Negative and positive predictive values of routine exercise testing in stable, medically-treated patients several years following a Q-wave myocardial infarction.

BACKGROUND

Exercise testing (ET) is the preferred initial strategy for risk stratification after acute myocardial infarction (MI) in patients who are able to exercise and have an interpretable electrocardiogram (ECG). Although the current guidelines do not recommend annual follow-up ET of symptom-free patients years after MI, this is still common practice worldwide. Thus, this study was undertaken to explore the value of ET in the prediction of cardiac events in stable, medically-treated patients with a remote history of Q-wave MI.

METHODS

Seven hundred sixty-six consecutive patients (male gender 89%, mean age 57 +/- 8.6 years) with a remote history of Q-wave MI (mean time from MI 2.8 +/- 0.75 years), who underwent Bruce treadmill ET and whose data were prospectively entered into our institutional database, were enrolled. Patients were followed up for an average of 7 +/- 0.6 years. The endpoints were: 1) primary (cardiac death or non-fatal reinfarction), 2) secondary (cardiac death, non-fatal reinfarction or unstable angina), and 3) all-cause mortality.

RESULTS

Two hundred and eighty-two recurrent ischemic events occurred [cardiac death (n = 67), non-fatal infarction (n = 54), and unstable angina (n = 161)] and an additional 103 patients underwent revascularization procedures. Multivariate risk predictors for the primary endpoints were: older age relative risk-RR 1.04 (95% confidence interval-CI 1.01-1.06 per year), baseline heart rate > or = 90 b/min RR 2.34 (95% CI 1.37-4.0), and ST segment depression at rest ECG RR 1.91 (95% CI 1.22-2.98). For the secondary endpoints the predictors were: older age RR 1.02 (95% CI 1.01-1.04 per year), baseline heart rate > or = 90 b/min RR 1.61 (95% CI 1.06-2.45), ST segment depression at rest ECG RR 1.8 (95% CI 1.33-2.44), exercise angina RR 1.94 (95% CI 1.4-2.69), and exercise time stage < or = II RR 1.56 (95% CI 1.16-2.1). The addition of exercise variables improved the predictive power of the multivariate model only for secondary and all-cause mortality endpoints. Furthermore, clinical stratification alone had a predictive value comparable to that of ET results.

CONCLUSIONS

Although the identification of patients at risk for recurrent cardiac events is still the main goal of re-stratification in stable, asymptomatic patients with previous MI, the value of ET in these cases is negligible. Markers of exercise ischemia or ventricular dysfunction would be weak at best. The poor predictive performance of ET severely limits its usefulness as a screening measure for identifying patients likely to benefit from cardiac catheterization and revascularization. Therefore, cost-ben-efit considerations would suggest that risk stratification by means of ET in stable, asymptomatic patients with a remote history of Q-wave MI is inappropriate.