A-H

Abdomen – The area of the body between the bottom of the ribs and the top of the thighs.

Abdominal aorta – The portion of the aorta in the abdomen.

Ablation – Elimination or removal.

ACE (angiotensin-converting enzyme) inhibitor – A medicine that lowers blood pressure by interfering with the breakdown of a protein-like substance involved in blood pressure regulation.

Acetylcholine – A type of chemical (called a neurotransmitter) that transmits messages among nerve cells and muscle cells.

Acquired heart disease – Heart disease that arises after birth, usually from infection or through the build-up of fatty deposits in the arteries that feed the heart muscle.

Alveoli – Air sacs in the lungs where oxygen and carbon dioxide are exchanged.

Amiodarone – A kind of medicine (called an antiarrhythmic) used to treat irregular heart rhythms such as atrial fibrillation and ventricular tachycardia. It works by regulating nerve impulses in your heart. Amiodarone is mainly given to patients who have not responded to other antiarrhythmic medicines.

Aneurysm – A sac-like protrusion from a blood vessel or the heart, resulting from a weakening of the vessel wall or heart muscle.

Angina or angina pectoris – Chest pain that occurs when diseased blood vessels restrict blood flow to the heart.

Angiography – An x-ray technique in which dye is injected into the chambers of your heart or the arteries that lead to your heart (the coronary arteries). The test lets doctors measure the blood flow and blood pressure in the heart chambers and see if the coronary arteries are blocked.

Angioplasty – A nonsurgical technique for treating diseased arteries by temporarily inflating a tiny balloon inside an artery.

Angiotensin II receptor blocker – A medicine that lowers blood pressure by blocking the action of angiotensin II, a chemical in the body that causes the blood vessels to tighten (constrict).

Annulus – The ring around a heart valve where the valve leaflet merges with the heart muscle.

Antiarrhythmics – Medicines used to treat patients who have irregular heart rhythms.

Anticoagulant – Any medicine that keeps blood from clotting; a blood thinner.

Antihypertensive – Any medicine or other therapy that lowers blood pressure.

Antiplatelet therapy – Medicines that stop blood cells (called platelets) from sticking together and forming a blood clot.

Aorta – The largest artery in the body and the main vessel to supply blood from the heart.

Aortic valve – The valve that regulates blood flow from the heart into the aorta.

Aphasia – The inability to speak, write, or understand spoken or written language because of brain injury or disease.

Arrhythmia (or dysrhythmia) – An abnormal heartbeat.

Arrhythmogenic right ventricular dysplasia (ARVD) – ARVD is a type of cardiomyopathy with no known cause. It appears to be a genetic condition (passed down through a family’s genes). ARVD causes ventricular arrhythmias.

Arteriography – A test that is combined with cardiac catheterization to visualize an artery or the arterial system after injection of a contrast dye.

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

Artery – A vessel that carries oxygen-rich blood to the body.

Arteritis – Inflammation of the arteries.

Arteriosclerosis – A disease process, commonly called “hardening of the arteries”, which includes a variety of conditions that cause artery walls to thicken and lose elasticity.

Artificial heart – A manmade heart. Also called a total artificial heart (TAH).

Ascending aorta – The first portion of the aorta, emerging from the heart’s left ventricle.

Aspirin – Acetylsalicylic acid; a medicine used to relieve pain, reduce inflammation, and prevent blood clots.

Atherectomy – A nonsurgical technique for treating diseased arteries with a rotating device that cuts or shaves away material that is blocking or narrowing an artery.

Atherosclerosis – A disease process that leads to the buildup of a waxy substance, called plaque, inside blood vessels.

Atrium (right and left) – The two upper or holding chambers of the heart (together referred to as atria).

Atrial flutter – A type of arrhythmia in which the upper chambers of the heart (the atria) beat very fast, causing the walls of the lower chambers (the ventricles) to beat inefficiently as well.

Atrial septal defect – See septal defect.

