Hypertrophic cardiomyopathy with latent obstruction: Clinical characteristics and surgical results

The role of mitral subvalvular anomalies in the etiology of latent left ventricular outflow tract (LVOT) obstruction has rarely been reported; and the results of surgical treatment for latent LVOT obstruction have been infrequently reported as a separate group by other medical centers other than Mayo clinic.

Among 292 eligible patients, 45 with resting gradients <30 mmHg had provoked obstruction. Their clinical characteristics and surgical results were compared with those of 247 patients with resting LVOT obstruction. The patients were followed up for a median of 13 months.

Comparatively, patients with latent obstruction were younger (51.6±12.1 years vs. 57.2±11.6 years, p=0.003) and had higher prevalence of mitral subvalvular abnormalities (73.3% vs. 16.2%, p<0.001) and basal variant of hypertrophic cardiomyopathy (84.5% vs. 62.0%, p=0.014), less marked septal thickness (16.9±2.8 mm vs. 18.6±3.8 mm, p=0.005), lower resting gradients (22.2±5.7 mmHg vs. 93.0±25.7 mmHg, p < 0.001), and lower mitral regurgitation severity (median, 2.0 vs. 3.0, p<0.001). After surgery, no surgical death occurred in patients with latent LVOT obstruction. Only one (2.2%) patient from the latent group developed complete atrioventricular block. No follow-up death or reoperation was recorded with a significant improvement in New York Heart Association functional status in either group. The provoked LVOT gradients of patients with latent obstruction decreased sharply from the preoperative value (11.8±3.7 mmHg vs. 89.8±16.4 mmHg, p < 0.001), with no occurrence of residual obstruction.

Symptomatic patients with latent LVOT obstruction may have a higher prevalence of mitral subvalvular abnormalities and have less marked septal hypertrophy; and concomitant mitral management during myectomy for the treatment of this patient group achieved excellent results.