Relationship between left ventricular mass, wall thickness, and survival after subaortic septal myectomy for hypertrophic obstructive cardiomyopathy

Objective: In natural history studies, increased left ventricular mass and wall thickness are strongly associated with increased late mortality in patients with hypertrophic cardiomyopathy. Our objective was to determine the impact of left ventricular mass and wall thickness on survival after myectomy for hypertrophic obstructive cardiomyopathy. Methods: We reviewed the case histories of 796 patients who underwent transaortic septal myectomy for hypertrophic obstructive cardiomyopathy from January 1993 to December 2006. We then selected for study patients who had transthoracic echocardiography within 30 days after myectomy, which included complete measurements of interventricular wall thickness, posterior wall thickness, and left ventricular end diastolic dimension. Late survival was determined for all patients using medical records and surveys. Results: Our study group included 416 patients with a mean age of 50 ± 15 years, and 58% were male. Eight percent of patients had coronary artery disease, 17% had a history of arrhythmia, and 17% had a previous or concomitant insertion of an internal cardioverter defibrillator. All patients had successful myectomy, and 17% required an additional mitral valve procedure, most often mitral valve repair. On predismissal echocardiography, the average interventricular wall thickness was 16 ± 5 mm, the posterior wall thickness was 13 ± 3 mm, and the left ventricular end diastolic dimension was 45 ± 6 mm. The indexed left ventricular mass was 135 ± 46 g/m². Late survival at 1, 5, and 10 years was 99%, 97%, and 85%, which was similar to that of an age- and gender-matched population (P = .453). On multivariate analysis, preoperative and postoperative wall thickness and left ventricular mass were not associated with death; only a history of coronary artery disease (hazard ratio 4.9) was predictive of late mortality. Conclusions: Left ventricular mass and wall thickness were not predictors of late survival after myectomy for hypertrophic obstructive cardiomyopathy, and this is in contrast to natural history studies of patients who were not treated surgically. Late survival was similar to that of an age- and gender-matched population.