Evaluation of Outpatient Cardiac Stress Testing After Emergency Department Encounters for Suspected Acute Coronary Syndrome

Study objective: Professional guidelines recommend 72-hour cardiac stress testing after an emergency department (ED) evaluation for possible acute coronary syndrome. There are limited data on actual compliance rates and effect on patient outcomes. Our aim is to describe rates of completion of noninvasive cardiac stress testing and associated 30-day major adverse cardiac events. Methods: We conducted a retrospective analysis of ED encounters from June 2015 to June 2017 across 13 community EDs within an integrated health system in Southern California. The study population included all adults with a chest pain diagnosis, troponin value, and discharge with an order for an outpatient cardiac stress test. The primary outcome was the proportion of patients who completed an outpatient stress test within the recommended 3 days, 4 to 30 days, or not at all. Secondary analysis described the 30-day incidence of major adverse cardiac events. Results: During the study period, 24,459 patients presented with a chest pain evaluation requiring troponin analysis and stress test ordering from the ED. Of these, we studied the 7,988 patients who were discharged home to complete diagnostic testing, having been deemed appropriate by the treating clinicians for an outpatient stress test. The stress test completion rate was 31.3% within 3 days and 58.7% between 4 and 30 days, and 10.0% of patients did not complete the ordered test. The 30-day rates of major adverse cardiac events were low (death 0.0%, acute myocardial infarction 0.7%, and revascularization 0.3%). Rapid receipt of stress testing was not associated with improved 30-day major adverse cardiac events (odds ratio 0.92; 95% confidence interval 0.55 to 1.54). Conclusion: Less than one third of patients completed outpatient stress testing within the guideline-recommended 3 days after initial evaluation. More important, the low adverse event rates suggest that selective outpatient stress testing is safe. In this cohort of patients selected for outpatient cardiac stress testing in a well-integrated health system, there does not appear to be any associated benefit of stress testing within 3 days, nor within 30 days, compared with those who never received testing at all. The lack of benefit of obtaining timely testing, in combination with low rates of objective adverse events, may warrant reassessment of the current guidelines.