Heart rate reduction (HRR) by ivabradine (IVA), a selective inhibitor of the pacemaker If current, for 4 weeks after myocardial infarction (MI) was associated with the reduced collagen accumulation in surviving left ventricular (LV) myocardium. Although this effect is considered to benefit LV performance, the decrease in fibrillar collagen (FC) can diminish a tensile strength of the scar. Therefore, we designed our study to determine whether chronic HRR with IVA affects a structural composition of the MI scar. A large MI (> 50% of the LV free wall) was induced in 12-month-old male Sprague-Dawley rats by ligation of the left coronary artery and the rats were then assigned in two experimental groups. In the first group, rats were treated with IVA i.p. via osmotic pumps in a dose of 10.5 mg/kg/d for 3 months (MI+IVA), while in the second group, rats received placebo (MI). After three months, the fractional volume of FC was determined in the myocardium of LV free wall and the scar. The scar size and thickness were comparable between MI and MI+IVA rats (63.1±2.7% vs. 59.6±1.8% and 0.93±0.09mm vs. 0.90±0.05mm, respectively). Although, there was a significant reduction of FC in LV free wall of IVA-treated rats (5.1±0.5% vs. 7.8±0.8%, p≤0.01) the content of FC was comparable in scars of MI and MI+IVA rats (71.8±3.9% vs. 71.7±6.9%, respectively). Our data show that chronic IVA-induced HRR does not reduce the content of collagen in MI scar.