Atrial tachycardia – A type of arrhythmia that begins in the heart’s upper chambers (the atria) and causes a very fast heart rate of 160 to 200 beats a minute. A resting heart rate is normally 60 to 100 beats a minute.

Atrioventricular block – An interruption or disturbance of the electrical signal between the heart’s upper two chambers (the atria) and lower two chambers (the ventricles).

Atrioventricular (AV) node – A group of cells in the heart located between the upper two chambers (the atria) and the lower two chambers (the ventricles) that regulates the electrical current that passes through it to the ventricles.

Atrium – Either one of the heart’s two upper chambers.

Autologous – Relating to self. For example, autologous stem cells are those taken from the patient’s own body.

Autoregulation – When blood flow to an organ stays the same although pressure in the artery that delivers blood to that organ may have changed.

Bacteria – Germs that can lead to disease.

Bacterial endocarditis – A bacterial infection of the lining of the heart’s chambers (called the endocardium) or of the heart’s valves.

Balloon catheter – A long tube-like device with a small balloon on the end that can be threaded through an artery. Used in angioplasty or valvuloplasty.

Balloon valvuloplasty – A procedure to repair a heart valve. A balloon-tipped catheter is threaded through an artery and into the heart. The balloon is inflated to open and separate any narrowed or stiffened flaps (called leaflets) of a valve.

Beta-blocker – An antihypertensive medicine that limits the activity of epinephrine, a hormone that increases blood pressure.

Biopsy – The process by which a small sample of tissue is taken for examination.

Blalock-Taussig procedure – A shunt between the subclavian and pulmonary arteries used to increase the supply of oxygen-rich blood in “blue babies” (see below).

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. Clots can also form inside an artery when the artery’s walls are damaged by atherosclerotic buildup, possibly causing 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.

Blue babies – Babies who have a blue tinge to their skin (cyanosis) resulting from insufficient oxygen in the arterial blood. This condition often indicates a heart defect.

Body mass index (BMI) – A number that indicates an increased risk of cardiovascular disease from a person being overweight. BMI is calculated using a formula of weight in kilograms divided by height in meters squared (BMI =W [kg]/H [m²]).

Bradycardia – Abnormally slow heartbeat.

Bridge to transplant – Use of mechanical circulatory support to keep heart failure patients alive until a donor heart becomes available.

Bruit – A sound made in the blood vessels resulting from turbulence, perhaps because of a buildup of plaque or damage to the vessels.

Bundle branch block – A condition in which parts of the heart’s conduction system are defective and unable to conduct the electrical signal normally, causing an irregular heart rhythm (arrhythmia).

Bypass – Surgery that can improve blood flow to the heart (or other organs and tissues) by providing a new route, or “bypass” around a section of clogged or diseased artery.

Calcium channel blocker (or calcium blocker) – A medicine that lowers blood pressure by regulating calcium-related electrical activity in the heart.

Capillaries – Microscopically small blood vessels between arteries and veins that distribute oxygen-rich blood to the body’s tissues.

Cardiac – Pertaining to the heart.

Cardiac amyloidosis – A disorder caused by deposits of an abnormal protein (amyloid) in the heart tissue, which make it hard for the heart to work properly. Also called “stiff heart syndrome.”

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

Cardiac cachexia – A term for the muscle and weight loss caused by severe heart disease. It is often related to the depressed cardiac output associated with end-stage heart failure, but it can also occur with severe coronary artery disease.

Cardiac catheterization – A procedure that involves inserting a fine, hollow tube (catheter) into an artery, usually in the groin area, and passing the tube into the heart. Often used along with angiography and other procedures, cardiac catheterization has become a primary tool for visualizing the heart and blood vessels and diagnosing and treating heart disease.

Cardiac enzymes – Complex substances capable of speeding up certain biochemical processes in the heart muscle. Abnormal levels of these enzymes signal heart attack.

Cardiac output – The amount of blood the heart pumps through the circulatory system in one minute.

Cardiologist – A doctor who specializes in the study of the heart and its function in health and disease.

Cardiology – The study of the heart and its function in health and disease.

