Ventricular buckling: a factor in the abnormal ventriculogram and peculiar hemodynamics associated with mitral valve prolapse.

Because of intractable ventricualr arrhythmias after a near-fatal episode of ventricular fibrillation, a patient with idiopathic mitral valve prolapse was subjected to mitral valve replacement. Vector analysis and intraoperative epicardial mapping localized the ectopic focus to the region of the posterior papillary muscle. The patient is alive and well two years after surgery; chronically inverted T waves have become upright. But propranolol and diphenylhydantoin are needed to prevent arrhythmias and T wave abnormalities during standing and exercise. Preoperatively, with the onset of mitral regurgitation and a second rapid phase of prolapse, the ventriculogram was deformed by abnormal midsystolic hyperkinesis at both sites of papillary muscle insertion. Postoperatively, focal hypokinesis appeared in the same areas, implying that they had been retracted by the prolapsing valve. Preoperatively, a papillary tip could be seen entering the mitral ring while coronary arteriography showed late systolic elongation of a small vessel feeding the anterior papillary muscle, suggesting that the papillary apparatus was indeed subject to damaging stress during the abnormal basal movement. Three other persons with severe mitral prolapse (but intact chordae) have had valve repacement and developed qualitatively similar changes in the ventriculogram. Papillary speciments in two showed significant fibrosis. Indication for operation in one of these was edpisodic ventricular fibrillation, which has not recurred. A spectrum of ventriculographic abnormality associated with mitral prolapse could be partly explained by hypokinesis of the papillary loops, variably disguised by retraction stress tansmitted from the billowing leaflets, translocation of blood into the expanding valve sail, and various degrees of unloading into the left atrium. Abnormal intraventicular flow may probably result from associated prolapse of the anterior leaflet and from buckling of the papillary sties toward the mitral annulus. Unusual physical findings in the operated cases and in eight other patients define a clinically recognizable syndrome in which severe prolapse abbreviates left ventricular ejection. Liability to symptoms and to progression of disease seems high in this group.