A67-13 When Fainting Signals the Clot: Characterizing Syncope in Acute Pulmonary Embolism Through Clinical and Imaging Correlates

Rationale Syncope is a well-recognized presentation of acute pulmonary embolism (PE), occurring in approximately 10–15% of cases, and often signals hemodynamic compromise. The mechanism is attributed to sudden right ventricular (RV) failure and reduced cardiac output secondary to pulmonary arterial obstruction. Prior registries, systematic reviews, and meta-analyses have linked syncope to increased mortality and hemodynamic instability; however, there remains limited evaluation of the biochemical and diagnostic imaging features associated with syncopal presentations of PE. This study aimed to characterize the demographic, biochemical, and imaging features associated with syncope in acute PE. Methods A retrospective analysis was conducted on adults admitted with acute PE (03/2021–08/2025) from our institutional Pulmonary Embolism Response Team (PERT) registry in a tertiary community hospital setting. Demographics, biomarkers, echocardiographic parameters, and computed tomographic angiography (CTA) features were compared between patients presenting with and without syncope. Statistical testing included χ² or Fisher’s exact tests for categorical variables, and t-tests or Wilcoxon rank-sum tests for continuous data, with p < 0.05 considered significant. Results Among 571 patients with acute PE, 69 (12.1%) presented with syncope. There were no significant differences in age, sex, left ventricular ejection fraction, pulmonary artery systolic pressure, or tricuspid annular systolic planar excursion. Black/African American patients demonstrated a higher prevalence (18.3% vs 11.0%, p=0.06). Compared with non-syncopal presentations, those with syncope had more proximal and bilateral clot burden, including saddle PE (21.5% vs 10.3%, p=0.002), right main (15.7% vs 8.6%, p=0.010), left main (15.4% vs 9.7%, p=0.038), left lobar (16.4% vs 8.1%, %, p=0.002), and left segmental (16.8% vs 7.7%, p=0.001) involvement. CT-defined right heart strain was more common (16.1% vs 8.5%, p=0.008). On echocardiography, McConnell’s sign (22.5% vs 10.6%, p=0.004) and right heart strain (14.9% vs 9.6%, p=0.05) were more frequent. Troponin-T, D-dimer, and lactate levels were significantly higher (all p ≤ 0.01); BNP did not differ. Conclusions This study provides a first clinical, biochemical, and imaging characterization of syncope in acute PE. Syncope occurred in one in eight presentations and was associated with more proximal clot burden and RV strain. These findings are supported by elevations in lactate and troponin, further highlighting the risk for hemodynamic compromise associated with syncopal-PE. Clinically, syncope can serve as a marker of intermediate or high-risk PE, emphasizing proactive monitoring and expedited imaging, particularly in under-resourced hospitals. Future studies should validate these findings and further assess the prognostic impact of syncope in PE on clinical stability and management.