Glossary of Terms

This glossary of terms has been compiled for your reference. Select the first letter of the word you’re searching for to begin.

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z All

“Strep” Infection (Streptococcal Infection)

An infection, usually in the throat, resulting from streptococcus bacteria.


A group of therapeutic methods that physically destroy the cardiac tissue that causes or contributes to some types of tachycardia (fast heartbeat). May be done through surgery or using a transcatheter approach with an electrode catheter.


A substance produced in humans that helps protect against ischemia (lack of blood flow). It’s produced in blood vessels, heart and skeletal muscle, and other organs.


A ballooning-out of the wall of an artery, a vein or the heart due to weakening of the wall by disease, injury or an abnormality present at birth.


Medical term for chest pain or discomfort due to coronary heart disease. A condition in which the heart muscle doesn’t get enough blood, resulting in chest pain.


An X-ray examination of the blood vessels or chambers of the heart. A special fluid (contrast medium or dye) visible by X-ray is injected into the bloodstream. Tracing the course of this fluid produces X-ray pictures called angiograms.


The creation of blood vessels. The body creates small blood vessels called “collaterals” to help compensate for reduced blood flow.


An X-ray picture of blood vessels or chambers of the heart that shows the course of a special fluid (contrast medium or dye) injected into the bloodstream.


A procedure sometimes used to dilate (widen) narrowed arteries. A catheter with a deflated balloon on its tip is passed into the narrowed artery segment, the balloon inflated, and the narrowed segment widened. Then the balloon is deflated and the catheter is removed.

Angiotensin Converting Enzyme (ACE) Inhibitors

A class of drugs used to treat high blood pressure and heart failure. ACE inhibitors interfere with the body’s production of angiotensin.

Angiotensin II Receptor Blockers

A class of drugs used to treat high blood pressure and heart failure. They block the effects of angiotensin.


A blood-thinning drug used to reduce the risk of clots.


The large artery that receives blood from the heart’s left ventricle and distributes it to the body.

Aortic Stenosis (AS)

A congenital heart defect in which the aortic valve, between the left ventricle and the aorta, is narrowed.

Aortic Valve

The heart valve between the left ventricle and the aorta. It has three flaps (cusps).

Arrhythmia (or Dysrhythmia)

An abnormal rhythm of the heart.


A testing procedure in which a dye visible to X-rays is injected into the bloodstream, then X-ray pictures are taken and studied to see if the arteries are damaged.


Small, muscular branches of arteries. When they contract, they increase resistance to blood flow, and blood pressure in the arteries increases.


Commonly called hardening of the arteries, this includes a variety of conditions that cause artery walls to thicken and lose elasticity. Some hardening of arteries often occurs when people grow older.


One of a series of vessels that carry blood from the heart to the various parts of the body. Arteries have thick, elastic walls that expand as blood flows through them.


A procedure to remove plaque from arteries. An ultra-thin wire is threaded through a special catheter into the blocked artery. Several devices then may be used. One is a high-speed rotating “burr” that grinds the plaque into very tiny pieces. Another is a small rotating cutter that “shaves off” pieces of the blockage. Another is a laser catheter that vaporizes the plaque. (See Laser Angioplasty.)


A form of arteriosclerosis in which the inner layers of artery walls become thick and irregular due to deposits of fat, cholesterol and other substances. This buildup is called “plaque.” As the interior walls of arteries become lined with these deposits, the arteries become narrowed, reducing the blood flow through them.


The heart’s two upper chambers.

Atrial Fibrillation

A disorder in which the heart’s two small, upper chambers quiver instead of beating effectively. Blood that isn’t pumped completely out of the atria when the heart beats may pool and clot. Then a blood clot may enter the bloodstream, become a cerebral embolus and cause an ischemic stroke.

Atrial Septal Defect (ASD)

A congenital heart defect in which an opening exists between the heart’s two upper chambers.

Atrioventricular (AV) Canal Defect (or Atrioventricular Septal Defect)

A congenital heart defect in which a large hole in the center of the heart exists where the wall between the upper chambers joins the wall between the lower chambers. Also, a single large valve crosses the defect.

Atrioventricular (AV) Node

A small mass of specialized conducting tissue at the bottom of the right atrium. The electrical impulse stimulating the heart to contract must pass through this node to reach the ventricles.