Cardiomegaly – An enlarged heart. It is usually a sign of an underlying problem, such as high blood pressure, heart valve problems, or cardiomyopathy.

Cardiomyopathy – A disease of the heart muscle that leads to generalized deterioration of the muscle and its pumping ability.

Cardiopulmonary bypass – The process by which a machine is used to do the work of the heart and lungs so the heart can be stopped during surgery.

Cardiopulmonary resuscitation (CPR) – An emergency measure that can maintain a person’s breathing and heartbeat. The person who performs CPR actually helps the patient’s circulatory system by breathing into the patient’s mouth to give them oxygen and by giving chest compressions to circulate the patient’s blood. Hands-only CPR involves only chest compressions.

Cardiovascular (CV) – Pertaining to the heart and blood vessels that make up the circulatory system.

Cardiovascular Disease (CVD) – A general term referring to conditions affecting the heart (cardio) and blood vessels (vascular system). May also simply be called heart disease. Examples include coronary artery disease, valve disease, arrhythmia, peripheral vascular disease, congenital heart defects, hypertension, and cardiomyopathy. Refer to specific conditions for detailed explanations.

Cardioversion – A technique of applying an electrical shock to the chest to convert an abnormal heartbeat to a normal rhythm.

Carotid artery – A major artery (right and left) in the neck supplying blood to the brain.

Cerebral embolism – A blood clot formed in one part of the body and then carried by the bloodstream to the brain, where it blocks an artery.

Cerebral hemorrhage – Bleeding within the brain resulting from a ruptured blood vessel, aneurysm, or head injury.

Cerebral thrombosis – Formation of a blood clot in an artery that supplies part of the brain.

Cerebrovascular – Pertaining to the blood vessels of the brain.

Cerebrovascular accident – Also called cerebral vascular accident, apoplexy, or stroke. Blood supply to some part of the brain is slowed or stopped, resulting in injury to brain tissue.

Cerebrovascular occlusion – The blocking or closing of a blood vessel in the brain.

Cholesterol – An oily substance that occurs naturally in the body, in animal fats and in dairy products, and that is transported in the blood. Limited amounts are essential for the normal development of cell membranes. Excess amounts can lead to coronary artery disease.

Cineangiography – The technique of using moving pictures to show how a special dye passes through blood vessels, allowing doctors to diagnose diseases of the heart and blood vessels.

Circulatory system – Pertaining to circulation of blood through the heart and blood vessels.

Claudication – A tiredness or pain in the arms and legs caused by an inadequate supply of oxygen to the muscles, usually due to narrowed arteries or peripheral arterial disease (PAD).

Collateral circulation – Blood flow through small, nearby vessels in response to blockage of a main blood vessel.

Commissurotomy -A procedure used to widen the opening of a heart valve that has been narrowed by scar tissue.

Computed tomography (CT or CAT scan) – An x-ray technique that uses a computer to create cross-sectional images of the body.

Conduction system – Special muscle fibers that conduct electrical impulses throughout the heart muscle.

Congenital – Refers to conditions existing at birth.

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

Congestive heart failure – A condition in which the heart cannot pump all the blood returning to it, leading to a backup of blood in the vessels and an accumulation of fluid in the body’s tissues, including the lungs.

Coronary arteries – Two arteries arising from the aorta that arch down over the top of the heart and divide into branches. They provide blood to the heart muscle.

Coronary artery anomaly (CAA) – A congenital defect in one or more of the coronary arteries of the heart.

Coronary artery bypass (CAB) – Surgical rerouting of blood around a diseased vessel that supplies blood to the heart. Done by grafting either a piece of vein from the leg or a piece of the artery from under the breastbone.

Coronary artery disease (CAD) – A narrowing of the arteries that supply blood to the heart. The condition results from a buildup of plaque and greatly increases the risk of a heart attack.

Coronary heart disease – Disease of the heart caused by a buildup of atherosclerotic plaque in the coronary arteries that can lead to angina pectoris or heart attack.

Coronary occlusion – An obstruction of one of the coronary arteries that hinders blood flow to the heart muscle.

