Prognostic value of treadmill stress testing in patients admitted to the emergency room with chest pain

Background

Treadmill stress test (TST) is an easily available, inexpensive and well-studied tool for the diagnosis of coronary artery disease. However, very few studies have been done to determine the prognostic value of TST in patients seen in the emergency room with chest pain and unclear diagnosis.

Methods

A total of 1060 consecutive patients were evaluated in our Chest Pain Unit using an algorithm that determines the pretest probability of acute myocardial infarction (AMI) or unstable angina (UA) based on chest pain characteristics and admission ECG. Patients with unclear diagnosis were submitted to a systematic strategy of serial ECG and CKMB determinations (0-3-6-9 h). TST was indicated for those in whom AMI or high-risk UA was ruled out. Of the 677 eligible patients 268 (40%) underwent TST (150 within 12 h post-admission) and constitute the study sample that was followed for 1 year (age 51.8 ± 12.1 years, males 70%).

Results

TST was positive for myocardial ischemia in 22% of 82 patients initially classified as intermediate probability of AMI/UA, and in 9% of 186 patients classified as low probability (P = 0.004). Cardiac events (death, AMI, UA, revascularization) occurred in 20.6% of 34 patients with positive TST, 0.5% of 191 patients with negative TST and 7% of 43 patients with nondiagnostic TST (submaximal heart rate not achieved; P = 0.0000). Diagnostic accuracy of a positive or nondiagnostic TST for cardiac events: sensitivity 91%, specificity 74%, positive predictive value 13%, and negative predictive value 99%. Likelihood ratio of a positive or nondiagnostic TST was 3.5 and a negative TST was 0.1. Multivariate logistic regression analysis disclosed a positive or nondiagnostic TST as the strongest predictor of cardiac events (OR 19; P = 0.0006) followed by ischemic ST or T changes on the admission ECG (OR 5.7; P = 0.04).

Conclusion

Patients with chest pain and unclear diagnosis on admission in whom AMI or high-risk UA were ruled out can be safely and accurately risk stratified by immediate TST. Patients with negative TST can be safely discharged, but those with a positive or nondiagnostic TST need further evaluation due to an elevated rate of cardiac events.