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.