In congenital mitral insufficiency, forward flow is maintained despite significant regurgitation due to compensatory increases in left ventricular volume.
Clinical, hemodynamic, and angiocardiographic findings are described in seven cases of congenital mitral insufficiency. The volumes and changes in volume of the left atrium and left ventricle were calculated from the angiocardiograms and were found to be increased above the range of normal. Left ventricular stroke volumes thus obtained were compared with forward flows calculated from indicatordilution curves in order to quantitate regurgitant flow. Regurgitant flows varied between 19 and 94 per cent of the total left ventricular ejection volume, and forward flow was maintained as a result of a considerable increase in left ventricular volume. The left ventricular ejection volume was 50 to 64 per cent of the end-diastolic volume.
Miller et al. (1964) studied this question.