Ventricular interaction is described by three coupling coefficients.

Abstract

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.