Abstract 1509: Exercise Training Started Before Myocardial Infarction Improves Survival but Aggravates Left Ventricular Dysfunction
Introduction: Regular physical activity in patients with established coronary heart disease not only reduces the incidence of cardiac events, but also reduces the risk of all-cause mortality. Recently, we showed in mice that exercise training (EX) started immediately after myocardial infarction (MI) ameliorates left ventricular (LV) dysfunction. Here we tested the hypothesis that additional exercise training prior to an acute MI, i.e. a higher level of physical fitness at the time of MI, is associated with improved survival and attenuated LV dysfunction after MI.
Methods and Results: MI was induced by permanent coronary ligation in 128 C57Bl/6 mice and subsequently followed by 8 weeks of voluntary wheel running (MI-EX) or sedentary housing (MI). In a third group, voluntary wheel running was started two weeks before induction of MI (EX-MI-EX). Sham operated mice served as controls. EX after MI had no effect on survival, infarct size, LV hypertrophy or dilation (Table⇓). However, EX improved LV function, reflected in enhanced LV fractional shortening (FS), rate of rise in LV pressure at 30 mmHg (LVdP/dtP30), and decreased pulmonary congestion and right ventricular weight (RVW). When EX was started prior to MI, post-MI survival nearly doubled and mice ran an average post-MI distance of ~7km/d compared to ~5km/d in MI-EX mice. Infarct cross-sectional area was larger, which was principally due to an increased infarct thickness (0.15±0.02mm EX-MI-EX vs 0.11±0.01mm MI; P=0.06). Surprisingly, however, LV hypertrophy and dysfunction were aggravated in the EX-MI-EX group compared to MI-EX.
Conclusion: In line with our hypothesis, EX started prior to MI improved survival. However, contrary to our hypothesis, the improved survival was associated with a deterioration of LV dysfunction. The latter may have been the result of survival and hence inclusion of mice with the most severe LV dysfunction.