Comparative effects of heart rate and aortic blood pressure on MVO2 in the anesthetized open-chest dog.

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Abstract
Comparative effects of heart rate and aortic blood pressure on myocardial O2 consumption (M.ovrhdot.VO2) were studied in anesthetized open-chest dogs. The left coronary artery was perfused through the external shunt with blood from the left common carotid artery. Heart rate was changed with the left atrial pacing and the constriction of the descending thoracic aorta was used to elevate the proximal aortic blood pressure (BP). The left ventricular end-diastolic pressure was insignificantly changed with the atrial pacing and with the aortic constriction. With the constant BP (100 .+-. 5 mm Hg), an unit increase in heart rate per min augmented M.ovrhdot.VO2 by 0.027 ml/min per 100 g of left ventricular muscle, while 1 mm Hg elevation of BP caused 0.15 ml increment in M.ovrhdot.VO2 per min per 100 g of left ventricular muscle under the constant heart rate (115 .+-. 5 beats/min). A unit change in BP caused 5- to 6-fold greater increase in M.ovrhdot.VO2 compared with that in heart rate, indicating extremely important roles of BP in M.ovrhdot.VO2.