Left ventricular function during systole and diastole in mitral incompetence

Left ventricular function during systole and diastole was studied in 17 young patients with mitral incompetence and sinus rhythm; 13 had established chronic mitral incompetence, 3 had prolapsing posterior leaflet syndrome and 1 had ruptured chordae tendineae. In chronic mitral incompetence and prolapsing posterior leaflet syndrome, clinical disability was related to a low forward stroke index, a large regurgitant volume and tall left atrial V wave. The defect was mechanical, and the ventricle had adapted by compensatory dilatation so that overall systolic function was normal, as measured by peak rate of rise of left ventricular pressure ($\text{dP}\text{dt}$) and ejection fraction. The dilated ventricle operated at a normal or slightly increased end-diastolic pressure, a consequence of normal resting tension (O point) and a more elastic myocardium with a low rate of change of instantaneous stiffness (m) and a flattened diastolic pressure-volume curve.In acute mitral incompetence, systolic function was normal but the sudden volume overload caused the unprepared ventricle with an almost normal modulus of elasticity and slope (m) to ascend its pressure-volume curve in diastole. End-diastolic pressure was increased.