Prognosis in myocardial infarction--the benefits of exercise as seen in non-randomised trials

Previous uncontrolled studies suggest that exercise rehabilitation reduces recurrence rates in post-myocardial infarction patients. Six hundred and ten consecutive post-coronary patients referred to an exercise rehabilitation programme have been followed for an average of 36.5 months (1-8 years). Total deaths amounted to 36 (1.89% p.a.) of which 23 were cardiac deaths, with an annual death rate averaging only 0.85% after the first year of conditioning had been completed. There were also a total of 21 non-fatal recurrences of infarction. comparison has been made with 700 patients enrolled in the Health Insurance Plan of New York. On the basis of smoothed probabilities for the risk factors reported in the New York series, we should have seen 89 deaths (P less than 0.001). Correcting for differences between the two groups (age and number of diabetics) gives a predicted mortality for the Toronto series of 63.5 deaths (3.42% p.a.). This discrepancy in favour of the exercised group is significant in terms of an infinitely large control population (P less than 0.001) and also sample sizes of 610 exercised and 700 control patients (0.01 greater than P greater than 0.001). Unfortunately, formally to prove such a 45% reduction in mortality by way of a randomised control trial would be extremely costly, possibly prohibitively so.