Coronary thrombosis – Formation of a clot in one of the arteries carrying blood to the heart muscle. Also called coronary occlusion.

Cryoablation – The removal of tissue using an instrument called a cold probe.

Cyanosis – Blueness of the skin caused by a lack of oxygen in the blood.

Cyanotic heart disease – A birth defect of the heart that causes oxygen-poor (blue) blood to circulate to the body without first passing through the lungs.

Death rate (age-adjusted) – A death rate that has been standardized for age so different populations can be compared or the same population can be compared over time.

Deep vein thrombosis – A blood clot in a deep vein in the calf (DVT).

Defibrillator – A device that helps restore a normal heart rhythm by delivering an electric shock.

Diabetes (diabetes mellitus) – A disease in which the body doesn’t produce or properly use insulin. Insulin is needed to convert sugar and starch into the energy used in daily life.

Diastolic blood pressure – The lowest blood pressure measured in the arteries. It occurs when the heart muscle is relaxed between beats.

Digitalis – A medicine made from the leaves of the foxglove plant. Digitalis is used to treat congestive heart failure (CHF) and heart rhythm problems (arrhythmias).

Dissecting aneurysm – A condition in which the layers of an artery separate or are torn, causing blood to flow between the layers. Dissecting aneurysms usually happen in the aorta, the large vessel that carries blood from the heart to other parts of the body and can cause sudden death.

Diuretic – A drug that lowers blood pressure by causing fluid loss. Diuretics promote urine production.

Doppler ultrasound – A technology that uses sound waves to assess blood flow within the heart and blood vessels and to identify leaking valves.

Dysarthria – A speech disorder resulting from muscular problems caused by damage to the brain or nervous system.

Dyspnea – Shortness of breath.

Echocardiography – A method of studying the heart’s structure and function by analyzing sound waves bounced off the heart and recorded by an electronic sensor placed on the chest. A computer processes the information to produce a one-, two- or three-dimensional moving picture that shows how the heart and heart valves are functioning.

Edema – Swelling caused by fluid accumulation in body tissues.

Ejection fraction – A measurement of the rate at which blood is pumped out of a filled ventricle. The normal rate is 50% or more.

Electrocardiogram (ECG or EKG) – A test in which several electronic sensors are placed on the body to monitor electrical activity associated with the heartbeat.

Electroencephalogram (EEG) – A test that can detect and record the brain’s electrical activity. The test is done by pasting metal disks, called electrodes, to the scalp.

Electrophysiological study (EPS) – A test that uses cardiac catheterization to study patients who have arrhythmias (abnormal heartbeats). An electrical current stimulates the heart in an effort to provoke an arrhythmia, determine its origin, and test the effectiveness of medicines to treat the arrhythmias.

Embolus – Also called embolism; a blood clot that forms in a blood vessel in one part of the body and travels to another part.

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

Endocardium – The smooth membrane covering the inside of the heart. The innermost lining of the heart.

Endothelium – The smooth inner lining of many body structures, including the heart (endocardium) and blood vessels.

Endocarditis – A bacterial infection of the heart’s inner lining (endothelium).

Enlarged heart – A state in which the heart is larger than normal because of heredity, long-term heavy exercise, or diseases and disorders such as obesity, high blood pressure, and coronary artery disease.

Enzyme – A complex chemical capable of speeding up specific biochemical processes in the body.

Epicardium – The thin membrane covering the outside surface of the heart muscle.

Estrogen – A female hormone produced by the ovaries that may protect premenopausal women against heart disease. Estrogen production stops after menopause.

Estrogen (or hormone) replacement therapy (ERT or HRT) – Hormones that some women may take to offset the effects of menopause.

Exercise stress test – A common test to help doctors assess blood flow through coronary arteries in response to exercise, usually walking, at varied speeds and for various lengths of time on a treadmill. A stress test may include use of electrocardiography, echocardiography, and injected radioactive substances. Also called exercise test, stress test, nuclear stress test, or treadmill test.

