Chest Pain Triage by Exercise Testing
ABSTRACT & COMMENTARY
Synopsis: Exercise testing could be safely used to identify patients who present to the emergency room with chest pain and are at low risk of subsequent cardiac events. Patients with positive or inconclusive tests have an increased risk of events and should be evaluated expeditiously.
Source: Polanczyk CA, et al. Am J Cardiol 1998;81: 288-292.
Guidelines for unstable angina management and chest pain triage recommend exercise tolerance testing for deciding who can safely be sent home. Although a negative exercise test indicates an excellent prognosis in outpatients, its performance for triaging emergency room patients is unknown. Thus, Polanczyk and colleagues prospectively evaluated 276 low-risk patients who underwent exercise testing within 48 hours of an emergency visit for chest pain unexplained by local trauma or chest x-ray findings. The exercise test was considered vegetative if at least three METS were achieved and showed no evidence of ischemia. Follow-up data at six months was available in 92% of the patients. Negative exercise tests occurred in 71%. These patients were younger and less likely to have a history of heart disease and an abnormal ECG. During follow-up, none of the patients with a negative exercise test died, but 21% had additional emergency visits, and 18% were readmitted to the hospital. Only four (2%) experienced a cardiac event (myocardial infarction, bypass surgery, or angioplasty), and only one occurred within four months. By contrast, 12 of 81 patients (15%) with a positive or inconclusive exercise test had an event in six months for a sensitivity of 73% and a specificity of 74%. Polanczyk et al conclude that exercise testing could be safely used to identify patients who present to the emergency room with chest pain at low risk of subsequent cardiac events. Patients with positive or inconclusive tests have an increased risk of events and should be evaluated expeditiously.
COMMENT BY MICHAEL H. CRAWFORD, MD
The Agency for Health Care Policy and Research Guidelines on Unstable Angina discuss emergency room chest pain triage and recommend discharge with an exercise test in 72 hours for those with low likelihood of a cardiac event in less than 72 hours. However, many physicians feel uncomfortable letting patients out of their sight with a promise of a scheduled exercise test and perform the test prior to emergency department discharge (< 24 hours from admission) in low-risk patients. This study gives us information about the safety and value of such testing. The data suggest that a negative test identifies a truly low-risk group for cardiac events, and a positive test is relatively sensitive for identifying patients likely to have events. Thus, these data confirm the value of the exercise test before discharge in these patients.
This prospective, observational study may have suffered from patient selection biases. Patients at high risk for an event were probably not exercised, nor were those deemed low risk on clinical grounds. Thus, these data only apply to patients at enough perceived risk to be held for observation with serial ECG and enzyme studies. Their definition of clinical low risk was: no acute ischemia on the ECG; no history of worsening chest pain; systolic blood pressure higher than 110 mmHg; and no pulmonary rales. Most of the patients probably had normal ECGs since only 9% had nuclear imaging with their exercise test. Despite these potential selection biases, this represents a realistic population that all emergency centers see frequently and often hold for observation.
The most interesting aspect of the study was that resource use after a negative exercise test and discharge was still high, but it was lower in those with a positive or inconclusive test; return to emergency center (17 vs 21%; P < 0.05), and hospital admissions (12 vs 17%; P < 0.01), but the differences are not impressive. This finding highlights that patients who seek emergency care for chest pain and have a negative stress test still require further evaluation and management. In many systems, such follow-up is lacking because primary care doctors are often too busy to handle such referrals in a timely fashion or due to the demographic of the emergency center patient, who often do not have primary care doctors.
Finally, this study did not define a very low-risk group in whom discharge without an exercise test is feasible. A multivariate analysis of individuals younger than 60 years and a normal ECG identified 83% of the patients with a negative exercise test. Thus, this study would encourage exercise testing in all chest pain patients observed in the emergency department.
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