Does normal pulmonary impedance constitute the optimum load for the right ventricle?

Abstract

Right ventricular performance of isolated supported cat hearts was experimentally characterized by a relationship among ventricular pressure (P), volume (V), and time after onset of systole. This characterization was combined with a hypothetical load network consisting of lumped central and peripheral lung vascular resistances (Rc and Rp), inertance (L), and compliance (C). We calculated ventricular and load pressure, flow, external ventricular work (Wext), static ventricular P-V energy (Wstat), and pump efficiency Q = Wext/Wstat over a broad range of load conditions. Magnitudes of load network variables resulting in a maximum value of Q would define the load impedance matching the ventricle. A practical optimum magnitude of lumped vascular compliance was obtained at C = 150 x 10(-6) g-1 . cm4, above which no substantial change in Q took place. We obtained maximum Q at approximately 4 ml stroke volume (heart rate = 2 Hz) and at characteristic impedance between 0.75 and 1.1 x 10(3)g . cm-1 . s-1. As these values are quite close to those encountered in the intact animal, we conclude that the right ventricular and the pulmonary arterial tree appear to constitute a matched pump-load system.

Importance of mitral subvalvular apparatus in terms of cardiac energetics and systolic mechanics in the ejecting canine heart.

“…Recently, several studies have provided evidence that the left ventricle and the arterial circulation interact in such a manner as to optimize cardiac energetics (28)(29)(30)(31)(32)(33)(34)(35)(36) Ee;S at any given EDV (35). In this study, the EJEfS ratio was near unity at baseline (0.91±0.53), suggesting that the ventricle and arterial properties were matched such that external stroke work was maximized; however, Ea/Ee, was not statistically different from 0.5.…”

Dynamic effects of carotid sinus baroreflex on ventriculoarterial coupling studied in anesthetized dogs.

“…On the other hand, some investigators have looked for the condition that maximizes mechanical efficiency of the left ventricle. [31][32][33][34][35] The mechanical efficiency of the left ventricle is defined as the ratio of the external work to myocardiUal oxygen consumption. Burkhoff and Sagawa34 showed in a theoretical study that the mechanical efficiency per beat is maximized when Ea/Bes is about 0.5.…”

Effects of Proximal Pulmonary Artery Occlusion on Pulsatile Right Ventricular Afterload in Rats

“…In the pulmonary circulation, higher ZC would decrease RV flow and the 'pump efficiency' of RV, as demonstrated in an isolated feline heart preparation. 25 Thus, our results suggest…”