HEART FAILURE ANALYZED IN THE ISOLATED HEART CIRCUIT

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Abstract
A single isolated heart circuit is described for the study of the dynamics and energetics of spontaneous heart failure. It is possible in this prep. to permit failure to occur with little or no change in total diastolic vol. With the development of heart failure, and with a relatively unchanged diastolic vol., there is a progressive decrease in the work and 0 consumption of the heart and little change in its mechanical efficiency. When the work of the heart is kept constant, no change in O consumption or mechanical efficiency occurs, despite a progressive increase in the diastolic vol. and the left auricular pressure. These expts. demonstrate that heart failure must be defined in terms of a single chamber, rather than the heart as a whole. Failure of a heart chamber is due to an increase in load, a decrease in contractile power or both of such a degree that the chamber begins to fail to do the work imposed upon it by the load. Loss of contractile power is manifested by a reduction in total energy release and hence work at a given diastolic vol. and (except terminally) not by a decrease with which the liberated energy is utilized for mechanical work.

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