Utility of the emergency department observation unit in ensuring stress testing in low-risk chest pain patients.

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 indeterminate (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.