Cardiac Biomarkers, Echocardiography, and Outpatient Cardiac Monitoring for Evaluation of Emergency Department Patients With Syncope: A Systematic Review and Analysis of Direct Evidence for SAEM GRACE.

Abstract

Syncope places a significant burden on emergency departments (EDs), often prompting extensive testing to exclude life-threatening conditions. However, the diagnostic utility of troponin, B-type natriuretic peptide (BNP), transthoracic echocardiography (TTE), and outpatient cardiac monitoring remains unclear. This systematic review assessed the diagnostic accuracy of these tests in adults presenting with syncope. The research question was: In ED patients with syncope, does TTE, cardiac biomarkers (troponin, BNP), or outpatient arrhythmia monitoring, compared with no testing, improve outcomes within 30 days? Primary outcomes included adverse events (death, arrhythmias, structural/ischemic heart disease, and select non-cardiac causes such as pulmonary embolism or aortic dissection) for biomarkers and diagnostic yield for TTE and monitoring. Sensitivity, specificity, and likelihood ratios (LR+ and LR-) were calculated for biomarkers, while diagnostic yield with 95% CI was reported for TTE and monitoring. Risk of bias was assessed using JBI and QUADAS-2. The database searches identified 1759 citations. After applying inclusion and exclusion criteria, 41 studies (21,557 patients) were included. Significant heterogeneity among the included trials (all with I² > 90%) precluded meta-analysis. For BNP, LR+ ranged 1.4-47 and LR- 0.06-0.4; for troponin, LR+ 1.9-11.2 and LR- 0.2-0.9. TTE diagnostic yield was 0%-29% overall and 8%-28% in high-risk groups. Outpatient monitoring yielded 1%-59% overall and 12%-42% in high-risk patients. In ED patients with syncope, the diagnostic accuracy and yield of cardiac biomarkers, TTE, and outpatient monitoring show substantial variability, largely due to differences in patient populations, outcome measures, and study methodologies. Based on the existing evidence, these modalities in isolation cannot be recommended for routine use in syncope evaluation. Among these tests, the diagnostic yield of TTE and outpatient monitoring is greater in patients with cardiac risk factors and could potentially contribute to a more accurate diagnosis.