ORIGINAL ARTICLE Utility of the Emergency Department Observation Unit in Ensuring Stress Testing in Low-Risk Chest Pain Patients Troy Madsen, MD, Michael Mallin, MD, Joseph Bledsoe, MD, Philip Bossart, MD, Virgil Davis, MD, Christopher Gee, MD, and Erik Barton, MD, MS Background: Recent research has noted low rates of compliance among ED chest pain patients referred for outpatient stress testing. The practice at our institution, a 39,000 visits per year emergency department (ED), is to place chest pain patients considered low risk for acute coronary syndrome in an observation unit for serial biomarker testing and provocative cardiac testing. Our objective was to determine the rates of positive stress tests among this group and to extrapolate from this the potential missed positive stress tests if these patients were referred instead for outpatient stress testing. Methods: This was a retrospective chart review of all chest pain patients admitted to the ED observation unit between April 2006 and June 2007. Baseline information, including a history of coronary disease, was recorded. Patients underwent a treadmill stress test, nuclear stress test, or coronary CT scan at the discretion of the attending emergency physician and/or the consulting cardiologist. Rates of positive stress test or coronary CT and patient disposition (admission to an inpatient unit versus discharge for outpatient follow-up) were noted. Results: A total of 353 patients underwent stress testing or coronary CT during the study period: 257 (72.8%) patients had an exercise treadmill echocardiogram, 61 (17.3%) patients underwent nuclear stress testing, and 35 (9.9%) patients had a coronary CT. Seventy patients (19.8%) had a history of coronary disease but had been considered appropriate for observation by the attending emergency physician. Thirty-nine stress tests were positive (11%) and 11 were indeterminate (3.1%). Among patients with no history of coronary disease, 20 stress tests were positive (7.1%), and 10 were indeter- minate (3.5%). Of all patients with a positive stress test, 19 (48.7%) underwent cardiac catheterization and 1 (2.6%) had coronary artery bypass graft. Twenty-one of 39 patients with a positive stress test (54%) were ultimately admitted to an inpatient unit per the recommendation of the consulting cardiologist. Assuming a best-case scenario in which 70% of patients referred for outpatient stress testing actually have the testing done (based on a recent report of outpatient compliance), physicians would miss approximately 3.3% of patients with a positive stress test if these patients were discharged directly from the ED. Conclusion: Among chest pain patients admitted to an ED observation unit, the rate of positive stress tests was 11%. Approximately 3.3% of patients with positive stress tests may have been missed if these patients were instead referred for outpatient testing. Key Words: observation unit, chest pain, stress test (Crit Pathways in Cardiol 2009;8: 122–124) O bservation units for chest pain patients are commonly used to expedite the diagnosis and treatment of patients with the potential for acute coronary syndrome and unstable angina. 1–6 Earlier research has focused on the use of chest pain units or observation units to expedite the care of patients presenting with chest pain, and many studies have focused on the cost effectiveness of these units. 7–9 One advantage of an observation unit for these chest pain patients is the performance of stress testing once an acute myocardial infarction has been ruled out. An in-hospital stress test thus removes the variable of patient compliance to outpatient stress testing in addition to facilitating more urgent additional testing such as cardiac catheterization. A recent study has noted the low rates of compliance among patients who present to the emergency department (ED) with chest pain and are subsequently referred for outpatient stress testing. 1 Our objective was to determine the rates of positive stress testing among low-risk chest pain patients admitted to our observation unit and to extrapolate the potential missed rates of positive stress tests if these patients were to be referred instead for outpatient stress testing. METHODS We performed a retrospective chart review of all patients admitted to the University of Utah observation unit under the chest pain protocol during the 14-month period between April 2006 and June 2007. The University of Utah Emergency Department is an urban emergency department with 39,000 patient visits per year. The observation unit is a 10-bed unit under the direction of the emer- gency physicians and midlevel providers. The observation unit uses complaint-driven protocols with strict inclusion and exclusion cri- teria. The inclusion criteria for a chest pain patient who is deemed low risk for acute coronary syndrome is a normal or nondiagnostic EKG, normal or indeterminate troponin I on initial ED testing, hemodynamic stability, and no ongoing chest pain. A history of coronary artery disease is not an exclusion criterion (Table 1). Emergency physicians admitting patients to the observation unit write the initial order set for testing (ie, serial troponin, stress testing). Cardiologists evaluate these chest pain patients in the morning after their observation unit admission and make further decisions on additional testing (nuclear versus treadmill stress test versus coronary CTA), cardiac catheterization, and inpatient admis- sion based on patient history, characteristics, and testing results. Six fourth-year medical students who had worked in the emergency department and were familiar with the observation unit performed the chart review. The reviewers were blinded to the goals of this study. Reviewers were given a template form and a guide with definitions of categories for data entry. Data entry was re- viewed on 20% of patients by one of the study’s lead investigators (J.B.) to ensure consistent data acquisition between reviewers. We recorded baseline characteristics, including age, past medical history, gender, and cardiac history on all patients admitted to the observation unit. Rates of positive stress test or coronary CT, in addition to patient disposition (admission to an inpatient unit versus discharge for outpatient follow-up), were noted. As stress testing and coronary CT were often used interchangeably as a testing From the University of Utah, Salt Lake City, UT. This study was presented at the 2008 Scientific Assembly for the American College of Emergency Physicians; October 28 –31, 2008; Chicago, IL. Reprints: Troy E. Madsen, MD, Division of Emergency Medicine, University of Utah School of Medicine, 30 North 1900 East, 1C26, Salt Lake City, UT 84132. E-mail: troy.madsen@hsc.utah.edu. Copyright © 2009 by Lippincott Williams & Wilkins ISSN: 1535-282X/09/0803-0122 DOI: 10.1097/HPC.0b013e3181b00782 Critical Pathways in Cardiology • Volume 8, Number 3, September 2009 122 | www.critpathcardio.com