THE OXYGEN CONSUMPTION AND MECHANICAL EFFICIENCY OF THE HEART BEFORE AND DURING HEART FAILURE

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Abstract
Further expts. were carried out on the isolated heart and the closed heart-lung prepns. under conditions of constant work and constant aortic pressure in order to compare the mechanical efficiency of the failing heart with its efficiency before failure develops. Repeated efficiency detns. in 8 isolated heart and 11 heart-lung prepns. fail to reveal any significant differences in efficiency between control and failure periods. The effect upon mechanical efficiency of different work loads imposed upon different hearts was investigated in the same prepns. For hearts whose efficiency at a certain work level is similar, efficiency is an asymptotic function of work according to the equation:[image] is considered to be constant for each heart. The hearts used in this study have been arranged into 3 efficiency groups. The values for resting O2 consumption and for the constant [image] efficiency and O2 curves have been calculated according to the above equation. A fair degree of agreement between the calculated and the exptl. curves was found.

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