Transmyocardial Temperature Gradient in Dog and Man: Relation to the Polarity of the T wave of the Electrocardiogram

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Abstract
The transmyocardial temperature gradient was measured in both right and left ventricles and in the septum of the dog by percutaneous ventricular puncture, using a no. 21 thin-wall needle fitted with a thermocouple stylus. The outer half of the left ventricular myocardium was invariably warmer than the endocardium. The peak temperature of the right ventricle was located midway between the endocardium and epicardium. The midseptal region was found to have a higher temperature than either its right or left endocardial aspects. The left ventricular cavity was cooler than the right ventricular cavity by a mean of 0.1°C. The transmyocardial temperature gradient was measured successfully in the left ventricle of two patients with cardiac disease. As in the dog, the outer layers of the myocardium were warmer than either the endocardium or cavity in these two patients. In one patient the T waves in the left precordial leads were negative and in the other the T waves were upright in the same lead. The location of peak temperature consistently in the outer half of the left ventricular wall may partly explain the normal upright T wave and may contribute to a more rapid recovery in the outer layers of the ventricle compared with the inner layers. However, reversal of the T wave must be explained by other factors and it is apparent that the polarity of the T wave is not governed exclusively by the transmyocardial temperature gradient. The transmyocardial temperature gradient may be explained partly on the basis of differences in heat removal by blood flow in the coronary system as well as in the ventricular cavity. The latter was found to be an important factor, because during ventricular fibrillation the transmyocardial temperature gradient was abolished.