Either of the heart’s two upper chambers in which blood collects before being passed to the ventricles.

Bacterial Endocarditis

See Endocarditis.

Balloon Angioplasty

See Angioplasty.

Beta Blocker

A medicine to treat high blood pressure and some other heart conditions by reducing the heart rate and the heart’s output of blood.

Bicuspid Aortic Valve

A congenital heart defect in which the aortic valve has only two flaps (cusps) instead of the normal three.

Blood Clot

A jelly-like mass of blood tissue formed by clotting factors in the blood. Clots stop the flow of blood from an injury. Blood clots also can form inside an artery whose walls are damaged by atherosclerotic buildup, or inside the atria if blood isn’t pumped out completely and pools. Blood clots that block an artery can cause a heart attack or stroke.

Blood Pressure

The force or pressure exerted by the heart in pumping blood; the pressure of blood in the arteries.

Body Mass Index (BMI)

A formula to assess a person’s body weight relative to height. It correlates highly with body fat in most people. Weight in kilograms is divided by height in meters squared (kg/m2).


Slowness of the heart rate (less than 60 beats per minute).

Calcium Antagonists (Calcium Channel Blockers)

A class of drugs used to treat high blood pressure and some other heart conditions. They can slow the heart rate and relax blood vessels.


Microscopically small blood vessels between arteries and veins that distribute oxygenated blood to the body’s tissues.


Pertaining to the heart.

Cardiac Arrest

The stopping of the heartbeat, usually because of interference with the electrical signal (often associated with coronary heart disease).

Cardiac Catheterization

The process of examining the heart by introducing a thin tube (catheter) into a vein or artery and passing it into the heart.

Cardiac Computed Tomography (CT), Computerized Axial Tomographic Scan (CAT scan)

An X-ray imaging technique that provides cross-sectional images of the chest, including the heart and great vessels, or the brain. It’s used to evaluate certain heart diseases and define the areas affected by stroke.

Cardiac Positron Emission Tomography (PET)

A test that lets physicians study and quantify how the heart tissue works. PET combines tomographic imaging with radionuclide tracers and tracer kinetic principles.


The study of the heart and its functions in health and disease.


A serious disease affecting the heart. It involves an inflammation and reduced function in heart muscle. There are multiple causes including viral infections.

Cardiopulmonary Resuscitation (CPR)

A combination of chest compression and mouth-to-mouth breathing. This technique is used during cardiac arrest to keep oxygenated blood flowing to the heart muscle and brain until advanced cardiac life support can be started or an adequate heartbeat resumes.


Pertaining to the heart and blood vessels. (“Cardio” means heart; “vascular” means blood vessels.) The circulatory system of the heart and blood vessels is the cardiovascular system.

Carotid Artery

One type of major artery in the neck carrying blood from the heart to the brain. The other type is vertebral artery.

Carotid Artery Disease (Carotid Artery Stenosis)

A carotid artery narrowed by a buildup of plaque. A type of atherosclerosis. Carotid artery disease is a major risk factor for ischemic stroke.


A fat-like substance found in the blood and produced by the liver. Also found in animal tissue and present only in foods from animal sources such as wholemilk dairy products, meat, fish, poultry, animal fats and egg yolks.


Fatty particles in the blood containing mainly triglycerides, but also cholesterol, phospholipids and protein. They’re made in the intestinal wall as foods are digested.

Circulatory System

Pertaining to the heart, blood vessels and the blood’s circulation.

Coarctation of the Aorta (“Coarct”)

A congenital heart defect in which the aorta is pinched or constricted. This obstructs blood flow to the lower part of the body and increases blood pressure above the constriction.

Collateral Circulation

The process in which a system of small, normally closed arteries opens up and starts to carry blood to part of the heart when a coronary artery is blocked, or to part of the brain when a cerebral artery is blocked. They can serve as alternate routes of blood supply.


Refers to conditions existing at birth.

Congenital Heart and Blood Vessel Defects (Congenital Cardiovascular Defects, Congenital Cardiovascular Disease)

Malformation of the heart or its major blood vessels present at birth.

Congestive Heart Failure

The inability of the heart to pump out all the blood that returns to it. This results in blood backing up in the veins that lead to the heart and sometimes in fluid accumulating in various parts of the body.

