BACKGROUND: The regeneration of cardiomyocytes after a myocardial infarction (MI) is more evident in young animals; however, it is not known whether it is associated with functional improvement. OBJECTIVE: To perform the functional analysis by echocardiography (echo) of young adult rats submitted to MI. METHODS: Seventy-two animals were included in the study: 35 young rats (group Y) that were 28 days old and 37 adult rats (group A) that were 153 days old. The rats were subdivided in two subgroups: infarcted (YI and AI) and control (YC and AC). The animals were assessed by echocardiogram on the 7thand 30th postoperative days for the analysis of the ejection fraction (EF) and the final systolic (FSV) and diastolic volume (FDV) of the left ventricle. Only animals with EF < 40% were included in the study. RESULTS: The comparison of the FDV and FSV between infarcted and control animals showed that there was a significant increase in infarcted adult animals at the two analyzed phases. Among young animals only the FSV was significantly higher on the 7th day. The intragroup evolution analysis showed an increase in FDV and FSV in the two young subgroups, which was proportional to growth and only increase in FDV in the infarcted adult group. There was an improvement in EF in young rats, whereas EF remained decreased in adult rats when compared to controls. CONCLUSION: The infarcted young rats presented improvement in the systolic function and ventricular volumes 30 days after the infarction, whereas the adult rats presented increased FDV with no improvement in systolic function.
Echocardiography; myocardial infarction; clinical evolution; rats
