Valvular stenosis is the result of diseases such as rheumatic fever, which causes the opening through the valve to become so narrow that blood can flow through only with difficulty. The result can be blood damming up behind the valve. Valvular regurgitation occurs when the valves become so worn that they cannot close completely, and blood flows back into the atria or the ventricles. If the blood can flow backward, the efficiency of the cardiac stroke is drastically reduced. The coronary arteries are also subject to problems.
Atherosclerosis is a degenerative disease that results in narrowing of the coronary arteries.
This is caused by fatty deposits, most notably cholesterol, on the interior walls of the coronary arteries. When the walls become narrowed or occluded, they reduce the blood flow to the heart muscle. If the artery remains open to some degree, the reduced blood flow is noticed when the heart is under stress during periods of rapid heartbeat. The resulting pain is called angina. When the artery is completely closed or occluded, a section of the heart muscle can no longer get oxygenated blood, and begins to die.