Temperature distribution cannot predict local cardiac metabolism.
The objective of this study was to investigate if local myocardial metabolism can be determined from the transmural temperature distribution. Heat produced metabolically in the myocardium is carried away by the coronary blood and by diffusion. Transport by coronary flow (convectional heat loss) was determined from the coronary blood flow and the transcoronary temperature difference. This measured value was compared with one predicted from measured oxygen consumption, assuming a slab of tissue for the left ventricular free wall with homogeneous flow distribution and homogeneous metabolism. Measured and predicted convectional heat loss could not be shown to differ. Endocardial and epicardial heat production were estimated in two ways: 1) from the transmural temperature distribution (AT) and 2) from local flow (radioactive microspheres) and oxygen consumption (AO2). Ideally the ratio AT/AO2 should be unity. For flows in the resting physiological state (up to 100 ml X min-1 X 100 g-1) this ratio was not statistically different from one for both endocardium and epicardium: 0.86 +/- 0.11 and 1.09 +/- 0.07 (SE), respectively. For larger flows the ratio reduced to 0.66 +/- 0.08 endocardially. It is concluded that overall left ventricular metabolism can be predicted from conventional heat loss and that for physiological, but not for increased flow, the transmural temperature distribution predicts local metabolism.
D000818:Animals; D001833:Body Temperature Regulation; D003326:Coronary Circulation; D004285:Dogs; D008297:Male; D008433:Mathematics; D009206:Myocardium / Q000378:metabolism*; D010101:Oxygen Consumption; D012039:Regional Blood Flow; D014018:Tissue Distribution