Coronary Arteries

Two arteries arising from the aorta that arch down over the top of the heart, branch and provide blood to the heart muscle.

Coronary Artery Disease (CAD)

Conditions that cause narrowing of the coronary arteries, reducing blood flow to the heart muscle. A type of atherosclerosis.

Coronary Bypass Surgery

Surgery that reroutes, or “bypasses,” blood around clogged coronary arteries and improves the supply of blood and oxygen to the heart muscle. It’s sometimes called CABG (for coronary artery bypass graft) or “cabbage.”

Coronary Care Unit (CCU)

A specialized facility in a hospital or emergency mobile unit that’s equipped with monitoring devices and staffed with trained personnel. It’s designed specifically to treat heart patients.

Coronary Heart Disease (CHD)

Disease of the heart caused by atherosclerotic narrowing of the coronary arteries likely to produce angina pectoris or heart attack.

Coronary Occlusion

An obstruction of a coronary artery that hinders blood flow to some part of the heart muscle. A cause of heart attack.

Coronary Thrombosis

Formation of a clot in one of the arteries that conduct blood to the heart muscle. Also called coronary occlusion.

Creatine Kinase (CK)

A blood enzyme. Tests for CK and the fraction CK-MB are used to confirm the existence of heart muscle damage.


Blueness of skin caused by insufficient oxygen in the blood.


An electronic device that helps reestablish normal contraction rhythms in a malfunctioning heart.


The inability of the body to produce or respond properly to insulin. The body needs insulin to convert sugar and starch into the energy needed in daily life. The full name for this condition is diabetes mellitus; defined as a fasting blood glucose of 126 mg/dL or more measured on two occasions.

Diastolic Blood Pressure

The lowest blood pressure measured in the arteries, it occurs when the heart muscle relaxes between beats. In a typical blood pressure reading, such as 120/78, the lower number is diastolic blood pressure.


A drug that increases the rate at which urine forms by promoting the excretion of water and salts. It’s used to treat high blood pressure, congestive heart failure and some congenital heart defects.

Doppler Ultrasound

A test that uses high-frequency sound waves to detect blockages in an artery.


A diagnostic method in which pulses of sound are transmitted into the body. The echoes returning from the surfaces of the heart and other structures are electronically plotted and recorded to produce a “picture” of the heart’s size, anatomic shape and movements.


Swelling due to an abnormally large amount of fluid in body tissues.

Electrocardiogram (ECG or EKG)

A graphic record of electrical impulses produced by the heart.

Electroencephalogram (EEG)

A graphic record of the electrical impulses produced by the brain.

Electrophysiologic Testing

A procedure used to provoke known but infrequent arrhythmias and to unmask suspected arrhythmias. Using local anesthesia, temporary electrode catheters are positioned in the heart’s atria, ventricles or both, and at strategic locations along the conduction system. They record cardiac electrical signals and “map” the spread of electrical impulses during each heartbeat.


A blood clot or other particle that forms in one part of the body, then is carried to another part of the body.


Surgical removal of plaque deposits or blood clots in an artery.


An infection of the heart lining or valves, usually caused by bacteria. People with prosthetic heart valves, abnormal heart valves, a history of endocarditis or congenital heart defects are at increased risk of this disease.


A complex chemical that can speed up specific biochemical processes in the body.


A hormone produced in a woman’s body. Synthetic forms of estrogen are used in oral contraceptives and hormone replacement therapy.

Exercise Stress Test (or Treadmill Test)

A diagnostic test in which a person walks on a treadmill or pedals a stationary bicycle while hooked up to equipment to monitor the heart. The test monitors heart rate, breathing, blood pressure, electrical activity (on an electrocardiogram) and the person’s level of tiredness. It shows if the heart’s blood supply is sufficient and if the heart rhythm is normal.


Fast, uncoordinated contractions of individual heart muscle fibers. The heart chamber involved can’t contract all at once and pumps blood ineffectively, if at all.

HDL Cholesterol

Often called “good” cholesterol because a high level of it seems to protect against heart attack. People with a low HDL cholesterol level (less than 40 mg/dL) have a higher heart disease risk. A low level of HDL cholesterol also may raise stroke risk. (See High- Density Lipoprotein.)

