FAVORABLE LEFT-VENTRICULAR REMODELING FOLLOWING LARGE MYOCARDIAL-INFARCTION BY EXERCISE TRAINING - EFFECT ON VENTRICULAR MORPHOLOGY AND GENE-EXPRESSION

Continued adverse remodeling of myocardium after infarction may lead t o progressive ventricular dilation and heart failure, We tested the hy pothesis that exercise training in a healed myocardial infarction-dysf unction rat model can favorably modify the adverse effects of ventricu lar remodeling including attenuation of abnormal myosin gene expressio n. Sprague-Dawley rats were subjected to either proximal LAD ligation or sham operation, At 5 wk after the operation, animals were randomly assigned to sedentary conditions or 6 wk of graduated swim training, c reating four experimental groups: infarct sedentary (IS), infarct exer cise (IE), sham sedentary (SS), and sham exercise (SE), At 11 wk all r ats were sacrificed and analyzed. Compared to sedentary infarct contro ls, exercise training attenuated left ventricular (LV) dilation and al lowed more hypertrophy of the non infarct wall, The exercise trained h earts also showed a reduction in the estimated peak wall tension, Nort hern blot analysis showed an increase in beta-myosin heavy chain expre ssion in the hearts of the sedentary infarction group soon after infar ction when compared to sham controls, However, with exercise training, there was a significant attenuation of the beta-myosin heavy chain ex pression in the myocardium. Exercise training in a model of left ventr icular dysfunction after healed myocardial infarction can improve the adverse remodeling process by attenuating ventricular dilation and red ucing wall tension. The abnormal beta-myosin expression was also atten uated in the exercise trained group, This is evidence that abnormal ge ne expression following severe myocardial infarction dysfunction can b e favorably modified by an intervention.