RESUMO
BACKGROUND: The effect of exercise on left ventricular remodeling after myocardial infarction is unclear. The purpose of this investigation was to test whether exercise undertaken during the healing phase of an acute myocardial infarction has an adverse effect on left ventricular remodeling. METHODS: Before surgery, rats (n = 94) were allocated randomly to one of four groups: 1) infarct, swimming exercise; 2) infarct, no exercise; 3) sham operation, swimming exercise; 4) sham operation, no exercise. Beginning 1 week after infarction or sham operation, the rats in the exercise groups swam twice daily for 2 weeks. After a deconditioning period of 5 days, the rats were re-anesthetized, hemodynamic measurements were made, and the hearts were fixed for morphometric analysis. RESULTS: Swimming exercise had no effect on remodeling of infarcted myocardium. Rats with infarcts in the swimming and no exercise groups had similar infarct thicknesses (1.1 +/- 0.2 mm and 0.8 +/- 0.2 mm respectively; NS), and similar degrees of infarct expansion (expansion index 1.2 +/- 0.3 and 1.4 +/- 0.3 respectively; NS). Swimming exercise also had no effect on remodeling of non-infarcted myocardium. Left ventricular volumes and pressure-volume relationships were similar in exercised and non-exercised infarcted rats. CONCLUSION: In rats, 2 weeks of swimming exercise, started 1 week after acute experimental myocardial infarction and followed by 5 days of deconditioning, does not have an adverse effect on left ventricular remodeling.
