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Addison's disease . A disease caused by destruction of the adrenal glands, characterized by weakness, low blood pressure, and brown pigmentation of the skin.

Adventitia . The outer layer of an artery.

Aldosterone . A hormone of the cortex (outer part) of the adrenal gland, regulating salt and water balance in body tissues.

Alveolus . The terminal air sac in the lungs, into which blood from the capillaries deposits carbon dioxide and from which oxygen is extracted.

Amyloidosis . A disease in which an abnormal protein substance, amyloid, is deposited in various tissues, including the heart.

Aneurysm . An abnormal outpouching of a wall of the heart or a blood vessel (particularly the aorta).

Angiocardiography . Visualization of the contents of the heart or blood vessels by injecting a contrast liquid into the bloodstream and recording the X-ray image.

Angiography . Contrast visualization of the blood vessels only. See also angiocardiography .

Angioplasty . A catheter procedure on blood vessels, using a balloon or other special device. See also balloon angioplasty .

Angiotensin . One of the hormones regulating blood pressure.

Anticoagulant . A drug or agent interfering with the clotting of blood.

Aortic valve . See semilunar valves .


Arrhythmia . A general term for various disturbances of the rhythm or rate of the heartbeat.

Arteriography . Contrast visualization of the arteries only. See also angiocardiography .

Arteriole . The smallest-caliber vessel of the arterial system, which plays an important role in regulating blood pressure.

Arteriosclerosis . "Hardening of the arteries," a broad term referring to degenerative, age-related diseases of the arteries.

Ascites . Abnormal accumulation of serous fluid in the abdominal cavity.

Asymptomatic . Showing no symptoms from an existing disease.

Atherosclerosis . A disease of the arteries affecting the intima and tending to narrow the vessels.

Atrioventricular . Located at the junction between the atria and the ventricles of the heart.

Atrioventricular block . Disturbance of the conduction of impulses from atrium to ventricle of the heart.

Atrioventricular node . Small structure through which impulses are conducted from atrium to ventricle.

Atrioventricular valves . The mitral valve (left side) and tricuspid valve (right side), separating the atria from the ventricles.

Auscultation . The act of listening to the sound of the heart, lungs, or other organs, usually with the aid of a stethoscope.

Autonomic . Self-regulating.

Autonomic nervous system . A system of nerves controlling the function of the heart, blood vessels, and certain other organs.

A-V . Atrioventricular (node or block).

Balloon angioplasty . A procedure for dilating a stenotic blood vessel by inflating a balloon at the end of a catheter.

Balloon valvuloplasty . A procedure for dilating a stenotic valve by inflating a balloon at the end of a catheter.

Block (in reference to the conduction of cardiac impulses). Interruption or delay in the conductive pathway.

Bradycardia . Abnormally slow heartbeat.


Bundle branch . One of the two divisions of the bundle of His.

Bundle of His . The part of the cardiac conductive system transmitting impulses from the atrio-ventricular node to the ventricles.

Calcific . Containing deposits of calcium.

Capillary . The thinnest of the blood vessels, through which oxygen is supplied to tissues.

Cardiogenic . Related to or caused by the heart (such as cardiogenic shock).

Carditis . An inflammatory disease of the heart involving all three of its layers.

Cardioversion . The administration of electric shock to the chest to treat certain arrhythmias.

Catheterization (pertaining to the heart). Diagnostic tests involving the insertion of a catheter into the vascular system.

Chordae tendineae . Cordlike structures connecting the edges of the mitral valve with the papillary muscles.

Collateral circulation . Arteries or veins providing detours for supplying blood to a portion of an organ in which the normal channels are blocked or narrowed.

Commissure (in cardiac valves). The junction or the free space between leaflets of a valve.

Congestion . Excessive accumulation of blood in an organ or part of the body.

Coronary . Pertaining to the blood supply to the heart itself.

Corticosteroid . A hormone produced by the adrenal cortex or its synthetic equivalent.

