Septal myotomy-myomectomy versus mitral valve replacement in hypertrophic cardiomyopathy. Ten-year follow-up in 185 patients.

Between 1963 and 1985, 185 patients with hypertrophic cardiomyopathy (HCM) were treated with septal myotomy-myomectomy (MM) or mitral valve replacement (MVR) at our institution; 127 of these underwent septal MM, and 58 underwent MVR alone. The 1-month mortality was 4.7% for the septal MM group and 6.9% for the MVR group (p = NS). The mean time of postoperative follow-up was 118 months, ranging between 1 and 196 months. The annual mortality was 0.7% for the septal MM group and 1.3% for the MVR group (p = NS). In the MVR group, 98% of patients had been assigned to New York Heart Association (NYHA) functional classes III and IV before surgery; only 24% were classified as such at 10-year follow-up (p less than 0.001). In the septal MM group, 90% were in NYHA functional classes III and IV before surgery whereas only 27% were in these two classes postoperatively (p less than 0.001). A comparison of preoperative and postoperative hemodynamic findings revealed a significant reduction in left ventricular outflow gradient at rest: from 69 +/- 41 mm Hg preoperatively to 10 +/- 22 mm Hg postoperatively (p less than 0.001) in the septal MM group and from 75 +/- 45 mm Hg preoperatively to 10 +/- 21 mm Hg postoperatively (p less than 0.001) in the MVR group. In addition, the MVR group had a significant postoperative reduction in mean left ventricular end-diastolic pressure, from 21 mm Hg preoperatively to 15 mm Hg postoperatively (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)