Effect of enalaprilat on splanchnic vascular capacitance during acute ischemic heart failure in dogs

This study investigates the effect of angiotensin-converting-enzyme inhibition by intravenous enalaprilat (100 micrograms/kg) on splanchnic vascular capacitance during acute left ventricular failure induced by coronary microembolization in alpha-chloralose/urethan anesthetized dogs. Changes in hepatic and splenic vascular volumes were determined from organ diameters (sonomicrometry) at 15, 30, and 45 min after enalaprilat injection. Changes in vascular capacitance were assessed from organ pressure-diameter curves obtained during transient hepatic outflow occlusion. Thirty minutes after enalaprilat, hepatic volume was increased by 52 +/- 14 ml (P < 0.01), and portal and hepatic vein pressures were decreased from 10.2 +/- 0.9 to 8.7 +/- 0.8 mmHg (P < 0.01) and from 3.9 +/- 1.6 to 3.1 +/- 0.7 mmHg (P < 0.05), respectively. Splenic volume did not change. Enalaprilat shifted the hepatic pressure-diameter curve upward, resulting in a larger hepatic volume at any given pressure. Curve intercept was increased, suggesting an increase in unstressed vascular volume. Curve slope was unchanged. In conclusion, enalaprilat increased hepatic vascular volume during acute left ventricular failure in dogs. The pressure-diameter curve shift suggests a reduction in the smooth muscle tone of hepatic capacitance vessels.