Right Ventricular Energetics in Patients With Hypertrophic Cardiomyopathy and the Effect of Alcohol Septal Ablation

Abstract

Background Diastolic dysfunction in hypertrophic cardiomyopathy (HCM) is accompanied by augmented left ventricular (LV) end-diastolic pressure, above all in the presence of LV outflow tract (LVOT) obstruction. Increased back-pressure may augment right ventricular (RV) afterload and induce an oxidative metabolic imbalance between the 2 ventricles. The aim was to study right-to-left ventricular oxidative metabolism in HCM and the effects of alcohol septal ablation (ASA). Methods and Results Twenty-one HCM patients were enrolled. Eleven healthy subjects served as a control group. Subjects underwent 2-dimensional echocardiography to assess LVOT gradient, left atrial size, and diastolic function. [ 11C]Acetate positron-emission tomography (PET) was performed to determine RV k 2 and LV k 2, as a noninvasive index of oxidative metabolism. Seven HCM patients with LVOT obstruction, scheduled to undergo ASA, were also studied 6 months after the procedure. RV k 2 was higher in HCM patients than i control subjects (0.081 ± 0.021 min −1 vs. 0.061 ± 0.017 min −1; P = .05), whereas LV k 2 was similar between groups. Consequently, RV k 2/LV k 2 was increased in the patients (0.85 ± 0.19 vs 0.59 ± 0.13; P = .004). In patients with obstructive HCM, ASA reduced RV k 2 (0.085 ± 0.021 min −1 to 0.072 ± 0.022 min −1; P = .001). Inasmuch as LV k 2 remained unaffected by the procedure, RV k 2/LV k 2 was decreased after ASA (0.66 ± 0.18; P = .03). The absolute change in LVOT gradient was related to the absolute change in RV k 2 ( r = 0.77; P = .044). Conclusions In HCM patients, RV oxygen consumption is increased in relation to the LV. ASA reduces RV oxygen consumption in HCM patients with LVOT obstruction, suggesting that increased LV loading conditions and diastolic dysfunction play a predominant role in augmenting RV workload in these patients.