Predictors of Short-Term Outcomes after Syncope: A Systematic Review and Meta-Analysis

Introduction: We performed a systematic review and meta-analysis to identify predictors of serious clinical outcomes after an acute-care evaluation for syncope. Methods: We identified studies that assessed for predictors of short-term (<= 30 days) serious clinical events after an emergency department (ED) visit for syncope. We performed a MEDLINE search (January 1, 1990 - July 1, 2017) and reviewed reference lists of retrieved articles. The primary outcome was the occurrence of a serious clinical event (composite of mortality, arrhythmia, ischemic or structural heart disease, major bleed, or neurovascular event) within 30 days. We estimated the sensitivity, specificity, and likelihood ratio of findings for the primary outcome. We created summary estimates of association on a variable-by-variable basis using a Bayesian random-effects model. Results: We reviewed 2,773 unique articles; 17 met inclusion criteria. The clinical findings most predictive of a short-term, serious event were the following: 1) An elevated blood urea nitrogen level (positive likelihood ratio [LR+]: 2.86, 95% confidence interval [CI] [1.15, 5.42]); 2); history of congestive heart failure (LR+: 2.65, 95% CI [1.69, 3.91]); 3) initial low blood pressure in the ED (LR+: 2.62, 95% CI [1.12, 4.9]); 4) history of arrhythmia (LR+: 2.32, 95% CI [1.31, 3.62]); and 5) an abnormal troponin value (LR+: 2.49, 95% CI [1.36, 4.1]). Younger age was associated with lower risk (LR-: 0.44, 95% CI [0.25, 0.68]). An abnormal electrocardiogram was mildly predictive of increased risk (LR+ 1.79, 95% CI [1.14, 2.63]). Conclusion: We identified specific risk factors that may aid clinical judgment and that should be considered in the development of future risk-prediction tools for serious clinical events after an ED visit for syncope.