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Published Online
on December 9, 2002

Circulation. 2002
Published online before print December 9, 2002, doi: 10.1161/01.CIR.0000047068.02226.95
A more recent version of this article appeared on January 7, 2003
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Submitted on September 13, 2002
Accepted on October 28, 2002

Effect of Cardiac Resynchronization on Myocardial Efficiency and Regional Oxidative Metabolism

Heikki Ukkonen MD, Rob S.B. Beanlands MD, Ian G. Burwash MD, Robert A. de Kemp PhD, Claude Nahmias PhD, Ernest Fallen MD, Michael R.S. Hill PhD, and Anthony S.L. Tang MD*

From the Division of Cardiology, University of Ottawa Heart Institute, Ottawa, Ontario, Canada (H.U., R.S.B.B., I.B., R.A.d.K., A.S.L.T.); Divisions of Cardiology (E.F.) and Nuclear Medicine, McMaster University, Hamilton, Ontario, Canada (C.N.); and Heart Failure Research, Medtronic Inc, Minneapolis, Minn (M.R.S.H.).

* To whom correspondence should be addressed. E-mail: atang{at}ottawaheart.ca.

Background—Recent studies have demonstrated increased left ventricular contractility with cardiac resynchronization therapy (CRT) using atriobiventricular stimulation. This study evaluated the effect of CRT on myocardial oxidative metabolism and efficiency.

Methods and Results—Eight patients with New York Heart Association functional class III-IV congestive heart failure were studied during atrial pacing (control) and atriobiventricular stimulation at the same rate. The monoexponential clearance rate of [11C]acetate (kmono) was measured with positron emission tomography to assess myocardial oxidative metabolism in the left and right ventricles (LV and RV, respectively). Myocardial efficiency was measured using the work metabolic index (WMI). Stroke volume index improved by 10% (P=0.011) with CRT, although both global LV and RV kmono were unchanged compared with control. Septal kmono increased by 15% (P=0.04), and the septal/lateral wall kmono ratio increased by 22% (P=0.01). WMI increased by 13% (P=0.024) with CRT.

Conclusions—CRT improves LV function without increasing global LV oxidative metabolism, resulting in improved myocardial efficiency. Oxidative metabolism of the interventricular septum increases relative to the lateral wall, which suggests successful resynchronization.
Key words: heart failure • pacemakers • oxygen • metabolism • tomography






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