Myocardial infarction size; effect on the training response

The influence of myocardial infarction size, as indicated by the maximum elevation of creatine kinase (CK) and its iso-enzyme CK-MB, on the exercise training response and resting left ventricular function was studied in 15 male patients who underwent exercise training for 8 weeks. Patients were found to divide themselves into two subgroups; those with maximum CK less than or equal to 200 IU/l (n = 7) and greater than or equal to 400 IU/l (n = 8). All were evaluated by treadmill exercise testing (Bruce Protocol), M-mode echocardiography and radionuclide ventriculography before training, immediately after, 3 and 6 months after training. Both of the subgroups showed statistically significant improvements in exercise duration, heart rates for doing equal workloads, energy expenditure and functional aerobic impairment immediately after training which were maintained 3 and 6 months later, with no inter-group differences. Resting left ventricular function, both by radionuclide and echocardiography, did not demonstrate significant changes throughout the study period, again with no inter-group differences. It is suggested that myocardial infarction size in the absence of heart failure does not appear to have a significant influence on the exercise training response and resting left ventricular function in those patients who recovered sufficiently to participate in exercise training.