Left ventricular interaction with arterial load studied in isolated canine ventricle

Abstract

We developed a framework of analysis to predict the stroke volume (SV) resulting from the complex mechanical interaction between the ventricle and its arterial system. In this analysis, we characterized both the left ventricle and the arterial system by their end systolic pressure (Ps)-SV relationships and predicted SV from the intersection of the two relationship lines. The final output of the analysis was a formula that gives the SV for a given preload as a function of the ventricular properties (Ees, V0, and ejection time) and the arterial impedance properties (modeled in terms of a 3-element Windkessel). To test the validity of this framework for analyzing the ventriculoarterial interaction, we first determined the ventricular properties under a specific set of control arterial impedance conditions. With the ventricular properties thus obtained, we used the analytical formula to predict SVs under various combinations of noncontrol arterial impedance conditions and four preloads. The predicted SVs were compared with those measured while actually imposing the identical set of arterial impedance conditions and preload in eight isolated canine ventricles. The predicted SV was highly correlated (P less than 0.0001) with the measured one in all ventricles. The average correlation coefficient was 0.985 +/- 0.004 (SE), the slope 1.00 +/- 0.04, and the gamma-axis intercept 1.0 +/- 0.2 ml, indicating the accuracy of the prediction. We conclude that the representations of ventricle and arterial system by their Ps-SV relationships are useful in understanding how these two systems determine SV when they are coupled and interact.

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.…”

Clinical and Research Considerations for Patients With Hypertensive Acute Heart Failure: A Consensus Statement from the Society of Academic Emergency Medicine and the Heart Failure Society of America Acute Heart Failure Working Group

“…[8] A compliant aorta acts as a capacitor, reducing the peak pressure generated during ventricular systole and promoting continuous forward flow throughout the cardiac cycle. Central aortic pressure is further augmented during diastole by the reflected pressure wave generated downstream at the junction of the medium and small resistance arterioles.…”

Ventriculo-arterial Decoupling in Acutely Altered Hemodynamic States

“…Th is ratio was fi rst proposed by Suga [11] as a method t o evaluate the mechanical effi ciency of the cardiovascular system and the interaction between cardiac performance and vascular function. Th e Ea/Ees ratio has been consistently demonstrated to be a reliable and eff ective measure of cardiovascular performance [9,11,12]. Bur khoff and Sagawa, and successively many other investigators, have demonstrated that when the Ea/Es is near unity, the effi ciency of the system is optimal.…”

“…Th is optimization means that the LV workload and the arterial system optimally match when the left ventricle ejects the blood into the arterial system and is quantifi ed by ventriculo-arterial (V-A) coupling analysis. Th is process is optimized without excessive changes in LV pressure, and the mechanical energy of LV ejection is completely transferred from the ventricle to the arterial system [9,10]. Th e ro le o f V-A coupling in the management of critically ill patients with severe hemodynamic instability and shock is becoming increasingly clear.…”