It remains unclear whether patients with largesize myocardial infarction (MI) achieve the same benefit from exercise training as do those with small-to medium-size MI. Hypothesis: This study was designed to determine the magnitude and mechanisms underlying improvement in exercise capacity in patients with large-size MI after cardiac rehabilitation. Methods: In all, 296 patients who participated in a cardiac rehabilitation program after acute MI were divided into two groups according to the peak

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... serum creatine phosphokinase (CPK) level: the group with large infarction (Group 1) (≥ 5000 U/l peak CPK, 64 patients) and the group with less extensive infarction (Group 2) (< 5000 U/l, 232 patients). Exercise capacity was assessed before and after a 3-month cardiac rehabilitation program that included exercise training. Results: Before exercise training, both the peak work rate (p < 0.05) and peak oxygen uptake (VO2) (p < 0.01) were significantly lower in Group 1 than in Group 2. After exercise training, the changes in peak work rate and peak VO2 were significantly greater in Group 1 than in Group 2 (both p < 0.01). The infarction size measured by the peak CPK level correlated significantly with both the baseline exercise capacity and its improvement after exercise training, although these correlations were insignificant in a multivariate analysis. In the multivariate analysis, the improvement in exercise capacity is determined by age and baseline exercise capacity, which is determined by the duration of inactivity, minute ventilation (VE)/ VCO 2 slope and left ventricular end-diastolic pressure. Conclusions: Compared with patients with small-to medium-size myocardial infarction, patients with large infarction gain a greater improvement in exercise capacity after exercise training due to reversal of physical deconditioning and improvement in congestive heart failure.