Outcomes of septal myectomy in patients with obstructive hypertrophic cardiomyopathy and minimal septal hypertrophy.

OBJECTIVE

To describe the clinical characteristics of patients with obstructive hypertrophic cardiomyopathy and less severe hypertrophy (septal thickness <15 mm) undergoing transaortic septal myectomy, explore possible mechanisms of obstruction, and assess operative outcomes.

METHODS

We identified 51 consecutive patients with septal thicknesses <15 mm who underwent septal myectomy for obstructive hypertrophic cardiomyopathy between 2000 and 2021. They were matched in a 1:2 ratio with patients with obstructive hypertrophic cardiomyopathy with septal thickness ≥15 mm undergoing myectomy.

RESULTS

After propensity matching, the preoperative left ventricular outflow tract (LVOT) gradient and severity of mitral valve regurgitation were similar in the 2 groups, but patients with less hypertrophy were more likely to have latent obstruction (55% vs 30%; P = .004). Both propensity score-matched groups had similar mitral valve anterior leaflet lengths (27 mm in both; P = .4). Patients with lesser hypertrophy had more acute angulation between the septum and the LVOT tract (118° vs 130°; P < .001). There was no significant difference in operative outcomes (bypass time median, 31 vs 34 minutes; P = .4), crossclamp time was 25 minutes in both; (P = .5), nor postoperative complications, including iatrogenic ventricular septal defect (1 [2%] vs 0 [0%]; P = .3). LVOT gradient before discharge was similar in both groups (median gradient, 0 mm Hg in both; P = .1). No patients died during their hospital stay.

CONCLUSIONS

Severe LVOT obstruction in patients with hypertrophic cardiomyopathy can occur in the absence of significant septal hypertrophy, particularly in women with acute LVOT angulation. Extended septal myectomy can be performed safely in these patients, with favorable outcomes, and mitral valve replacement is not necessary for most patients.