Temporal relationship between left ventricular and arterial system elastances

The authors investigated the temporal relationship of arterial compliance to ventricular elastance of the left ventricle (E _lv(t)) in five open-chest anesthetized dogs, where simultaneous aortic pressure and flow and left-ventricular pressure were measured. E _lv(t) was derived using an elastance-resistance model of the left ventricle. The nonlinear pressure-dependent compliance (C(P)) of the arterial system was incorporated in a three-element Windkessel model and determined by accurate prediction of aortic pressure from aortic flow. The resulting arterial elastance E _as(t) was computed as E _as(t)=1/C(P). Results show that E _as(t) reaches a minimum value at or near the start of ventricular ejection and attains its peak value at or near the time that maximum left ventricular elastance is reached, at end-systole. Numerical simulation of the model demonstrates its ability to adequately reproduce measured pressure and flow. Thus, the arterial system, in terms of elastance, is dynamically and temporally coupled to the left-ventricle during ejection.