Acute Effects of Ivabradine on Dynamic Obstruction of the Left Ventricular Outflow Tract in Cats with Preclinical Hypertrophic Cardiomyopathy

Background Ivabradine is a negative chronotropic drug with minimal effects on central hemodynamics. Its effect on dynamic obstruction of the left ventricular outflow tract (LVOT) in cats with hypertrophic cardiomyopathy (HCM) remains unknown. Hypothesis/Objectives Ivabradine reduces dynamic obstruction of the LVOT in cats with HCM. Animals Twenty‐eight client‐owned cats with preclinical HCM and dynamic LVOT obstruction. Methods Randomized, double‐blind, active‐control single dose study. Cats received a single dose of either ivabradine (0.3 mg/kg PO) or atenolol (2 mg/kg PO). Heart rate, echocardiographic variables, and systolic blood pressure (SBP) were recorded before and 3 hours after drug administration. Statistical comparisons were made using ANCOVA. Results Peak velocity in the LVOT was significantly decreased compared to baseline for both drugs; however, the effect was more prominent with atenolol (mean reduction 2.53 m/s; 95% CI 2.07–3.13 m/s) compared to ivabradine (mean reduction 0.32 m/s; 95% CI −0.04 to 0.71 m/s; P < .0001). Echocardiographic indices of systolic function were largely unchanged by ivabradine, but significantly reduced by atenolol. Conclusions and Clinical Importance A single dose of ivabradine decreases dynamic LVOT obstruction in cats with HCM, but the clinical effect is negligible and inferior compared to that achieved by atenolol.