Ventriculo–Vascular Interaction

Abstract

The complex relationship between the pressure generated by the ventricle and the blood flow has been extensively investigated in the mature circulation. Numerous difficulties in studying the coupling between the ventricle and the arterial compartment arise on account of rapid changes within the ventricle itself, i.e., in its dimension and contractility, as well as due to dynamic changes in the aorta and the associated arterial compartment. A simultaneous recording of ventricular pressure and volume during cardiac cycle generates pressure–volume (P-V) loops which represent the periodic nature of this event. Data on P-V and end-systolic pressure–volume relationship (ESPVR) now exists also for avian embryonic hearts. The performance of the ventricle (contractility) can be characterized as time-varying elastance which waxes and wanes during the heart cycle but is independent of instantaneous pressure and volume. The heart’s energy expenditure is related to its mechanical work, and a close relationship exists between its energetic demands and mechanical activity. The total work of the heart consists of the external work, which the heart performs against the aortic pressure (afterload), and the internal work needed in excitation–contraction coupling. It has been shown that the embryonic ventricle works near optimal working volume and that a close, highly responsive matching exists between the heart and the circulation.