Heart Attack

Death of or damage to part of the heart muscle due to an insufficient blood supply. The medical term for heart attack is myocardial infarction. It’s also sometimes called a coronary thrombosis or coronary occlusion.

Heart Block (or AV Block)

An impaired electrical signal from the heart’s upper to lower chambers (through the AV or sinus node).

Heart Murmur

An abnormal sound in the heart caused by defective heart valves or holes in the heart walls. Can also be caused by pregnancy, fever and other conditions.

Heart-Lung Machine

An apparatus that oxygenates and pumps blood to the body while a person’s heart is opened for surgery.


Severe bleeding leading to excessive blood loss.


The passing of a genetic quality or trait from parent to offspring.

High Blood Pressure

A chronic increase in blood pressure above its normal range (systolic pressure of 140 mm Hg or higher and/or diastolic pressure of 90 mm Hg or higher).

High-Density Lipoprotein (HDL)

A type of protein believed to transport cholesterol away from the tissues and to the liver, where it can be removed from the bloodstream. (See HDL Cholesterol.)


An amino acid. Too much homocysteine in the blood is related to a higher risk of coronary heart disease, stroke and peripheral vascular disease.


High levels of blood cholesterol, a major risk factor for coronary heart disease, heart attack and stroke.


Same as High Blood Pressure.


High levels of triglycerides in the blood. A high triglyceride level combined with low HDL cholesterol or high LDL cholesterol seems to speed up atherosclerosis (fatty buildups of plaque in the arteries).

Hypoplastic Heart

A rare congenital defect in which the right or left side of the heart is incompletely formed.


Low blood pressure.

Implantable Cardioverter Defibrillator

A device used in patients at risk for recurrent, sustained ventricular tachycardia or fibrillation. Leads positioned inside the heart or on its surface are used to deliver electrical shocks, sense the cardiac rhythm and pace the heart, as needed. The leads are tunneled to a pulse generator implanted in a pouch beneath the skin of the chest or abdomen.

Inferior Vena Cava

A major vein that carries blood from the lower body (legs and abdomen) to the heart.

Intermittent Claudication

Cramping or fatigue in the legs and buttocks during activity that subsides when a person stands still. It’s a common, early symptom of peripheral artery disease.


Reduced blood flow to an organ, usually due to a constricted or blocked artery.

Ischemic Heart Disease (Coronary Artery Disease, Coronary Heart Disease)

This term is applied to heart ailments caused by narrowed coronary arteries and characterized by a reduced blood supply to the heart.

Ischemic Stroke

The death of or injury to brain cells caused when a blood clot or other particle blocks a cerebral artery. Cerebral thrombosis and cerebral embolism are ischemic strokes.

Laser Angioplasty

A technique used to open coronary arteries blocked by plaque. A catheter with a laser at its tip is inserted into an artery. Then it’s advanced through the artery to the blockage. When the laser is in position, it emits pulsating beams of light that vaporize the plaque.

LDL Cholesterol

Often called “bad” cholesterol. A high level of LDL cholesterol (160 mg/dL and above) reflects an increased risk of heart disease and stroke. (See Low- Density Lipoprotein.)


A fatty substance insoluble in blood.


The combination of lipid (fat) surrounded by a protein; the protein makes the fat soluble in blood.

Low-Density Lipoprotein (LDL)

A type of protein that transports “harmful” cholesterol in the blood. It’s the major cholesterol carrier in the blood. (See LDL Cholesterol.)

Lp(a) Cholesterol

A genetic variation of LDL cholesterol. A high level of Lp(a) is an important risk factor for developing atherosclerosis prematurely.

Magnetic Resonance Imaging (MRI), Nuclear Magnetic Resonance (NMR) Imaging

An imaging procedure that uses powerful magnets to look inside the body. Computergenerated pictures can image the heart muscle and evaluate various heart problems. It can outline the affected part of the brain and help define problems created by stroke.

Mitral Valve

The heart valve between the left atrium and left ventricle. It has two flaps (cusps).

Monounsaturated Fats

A type of fat found in many oils but mostly in canola, olive and peanut oil, nuts and avocados.


The total number of deaths from a given disease in a population during an interval of time, usually a year.

