Results of the veterinary enalapril trial to prove reduction in onset of heart failure in dogs chronically treated with enalapril alone for compensated, naturally occurring mitral valve insufficiency

Objective-To determine the efficacy of long-term enalapril administration in delaying the onset of congestive heart failure (CHF). Design-Placebo-controlled, double-blind, multicenter, randomized trial. Animals-124 dogs with compensated mitral valve regurgitation (MR). Procedures-Dogs randomly assigned to receive enalapril or placebo were monitored for the primary endpoint of onset of CHF for : 58 months. Secondary endpoints included time from study entry to the combined endpoint of CHF-all-cause death-, number of dogs free of CHF at 500, 1,000, and 1,500 days; and mean number of CHF-free days. Results-Kaplan-Meier estimates of the effect of enalapril on the primary endpoint did not reveal a significant treatment benefit. Chronic enalapril administration did have a significant benefit on the combined endpoint of CHF-all-cause death (benefit was 317 days [10.6 months]). Dogs receiving enalapril remained free of CHF for a significantly longer time than those receiving placebo and were significantly more likely to be free of CHF at day 500 and at study end. Conclusions and Clinical Relevance-Chronic enalapril treatment of dogs with naturally occurring, moderate to severe MR significantly delayed onset of CHF compared with placebo, on the basis of number of CHF-free days, number of dogs free of CHF at days 500 and study end, and increased time to a combined secondary endpoint of CHF-all-cause death. Improvement in the primary endpoint, CHF-free survival, was not significant. Results suggest that enalapril modestly delays the onset of CHF in dogs with moderate to severe MR. Q Am Vet Med Assoc 2007;231:1061-1069)