The problem of nonejection systolic clicks and associated mitral systolic murmurs: emphasis on the billowing mitral leaflet syndrome.

Nonejection clicks and associated mitral systolic murmurs are common in routine cardiologic practice and can result from multiple etiologic factors affecting the complex mitral valve mechanism. Such factors include a specific syndrome the essential feature of which is that the mitral leaflets or part thereof, primarily the posterior one, are voluminous. The syndrome has stimulated widespread interest and study during the last decade and various descriptive terms, including the "billowing mitral leaflet syndrome" (BMLS), have been applied to it. A familial occurrence of the BMLS may be detected and symptoms include chest pain, palpitations, syncope, and anxiety. Arrhythmias, conduction defects, and ECG abnormalities which mimic occlusive coronary artery disease are important features which remain ill understood. It is suggested that there is a possible relationship between the so-called "athlete's heart" and the BMLS. We also postulate that the entity of acute myocardial infarction without demonstrable occlusive coronary artery disease is, in at least some instances, a complication of the BMLS-possibly on the basis of coronary spasm. More severe mitral regurgitation, infective endocarditis, or, rarely, sudden death may supervene in the BMLS but we conclude, from published data and our own experience, that the prognosis is generally good.