The Prognostic Value of Syncope on Mortality in Patients With Pulmonary Embolism: A Systematic Review and Meta-analysis

STUDY OBJECTIVE: Syncope is a presenting symptom in 10% to 20% of patients with pulmonary embolism. We perform a meta-analysis to clarify the prognostic value of syncope on short-term mortality in pulmonary embolism patients and its association with hemodynamic instability.

METHODS: PubMed, EMBASE, and the Cochrane Library were searched up until January 7, 2020. Studies reporting inhospital or 30-day mortality of adults with pulmonary embolism with and without syncope were included. Quality of included studies was evaluated with the Quality in Prognosis Studies tool. Meta-analysis was conducted to derive pooled odds ratios (ORs) and risk differences for the relation of syncope with mortality and hemodynamic instability. To study the influence of hemodynamic instability on the association between syncope and mortality, meta-regression was performed.

RESULTS: Search and selection resulted in 26 studies, of which 20 were pooled, involving 9,419 of 335,120 patients (3%) with syncope. Syncope was associated with higher mortality (OR 1.82; 95% confidence interval [CI] 1.14 to 2.90; I2 88%; risk difference 4% [95% CI 1% to 8%]) and higher prevalence of hemodynamic instability (OR 4.36; 95% CI 2.27 to 8.37; I2 93%; risk difference 12% [95% CI 7% to 18%]). OR for mortality in patients with pulmonary embolism with syncope versus without it was higher in the presence of a larger difference in hemodynamic instability between groups (coefficient 0.05; 95% CI 0.01 to 0.09).

CONCLUSION: The association between syncope and short-term mortality in patients with pulmonary embolism is explained by a difference in hemodynamic instability. This emphasizes the importance of risk stratification by hemodynamic status in pulmonary embolism patients with and without syncope.