BENEFICIAL INFLUENCE OF VASOACTIVE-INTESTINAL-PEPTIDE ON VENTRICULOVASCULAR COUPLING IN CLOSED-CHEST DOGS

The effect of vasoactive intestinal peptide (VIP) on ventriculovascular coupling in the intact cardiovascular system has not been defined. We studied seven dogs chronically instrumented with left ventricular (LV) pressure manometers and three sets of diameter gauges before and after infusions of 0.02, 0.05, and 0.10 mug.kg-1.min-1 VIP. The dogs were studied after autonomic blockade, anesthesia, and intubation, with a fixed heart rate of 160 beats/min. Contractility was assessed using LV elastance at end systole (E(es)) and the slope of the stroke work-end-diastolic volume relation. The vascular influence of VIP was quantified by determining effective arterial elastance (E(a)) under steady-state conditions. The overall effect on ventriculovascular coupling was assessed using the transfer of mechanical energy from LV to the arterial system (Trans(PVA)) quantified as the percentage of pressure-volume area (PVA) expressed as stroke work. LV relaxation was measured using the time constant of LV pressure decay. The results showed that VIP increased contractility (E(es) increased to 129, 156, and 181% of control; P < 0.01 for all vs. control) and decreased effective arterial elastance (E(a) fell to 84, 68, and 64% of control; P < 0.0155 vs. control for the two higher doses). VIP had no consistent effects on LV relaxation. Thus, in addition to its positive ventricular effects (increased contractility), VIP has beneficial vascular effects (reduced E(a)). These properties combine to improve ventriculovascular coupling, such that VIP enhances delivery of mechanical energy from the LV to the circulatory bed.