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Two-hour protocol identifies patients at low risk of ACS

Clinical Question:
Can a 2-hour rule-out protocol for acute coronary syndrome replace the standard protocol in the emergency department?

Bottom Line:
A 2-hour protocol of initial electrocardiography (ECG), troponin testing, and Thrombolysis in Myocardial Infarction (TIMI) scoring, followed by repeat testing in 2 hours, resulted in almost twice as many patients with chest pain and symptoms consistent with acute coronary syndrome (ACS) being discharged within 6 hours of presentation to an emergency department. (LOE = 1b-)

Than M, Aldous S, Lord SJ, et al. A 2-hour diagnostic protocol for possible cardiac chest pain in the emergency department. A randomized clinical trial. JAMA Intern Med 2014;174(1):51-58.  [PMID:24100783]

Study Design:
Randomized controlled trial (single-blinded)



Emergency department

These researchers enrolled 542 consecutive patients who presented to an emergency department with chest pain and symptoms consistent with ACS. Patients were excluded if they had ST-elevated myocardial infarction or a clear cause of chest pain other than ACS. The eligible patients were randomly assigned, allocation concealment unknown, to different diagnostic pathways. All patients received initial ECG and troponin testing upon arrival. In the standard treatment group, the patients were admitted for observation and a second troponin test was conducted 6 to 12 hours after the onset of symptoms. The rapid protocol group were scored using the TIMI scoring system. If their score was 0 and the initial ECG and troponin test results were normal, the patients were observed for 2 hours and had the tests repeated; if the results were normal a second time, the patients were discharged and followed up with a stress test, as an outpatient, within 3 days. Any abnormality found during the 2-hour rapid protocol bounced patients to the standard protocol. The faster protocol resulted in the discharge of 19.3% of patients within 6 hours of presentation as compared with 11.0% in the usual care group (P = .008). However, an additional 12.9% were admitted despite being ruled out; none of these patients subsequently were diagnosed with ACS. One patient discharged following the accelerated diagnostic protocol subsequently had a major coronary event within the following 30 days.


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