Familial hypercholesterolemia – A genetic predisposition to dangerously high cholesterol levels.

Fatty acids (fats) – Substances that occur in several forms in foods; different fatty acids have different effects on lipid profiles.

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

First-degree heart block – Occurs when an electrical impulse from the heart’s upper chambers (the atria) is slowed as it moves through the atria and atrioventricular (AV) node.

Flutter – The rapid, ineffective contractions of any heart chamber. A flutter is considered to be more coordinated than fibrillation.

Fusiform aneurysm – A tube-shaped aneurysm that causes the artery to bulge outward. Involves the entire circumference (outside wall) of the artery.

Gated blood pool scan – An x-ray analysis of how blood pools in the heart during rest and exercise. The test uses a radioactive substance to tag red blood cells to allow doctors to estimate the heart’s overall ability to pump and its ability to compensate for one or more blocked arteries. Also called MUGA (multiple gated acquisition scan) or nuclear ventriculography.

Genetic testing – Blood tests that study a person’s genes to find out if he or she is at risk for certain diseases that are passed down through family members.

Guidewire – A small, bendable wire that is threaded through an artery; it helps doctors position a catheter so they can perform angioplasty or stent procedures.

Heart assist device – A mechanical device that is surgically implanted to ease the workload of the heart.

Heart attack – Death of, or damage to, part of the heart muscle caused by a lack of oxygen-rich blood flowing to the heart.

Heart block – General term for conditions in which the electrical impulse that activates the heart muscle cells is delayed or interrupted somewhere along its path.

Heart failure – See congestive heart failure.

Heart-lung machine – An apparatus that oxygenates and pumps blood to the body during open heart surgery; see cardiopulmonary bypass.

Heart murmur -An abnormal heart sound caused by turbulent blood flow. The sound may indicate that blood is flowing through a damaged or overworked heart valve, that there may be a hole in one of the heart’s walls, or that there is a narrowing in one of the heart’s vessels. Some heart murmurs are a harmless type called innocent heart murmurs.

Hematocrit – A measure of the percentage of red blood cells in a given amount (or volume) of whole blood.

Hemochromatosis – A disease in which too much iron builds up in your body (iron overload). Too much iron in the heart can cause irregular heartbeats (arrhythmias) and heart failure. Too much iron in the pancreas can lead to diabetes.

Heredity – The genetic transmission of a particular quality or trait from parent to child.

High blood pressure – A chronic increase in blood pressure above its normal range.

High density lipoprotein (HDL) – A component of cholesterol, HDL helps protect against heart disease by promoting cholesterol breakdown and removal from the blood; hence, its nickname “good cholesterol.”

Holter monitor – A portable device for recording heartbeats over a period of 24 hours or more.

Homocysteine – An amino acid (one of the building blocks that makes up a protein) normally found in small amounts in the blood. Too much homocysteine in the blood may promote the buildup of fatty plaque in the arteries. For some people, high homocysteine levels are genetic. For others, it is because they do not get enough of certain B vitamins in their diet. (Common misspelling: homocystine)

Hormones – Chemicals released into the bloodstream that control different functions in the body, including metabolism, growth, sexual development, and responses to stress or illness.

Hypertension – High blood pressure.

Hypertrophic obstructive cardiomyopathy (HOCM) – An overgrown heart muscle that creates a bulge into the ventricle and impedes blood flow.

Hypertrophy – Enlargement of tissues or organs because of increased workload.

Hyperventilation – Rapid breathing usually caused by anxiety. People feel like they can’t get enough air, so they breathe heavily and rapidly, which can lead to numb or tingly arms and legs, or fainting.

Hypoglycemia – Low levels of glucose (sugar) in the blood.

Hypokinesia – Decreased muscle movement. In relation to the heart, hypokinesia refers to decreased heart wall motion during each heartbeat. It is associated with cardiomyopathy, heart failure, or heart attack. Also called hypokinesis.

Hypotension – Abnormally low blood pressure.

Hypoxia – Less than normal content of oxygen in the organs and tissues of the body.