Optimal arterial resistance for the maximal stroke work studied in isolated canine left ventricle.

Abstract

In a previous analysis of ventricular arterial interaction (Sunagawa et al., 1983), we represented the left ventricle as an elastic chamber which periodically increases its volume elastance to a value equal to the slope of the linear end-systolic pressure-volume relationship. Similarly, the arterial load property was represented by an effective elastance which is the slope of the arterial end-systolic pressure-stroke volume relationship. Since the maximal transfer of potential energy from one elastic chamber to another occurs when they have equal elastance, we hypothesized that the left ventricle would do maximal external work if the ventricular elastance and the effective arterial elastance were equal. We tested this hypothesis in 10 isolated canine left ventricles, ejecting into a simulated arterial impedance, by extensively altering arterial resistance and finding the optimal resistance that maximized left ventricular stroke work under various combinations of end-diastolic volume, contractility, heart rate, and arterial compliance. Each of these parameters was set at one of three levels while others were at control. The optimal resistance varied only slightly with arterial compliance, whereas it varied widely with contractility and heart rate. We thus determined that the ratio of the optimal effective arterial elastance to the given ventricular elastance remained nearly unity. This result supports the hypothesis that the left ventricle does maximal external work to the arterial load when the ventricular and arterial elastances are equalized.

Ventricular–vascular coupling in hypertension

“…53 The ability of E a , however, to represent the pulsatile component of arterial load has been questioned, 54 because it can be approximated by the ratio between total peripheral resistance (R) and heart cycle length (T). 52 If this was true, E a should have no relationship with the pulsatile component of the arterial load. Mathematical models 55 and human studies 56 have however demonstrated that arterial stiffness and pulsatile components of arterial load, although with a significantly Ventricular-vascular coupling in hypertension Saba et al 777 lesser extent than total peripheral resistance, play a role in determining the effective arterial elastance.…”

Single-Beat Estimation of End-Systolic Elastance Using Bilinearly Approximated Time-Varying Elastance Curve

“…E a was derived as the ratio of P es to SV. 19 We also calculated effective ejection fraction (EF e ) as the ratio of SV to stressed end-diastolic volume [end-diastolic volume (V ed )ϪV 0 ] as a measure of loading conditions. According to the framework of ventriculararterial coupling, EF e approximates the ratio of E es to E es ϩE a (Appendix).…”

Effects of Cardiopulmonary Exercise Rehabilitation on Left Ventricular Mechanical Efficiency and Ventricular‐Arterial Coupling in Patients With Systolic Heart Failure

“…A more powerful and largely load‐independent measure of contractile function is LV end‐systolic elastance (E es ), which can be defined as the stiffness of the left ventricle at the end of the systole. The arterial system can also be assessed in elastance terms; hence, ventricular‐arterial coupling (VAC) can be expressed by the comparison of ventricular and arterial elastances (E a ) 12, 13, 14, 15. Experimental models showed that LV EW is maximal when the VAC (E es /E a ) ratio is 1,12 whereas the mechanical efficiency is maximal when the ratio is 2 13, 14.…”