HYPERTROPHIC OBSTRUCTIVE CARDIOMYOPATHY WITH ABNORMALITIES OF THE MITRAL-VALVE COMPLEX

The mechanism of obstruction of the left ventricular outflow tract (LV OT) in hypertrophic obstructive cardiomyopathy (HOCM) is mainly due to dynamic systolic anterior motion (SAM) of the mitral valve. We report a case of HOCM with mitral regurgitation (MR) associated with complic ated abnormalities of the mitral apparatus which contributed to a high pressure gradient through the LVOT. A small, 53-year-old woman was ad mitted for chest pain and palpitation. Examinations revealed asymmetri c septal hypertrophy of the left ventricle, MR, SAM of the mitral valv e and a high pressure gradient (108 mmHg) through the LVOT. Operative findings revealed an abnormally hypertrophied interventricular septum, an extensively thickened and enlarged anterior mitral leaflet (AML), malposition of the origin of the anterior papillary muscle arising clo ser to the aortic annulus than normal, and its direct insertion into t he AMI, without any distinguishable chordae tendineae. The hypertrophi ed septum and the large and protruding AML appeared to obstruct the LV OT, resulting in a loss of subaortic clearance that was recovered afte r mitral valve replacement and myectomy. Pathology of the papillary mu scle was characteristic of HOCM, showing disorganization and disarray of myocardial fibers, bizarre-shaped nuclei, and intercellular fibrosi s, while those of the mitral leaflets negated both rheumatic changes a nd endocarditis.