Abstract Body: Background: Many benefits related to exercise are ascribed to reduction in cardiovascular disease risk. Yet, the impact of exercise after the event—i.e., during ventricular remodeling after myocardial infarction (MI)—is unresolved. Because physical exercise alters myocardial structure and function in the healthy heart, it is reasonable to wager that exercise can also impact the remodeling heart. Unfortunately, the mechanism and magnitude of impact of exercise on ventricular remodeling following MI is largely unexplored.
Goal: Establish whether and the extent to which exercise impacts ventricular remodeling post-MI.
Methods: Twenty-six adult male mice were subjected to non-reperfused MI. Five days after MI, echocardiography was performed, and the next day mice were allocated into Exercise (EXE; n=13) or Sedentary (SED; n=13) groups based on ventricular dysfunction. EXE mice were single housed and given ad libitum access to a voluntary exercise wheel for the duration of the study; SED mice had no wheel access. Mice in the EXE group ran an average of 9 km/d. An exercise capacity test and echocardiography were performed at the end of the five-week protocol and tissue was harvested.
Results: Ventricular chambers were significantly larger (p<0.05) in the EXE group than the SED group. These unexpected findings, along with an observed trend towards improved survival in the EXE group led us to ponder the potential implications. Because the study design included a pre-treatment (but post-MI) echocardiogram, we assessed a potential relationship between survival and starting chamber dimensions. Of the mice with the largest chamber dimensions (i.e., >100 µL), 0% of the SED mice survived while 62% of the EXE mice survived.
Conclusions: This study affirms the positive impact of exercise following MI. Furthermore, the benefits of exercise may be most noticeable in subjects with the most severe ventricular dilation.