Cushing's disease (or syndrome ). A disease caused by malfunction of the pituitary gland or adrenal gland, characterized by obesity and high blood pressure.

Cyanosis . A bluish coloration of the skin, especially visible in the lips and fingertips, due to reduced oxygen content in blood vessels near the surface.

Depolarization . The discharge of electrical potential by heart muscle cells just before contraction.


Diastole . The stage of the heart cycle comprising the entire period of relaxation of the heart muscle.

Dissection of the aorta (or dissecting aneurysm ). Separation of the layers of the aorta, permitting the blood to create a second, abnormal channel.

Dissociation (in arrhythmias). Abnormal, independent electrical activity of the atria and the ventricles.

Diuretic . A drug increasing the flow of urine.

Dyspnea . Abnormal shortness of breath.

Eclampsia . Convulsions occurring in pregnant women with hypertension.

Ectopic (pertaining to cardiac rhythm). Originating from a source other than the normal pacemaker.

Edema . Abnormal accumulation of fluid in the body, usually manifested as swelling of the ankles or other parts of the body.

Effusion . Accumulation of fluid in a body cavity, such as the chest (pleural effusion) or pericardum.

Electrolyte . A chemical substance in ionic form in solution capable of conducting electricity, such as sodium, potassium, or calcium.

Electrophysiology . The study of the electrical activity of an organ.

Embolus . A plug of abnormal material (usually a clot) obstructing blood flow in an artery, transported by the bloodstream from another part of the circulation.

Endocardium . The inner lining of the heart.

Enzyme . A protein capable of accelerating certain chemical reactions.

Epicardium . The outer lining of the heart; one of the two layers of the pericardium.

Extrasystole . A heartbeat occurring out of the normal sequence.

Fibrillation . Uncoordinated twitching of the heart muscle, replacing the normal beating sequence and causing heart failure.

Flutter . Abnormally rapid contraction of the atria or ventricles, reducing or eliminating the function of the effected chamber.

Glomerulonephritis . Inflammatory disease of the kidneys, often producing hypertension.


Gradient . A difference in pressure between two adjacent points of the circulation.

Hemodynamics . The dynamics of movement of the blood in the body.

Hemosiderosis . A condition associated with abnormal iron storage in various organs.

Hydrostatic pressure . Pressure exerted within a blood vessel in relation to other structures.

Hypercholesterolemia . An abnormally high level of cholesterol in the blood.

Hyperlipidemia . An abnormally high level of fat in the blood.

Hypertrophy . Excessive growth of a muscle or an organ.

Insufficiency, valvular . See regurgitation, valvular .

Intima . The inner layer of the wall of an artery.

Invasive (pertaining to a test or other procedure). Involving introduction of an instrument into the body.

Ischemia . Local deficiency of blood supply due to obstruction or spasm of the supplying artery.

Isometric . Referring to change in the tension of a muscle without a corresponding change in its size (such as isometric contraction and relaxation of the heart muscle).

Junctional (pertaining to cardiac rhythm). Originating at the junction between the A-V node and the bundle of His. Junctional rhythm is also referred to as A-V nodal rhythm .

Lipoprotein . A chemical substance in the blood combining proteins and fats.

Lumen . The cavity inside a tubular organ, such as an artery.

Media . The middle layer of a blood vessel.

Mitral valve . See atrioventricular valves .

Monitor (in the management of heart disease). Continuous visual display or record of an electrocardiographic lead, pressure curve, or other circulatory modality.

Murmur . An abnormal auscultatory sound originating in the heart and indicating turbulent blood flow.


Myocarditis . Inflammatory disease of the heart muscle.

Myocardium . The muscular layer of the heart; the heart muscle.

Node . A part of the conducting system. See atrioventricular node, sinoatrial node .

Oscilloscope . An instrument capable of displaying electrical impulses on a screen, used in electrocardiographic monitoring, echocardiography, and X-ray imaging.

Osmotic pressure . The pressure in a liquid exerted by substances dissolved in it.

Output, cardiac . The quantity of blood ejected by a cardiac ventricle in one minute.

