Left ventricular function in mitral valve disease.

Abstract

Approximately one-third of all patients with mitral stenosis can be found to have an impaired left ventricular ejection fraction attributable to a reduction in preload subsequent to inflow obstruction, that is, with a lack of adequate Frank-Starling compensation together with increased afterload, rather than to an impairment of left ventricular function. The left ventricular function is, thus, generally not a factor exerting influence on the natural history of mitral stenosis or on the surgical results. The easy unloading of the left ventricle via both aortic and mitral valves during systole is the hallmark of chronic mitral regurgitation. The volume overload in mitral regurgitation leads to eccentric hypertrophy of the left ventricle while the mass-to-volume quotient remains within normal limits. There is an increase in compliance. Since left ventricular pressure and radius decrease rapidly due to the regurgitation, the myocardial wall stress of the left ventricle at the end of systole is reduced. Even in the presence of substantially reduced contractility, however, the left ventricular function appears adequate. If the left atrium is distensible enough to act as a buffer against backward transmission of the left ventricular systolic pressure, the patient may have only mild symptoms in spite of severe regurgitation. At end-systole, due to the diminished afterload, near normal volumes are reached such that, in association with an increased end-diastolic volume, an increased stroke volume and normal ejection fraction are present. In many patients with decreased contractility, the end-systolic volume may be slightly or moderately increased but, generally, the ejection fraction remains satisfactory at values in excess of 50%.(ABSTRACT TRUNCATED AT 250 WORDS)