THE EFFECT OF VARYING RESISTANCE-LOAD AND INPUT-LOAD ON THE ENERGETICS OF THE SURVIVING MAMMALIAN HEART

Abstract

A method is described for obtaining a true mixed coronary venous blood sample in the heart-lung or isolated heart prep. of the dog, and for calculating the true O2 consumption of the heart. Measurements of O2 consumption and work of the heart prep. indicate that the increase in O2 consumption consequent upon an increase in work depends not only upon the magnitude of the work increase, but also on whether the augmented work is produced by raising the venous return or the peripheral resistance. In the former case the increase in O2 consumption is proportionally less than in the latter, so that a given amt. of work is done more efficiently with a large venous return and a low peripheral resistance than the same amt. of work done with a low venous return and a high peripheral resistance.