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First published online on May 15, 2007
Chest, doi:10.1378/chest.06-2872
A more recent version of this article appeared on July 1, 2007
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Effect of Biventricular Pacing on the Exercise Pathophysiology of Heart Failure

Karlman Wasserman, MD, PhD; Xing-Guo Sun, MD and James E. Hansen, MD

Department of Medicine, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, 1124 W Carson St, Torrance, CA 90502

kwasserman{at}labiomed.org

Abstract

BackgroundBiventricular pacing (BVP) is used for cardiac resynchronization therapy in wide-QRS-complex heart failure. We sought to quantify the effect of BVP on the exercise pathophysiology of heart failure patients.

MethodsUsing cardiopulmonary exercise testing, we analyzed exercise data for a multi-center study sponsored by St. Jude Medical. Patients had pacemaker electrodes implanted in both ventricles in the standard manner, and were randomized by St Jude before exercise testing. Exercise measurements included peak O2 uptake, peak O2 pulse, anaerobic threshold (AT ), and ventilatory equivalent for CO2 (reflecting change in peak exercise cardiac output, stroke volume, maximal sustainable exercise capacity, and ventilation-perfusion mismatching, respectively) at baseline and 6-months. The studies included progressively and uniformly increasing work rate to maximum tolerance. We were blinded both to sponsor-controlled randomization and pacemaker status. There were 239 paired 6-month studies: 47 studies served as control with the pacemaker-off (BVP-OFF); 192 patients had pacing (BVP-ON).

ResultsThe BVP-ON group significantly improved all exercise parameters in contrast to the control group (P<0.0001). When the BVP-ON group was ranked in quintiles, only the three functionally worst quintiles (peak Vo2 < 11.6 ml/min/kg, AT < 8.8 ml/min/kg, peak O2 pulse < 12.0 ml/min/beat, Ve/Vco2@AT>38.1) improved significantly at 6 months (P<0.01 to <0.0001).

ConclusionBVP benefited aerobic function and ventilation-perfusion mismatching most in those patients with the greatest physiological impairment.

Key Words: Cardiopulmonary exercise testing • heart failure • biventricular pacing • cardiac resynchronization therapy • oxygen transport • peak Vo2 • anaerobic threshold • peak O2 pulse • ventilatory efficiency






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