Resident The Ohio State University College of Veterinary Medicine Columbus, Ohio, United States
Abstract: Background – Arterial thromboembolism is a devastating consequence of hypertrophic cardiomyopathy (HCM) in cats due to left atrial (LA) enlargement and dysfunction. Prevention of ATE relies on antithrombotic medication, rather than improving atrial transport function.
Hypothesis – Pimobendan improves LA systolic function in cats with HCM and LA enlargement.
Animals – 14 client-owned cats with stage B2 HCM.
Methods – Prospective, double-blind, placebo-controlled clinical study. Echocardiographic assessment of left atrial and left auricular systolic function was performed before and one hour after administration of a single oral dose of pimobendan (0.3 mg/kg). Plasma concentrations of pimobendan and o-desmethylpimobendan (ODMP) were also analyzed.
Results – Nine cats received pimobendan and 5 placebo. Preliminary data analysis demonstrated that LA size based on LA area (cm2) (3.70 +/-1.27 vs. 3.10 +/-0.81; P=.08, power=.24) and LA volume (cm3) decreases (5.11 +/-2.54 vs. 4.55 +/-2.36; P=.19, power=.17), left auricular flow velocity (m/s) increases (.34 +/-.15 vs. .50 +/-.29, P=.14, power=.20), and pulmonary venous atrial reversal flow velocity (m/s) increases (.31 +/-.11 vs. .36 +/-.14, P=.08, power=.32) after pimobendan. Compared to the 6/8 cats with expected plasma concentrations (ng/mL) of pimobendan one hour after administration (7.57-33.98) and ODMP (2.75-11.23), plasma concentrations in 2 cats were notably lower (pimobendan 1.71 and 0.43 ng/mL and ODMP not detectable).
Conclusions – Pimobendan may reduce LA size and improve LA transport function in cats with HCM and LA enlargement, but larger a number of cats need to be studied.
