Preliminary investigation of orally administered benazepril in horses with left-sided valvular regurgitation.

Authors: Afonso T, Giguère S, Brown S A, Barton M H, Rapoport G, Barba M, Dembek K A, Toribio R E, Coleman A E

Journal: Equine veterinary journal

DOI: 10.1111/evj.12773 PubMed: 29044678Log in to save

Summary

# Editorial Summary: Benazepril for Left-Sided Valvular Regurgitation in Horses Angiotensin-converting enzyme (ACE) inhibitors are increasingly used empirically in equine practice to manage valvular regurgitation, yet robust clinical evidence supporting this approach remains sparse. A small randomised, double-blind, placebo-controlled trial examined whether oral benazepril at 1 mg/kg twice daily produces measurable echocardiographic and hormonal changes in horses with mitral and/or aortic regurgitation over a 28-day period. The benazepril-treated group (n = 6) demonstrated statistically significant reductions in left ventricular internal diameter during systole (0.97 cm reduction), aortic sinus diameter (0.31 cm reduction), and the proportion of the aortic annulus occupied by the regurgitant jet (17.05% reduction), alongside improvements in cardiac output (11.95 L/min greater increase) and fractional shortening (7.59% greater improvement) compared to placebo controls. Notably, despite profound ACE inhibition at the tissue level, plasma renin activity, angiotensin II, and aldosterone concentrations showed no significant differences between groups, suggesting the echocardiographic benefits may operate through alternative mechanisms affecting cardiac afterload rather than classical neuroendocrine suppression. Whilst these findings suggest benazepril may reduce structural and functional cardiac strain in valvular disease, the small sample size and brief treatment window limit clinical extrapolation; larger, longer-duration studies are essential before this intervention can be confidently recommended as standard practice for valvular regurgitation management.

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Practical Takeaways

•Oral benazepril may reduce cardiac workload in horses with mitral and aortic valve regurgitation, though clinical benefit remains unproven and larger studies are needed
•The lack of hormonal compensation (renin-angiotensin-aldosterone system) despite ACE inhibition suggests the drug's effect is primarily mechanical rather than neurohormonal
•Current evidence is too limited (n=11, 28-day duration) to recommend routine benazepril use; horses with valvular disease should continue conventional management pending larger clinical trials

Key Findings

•Benazepril (1 mg/kg q12h) significantly reduced left ventricular internal diameter in systole by 0.97 cm compared to placebo over 28 days
•Benazepril treatment resulted in significantly greater increases in cardiac output (11.95 L/min) and fractional shortening (7.59%) relative to placebo
•Aortic sinus diameter decreased by 0.31 cm and aortic regurgitation jet width decreased by 17.05% with benazepril versus placebo
•Despite profound serum ACE inhibition, renin activity and angiotensin II and aldosterone concentrations showed no significant differences between treatment and placebo groups

Conditions Studied

mitral valve regurgitationaortic valve regurgitationleft-sided valvular regurgitation

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