Beneficial hemodynamic and renal effects of intravenous enalaprilat following coronary artery bypass surgery complicated by left ventricular dysfunction

Abstract

Objective: Angiotensin-converting enzyme inhibitors are an effective therapy for all stages of heart failure due to reduced systolic left ventricular function. Because sufficient data on intravenous angiotensin-converting enzyme inhibitors following coronary artery bypass surgery complicated by postoperative left ventricular dysfunction are unavailable, the efficacy and safety of intravenously administered enalaprilat were evaluated.

Design: A placebo-controlled, randomized, double-blind protocol.

Setting: Postoperative intensive care unit at the German Heart Institute Berlin.

Patients: Forty patients with a left ventricular ejection fraction <35% following coronary artery bypass surgery on the second postoperative day or after weaning from intra-aortic balloon counterpulsation.

Interventions: A loading dose of enalaprilat 0.625 mg infused over 1 hr was followed by 5 mg/24 hrs administered continuously for up to 72 hrs.

Measurements and main results: Systemic and pulmonary hemodynamic variables, blood gases, hormonal variables, renal function, and electrolytes were measured before and repeatedly during therapy. Acute effects were as follows: At 1 hr, enalaprilat increased the cardiac index (p <.001), stroke volume index (p <.001), and right ventricular stroke work index (p <.03) compared with placebo, whereas mean arterial pressure (p <.008) and both systemic (p <.001) and pulmonary (p <.02) vascular resistance decreased. Continuous effects were as follows: Over 72 hrs, enalaprilat decreased diastolic pulmonary artery pressure (p <.019), pulmonary artery occlusion pressure (p <.02), and central venous pressure (p <.02). The cardiac and stroke volume indexes were consistently higher in the enalaprilat group, whereas systemic and pulmonary vascular resistances were lower. The arterial blood-pressure lowering effect was blunted and heart rate remained unchanged. Mixed venous oxygenation (p <.02) was higher and arterial oxygenation was not modified. Finally, enalaprilat increased creatinine clearance (p <.002) and decreased creatinine (p <.02) and urea (p <.03).

Conclusions: Intravenous enalaprilat safely and effectively improves cardiac and renal function following coronary artery bypass surgery complicated by postoperative left ventricular dysfunction.