Myocardial Infarction

The damaging or death of an area of the heart muscle (myocardium) resulting from a blocked blood supply to that area; medical term for a heart attack.


Inflammation of the heart muscle (myocardium).


The muscular wall of the heart. It contracts to pump blood out of the heart and then relaxes as the heart refills with returning blood.


A drug that causes blood vessels to dilate and is often used to treat angina pectoris (chest pain or discomfort).


The condition of being significantly overweight. It’s defined as a body mass index (BMI) of 30.0 or greater, or about 30 pounds or more over ideal body weight. Extreme obesity is defined as a BMI of 40.0 or more.

Occluded Artery

An artery in which blood flow has been impaired by a blockage.

Open-Heart Surgery

Surgery performed on the opened heart while the bloodstream is diverted through a heart-lung machine.


Defined as a body mass index (BMI) of 25.0–29.9 kg/m2. A BMI of 25 corresponds to about 10 percent over ideal body weight.


The “natural” pacemaker of the heart is called the sinus node. It’s a small group of specialized cells in the top of the heart’s right atrium. It produces the electrical impulses that travel down to the ventricular muscle, causing the heart to contract. An “artificial pacemaker” is an electrical device that can substitute for a defective natural pacemaker or conduction pathway. The artificial pacemaker controls the heart’s beating by emitting a series of rhythmic electrical discharges.


Blood flow.


Inflammation of the outer membrane surrounding the heart.


The outer fibrous “sac” that surrounds the heart.

Peripheral Artery Disease

A type of peripheral vascular disease that affects blood circulation, primarily in arteries leading to the legs and feet. It’s caused by atherosclerosis.

Peripheral Vascular Disease

Diseases of blood vessels outside the heart and brain or diseases of the lymph vessels. Often a narrowing of vessels carrying blood to leg and arm muscles.


Also called atheroma, this is a deposit of fatty (and other) substances in the inner lining of the artery wall characteristic of atherosclerosis.


An element in blood that aids in blood clotting.

Polyunsaturated Fats

A type of fat found mainly in vegetable oils such as corn, safflower, sunflower and soybean oils. They’re usually liquid at room temperature.


A synthetic form of the female hormone progesterone, used in oral contraceptives and hormone replacement therapy.


Preventive treatment.


Pertaining to the lungs.

Pulmonary Stenosis (PS)

A congenital heart defect in which the pulmonary or pulmonic valve is defective and doesn’t open properly.

Pulmonic (Pulmonary) Valve

The heart valve between the right ventricle and the pulmonary artery. It has three flaps (cusps).


The leakage that results when a heart valve that doesn’t close properly lets blood leak back into the chamber from which it was pumped.

Reperfusion Therapy

One or more techniques to restore blood flow to part of the heart muscle damaged during a heart attack, or part of the brain injured during a stroke. It may include clot-dissolving drugs (thrombolysis), balloon angioplasty or surgery.


The reclosure of an opening, such as a blood vessel or heart valve, after an angioplasty, stent or other procedure has been performed to open it.

Rheumatic Heart Disease

Damage done to the heart, particularly the heart valves, by one or more attacks of rheumatic fever.

Risk Factor

An element or condition involving certain hazard or danger. When referring to the heart and blood vessels, a positive risk factor is associated with an increased chance of developing cardiovascular disease including stroke. A negative risk factor is associated with a reduced chance of developing heart and blood vessel disease.

Saturated Fats

Types of fat found in all foods from animals and from some plants, like coconut, palm and palm kernel oils. They’re typically solid at room temperature.


The muscular wall dividing the chambers on the heart’s left side from the chambers on the right.

Sickle Cell Anemia

A genetic blood disorder that mainly affects African Americans. “Sickled” red blood cells are less able to carry oxygen to the body’s tissues and organs. They also tend to stick to blood vessel walls. This can block arteries to the brain and cause a stroke.

Silent Ischemia

Episodes of ischemia that aren’t accompanied by pain.

Single Photon Emission Computed Tomography (SPECT)

A nuclear imaging technique that involves injecting a radioactive liquid into the blood, then taking a series of pictures around the chest.

Sinoatrial (SA) or Sinus Node — See Pacemaker. Sodium

A mineral essential to life found in nearly all plant and animal tissue. Table salt (sodium chloride) is nearly half sodium.


