CARDIAC PUMP PERFORMANCE IN LAMBS: MATURATIONAL DIFFERENCES OF LEFT AND RIGHT VENTRICULAR FUNCTION

Abstract

We examined the pump performance of the newborn heart by determining the contribution of the Frank-Starling principle to both left (LV) and right (RV) ventricular function in 16 open chested lambs (1-44 days) anesthetized with alpha chloralose and instrumented with aortic and pulmonary flow probes and pressure catheters, and left and right ventricular microtransducers. Alterations in ventricular filling pressure (VFP) were induced by venous infusion of warmed (37°C) saline (60 cc/kg/2min). Ventricular function curves were constructed relating stroke volume (SV) and stroke work (SW) to VFP. With maturation, LV responded to increasing VFP by delivering progressively larger SV. Older animals showed a greater change from resting to peak stroke volume (ΔSV) and stroke work (ΔSW), and peak SVs were achieved at higher VFP. Results for the LV were: In contrast, at all ages, RV had a limited response to increased VFP (ΔSV=30-35%) (SW=28-40%), and peak SV was achieved at lower VFP (11-16 mmHg). An age-related increase in pump performance was found for LV, while RV retained functional characteristics of the newborn. (Sponsor: F.H. Adams)