Comparison of the effects of dual, triple, and quadruple medical therapy on cardiac death in a retrospective cohort of dogs with myxomatous mitral valve disease at American College of Veterinary Internal Medicine stage C: is more necessarily better?

Objective: To compare selected cardiac effects of dual therapy (DT; furosemide and pimobendan), triple therapy (TT; furosemide, pimobendan, and benazepril), and quadruple therapy (QT; furosemide, pimobendan, benazepril, and spironolactone) in dogs with myxomatous mitral valve disease at American College of Veterinary Internal Medicine (ACVIM) stage C. Methods: This was a multicenter retrospective study involving dogs with ACVIM stage C myxomatous mitral valve disease treated with DT, TT, or QT. Statistical analysis was aimed at comparing the effects of treatment protocols on a primary outcome (cardiac death) and selected cardiovascular intermediate events (progression from ACVIM stage C to D and development of clinically relevant pulmonary hypertension and arrhythmias). Results: 211 dogs were included (DT group, 65; TT group, 105; QT group, 41). No statistically significant differences were found when comparing the rate of cardiac death between the DT and TT groups (P = .29), DT and QT groups (P = .32), and TT and QT groups (P = .94). No statistically significant differences were observed among the DT, TT, and QT Kaplan-Meier cardiac death survival curves in either the unadjusted (P = .32) or adjusted (P = .37) analyses. Conclusions: In this study sample, QT and TT did not provide a higher clinically evident cardiac protective effect compared to DT. Clinical relevance: DT was not inferior to TT and QT in terms of cardiac death in dogs with ACVIM stage C myxomatous mitral valve disease included in this study.