Determination of left ventricular heat production in working dog heart

1 degree Total left ventricular heat production was reliably estimated from the coronary blood flow, the coronary arteriovenous thermal difference and the thermodilution curve areas recorded in aortic root and in coronary sinus after injection of cold glucose solution into the left ventricular cavity. The assumption was made that the distribution of a cold solution, purposely introduced into the coronary arteries, obeys the same law as the heat generated by the myocardium. 2 degrees Temperature measurements were achieved with thermistors and a linear ohmmeter. Experiments were performed on thoracotomized dogs, allowing the utilization of an ultrasonic method for determination of the entire coronary sinus blood flow diverted through a cannula positioned in the coronary sinus. The spontaneous changes in acid-base balance and hemodynamic state, which were not systematically avoided, provided a fairly large interval of variation for coronary flow and myocardial oxygen consumption. 3 degrees Within the power interval of 0.5-2.2 watts per 100 g of left ventricular weight, there was a good linear correlation between left ventricular oxygen consumption and the sum of left ventricular heat production and external pressure power. 4 degrees These results suggest that the proposed method is a valuable approach for determination of the cardiac energetics in the in situ working heart. This method permitted repeated determinations of left myocardial heat production and may lead to a practical approach for measuring the left ventricular efficiency in intact animals.