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Keywords:

  • Atenolol;
  • Feline;
  • If current;
  • Systolic anterior motion

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.