VENTRICULAR INTERACTION IS DESCRIBED BY 3 COUPLING-COEFFICIENTS

Previous studies of ventricular interaction have quantified interactio n by making small pressure or volume changes in one ventricle and meas uring the resulting pressure or volume changes in the opposite ventric le. The ratios between the pressure and volume changes in opposite ven tricles have been used as coupling coefficients or measures of ventric ular interaction. This method of calculating coupling coefficients imp licitly uses mathematical relationships that have useful features not generally appreciated. Starting from the definition of coupling coeffi cients 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 t he single assumption that the ventricles behave elastically, we show t hat the set of four coefficients can be reduced to a set of three. Thu s only three indexes are required to describe interaction, but these m ay vary with changes in ventricular volumes and pressures around which the indexes are measured. Furthermore, when comparisons between exper imental studies are made, it is necessary to normalize the indexes wit h respect to ventricular volume.