Cardiac Efficiency and Oxygen Consumption Measured with 11C-Acetate PET After Long-Term Cardiac Resynchronization Therapy

Cardiac resynchronization therapy (CRT) is a treatment option in patients with severe heart failure and left bundle-branch block (LBBB). This study evaluated the effects of 4 and 13 mo of CRT on myocardial oxygen consumption (MVO2) and cardiac effi-ciency as compared with mild heart failure patients without LBBB. Methods: Sixteen patients with severe heart failure and LBBBdue to idiopathic cardiomyopathywere studied at baseline and after 4 and after 13mo of therapy. Thirteen patients withmild heart failure without LBBB served as a comparison group. The clearance rate (k2) of 11C-acetate was measured with PET to as-sess MVO2. Stroke volume was derived from the dynamic PET data according to the Stewart–Hamilton principle and, further-more, cardiac efficiency using the work metabolic index. Re-sults: After 4 mo of CRT, stroke volume index (SVI) increased by 50 % (P 5 0.012) and cardiac efficiency increased by 41% (P, 0.001). Global k2 remained unchanged but regional k2 dem-onstrated amore homogeneous distribution pattern. The param-eters showed no significant changes during therapy. Under CRT, cardiac efficiency, SVI, and the distribution pattern of regional k2 did not differ frommild heart failure patients without LBBB. Con-clusion: CRT improves cardiac efficiency for at least 13 mo, as demonstrated by a higher SVI, whereas MVO2 remains unchanged. Cardiac efficiency, SVI, and the MVO2 distribution pattern reach the level of patients with mild heart failure without LBBB. The unfavorable hemodynamic performance in heart fail-ure with LBBB is effectively restored by long-term CRT to the level of an earlier disease state. Key Words: heart failure; bundle-branch block; pacing; cardiac outpu