Abstract 3418: Impact of Septal Myectomy on Left Atrial Volume and Left Ventricular Diastolic Filling Patterns: An Echocardiographic Study of Young Patients With Obstructive Hypertrophic Cardiomyopathy
Introduction: Septal myectomy in young patients (pts) with obstructive hypertrophic cardiomyopathy (HCM) can be performed with low mortality, excellent relief of left ventricular outflow tract gradient (LVOTG) and symptoms. Left atrial (LA) enlargement and left ventricular (LV) diastolic filling have been associated with exercise tolerance, severity of mitral regurgitation (MR) and LVOT obstruction in adults with HCM.
Method: Pts from1 to 22 yrs. old who had septal myectomy for obstructive HCM from 2002 to 2005 were identified. Retrospective analyses of pre and post myectomy (prior to hospital dismissal) echocardiograms were performed. Echocardiographic and Doppler parameters were obtained according to the recommendations of the American Society of Echocardiography.
Results: For this cohort of 32 subjects, median age at myectomy was 12.5 yrs. (1–22yrs), mean maximal LV wall thickness was 25 ± 9 mm, and average maximal LVOTG was 106 ± 44 mm Hg. Mitral regurgitation was present in all, mean grade = moderate. All pts had successful myectomy and there were no early deaths. After myectomy, mean LA volume index (LAVI) decreased from 52 ± 21 to 33 ± 12 ml/m2 (p < .0001). LVOTG decreased to 17 ± 13 mm Hg (p< .0001). Mean MR grade decreased to mild. Early mitral medial annular tissue Doppler velocity (E’, cm/sec) increased from 6±2 to 17±2 (p < .05). Post-myectomy, significant decrease in LV end diastolic pressure was demonstrated by a decrease in mean mitral inflow E/A ratio from 1.9 ± 0.7 to 1.3 ± 0.5 (p<.0001) and E/E’ from 20 ± 6.0 to 10 ± 4.0 (p <0.001). Linear regression analysis revealed a positive association of preoperative LAVI with increasing LVOTG, E/E’ and degree of MR (p < 0.01). Post-myectomy decrease in LAVI correlated with decrease in LVOTG (p = 0.001) and change in degree of MR (p < 0.05).
Conclusion: Septal myectomy not only reduces LVOTG and MR in young pts, but also significantly reduces LV diastolic filling pressure, evidenced by decreases in LAVI, E/A and E/e’ ratios. The hemodynamic improvements that stem from surgical myectomy likely contribute to the observed survival benefit and increased exercise tolerance observed following myectomy. This is the first series to show that left atrial volume correlates closely with hemodynamic status in children.