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Am J Physiol Heart Circ Physiol 277: H65-H73, 1999;
0363-6135/99 $5.00
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Vol. 277, Issue 1, H65-H73, July 1999

O2 cost of contractility but not of mechanical energy increases with temperature in canine left ventricle

Takeshi Mikane1,2, Junichi Araki1, Shunsuke Suzuki1,2, Ju Mizuno1,2, Juichiro Shimizu1, Satoshi Mohri1,3, Hiromi Matsubara1,3, Masahisa Hirakawa2, Tohru Ohe3, and Hiroyuki Suga1

Departments of 1 Physiology II, 2 Anesthesiology and Resuscitology, and 3 Cardiovascular Medicine, Okayama University Medical School, Okayama 700-8558, Japan

We investigated the effects of myocardial temperature on left ventricular (LV) mechanoenergetics in the excised, cross-circulated canine heart. We used the framework of the LV contractility (Emax)-pressure-volume area (PVA; a measure of total mechanical energy)-myocardial oxygen consumption (VO2) relationship. We have shown this framework to be useful to integrative analysis of the mechanoenergetics of a beating heart. In isovolumic contractions at a constant pacing rate, increasing myocardial temperature from 30 to 40°C depressed Emax and increased the oxygen cost of Emax, which was enhanced by dobutamine, in a linear manner. However, the slope of the VO2-PVA relation (reciprocal of contractile efficiency) and its VO2 intercept remained constant. Q10 values of Emax, the oxygen cost of Emax, and the oxygen cost of PVA were 0.4, 2.1 and 1.0, respectively, around normothermia. We conclude that the temperature-dependent processes of cross-bridge cycling and Ca2+ handling integratively depress Emax and augment its oxygen cost without affecting the oxygen cost of PVA as myocardial temperature increases by 10°C around normothermia.

end-systolic pressure-volume relation; pressure-volume area; myocardial oxygen consumption; contractile efficiency


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 Am. J. Physiol. Heart Circ. Physiol.Home page
J. Mizuno, J. Araki, S. Suzuki, S. Mohri, T. Mikane, J. Shimizu, H. Matsubara, M. Hirakawa, T. Ohe, and H. Suga
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