The sudden, temporary or prolonged contraction of a muscle or artery.

Stable Angina

Predictable chest discomfort that usually occurs on exertion (such as running to catch a bus) or under mental or emotional stress. Normally the chest discomfort is relieved with rest or nitroglycerin or both.


The narrowing or constriction of an opening, such as a blood vessel or heart valve.

Stent Procedure

Using a wire mesh tube (a stent) to prop open an artery that’s recently been cleared using angioplasty.


An instrument for listening to sounds within the body.


Bodily or mental tension resulting from a person’s response to physical, chemical or emotional factors. Stress can refer to physical exertion as well as mental anxiety.

Stroke (also called Apoplexy, Brain Attack or Cerebrovascular Accident)

Loss of muscle function, mental function, vision, sensation or speech resulting from brain cell injury caused by an insufficient supply of blood to part of the brain.

Sudden Cardiac Death, Sudden Death

Death resulting from the abrupt loss of heart function (cardiac arrest). The victim may or may not have diagnosed heart disease. The death occurs within minutes after symptoms appear. The most common underlying reason that patients die suddenly from cardiac arrest is coronary heart disease.

Superior Vena Cava

A major vein that carries blood from the upper body (head, neck, chest and arms) to the heart.

Supraventricular Tachycardia

A condition in which heart tissue in either the upper chambers (atria) or the middle region (above the ventricles) develops pacemaker activity, resulting in an abnormally fast heartbeat.

Systolic Blood Pressure

The highest blood pressure measured in the arteries. It occurs when the heart contracts with each heartbeat. In a typical blood pressure reading, such as 120/78, the upper number is systolic blood pressure.


An abnormally fast heartbeat (more than 100 beats per minute).


The breaking up of a blood clot.


The formation or presence of a blood clot (thrombus) inside a blood vessel or chamber of the heart.


A blood clot that forms inside a blood vessel or chamber of the heart.

Total Anomalous Pulmonary Venous (P-V) Connection

A congenital heart defect. The pulmonary veins that bring oxygen-rich (red) blood from the lungs back to the heart aren’t connected to the left atrium. Instead, the pulmonary veins drain through abnormal connections to the right atrium. The blood passing through the aorta to the body doesn’t have enough oxygen, which causes the child to look blue (cyanotic).

Trans Fats

A type of fat that results from adding hydrogen to vegetable oils used in commercial baked goods and for cooking in most restaurants and fast-food chains.

Transient Ischemic Attack (TIA)

A temporary strokelike event that lasts for only a short time and is caused by a temporarily blocked blood vessel leading to or within the brain. Also called a “little stroke” or “mini-stroke,” it’s an extremely important stroke indicator.

Tricuspid Atresia

A congenital heart defect in which there’s no tricuspid valve. That means no blood can flow from the right atrium to the right ventricle. This results in a blue discoloration of the skin (cyanosis).

Tricuspid Valve

The heart valve between the right atrium and the right ventricle. It has three flaps (cusps).


The most common type of fat in the body. The body gets triglyceride directly from some foods (fatty acids) and makes it in the liver from other energy sources (carbohydrates, alcohol and some cholesterol).


Proteins found in heart muscle. Blood tests for troponins can detect heart muscle injury.


High-frequency sound vibrations, not audible to the human ear, used in medical diagnosis.

Unstable Angina

Chest pain or discomfort that’s unexpected and usually occurs while at rest. The discomfort may be more severe and prolonged than typical angina or be the first time a person has angina.


Pertaining to blood vessels.


A group of drugs that cause the muscle in the walls of the blood vessels (especially the arterioles) to relax, allowing the vessels to dilate.


One of a series of vessels that carries blood from various parts of the body back to the heart.


One of the two lower chambers of the heart.

Ventricular Fibrillation

A condition in which the ventricles contract in an extremely fast, chaotic fashion so no blood is pumped from the heart.

Ventricular Septal Defect (VSD)

A congenital heart defect in which an opening exists between the heart’s two lower chambers.

Ventricular Tachycardia

A condition in which an area of the ventricle muscle develops pacemaker activity, resulting in a very fast, abnormal heartbeat.


Small veins, the blood vessels that carry blood back to the heart and lungs.