Figure 3.

Acute and chronic effects of ivabradine administration after MI. In order to examine the difference between the chronic administration of ivabradine over the course of 28 days and the acute effects of ivabradine after 28 days of LV remodeling, a crossover study was performed. A subgroup of 4 infarcted control mice was placed on ivabradine, and a subgroup of 4 mice from the ivabradine group was taken off the drug on day 28 post‐MI. Echocardiography was performed on both subgroups on day 30. A, Animals from the ivabradine group whose treatment was halted maintained 12% lower heart rates compared to mice that were never treated with the drug. Mice acutely treated with ivabradine showed a 10% decrease in heart rate compared with control animals. B, Mice that were treated with ivabradine for 28 days showed 31% smaller end‐systolic volumes (ESV) compared with mice acutely administered the drug after 28 days of LV remodeling. C, Animals from the ivabradine group whose treatment was halted showed a 27% improvement in ejection fraction (EF) compared to mice never treated with the drug. These mice also showed 23% greater EF than mice acutely administered ivabradine on days 28 to 30. *P<0.05 for all comparisons. EF indicates ejection fraction; ESV, end‐systolic volume; LV, left ventricular; MI, myocardial infarction.