[Etiology and incidence of pure mitral insufficiency: a morphological study of 926 native valves].

From July 1981 to October 1988, 1597 native valves, 926 (58%) mitral and 671 (42%) aortic, were excised. The gross and histological features of all valves were studied using routine histochemical, immunohistochemical and electron microscopy techniques. As far as mitral valve is concerned the lesions were: stenosis 263 (28.6%), stenosis + incompetence 537 (57.8%) and incompetence 126 (13.6%). Our study was limited to the valves of patients undergoing mitral valve replacement because of pure incompetence. The pathological alterations of the valves were: floppy mitral valve (FMV) 59 (46.8%), rheumatic disease (RD) 50 (39.6%), infective endocarditis (IE) 13 (10.3%), papillary muscles ischemic disease (PMID) 4 (3.1%). In the FMV group the associated lesions were: aortic valve incompetence due to floppy aortic valve and noninflammatory aortic root disease (9-15.2%), tricuspid valve incompetence (4-7.8%) and atrial septal defect (7-13.7%). The commonest complication in this group was rupture of chordae tendineae requiring urgent surgery. In the RD group there was a high incidence of active rheumatism, valvulitis and papillary muscles myocarditis (37-74%) despite the laboratory data were within normal ranges. In the IE group there was an associated aortic endocarditis in 7 patients (53.8%). The FMV was the commonest cause of pure incompetence in patients who had mitral valve replacement. Rheumatic pure mitral incompetence was always associated in our experience to signs of active rheumatic disease.