels fall into two basic types—arteries, which transport blood away from your heart, and veins, which carry blood back your heart (see also "Arteries" and "Veins")—and range in size from the so-called "great vessels" that connect your heart to the rest of your circulatory system down to your capillaries, which are finer than a human hair.
Warfarin: An anticoagulant medication. See also "Anticoagulant" and "Coumadin."