ABSTRACT
A 54-year-old man was admitted to our hospital because of hypertrophic obstructive cardiomyopathy (HOCM). Medical treatment was not effective. Cardiac catheterization showed a peak systolic pressure gradient of 143mmHg between the left ventricle and the ascending aorta. Echocardiogram showed a systolic anterior motion and moderate mitral regurgitation without asymmetric septal hypertrophy. He underwent mitral valve replacement (MVR) with a 27-mm SJM instead of myectomy due to his relatively thin ventricular septum of 16mm. Postoperative cardiac catheterization revealed no significant pressure gradient between the left ventricle and the ascending aorta. MVR is the most effective surgical treatment of HOCM without asymmetric septal hypertrophy.