Effects of pimobendan in cats with hypertrophic cardiomyopathy and recent congestive heart failure: Results of a prospective, double‐blind, randomized, nonpivotal, exploratory field study

BACKGROUND: The benefits of pimobendan in the treatment of congestive heart failure (CHF) in cats with hypertrophic cardiomyopathy (HCM) have not been evaluated prospectively. HYPOTHESIS/OBJECTIVES: To investigate the effects of pimobendan in cats with HCM and recent CHF and to identify possible endpoints for a pivotal study. We hypothesized that pimobendan would be well‐tolerated and associated with improved outcome. ANIMALS: Eighty‐three cats with HCM and recently controlled CHF: 30 with and 53 without left ventricular outflow tract obstruction. METHODS: Prospective randomized placebo‐controlled double‐blind multicenter nonpivotal field study. Cats received either pimobendan (0.30 mg/kg q12h, n = 43), placebo (n = 39), or no medication (n = 1) together with furosemide (<10 mg/kg/d) with or without clopidogrel. The primary endpoint was a successful outcome (ie, completing the 180‐day study period without a dose escalation of furosemide). RESULTS: The proportion of cats in the full analysis set population with a successful outcome was not different between treatment groups (P = .75). For nonobstructive cats, the success rate was 32% in pimobendan‐treated cats versus 18.2% in the placebo group (odds ratio [OR], 2.12; 95% confidence interval [CI], 0.54‐8.34). For obstructive cats, the success rate was 28.6% and 60% in the pimobendan and placebo groups, respectively (OR, 0.27; 95% CI, 0.06‐1.26). No difference was found between treatments for the secondary endpoints of time to furosemide dose escalation or death (P = .89). Results were similar in the per‐protocol sets. Adverse events in both treatment groups were similar. CONCLUSIONS AND CLINICAL IMPORTANCE: In this study of cats with HCM and recent CHF, no benefit of pimobendan on 180‐day outcome was identified.