Increasing emergency department referral of chest pain patients for non-invasive cardiac testing does not improve two-year clinical outcomes

Background Non-invasive cardiac testing (NICT) has been associated with decreased long-term risks of major adverse cardiac events (MACE) among emergency department (ED) patients at high coronary risk. It is unclear whether this association extends to patients without evidence of myocardial injury on initial electrocardiogram and cardiac troponin testing. Methods Retrospective cohort study of patients presenting with chest pain between 2013-2019 to 21 EDs within an integrated health care system, excluding patients with ST-elevation myocardial infarction or myocardial injury by serum troponin testing. To account for confounding by indication, we grouped patient encounters by the NICT referral rate of the initially assigned emergency physician, relative to local peers within discrete time periods. The primary outcome was MACE within two years. Secondary outcomes were coronary revascularization and MACE inclusive of all-cause mortality (MACE-ALL). Associations between NICT referral group (low, intermediate, or high) and outcomes were assessed using risk-adjusted proportional hazards methods with censoring for competing events. Results Among 144,577 eligible patient encounters, 30-day NICT referral was 13.0%, 19.9% and 27.8% in low, intermediate, and high NICT referral groups, respectively, with good balance of baseline covariates between groups. Compared with the low group, there was no significant decrease in the adjusted hazard ratio (aHR) of MACE within the intermediate (aHR 1.08, 95% CI 1.02-1.14, adjusted p = 0.024) or high (aHR 1.05, 95% CI 0.99-1.11, adjusted p = 0.13) NICT referral groups. Results were similar for MACE-ALL and coronary revascularization, as well as subgroup analyses stratified by estimated risk (HEART score; 48.2% low-risk, 49.2% moderate-risk, 2.7% high-risk). Conclusion Increased NICT referral was not associated with a decreased hazard of MACE within two years following ED visits for chest pain without evidence of acute myocardial injury. These findings further highlight the need for evidence-based guidance regarding appropriate use of NICT in this population. What is Known In emergency department patients with chest pain but no evidence of acute myocardial injury, referral for non-invasive cardiac testing is not associated with improved outcomes within 6 to 12 months. There is some evidence that non-invasive cardiac testing may improve longer-term outcomes, especially among patients at moderate to high risk of coronary disease. What the Study Adds Higher non-invasive cardiac testing was not associated with improved outcomes within two years following emergency department visits for chest pain, absent evidence of acute myocardial injury. This finding was most evident among patients at low to moderate predicted coronary risk.