Retrospective evaluation of the safety and tolerability of pimobendan in cats with obstructive vs nonobstructive cardiomyopathy

Abstract

<p><strong>Background</strong> Pimobendan is frequently used off‐label for treatments of cats with congestive heart failure (CHF). Concern exists regarding the safety of pimobendan in cats with outflow tract obstruction (OTO).</p> <p><strong>Objectives</strong> In cats treated with pimobendan, incidence of adverse effects will not differ between cats with OTO vs cats with nonobstructive cardiomyopathy.</p> <p><strong>Animals</strong> Two‐hundred sixty cats with CHF (57 with OTO, 203 with nonobstructive disease).</p> <p><strong>Methods</strong> Retrospective medical record review. Groups were compared using 2‐sample t‐tests, Wilcoxon rank‐sum tests, and Fisher exact tests.</p> <p><strong>Results</strong> Compared to cats with nonobstructive cardiomyopathy, cats with OTO were younger (8.9 [interquartile range (IQR) 6.6] vs 10.8 [6.3] years, P = .0036), more likely to have a heart murmur (51/57 [90%] vs 76/203 [37.8%] cats, P < .0001), more likely to manifest CHF as pulmonary edema (53/57 [83%] vs 144/203 [70.9%] cats, P = .0004), and less likely to have pleural effusion (19/57 [33%] vs 122/203 [60.1%] cats, P = .0005). Adverse effects suspected to be related to pimobendan administration occurred in 12/260 cats (4.6%), including 11/203 cats (5.4%) with nonobstructive cardiomyopathy and 1/57 cat (2%) with OTO (P = .7). Pimobendan was discontinued due to adverse effects in 4/260 cats (1.5%), 3 with nonobstructive disease and 1 with OTO (P = 1.0). Acute adverse hemodynamic effects after pimobendan administration were not detected in any cats.</p> <p><strong>Conclusions and Clinical Importance</strong> Pimobendan is well tolerated in cats with cardiomyopathy and CHF, regardless of the presence of OTO.</p>