Aneurysm -- A ballooning of the wall of an artery, a vein, or the heart, at a weak spot in the wall; it is filled with fluid or clotted blood, often forming a pulsating tumor. A sacciform or saccular aneurysm is a localized distension involving only part of the vessel wall; a fusiform aneurysm distends the whole circumference of the artery; in a dissecting aneurysm, the artery wall is split longitudinally by blood pumping through a tear in the inner arterial wall.

Angioplasty, patch-graft -- The surgical repair of an artery in which a patch of synthetic material is inserted into an incision in the artery wall (done for endarterectomy or aneurysm removal, e.g.) to counteract the narrowing of the vessel that would result from simple suturing of the incision. Aorta -- The great arterial trunk that carries oxygenated blood from the heart to be distributed throughout the body by branch arteries.

Atherosclerosis -- A disease caused by the build-up of atherosclerotic plaques (hardened cholesterol, cell debris, collagen, calcium, and other material) on the inside of the arteries. As the plaque deposits accumulate, they can partially block the blood vessel, reducing blood flow to limbs and organs. This in turn can cause high blood pressure, poor circulation, heart attacks, or strokes. Plaques can also weaken the artery walls, thus contributing to the formation of aneurysms.

Carotid artery -- The artery or pair of arteries that pass up the neck and supply the head.

Coarctation of the aorta -- A congenital deformity in which the aorta's upper portion is narrowed.

Coronary bypass -- A surgical procedure in which a section of vein or other conduit is grafted between the aorta and a coronary artery to circumvent a blockage in that artery, and thus keep the heart muscle adequately supplied with blood.

Endarterectomy -- The surgical removal of atherosclerotic plaque from the inner wall of an artery, to restore full circulation through the artery.

Homograft -- A graft of tissue between individuals of the same species. Also called allograft.

Hypothermia -- subnormal temperature of the body.

Lobectomy, pulmonary -- The surgical removal of one or more lobes of the lung.

Marfan syndrome -- A hereditary disorder of connective tissue that is characterized by abnormal elongation of the bones and often by ocular and circulatory defects.

Mitral commissurotomy -- A surgical operation that re-opens the flaps of the mitral valve of the heart when they have been partially fused by scarring.

Mitral valve stenosis -- A narrowing of the mitral valve opening caused by partial fusing of the valve flaps. The fusing can occur as a congenital defect or as the result of inflammation and scarring (as in rheumatic fever.)

Peptic ulcer -- An ulcer of the mucous membrane of the digestive tract (often in the stomach), caused by the action of the acidic gastric juice.

Rheumatic fever -- An inflammatory disease that sometimes develops after streptococcal infections such as strep throat or scarlet fever. It can affect the heart, joints, skin, and brain, and is responsible for many cases of damaged heart valves. A primary cause of mitral valve stenosis.

Sympathectomy -- A surgical procedure that severs sympathetic nerves in the lumbar and thoracic region, thereby relaxing the blood vessels. Used in the 1930s and 1940s to treat severe hypertension and blocked circulation.

Ventricle -- A cavity of a bodily part or organ; in the heart, either of two larger lower chambers that receives blood from a corresponding atrium and from which blood is forced into the arteries. The right ventricle pumps blood back to the lungs to be oxygenated, while the left ventricle pumps oxygenated blood out to the body and to the coronary arteries that supply the heart muscle.