Valvular Heart Disease

Valvular involvement by disease causes stenosis, insufficiency (regurgitation or incompetence), or both. Stenosis is the failure of a valve to open completely, thereby impeding forward flow. Insufficiency, in contrast, results from failure of a valve to close completely, thereby allowing reversed flow. These abnormalities can be either pure, when only stenosis or regurgitation is present, or mixed, when both stenosis and regurgitation coexist in the same valve, but one of these defects usually predominates. Isolated disease refers to disease affecting one valve, and combined disease implies that more than one valve may be dysfunctional. Functional regurgitation results when a valve becomes incompetent owing to either (1) dilation of the ventricle, which causes the right or left ventricular papillary muscles to be pulled down and outward, thereby preventing coaptation of otherwise intact mitral or tricuspid leaflets during systole, or (2) dilation of the aortic or pulmonary artery, pulling the valve commissures apart and preventing full closure of the aortic or pulmonary valve cusps. Abnormalities of flow often produce abnormal heart sounds known as murmurs.