Percutaneous Mechanical Thrombectomy With or Without Low-Dose Catheter-Directed Thrombolysis in Acute Intermediate-High Risk Pulmonary Embolism

Acute pulmonary embolism (PE) is the third most common cardiovascular cause of death. In patients with intermediate-high risk acute PE, percutaneous mechanical thrombectomy (PMT) using large-bore catheters achieves rapid hemodynamic improvement while avoiding the bleeding risk of systemic thrombolysis, and low-dose catheter-directed thrombolysis (CDT) can dissolve residual thrombus with a lower systemic bleeding risk. This prospective, multicenter, non-randomized cohort study aims to compare the safety and efficacy of PMT alone versus PMT combined with low-dose CDT (PMT+LDCDT) in patients with acute intermediate-high risk PE. Approximately 150 patients will be enrolled and allocated to either PMT alone or PMT+LDCDT based on operator assessment. The primary safety endpoint is the composite incidence of major adverse events (MAE) within 48 hours, and the primary efficacy endpoint is the change in the right ventricular/left ventricular (RV/LV) diameter ratio from baseline to 48 hours assessed by a CTPA core laboratory.

Inclusion Criteria: * Age 18-80 years. * Acute pulmonary embolism confirmed by CTPA, with symptom onset to diagnosis ≤14 days. * Imaging evidence of right ventricular dysfunction (CTPA RV/LV diameter ratio ≥1.0, or echocardiographic right ventricular dilation/hypokinesia) and elevated cardiac injury biomarkers (troponin I or T above the upper limit of normal). * Presence of a contraindication to systemic thrombolysis, or failure of systemic thrombolysis, or clinical deterioration during anticoagulation. * Thrombus visible in the main pulmonary artery and/or lobar arteries on CTPA. * Provision of signed informed consent. Exclusion Criteria: * Cardiac arrest at enrollment; systolic blood pressure \15 minutes unresponsive to fluid resuscitation and vasopressors. * Active bleeding; known coagulopathy (INR \>2.0 or platelet count \