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.

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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.