Background: Both exercise testing and C-reactive protein (CRP) serum levels have been shown to predict clinical events in patients with unstable angina. However, no previous study carefully compared their relative prognostic value in this clinical setting.
Methods: We reviewed data of 96 consecutive patients with unstable angina (77 males, 19 females, mean age 63.1 +/- 9.5 years), who were free from clinical events during hospital stay. A symptom/sign-limited treadmill exercise test had been performed and CRP serum levels had been measured prior to discharge in all patients.
Results: During an average follow-up of 2.5 years (range 0.5-5 years), there were 8 major cardiac events (death or myocardial infarction) and 11 patients had recurrent unstable angina. Both exercise-induced myocardial ischemia [relative risk (RR) 3.02, 95% confidence interval (CI) 0.58-15.5, p = 0.29], and CRP levels > or = 10 mg/l (RR 2.4, 95% CI 0.51-11.2, p = 0.25) showed a non significant association with major cardiac events. Low workload ischemia, however, was significantly associated with major cardiac events (RR 8.58, 95% CI 1.66-44.2, p = 0.01) and was also the only predictive variable for the combined endpoint of major events and recurrent angina (RR 2.57, 95% CI 1.02-4.44, p = 0.045). Among patients with low workload ischemia, the occurrence of major events was higher in those with high, compared to those with low, CRP levels, but the difference was not significant (28.6 vs 15.4%, p = 0.64).
Conclusions: In this study, pre-discharge myocardial ischemia at low workload was the single most important predictor of major cardiac events during long-term follow-up among patients with stabilized unstable angina. Increased serum CRP levels did not add further significant prognostic information in this specific group of patients with unstable angina, although this issue needs to be addressed in larger studies.