Cardiology/original researchSafety and Efficiency of a Chest Pain Diagnostic Algorithm With Selective Outpatient Stress Testing for Emergency Department Patients With Potential Ischemic Chest Pain
Introduction
Approximately 15% to 25% of patients presenting to an emergency department (ED) with chest pain receive a diagnosis of acute coronary syndrome within 30 days, and between 2% and 5% of these patients are discharged inappropriately after receiving an incorrect minimizing diagnosis.1, 2 To improve early diagnostic accuracy, the 2007 American College of Cardiology/American Heart Association non-ST-elevation myocardial infarction guidelines recommend observation and serial investigations for up to 12 hours, followed by provocative cardiac testing, preferably with inpatients, but with outpatients if testing results can be obtained within 72 hours.3 Although the medical and legal consequences of missed acute coronary syndrome are high, hospital resources may not be sufficient to admit, observe, monitor, and investigate all at-risk patients. Keeping such patients in EDs may worsen crowding, which has been associated with a lower standard of care and increased incidence of adverse events in cardiac patients.4, 5, 6
To address these concerns, many hospitals have implemented chest pain observation units.7, 8, 9, 10, 11, 12, 13, 14, 15 Diagnostic algorithms vary by institution, but most units observe and monitor patients with potential cardiac ischemia, obtain serial cardiac biomarker and ECG results, and conduct provocative cardiac testing. Patients with negative chest pain unit investigation results are discharged, whereas those with worrisome results are hospitalized, and lengths of stay vary from 9 to 50 hours.7, 8, 9, 10, 11 Meyer et al discharged ED patients at low risk for cardiac ischemia and arranged for 72-hour outpatient provocative stress testing; 18 of 903 (2%) patients who were discharged with outpatient testing required cardiac revascularization within 6 months.11
In a previous study at our institution, in which emergency physicians used an individualized approach to patients with potential ischemia, we found that 35% of patients were admitted, median ED length of stay was 6.5 hours, and our 30-day acute coronary syndrome “miss” rate was 5.3%.4 To improve diagnostic accuracy, safety, and resource use at our hospital, collaborators from the Departments of Emergency Medicine, Cardiology, and Nuclear Medicine developed an algorithm to provide a streamlined approach to patients with potential cardiac chest pain. This intervention combined brief ED observation with expedited outpatient provocative testing when indicated. We hypothesized that this diagnostic strategy would provide a low (<2%) acute coronary syndrome miss rate while maintaining a median ED length of stay at approximately 6 hours.
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Setting
St Paul's Hospital in Vancouver, British Columbia, is an inner-city teaching hospital and provincial referral center affiliated with the University of British Columbia. The ED has an annual census of 60,000, and the hospital is a cardiac center with a 24-hour catheterization laboratory; cardiac surgery, including transplants; and 12-bed coronary care unit. This prospective cohort study was conducted between February and September 2006.
Triage nurses identified patients with potential ischemic
Results
During the study period, 1,255 consecutive patients presented with a triage code of “chest pain, cardiac features.” We analyzed 1,194 (95.1%) patients in the chest pain diagnostic algorithm protocol, with 54 exclusions (Figure 1). Of 1,140 eligible patients, 24 (2.1%) were lost to follow-up, but none of these patients had a regional ED visit or died within 30 days. Table 1 summarizes baseline characteristics and Table 2 describes clinical outcomes for the study cohort, showing that the acute
Limitations
This was a single-center cohort study performed in an inner-city Canadian ED with comprehensive cardiology services, and these results may be difficult to reproduce in other settings. The observational design is not ideal, but a randomized trial in our institution was not possible. Once the intervention was in place, subjecting patients to previous care without rapid outpatient testing was not considered ethical. Although an ideal comparison would have been similar structured care with
Discussion
In this intensive 30-day follow-up study of 1,116 ED patients with potential ischemic chest pain, 120 patients had definite acute coronary syndrome and 0% were missed (95% confidence interval 0% to 2.4%) with the diagnostic algorithm described. These results compare favorably to the 5% miss rate observed in an earlier chest pain cohort at the same setting before the implementation of the accelerated diagnostic protocol,4 whereas the median ED length of stay was similar.
Enhanced diagnostic
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Supervising editor: Deborah B. Diercks, MD
Author contributions: GI, EG, MK, DK, and JC developed the chest pain diagnostic algorithm. FS and JC conceived the study. BB supervised the conduct of the trial and data collection. BB and EY managed the database. FS provided statistical analysis. FS drafted the article, and all authors contributed to its revision, notably GI and JC. FS takes responsibility for the paper as a whole.
Funding and support: By Annals policy, all authors are required to disclose any and all commercial, financial, and other relationships in any way related to the subject of this article as per ICMJE conflict of interest guidelines (see www.icmje.org). The authors have stated that no such relationships exist.
Please see page 257 for the Editor's Capsule Summary of this article.
Publication date: Available online January 4, 2012.