AJP - Heart Calcium Transients and Cell-Sarcomere
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Am J Physiol Heart Circ Physiol 279: H2855-H2864, 2000;
0363-6135/00 $5.00
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Vol. 279, Issue 6, H2855-H2864, December 2000

Negative inotropism of hyperthermia increases oxygen cost of contractility in canine hearts

Akio Saeki1, Yoichi Goto1, Katsuya Hata1, Toshiyuki Takasago1, Takehiko Nishioka, and Hiroyuki Suga2

1 Departments of Cardiovascular Dynamics and Medicine, National Cardiovascular Center, 5 Fujishirodai, Suita, Osaka, 565-8565; and 2 Department of Physiology II, Okayama University Medical School, 2 Shikatacho, Okayama, 700-8558 Japan

Heart temperature affects left ventricular (LV) function and myocardial metabolism. However, how and whether increasing heart temperature affects LV mechanoenergetics remain unclear. We designed the present study to investigate effects of increased temperature by 5°C from 36°C on LV contractility and energetics. We analyzed the LV contractility index (Emax) and the relation between the myocardial oxygen consumption (MVO2) and the pressure-volume area (PVA; a measure of LV total mechanical energy) in isovolumically contracting isolated canine hearts during normothermia (NT) and hyperthermia (HT). HT reduced Emax by 38% (P < 0.01) and shortened time to Emax by 20% (P < 0.05). HT, however, altered neither the slope nor the unloaded MVO2 of the MVO2-PVA relation. HT increased the oxygen cost of contractility (the incremental ratio of unloaded MVO2 to Emax) by 49%. When Ca2+ infusion restored the reduced LV contractility during HT to the NT baseline level, the unloaded MVO2 in HT exceeded the NT value by 36%. We conclude that HT-induced negative inotropism accompanies an increase in the oxygen cost of contractility.

temperature; pressure-volume area; myocardial oxygen consumption


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