Heat transport in the canine left ventricular wall

The rate of rise of local myocardial temperature (dT/dt) evoked by left coronary artery main stem occlusion has been proposed in the literature as a measure of local metabolic heat production, assuming heat loss due to diffusion to be negligible. In a previous study (ten Velden, G. H. M., G. Elzinga, and N. Westerhof. Circ. Res. 50: 63-73, 1982), we showed that this assumption was not valid. With this information in mind, in an attempt to study local metabolism, we compared, in anesthetized dogs, the dT/dt with the temperature distribution over the left ventricular wall. We found the value of dT/dt to be reproducible in time and to reproducibly depend on location. Negative values as well as positive values were measured; values even higher than the maximal possible temperature slope, calculated from the energy equivalent of left ventricular oxygen consumption and the specific heat of cardiac tissue, were found. Transmural distribution of the dT/dt showed positive values epicardially and negative values endocardially, while, as previously shown, a parabola-like shape of the transmyocardial temperature distribution existed. Our findings demonstrate that dT/dt by left coronary main stem occlusion cannot be used as a measure of local myocardial heat production.