Hypertrophic obstructive cardiomyopathy with a basal septal thickness of 16 mm or less: clinical characteristics and surgical results.

Purposes: To characterize the clinical features and surgical outcomes of symptomatic hypertrophic obstructive cardiomyopathy (HOCM) in patients with only mild septal hypertrophy. Methods: The clinical characteristics and surgical outcomes of 53 HOCM patients with a basal septal thickness ≤ 16 mm (mild group) were compared with those of 128 HOCM patients with a basal septal thickness > 16 mm (control group). Results: The mild group had a greater prevalence of mitral subvalvular anomalies than the control group (79.2% vs. 6.3%, p < 0.001). Neither iatrogenic septal perforation nor inadequate septal myectomy was observed after myectomy in the mild group. There were no deaths during a median follow-up of 10 months. Transthoracic echocardiography 6 months after myectomy revealed a significant decrease in maximum gradients in both groups, from baseline 90.5 ± 21.5 mmHg to 10.3 ± 4.4 mmHg in the mild group (p < 0.001) and from 95.0 ± 22.0 mmHg to 12.0 ± 5.9 mmHg (p < 0.001) in the control group. Neither residual obstruction nor residual mitral regurgitation was recorded in the mild group. Conclusions: Symptomatic patients with hypertrophic obstructive cardiomyopathy and mild septal hypertrophy may have a higher prevalence of mitral subvalvular abnormalities. Mitral subvalvular management during myectomy can achieve outstanding results for these patients. [ABSTRACT FROM AUTHOR]