Circulation, Vol 86, 1291-1301, Copyright © 1992 by American Heart Association
K Hata, Y Goto, S Futaki, Y Ohgoshi, H Yaku, O Kawaguchi, T Takasago, A Saeki, TW Taylor and T Nishioka
BACKGROUND. We hypothesized that the effect of pimobendan (UD-CG 115 BS) to
increase calcium sensitivity of contractile protein might result in less
myocardial oxygen consumption (VO2) in comparison with dobutamine when they
enhance ventricular contractility to the same extent. To examine this
hypothesis, we compared the effects of pimobendan and dobutamine on left
ventricular contractility and energetics using the frameworks of Emax
(contractility index) and the relation between VO2 and PVA (systolic
pressure-volume area, a measure of left ventricular total mechanical
energy). METHODS AND RESULTS. We measured VO2, Emax, PVA, and force-time
integral (FTI) in excised, cross-circulated, nonfailing dog hearts. The
slope of the VO2-PVA relation reciprocally indicates the efficiency from
PVA-dependent VO2 to the total mechanical energy (contractile efficiency).
The VO2 intercept of the VO2-PVA relation, i.e., PVA-independent VO2,
reflects energy utilization for excitation-contraction coupling. The ratio
of FTI to PVA-dependent VO2 can be called contractile economy. Both drugs
comparably enhanced Emax. Although the contractile economy was greater by
14 +/- 19% (p less than 0.05) for pimobendan than for dobutamine, the
contractile efficiency was similar between the two drugs. Oxygen cost of
contractility, defined as the slope of the relation between the
PVA-independent VO2 and Emax, was the same between the two drugs. Other
mechanoenergetic effects of both drugs were similar except for a greater
coronary vasodilating effect of pimobendan. CONCLUSIONS. Pimobendan has
almost the same mechanoenergetic effects as dobutamine but slightly greater
contractile economy and coronary vasodilation. The calcium-sensitizing
effect of pimobendan did not save the oxygen cost of contractility.
ARTICLES
Mechanoenergetic effects of pimobendan in canine left ventricles. Comparison with dobutamine
Department of Cardiovascular Dynamics, National Cardiovascular Center, Osaka, Japan.
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