Left ventricular function in rheumatic mitral stenosis.

Haemodynamic factors contributing to clinical disability in patients with rheumatic mitral stenosis have been under discussion and investigation for decades. Prior to the development of left heart catheterization, a low cardiac output in the presence of little or no pulmonary hypertension was taken as evidence for a myocardial 'insufficiency'. With the use of left heart catheterization, it was possible to exclude the presence of coronary artery disease and to assess directly the size and function of the left ventricle. Such studies indicate a tendency toward low-normal left ventricular end-diastolic volumes and low-normal ejection fractions. Modest reductions in the ejection fraction may be due to: (1) a restriction or tethering of posterobasal myocardium by the scarred mitral apparatus, or (2) abnormal interventricular septal motion related to right ventricular overload and unequal filling of the two ventricles. These and other factors, such as limited LV distensibility and variable diastolic suction, may affect ventricular function in rheumatic mitral stenosis. Thus, left ventricular dysfunction can generally be explained without implicating a rheumatic myocardial factor.