AJP - Heart and Circulatory Physiology, Vol 266, Issue 1 228-H234, Copyright © 1994 by American Physiological Society
Ventricular interaction is described by three coupling coefficients
M. F. Taher, W. P. Santamore and D. K. Bogen
Department of Bioengineering, University of Pennsylvania, Philadelphia.
Previous studies of ventricular interaction have quantified interaction by
making small pressure or volume changes in one ventricle and measuring the
resulting pressure or volume changes in the opposite ventricle. The ratios
between the pressure and volume changes in opposite ventricles have been
used as coupling coefficients or measures of ventricular interaction. This
method of calculating coupling coefficients implicitly uses mathematical
relationships that have useful features not generally appreciated. Starting
from the definition of coupling coefficients we show that, without making
any assumptions about ventricular interaction, all 24 possible coupling
coefficients can be derived from a smaller set of four coupling
coefficients. Furthermore, by making the single assumption that the
ventricles behave elastically, we show that the set of four coefficients
can be reduced to a set of three. Thus only three indexes are required to
describe interaction, but these may vary with changes in ventricular
volumes and pressures around which the indexes are measured. Furthermore,
when comparisons between experimental studies are made, it is necessary to
normalize the indexes with respect to ventricular volume.
