Swimming training attenuates remodeling, contractile dysfunction and congestive heart failure in rats with moderate and large myocardial infarctions.

1. The aim of the present study was to evaluate the effect of swimming on myocardial remodelling after myocardial infarction (MI) in female rats induced by coronary occlusion, which was not performed in sham rats. 2. Rats were divided in six groups, three sedentary (sham (SSh; n = 14), moderate infarct (SMI; n = 8) and large infarct (SLI; n = 10)) and three trained (sham (TSh; n = 16), moderate infarct (TMI; n = 9) and large infarct (TLI; n = 8)) groups. Training (8 weeks, 60 min/day, 5 days/week) was initiated 4 weeks after MI or sham operation. Training did not affect mortality rate, but attenuated the increases in atrial/bodyweight (SSh: 0.07 +/- 0.02; TSh: 0.07 +/- 0.02; SMI: 0.11 +/- 0.03; TMI: 0.09 +/- 0.03; SLI: 0.17 +/- 0.09; TLI: 0.10 +/- 0.05 mg/g) and right ventricular/bodyweight (SSh: 0.15 +/- 0.02; TSh: 0.17 +/- 0.02; SMI: 0.17 +/- 0.07; TMI: 0.20 +/- 0.03; SLI: 0.29 +/- 0.13; TLI: 0.22 +/- 0.08 mg/g) ratios. Myocardial infarction increased pulmonary and myocardial water content in infarcted sedentary animals, whereas no changes were observed in trained infarcted rats. Sedentary infarcted rats showed inotropic and lusitropic depression proportional to the size of the infarct (SSh > SMI > SLI), whereas no differences were noted in trained rats (TLI = TMI = TSh). Indeed, in sedentary rats there was depression of +dT/dt (SSh: 68 +/- 25; TSh: 72 +/- 21; SMI: 53 +/- 20; TMI: 77 +/- 30; SLI: 33 +/- 15; TLI: 57 +/- 22 g/mm(2) per s) and -dT/dt (SSh: 33 +/- 13; TSh: 36 +/- 11; SMI: 24 +/- 5; TMI: 35 +/- 11; SLI: 15 +/- 4; TLI: 32 +/- 11 g/mm(2) per s) compared with trained rats. 3. In conclusion, swimming clearly favoured post-MI cardiac remodelling, attenuated myocardial hypertrophy, contractile and relaxation dysfunction and prevented pulmonary congestion.