Efficacy of high-dose carvedilol treatment for cats with stage B1 obstructive hypertrophic cardiomyopathy

Abstract

Objectives: The aim of the study was to investigate the effects of high-dose (HD) carvedilol treatment in client-owned cats with stage B1 obstructive hypertrophic cardiomyopathy (oHCM) where a standard dose (SD) had failed to adequately alleviate left ventricular outflow tract (LVOT) obstruction. Methods: A prospective, interventional study was conducted in which cats underwent echocardiography, including evaluation of myocardial strain using speckle-tracking echocardiography. Myocardial injury was quantified using a cardiac troponin I (cTnI) assay. Echocardiographic variables and the cTnI level were compared before treatment and after SD and HD carvedilol treatment. Results: LVOT velocity (LVOTV) decreased after SD compared with before treatment in all cats, but remained above 2.5 m/s after SD (before treatment 4.9 m/s [interquartile range [IQR] 4.3–5.0]; SD 4.3 m/s [IQR 3.9–4.7]), whereas HD decreased LVOTV to below 2.5 m/s in 10/11 cats (1.6 m/s [IQR 1.5–2.0]). Longitudinal strain was improved after SD and HD compared with before treatment (endocardial layer: before treatment 12.1% [IQR 9.6–15.8]; SD 20.0% [IQR 15.9–21.7]; HD 18.9% [IQR 12.9–22.8]; P = 0.003 and P = 0.006, respectively; epicardial layer: before treatment 9.4% [IQR 7.0–10.7]; SD 11.6% [IQR 10.0–12.7]; HD 12.5% [IQR 10.0–13.3]; P = 0.013 and P = 0.001, respectively). Circumferential strain demonstrated no changes. The cTnI level decreased after SD and HD compared with before treatment, and after HD compared with SD (before treatment 0.334 ng/ml [IQR 0.117–0.931]; SD 0.192 ng/ml [IQR 0.111–0.377]; HD 0.018 ng/ml [IQR 0.009–0.161]; P = 0.043, P = 0.043 and P = 0.043, respectively). No cats experienced adverse effects such as bradycardia or hypotension. Conclusions and relevance: HD improved LVOTV, myocardial function and cTnI level without adverse effects in cats with stage B1 oHCM.