Myocardial oxygen consumption and perfusion before and after cardiac resynchronization therapy: experimental observations and clinical implications

Aims Experimental studies indicated unfavourable effects on myocardial energetics and efficiency under asynchronous ventricular stimulation, also shown for left bundle branch block (LBBB) pattern. We noninvasively analyzed the effects on myocardial oxygen consumption (MVO2), perfusion (MBF) and pressure work efficiency by positron emission tomography (PET) before and after resynchronization therapy (CRT) in 31 patients with dilated cardiomyopathy (DCM) and LBBB. Methods 31 patients (19 mates, 12 females) with DCM were studied at baseline and PET 3-4 months follow-up. Baseline characteristics: age 61 +/- 7 years; NYHA class 3.0 +/- 0.4, ejection fraction 22.1 +/- 7.1%, QRS duration 187 +/- 19 ms. MVO2 and MBF were measured from C-11-acetate kinetics with PET by a one-compartment model. MVO2 and MBF were normalized to rate pressure product (RPP) to account for different pressure loads and predicted energy demands. Results Global MVO2 assessed from C-11-acetate clearance did not change significantly between baseline and follow-up (0.080 +/- 0.015/min vs. 0.082 +/- 0.020/min). RPP-normalized MVO2 significantly decreased after CRT (0.072 +/- 0.018/min) vs. baseline (0.081 +/- 0.017/ min; P < 0.05). Normalized MBF showed a concomitant decrease from 0.51 +/- 0.11 to 0.46 +/- 0.1 mL/min/g; P < 0.05 after CRT. Regional MVO2 significantly decreased in the lateral wall (0.083 +/- 0.020/min) compared to baseline (0.090 +/- 0.018/min; P < 0.05) and increased in the septum (0.081 +/- 0.022/min vs. 0.073 +/- 0.014/min at baseline). Conclusion 1. CRT does not increase absolute global MVO2 in the short-term. 2. RPP-normalized MVO2 even decreased suggesting improved pressure work efficiency. 3. CRT leads to a reverse remodelling of regional myocardial oxygen dysbalance. Q 2004 The European Society of Cardiology. Published by Elsevier Ltd. All rights reserved.