Myocardial mechanical remodeling after septal myectomy for severe obstructive hypertrophic cardiomyopathy.

BACKGROUND

Septal myectomy for symptomatic patients with hypertrophic obstructive cardiomyopathy (HOCM) is a well-established procedure for symptomatic relief. Myocardial mechanics are abnormal in patients with HOCM, demonstrating low longitudinal strain, high circumferential strain, and high apical rotation compared with healthy subjects. The aim of this study was to determine whether functional improvement after myectomy is associated with improved myocardial mechanics.

METHODS

Clinical data and paired echocardiographic studies before and after myectomy (6-18 months) were retrospectively analyzed and compared in 66 patients (mean age, 54 ± 13 years; 64% men) with HOCM. Myocardial mechanics including longitudinal and circumferential strain and rotation were assessed using two-dimensional strain software (Velocity Vector Imaging).

RESULTS

Patients had significant symptomatic alleviation (mean New York Heart Association class, 2.8 ± 0.4 at baseline and 1.3 ± 0.5 after myectomy; P < .05). Left ventricular outflow gradient decreased dramatically (from 93 ± 26 to 17 ± 12 mm Hg; P < .05), and left atrial volume index decreased (from 48 ± 16 to 37 ± 13 cm(3)/m(2); P < .05). Low longitudinal strain decreased at the myectomy site, increased in the lateral segments, and remained unchanged globally (-16 ± 4). High circumferential strain decreased (from -31 ± 5 to -25 ± 6, P < .05). High left ventricular twist normalized (from -15.5 ± 6.2° to 12.8 ± 4.2°, P < .05). Independent predictors of symptomatic response included younger age before myectomy, thinner posterior wall, and higher lateral early diastolic velocity (e').

CONCLUSION

In patients with HOCM, surgical myectomy alleviated symptoms, relieved obstruction, and decreased left atrial volume index. Longitudinal strain remained unchanged, but circumferential strain and rotation decreased, demonstrating different mechanical adaptations to chronic elevated afterload seen in patients with severe aortic stenosis undergoing valve replacement. Disease extent (age, posterior wall involvement) and the presence of diastolic dysfunction seem to be related to partial symptomatic response to myectomy.