The relationship between the pva and myocardial oxygen consumption
can be derived from thermodynamics.
Denslow, Stewart.
South Carolina Children's Heart Center, Medical University of South
Carolina, Charleston, South Carolina 29425
APStracts 2:0342H, 1995.
The pressure-volume area (PVA) has been shown to be an excellent,
linear index of myocardial oxygen consumption. The thermodynamic
basis for this result, however, has not been elucidated. The present
study was undertaken to determine what information could be gained
from analyzing the cardiac pressure-volume cycle as an approximation
to some "ideal" thermodynamic cycle operating under the
constraints imposed by cardiovascular anatomy and physiology. The
myocardium was approximated as a linear, chemically-driven elastance
in accordance with the time-varying elastance model. Analysis
provided descriptions of a Carnot cycle for myocardium and a sub
-optimal "ideal" cycle including isovolumic phases. Further
analysis of the "ideal" cycle indicated that the end systolic
pressure-volume ratio (ESPVR) is an approximation to the adiabatic
pressure-volume trajectory that primarily determines total energy
consumption. Analysis also indicated possible explanations of current
results seeming to be at odds with the time-varying elastance model.
These results suggest that thermodynamic cycle analysis may provide a
useful analytic tool for investigation of the cardiac cycle.
Received 14 March 1995; accepted in final form 2 August 1995.
APS Manuscript Number H245-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 14 August 1995.