Overload, cardiac . Increased work demands on the heart.

Pacemaker . (1) A group of cells in which rhythmic impulses governing heart actions are generated. (2) An electronic apparatus connected to the heart and inducing its rhythmic stimulation.

Pacing . Using an electronic pacemaker.

Papillary muscles . Two cone-shaped muscles arising from the apex of each cardiac ventricle, to which the chordae tendineae are attached.

Paroxysm . A sudden attack involving change from a normal to an abnormal state in a body function.

Percutaneous . Introducing an instrument into the body through the intact skin.

Pericardium . The outer coating of the heart, consisting of an inner membrane firmly attached to the heart (epicardium ) and an outer one forming a loose sack (parietal pericardium ).

Placebo . An inactive substance (such as sugar) placed in a tablet or capsule, used as a control in drug testing.

Pleura . The outer lining of the lungs.

Polycystic disease . A condition producing multiple cysts in various organs, frequently affecting the kidneys.

Prolapse (of the mitral valve). Abnormal displacement of a portion of a mitral-valve cusp during systole.


Prophylactic . Preventive.

Pulmonary . Relating to the lungs.

Pulmonary circulation . The smaller of the two circuits, in which blood ejected by the right ventricle is sent to the lungs before returning to the left atrium; also called the lesser circulation.

Pulmonary valve . See semilunar valves .

Pyelonephritis . An inflammatory disease of the portion of the kidneys that excretes urine.

Radiography . The procedure of recording X-ray images of film.

Reentry (in arrhythmias). Reactivation of the heart from a single impulse.

Regurgitation, valvular . Faulty function of a cardiac valve permitting backflow of blood.

Renin . A hormone produced by the kidney involved in regulating blood pressure.

Renal . Relating to the kidneys.

S-A . Sinoatrial (node).

Sarcoidosis . A chronic disease of unknown origin characterized by the formation of small nodules in various organs including the heart.

Septum, cardiac . The partition between the two sides of the heart, consisting of the atrial septum and the ventricular septum.

Semilunar valves . Either of the two outflow valves from the heart, the pulmonary valve (right side) and the aortic valve (left side).

Shunt . Blood flow through an abnormal connection between the two sides of the heart or between various vascular structures.

Standstill, cardiac . Absence of contraction of the atria or the ventricles due to failure of the electrical impulse to arrive, or failure to respond to the impulse.

Sinoatrial node . Uppermost part of the cardiac conduction system; the normally active pacemaker.

Stenosis . A narrowing of the diameter of any structure through which a liquid is conducted, including arteries and cardiac valves.


Sign (in diagnosis). An abnormality detected objectively by the physician (as opposed to a symptom).

Stroke volume . The quantity of blood ejected by each ventricle in a single contraction.

Supraventricular (pertaining to an abnormal cardiac rhythm). Originating in the atrium or the atrioventricular node.

Symptom . A subjective manifestation of disease felt or observed by the patient.

Syndrome . A group of signs and symptoms occurring together but not as well defined as a disease.

Systemic circulation . The larger of the two circuits, in which blood ejected by the left ventricle supplies most of the body before returning to the right atrium; also called the greater circulation.

Systole . The stage of the heart cycle involving muscular contraction.

Tamponade, pericardial . Excessive fluid in the pericardium interfering with cardiac action.

Tachycardia . Rapid heartbeat, usually defined as 100 beats a minute or more.

Therapy . Treatment.

Thrombosis . The process of intravascular clot formation.

Thrombus . A clot formed inside a blood vessel.

Tricuspid valve . See atrioventricular valves .

Valvotomy . Surgery on a cardiac valve to relieve valvular stenosis.

Valvuloplasty . Repair of a valvular abnormality either by surgery or by manipulation of a balloon-equipped cardiac catheter.

Ventriculography . Contrast visualization of the ventricle to observe its function.

Vegetation . A small wartlike structure developing on heart valves in infective endocarditis.

Vena cava . One of the two large veins (superior and inferior) entering the right atrium and returning blood to the heart.


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