Haemodynamic effects of enalaprilat and preload in acute severe heart failure complicating myocardial infarction

In this study, the acute haemodynamic effects of angiotensin converting enzyme (ACE) inhibition with intravenous enalaprilat alone or in combination with preload restoration were determined in patients with severe heart failure complicating acute myocardial infarction. Ten patients with raised pulmonary arterial wedge pressure (PAWP > or = 18 mmHg) were first studied during constant conventional vasodilation with diuretic and inotropic medication, by monitoring central haemodynamics and arterial blood gases. The same variables were measured before enalaprilat infusion, after preload reduction with enalaprilat (1 mg.h-1, rate doubled every 30 min until PAWP decreased > or = 25% or up to total cumulative dose of 10 mg) and after preload restoration with fluid loading (4% albumin given 15 ml.min-1 to restore PAWP to baseline) during continuous low dose enalaprilat infusion. Enalaprilat alone (median dose 0.9 mg) reduced significantly the PAWP (from 25 to 17 mmHg; P = 0.004), the mean arterial pressure (from 87 to 83 mmHg; P = 0.008), the mean pulmonary arterial pressure and the right atrial pressure. The cardiac index, stroke volume index and systemic vascular resistance index remained unchanged. Preload restoration during continuous enalaprilat infusion (median dose of 4% albumin 230 ml, and enalaprilat 0.2 mg) did not further enhance left ventricular function; rather, there was a nearly significant decrease in myocardial perfusion pressure. Arterial oxygenation remained unchanged throughout the study. In conclusion, adding intravenous enalaprilat to conventional therapy makes it possible to relieve pulmonary congestion while maintaining the cardiac function and arterial oxygenation. Preload restoration during continuous ACE inhibition offers no further advantages, and may have adverse effects, since the myocardial perfusion pressure may fall.