130: Ivabradine physiological effect on myocardial function during dobutamine infusion in healthy subjects

Introduction Ivabradine is a selective heart-rate-lowering agent that acts on the sinoatrial node without influence on myocardial contractility and cardiac output. Physiological effects of ivabradine during dobutamine infusion have never been studied. Methods The study included 11 healthy subjects (82% men, aged 29.1± 4.7 years). All underwent dobutamine transthoracic echocardiography before and after ivabradine (3 hours after 5 mg of ivabradine). Baseline left ventricular longitudinal global strain by speckle tracking and stroke volume at rest and during low dose of dobutamine (when heart rate increased by more than 10 points from baseline) were compared to those obtained under ivabradine. Results Baseline heart rate (64±8 bpm) decreased in 7 subjects (68±7 bpm vs. 60±6 bpm, P=0.009) but paradoxically increased in 3. Dobutamine rate required to increase the heart rate by 10 points was similar with and without ivabradine (11±2γ/kg/min vs. 12±3 γ/kg/min, P=0.4). Overall, global strain increased under low dose dobutamine before (−20±2% vs. −23±2%, P=0.008) and after ivabradine (−21±2% vs. −23±3%, P Conclusion In healthy subjects, heart rate reduction obtained by ivabradine allows to increase myocardial contractility and stroke volume for a similar rate of dobutamine. This propriety may be useful in decompensate heart failure patients with rapid tachycardia induced by catecholamine infusion.