Risk of subsequent cardiac events in stable convalescing patients after first non-Q-wave and Q-wave myocardial infarction: the limited role of non-invasive testing. The Multicenter Myocardial Ischemia Research Group.

BACKGROUND

Patients recovering from myocardial infarction are frequently evaluated by non-invasive tests for evidence of myocardial ischemia before returning to work or full activity. The purpose of this study was to evaluate the prognostic significance of clinical and non-invasive ischemic test variables assessed in 549 stable, convalescing patients (median 2 months) after their first Q-wave (n = 363) and non-Q-wave (n = 186) myocardial infarction.

METHODS

The ischemic tests performed were resting ECG, exercise ECG, ambulatory ECG, and stress thallium scintigraphy.

RESULTS

Cardiac events (unstable angina requiring hospitalization, non-fatal reinfarction, or death from cardiac causes) were observed during a mean 23-month follow-up in 57 patients (15.7%) with Q-wave and in 31 of patients (16.7%) with non-Q-wave infarction. In a step-wise Cox regression model, the only significant independent predictors of subsequent cardiac events (P < 0.001) were post-infarction angina and insulin-dependent diabetes mellitus. The type of infarction did not make a significant contribution to the risk of cardiac events (P = 0.29). However, an interaction between infarct type and post-infarction angina was of borderline significance (P = 0.065), with angina associated with more cardiac events in patients with non-Q-wave than in those with Q-wave infarction. None of the ischemic tests contributed significantly to the Cox model in predicting cardiac events in either infarct type.

CONCLUSION

Stable convalescing patients who have recovered from first Q-wave and non-Q-wave myocardial infarction have similar long-term prognoses. The occurrence of post-infarction angina is associated with increased risk of cardiac events in patients with both infarct types, with more marked effect in non-Q-wave than Q-wave infarctions. Ischemia detected by non-invasive tests performed in the convalescing phase after myocardial infarction was not prognostically useful in either infarct type.