Q wave versus non-Q wave myocardial infarction: morbidity and mortality patterns after cardiac rehabilitation

To document the impact of cardiac rehabilitation on morbidity and mortality patterns relative to the type (ie, Q wave vs non-Q wave) of myocardial infarction (MI).

Data (ie, diagnoses, cardiac risk factors, hospital readmissions, reinfarctions, comorbidity, and mortality) spanning 5 years from the time of initial diagnosis of MI were abstracted from the medical records of 357 and 163 patients with Q wave and non-Q wave MI, respectively, who participated in cardiac rehabilitation. Survival analyses were used to test the hypotheses of no difference in time to reinfarction and/or death between persons who had a Q wave MI and those who had a non-Q wave MI.

Although the numbers of reinfarctions (n = 64) and deaths (n = 38) within the sample were small and did not allow for statistical significance of findings, trends suggest that individuals who had non-Q wave MI had better survival rates for the first 3 years after cardiac rehabilitation (1.8% vs 4.5%) than did those who had Q wave MI. Reinfarction rates, however, were similar for both groups.

The small number of deaths and reinfarctions may be indicative of selection biases inherent in the current protocols that define the exclusion criteria for participation in cardiac rehabilitation. The results of this study call for a reevaluation of studies that have touted the efficacy of cardiac rehabilitation through the comparison of participating and nonparticipating cohorts. This study points to the need for a national database that would allow for a more comprehensive quality-controlled data collection that would provide more meaningful evaluation of direct and indirect effects of risk variables and intervention development.