Left ventricle-aortic coupling: prediction of contraction pattern.

In control heart beats of six open-chest dogs we established a relationship between ventricular diameter and change in volume during systolic ejection, described ventricular mechanical performance by a time-dependent pressure-diameter relationship, and represented ventricular afterload in subsequent variably loaded test beats by aortic input impedance calculated from aortic flow and pressure. Impedance was manipulated by means of an inflatable balloon in the aorta. A computational procedure was developed which combined the independent and general descriptions of ventricle (1 and 2 above) and load (3 above) to predict the time course and mean values of aortic pressure, flow, ventricular pressure, and diameter over a broad range of aortic impedance. Predicted data were compared with those directly observed at identical impedance. High degree of accordance between predicted and observed data of stroke volume, mean aortic and mean ventricular pressure was found, but diameter shortening was less accurately predicted. Previously assessed dependency of the ventricular pressure-volume-time relationship on aortic flow and "ejection history" was also incorporated in the calculations. This caused improved prediction of the flow pulse configuration, but the quality of predictions of mean values of pressures and flow was not enhanced.