Thrombus weight and volume alone do not predict drop in pulmonary artery pressure after large bore mechanical thrombectomy

Background Large-bore mechanical thrombectomy (LBMT) is an established catheter-directed therapy for acute pulmonary embolism (PE). The relationship between aspirated thrombus weight and volume with hemodynamic and echocardiographic outcomes remains unclear. Methods Patients undergoing LBMT for PE using the FlowTriever system between 2021 and 2024 were included. Thrombus weight and volume were quantified, and clot composition was assessed histopathologically. Associations between thrombus characteristics and clinical, invasive hemodynamics, echocardiographic parameters, and biomarkers were evaluated immediately after the procedure, at hospital discharge, and at 3 months follow-up. Results Thrombus material was available in 48 patients (31% women), of which 41 presented with intermediate-risk and 7 with high-risk PE. LBMT resulted in significant reductions in systolic pulmonary artery pressures (sPAP) intraprocedurally (-12.8±8.3 mmHg, p<0.001), with a further invasively measured decrease through 3 months (-9.6±10.6 mmHg, p<0.001). From baseline to discharge, right ventricular coupling improved (+0.24 (IQR 0-0.6), p<0.001), right ventricle (RV)/left ventricle (LV) ratio decreased (-0.28±0.2, p<0.001), driven by a reduction in RV end-diastolic diameter (-8±6.6 mm, p<0.001). NT-proBNP and troponin T declined significantly. Neither thrombus weight nor volume correlated with acute changes in sPAP (rvolume=0.06; rweight=0.10), RV-uncoupling (rvolume=0.47; rweight=0.46), and RV/LV ratio (rvolume=-0.08; rweight=-0.10) (p for all >0.05), nor with outcomes at 3 months. Conclusions Apirated thrombus weight and volume were not associated with hemodynamic or echocardiographic improvements after LBMT, suggesting that, beyond mechanical obstruction, additional mechanisms potentially including paracrine and endocrine effects of thrombus material may contribute to acute and chronic PE-related cardiopulmonary dysfunction. Acknowledgement Some icons in the graphical abtsract were generated by AI. Chat GPT was used for statistical troubleshooting.