Etiology and electrocardiographic features of the billowing posterior mitral leaflet syndrome. Analysis of a further 130 patients with a late systolic murmur or nonejection systolic click

The etiology of the mitral valve pathology in 130 patients with either a late systolic murmur (twenty-six), a nonejection systolic click (sixty-three) or both (forty-one) is analyzed. In the majority (eighty patients) no cause could be found, but in twenty-three of these a familial factor was present, and in eighteen others (including two sisters) there was association with congenital heart disease, in particular a secundum atrial septal defect. Other etiologic factors included the Marfan syndrome, rheumatic endocarditis, hypertrophic obstructive cardiomyopathy and ischemic heart disease. In eight patients the appearance of the nonejection click followed a mitral commissurotomy. Twelve patients had the characteristic electrocardiographic pattern of posteroinferior myocardial "ischemia," which is not infrequently encountered in the billowing posterior mitral leaflet syndrome, and six others had nonspecific abnormalities, including S-T segment and T wave changes and prolongation of the P-R interval. Ventricular or supraventricular premature contractions occurred at rest in nine patients. Multifocal ventricular premature contractions occurred after effort in six of the fifty patients subjected to strenuous exercise, particularly in those with the electrocardiographic pattern of posteroinferior myocardial ischemia. The mechanism of production of the myocardial pathology in patients with the billowing posterior mitral leaflet remains unknown, but the view is favored that the pathology of the leaflet precedes that of the papillary muscles in the majority of patients. © 1971.