AJP - Heart and Circulatory Physiology, Vol 236, Issue 3 494-H497, Copyright © 1979 by American Physiological Society
External mechanical work from relaxing ventricle
H. Suga
The possibility has been proposed earlier that the specific pressure-volume
(P-V) area bounded by the left ventricular end-systolic and end-diastolic
P-V curves and the isovolumic relaxation part of the P-V loop represents
mechanical potential energy that has been built during systole and is
stored at end systole in the wall of the ventricle. In the present study on
canine left ventricles, as much as 70% of the P-V area was actually
converted into external mechanical work when ventricular volume was allowed
to decrease at an appropriate speed (about 55 ml/s in 70 g left ventricle)
during relaxation. Less external work was extracted from the same P-V area
when the speed of volume reduction was either higher or lower than that
speed. These results indicate that the P-V area is equivalent to a form of
potential energy, which is wasted with isovolumic relaxation but most of
which is convertible to external mechanical work if the ventricle is
allowed to eject against an appropriately decreasing afterload during
relaxation.
