Right ventricular energetics in patients with hypertrophic cardiomyopathy and the effect of alcohol septal ablation

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 RVk2and LVk2, 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. RVk2was higher in HCM patients than i control subjects (0.081 ± 0.021 min-1vs. 0.061 ± 0.017 min-1; P =.05), whereas LVk2was similar between groups. Consequently, RVk2/LVk2was increased in the patients (0.85 ± 0.19 vs 0.59 ± 0.13; P =.004). In patients with obstructive HCM, ASA reduced RVk2(0.085 ± 0.021 min-1to 0.072 ± 0.022 min-1; P =.001). Inasmuch as LVk2remained unaffected by the procedure, RVk2/LVk2was decreased after ASA (0.66 ± 0.18; P =.03). The absolute change in LVOT gradient was related to the absolute change in RVk2(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.

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