(145) Predictors of Quaternary Interventions Among Patients With Pulmonary Embolism

Introduction: Treatment of pulmonary embolism (PE) varies from anticoagulation alone to mechanical support with venoarterial extracorporeal membrane oxygenation (VA-ECMO) and endovascular thrombectomy (ET) or catheter-directed thrombolysis (CDT). These modalities are only available at quaternary level centers, often prompting patient transfer. Existing scoring systems broadly risk stratify patients with PE, but clinicians need tools to assess patients' eligibility for these advanced therapies. We hypothesize that hemodynamic, laboratory, CT angiography (CTA), and ultrasound findings can stratify patients into those most or least likely eligible for advanced interventions for PE.

Methods: This was a retrospective study of adult patients transferred to a quaternary center for PE between 2019 and 2021. Patients with clot-in-transit were excluded. Our primary outcome was treatment with VA-ECMO, ET, or CDT. We used a Classification and Regression Tree (CART) to identify variables associated with higher likelihood of advanced interventions. CART is a machine learning tool using recursive partitioning to create a decision tree and identify significant predictors of an outcome based on relative variable importance (RVI).

Results: We analyzed 189 patients; 44 (23%) received advanced interventions, 23 (12%) VA-ECMO, 20 (14%) ET, 10 (7%) CDT. Massive PE was diagnosed in 44 patients (23%). Those treated with advanced interventions had a higher mean heart rate (113 v 103 bpm, p=0.002) and serum lactate (4.10 v 2.43 mmol/L, p=0.008) on arrival. CART identified right ventricular to left ventricular ratio (RV:LV) on CTA as the most important predictor of advanced intervention (RVI 100%), followed by reflux of contrast into the Inferior Vena Cava on CTA (RVI 45%). Two patients (4.1%) with RV:LV < 1.325 received advanced interventions, compared to 42 (30%) with RVLV>1.325. Our model demonstrated good discriminatory capability with an area under the receiver operating curve of 0.64.

Conclusions: Patients with high-risk PE can be stratified based on select CTA findings to determine likelihood of eligibility advanced interventions. Patients without significant RV dilation or other CTA findings of right heart dysfunction may be less likely to require advanced interventions.