heart failure A condition resulting from the heart’s inability to pump sufficient blood to maintain normal circulation. This often leads to congestive heart failure, in which blood and fluids back up in the lungs, causing congestion in the abdomen or legs.
heart murmur An abnormal sound caused by turbulent blood flow as a result of a defective heart valve or certain forms of congenital heart disease. It can also be of no medical importance.
heart transplant Replacement of a damaged or diseased heart with a healthy heart taken from a donor.
Heimlich maneuver A first-aid maneuver for choking victims.
hematoma A swelling in an organ or tissue containing blood; caused by a tear or break in a blood vessel wall.
hemochromatosis An inherited disorder characterized by the overabsorption of iron. It can result in liver damage, cardiac arrhythmias, and other heart disorders.
hemoglobin The red pigment in the blood that carries oxygen.
hepatomegaly Enlargement of the liver.
high-density lipoprotein (HDL) A lipid-carrying protein that transports the so-called good cholesterol in the bloodstream. HDL is responsible for carrying excess cholesterol away from the artery walls and to the liver, where it is metabolized.
Holter monitor A portable electrocardiographic device worn for a 24-hour period or longer to monitor irregular heart rhythms and other cardiac abnormalities.
hormones Chemicals produced by various endocrine glands or tissues, and released into the blood. Hormones are instrumental in controlling metabolism, reproduction, and virtually every body function.
hyperglycemia Abnormally high levels of blood sugar (glucose). It occurs mostly in patients with diabetes.
hyperlipidemia Excessive amount of fats (lipids) in the blood.
hyperplasia A noncancerous enlargement of an organ or a portion of an organ because of increases in its component cells.
hypertension The medical term for high blood pressure.
hyperthyroidism A condition in which an overactive thyroid gland secretes excessive thyroid hormones, resulting in a rapid heartbeat and other manifestations of speeded-up metabolism.
hypertrophic cardiomyopathy An abnormal increase in the thickness of the walls of the heart, usually because of an inherited heart muscle disorder.
hypertrophy Enlargement of muscle tissue resulting from an increased workload.
hypoglycemia Abnormally low levels of blood sugar (glucose), often a result of an insulin overdose in the treatment of diabetes.
hypothyroidism Reduced production of thyroid hormones because of a goiter or other thyroid disorder.
hypoxia Insufficient level of oxygen in the tissues of the body.