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 What the Study Adds ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This project was supported by The Permanente Medical Group?s Delivery Science and Applied Research program. No authors or their institutions at any time received payment or services from a third party for any aspect of the submitted work. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Kaiser Permanente Northern California Institutional Review Board approved this study with a waiver of informed consent. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes Because of the sensitive nature of the data collected for this study, requests to access the dataset from qualified researchers trained in human subject confidentiality protocols may be sent to KPNC at kpnc.irb@kp.org. * BMI : body mass index CAD : coronary artery disease ECG : electrocardiogram ED : emergency department HEART : history, electrocardiogram, age, risk factors, troponin KPNC : Kaiser Permanente Northern California LOQ : limit of quantitation MACE : major adverse cardiac event MACE-ALL : major adverse cardiac event, including all-cause mortality NICT : non-invasive cardiac test STEMI : ST-elevated myocardial infarction.