Impact of Septal Myectomy on Left Atrial Volume and Left Ventricular Diastolic Filling Patterns: An Echocardiographic Study of Young Patients with Obstructive Hypertrophic Cardiomyopathy

Abstract

Septal myectomy in young patients with obstructive hypertrophic cardiomyopathy (HCM) can be performed with low mortality, and leads to excellent improvement in symptoms. Left atrial (LA) enlargement has been associated with exercise intolerance, severity of mitral regurgitation (MR), and left ventricular (LV) outflow tract (LVOT) obstruction in adults with HCM. Young patients (1-22 years of age) who had a septal myectomy for obstructive HCM between 2002 and 2005 were identified. Retrospective analyses of premyectomy and postmyectomy echocardiograms were performed. In this cohort of 32 patients (25 male), the average maximal LV wall thickness was 25 +/- 9 mm and LVOT maximal instantaneous gradient was 106 +/- 44 mm Hg. MR was present in all patients with a mean grade of 3 +/- 1. All patients had successful myectomy and there were no early deaths. After myectomy, LVOT maximal instantaneous gradient decreased to 17 +/- 13 mm Hg (P < .0001). Mean LA volume (LAV) index decreased from 52.1 +/- 2.2 to 33.2 +/- 11.9 mL/m(2) (P < .0001). Mean MR grade decreased to 2 +/- 1. Early mitral medial annular tissue Doppler velocity (E') increased from 6.2 +/- 1.9 to 13 +/- 2.6 cm/s (P < .043). A postmyectomy decrease in LAV index correlated with decrease in LVOT obstruction (P = .001) and change in degree of MR (P = .04). Septal myectomy not only reduces LVOT maximal instantaneous gradient and MR in young patients, but also results in decreased LAV index, and E/A and E/E' ratios. These hemodynamic improvements may contribute to the observed survival benefit and increased exercise tolerance observed after myectomy. This is the first series to demonstrate that LAV correlates closely with hemodynamic status in children with obstructive HCM and may be a significant predictor of clinical outcome in these patients.