Abstract 11965: Heart Rate Reduction with Ivabradine Improves Regional Contractile Function and LV Dyssynchrony in a Mouse Model of Reperfused Myocardial Infarction
Introduction: Ivabradine selectively inhibits the If channel of the sinoatrial node, slowing heart rate. Few studies have examined the effects of ivabradine on the mechanical properties of the heart after reperfused MI. Recent advances in ultrasound speckle tracking allow strain analyses to be performed in small animal models, enabling the assessment of regional mechanical function.
Methods: C57BL/6 mice underwent 1 hr of cardiac ischemia followed by reperfusion. The mice were either immediately started on 10 mg/kg-day of ivabradine dissolved in drinking water (n=10), or used as infarcted controls (n=9). Echocardiography was performed at baseline and post-MI days 2, 7, 14, and 28. Heart rate (HR) was measured at 20-25 time points over the echo acquisitions. A speckle tracking package was used to calculate intramural longitudinal myocardial strain (Ell) and strain rate from long-axis cines at day 28. Standard deviation time to peak radial strain (SD Tpeak) was calculated from a single short axis cine acquired 1.5-2 mm inferior to the base of the heart.
Results: Ivabradine reduced HR by 8-16% over the course of remodeling compared to the infarcted controls (p<0.001; Panel A). On post-MI day 28, the ivabradine group was found to have significantly more peak Ell in the remote zone, as well as globally (Panel B). Ivabradine-treated mice were also found to have significantly better peak Ell rate on day 28 in both infarcted and remote zones of the heart, as well as globally (Panel C). SD Tpeak was significantly smaller in the ivabradine treated group by day 28 (p<0.01; Panel D). All data are presented as mean ± SEM, where * denotes p<0.05 and ** denotes p<0.01 vs. infarcted controls.
Conclusions: High-frequency ultrasound speckle tracking based strain analysis demonstrated decreased LV dyssynchrony and improved mechanical performance in non-infarcted myocardium, indicating heart rate reduction with ivabradine helps preserve contractile function in the remote myocardium. .
- © 2012 by American Heart Association, Inc.