Heart rate (HR) is often elevated in cats with cardiomyopathies (CMPs). Pharmacologic modulation of HR may reduce cardiac morbidity and mortality.
To investigate the effects of cilobradine vs. placebo, regarding time to cardiac mortality or morbidity in cats with first episode of congestive heart failure (CHF) due to primary CMP.
Three hundred and sixty-seven client-owned cats with primary CMP that had presented with a first episode of CHF at 50 centers in Europe. Per-protocol population comprised 193 cats (n = 89 cilobradine, n = 104 placebo). An interim analysis for futility was planned.
Prospective, randomized, placebo-controlled, double-blinded, multicenter clinical trial. Primary outcome variable was the time to a composite of cardiac mortality or cardiac morbidity.
Median time to primary outcome was 84 days (95% confidence interval [CI]: 63-219 days) in the cilobradine group (CG) and 203 days in the placebo group (95% CI: 145-377 days) with observed hazard ratio of 1.44, indicating a higher hazard for the CG (P = 0.057). Mean HR was 28 beats per minute (bpm) lower at Day 7 (P < 0.0001) and remained 29 bpm lower at Day 360 (P = 0.026) in the CG than that in the placebo group. Although the number of adverse events did not differ, there were more serious adverse events in the CG.
Heart rate reduction by cilobradine in cats with a first episode of CHF due to primary CMP did not reduce cardiac mortality and morbidity.

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