aldosterone : A hormone secreted by the adrenal glands that signals the kidneys to conserve sodium and water; the result is greater blood volume and thus higher blood pressure.

angiotensin-converting enzyme (ACE): Converts angiotensin I to angiotensin II, a protein that constricts blood vessels and stimulates the release of aldosterone, a hormone that raises blood pressure.

arrhythmia : An irregular pattern of heartbeats.

ascites : Buildup of excess fluid in the abdomen because of the inability of the heart to pump efficiently.

atrium : Either of the two upper chambers of the heart; in plural, atria.

brain natriuretic peptide (BNP): A hormone released by the heart muscle that is used to diagnose heart failure.

cardiac remodeling: Changes in the structure of the heart resulting from progressive weakening of the heart muscle.

cardiac resynchronization therapy (CRT): Use of a biventricular pacemaker to coordinate the contractions of the pumping chambers on the left and right sides of the heart.

cardiomyopathy : An umbrella term used to describe diseases that cause structural damage to the heart muscle. Types include dilated (enlarged), hypertrophic (thickened), and restrictive (stiffened) cardiomyopathy.

cholesterol : A waxy, fatlike substance present in animal tissues and produced by the liver. Excess cholesterol in the blood can build up in artery walls.

coronary artery disease: Narrowing or blockage of the small arteries that supply oxygen-rich blood to the heart muscle; the condition can cause angina and heart attack.

diastolic : Pertaining to the filling stage of the heart cycle (diastole).

diuretic : A drug that causes the body to excrete sodium and fluid.

echocardiography : A diagnostic procedure that uses ultrasound technology to create a video image of the structure and motion of the heart.

edema : Swelling from the abnormal accumulation of fluid in the body tissues.

ejection fraction: Percentage of blood the ventricle pumps out in one heartbeat.

heart attack: Damage to, or death of, heart muscle because of insufficient blood supply; the medical term is myocardial infarction.

heart valves: Structures in the heart that open and close with each heartbeat to keep blood flowing in a forward direction.

hypertension : Abnormally high blood pressure.

implantable cardioverter-defibrillator (ICD): A device that automatically administers an electric shock to the heart muscle to bring the heartbeat back into a normal rhythm.

implantable hemodynamic monitor: A device that measures the changing pressures inside the heart as a way to predict worsening heart failure.

rales : Crackling noises in the lungs that may indicate congestion.

renin : An enzyme released by the kidney that stimulates production of angiotensin.

sinoatrial (SA) node: A cluster of cells on the wall of the right atrium that controls the rhythm and pace of the heartbeat.

sodium : A mineral that works with calcium and potassium to maintain normal heart rhythm and control fluid balance. A diet high in sodium can worsen heart failure.

systolic : Pertaining to the pumping phase of the heart cycle (systole).

titration : A process of adjusting a medication dose until the target dose or maximum tolerated dose is achieved.

vasodilator : A substance that dilates blood vessels.

ventricle : Either of the two lower chambers of the heart.

ventricular assist device (VAD): An implantable pumping device that supports a weakened ventricle.

volume overload: A condition in which the heart is too weak to keep up with the amount of blood entering it.