Effects of myocardial infarction on cardiac function and on exercise capacity in obese mice

This study was designed to evaluate the effects of myocardial infarction on cardiac function and exercise capacity in obese mice. Female wild type and ob/ob mice (10 weeks) were randomized into (n=6): Control group (C), Obese group (O) and Obese Myocardial Infarction group (OMI). Coronary artery occlusion was performed on 10 week old. Cardiac morphology and function were assessed by echocardiography 24-48hs after myocardial infarction. The maximal exercise test was performed on a treadmill. The body weight was higher in obese groups (O: 50±0.5; IMO: 54±2 g) in relation to C group (20±0.2 g). The eject fraction was markedly reduced in OMI group (37.24±0.06%) than C (55.20±0.05%) and O groups (66.09±0.02%). Left ventricular mass corrected by body weight was reduced in obese groups (O: 1.99±0.1; IMO: 1.06±0.09 mg/g) when compared to C group (4.11±0.45 mg/g). The exercise capacity, verified by the running time, showed a reduction in O group (7.6±0.4 min) when compared to C group (16.0±0.5 min). The OMI group showed an additional decrease in left ventricular mass and exercise capacity (2.9±0.5 min) in relation to O group. We observed a positive correlation between eject fraction and exercise capacity (r=0.87, p<0.0001) when analyzed only obese groups. In conclusion, the myocardial infarction promoted cardiac dysfunction in ob/ob mice, which was correlated with an impairment on exercise capacity. These data suggest that maximal exercise test can be used as a tool to identify cardiac dysfunction and prognosis in obese subjects after an ischemic event.