ULTRAsound-assisted Catheter-guided Thrombolysis for Intermediate-high Risk Patients With PE

Inclusion Criteria: * Adults aged ≥ 18 years at time of enrollment; * Ability to provide written informed consent (or legally authorized representative consent where applicable); * Objectively confirmed acute pulmonary embolism (PE) by contrast-enhanced computed tomography pulmonary angiography (CTPA) demonstrating intraluminal filling defects in at least one segmental, lobar, or more proximal pulmonary artery; * Hemodynamically stable at presentation (i.e., not meeting high-risk PE criteria of sustained hypotension, shock, or need for vasopressor support per ESC 2019 and AHA/ACC risk stratification); * Evidence of right ventricular (RV) dysfunction on imaging (e.g., RV/LV ratio \> 1.0 on CTPA or echocardiography); * Elevated cardiac biomarkers, including troponin I or T above the upper limit of normal; * Intermediate-high risk features defined as the combination of imaging RV dysfunction and positive cardiac biomarkers, consistent with ESC stratification; * At least one clinical indicator of elevated early risk such as: 1. Tachycardia (e.g., HR ≥ 100 bpm), 2. Mild systolic blood pressure reduction (e.g., SBP ≤ 110 mmHg but not meeting high-risk thresholds), 3. Hypoxemia (SpO₂ \< 90% on room air). Exclusion Criteria: * Presence of hemodynamic instability, defined as at least one of the following: 1. Systolic blood pressure (SBP) \< 90 mmHg or a drop ≥ 40 mmHg from baseline for \> 15 minutes not attributable to arrhythmia, hypovolemia, or sepsis, 2. Requirement for vasopressors to maintain SBP ≥ 90 mmHg, 3. Cardiogenic shock, defined by clinical signs of end-organ hypoperfusion (e.g., altered mental status, oliguria, lactate elevation), 4. Need for ECMO or other mechanical circulatory support initiated prior to assessment, 5. Cardiac arrest requiring resuscitation. * Active major bleeding or conditions with high bleeding risk (e.g., known intracranial pathology predisposed to hemorrhage or associated with ongoing pharmacotherapy); * Recent (\< 3 months) intracranial or intraspinal surgery, major trauma, or stroke; * Known central nervous system neoplasm or metastatic cancer with high bleed risk. * Administration of systemic thrombolytic agents or catheter-directed thrombolysis prior to registry assessment for the index PE episode; * Known hypersensitivity to alteplase, unfractionated heparin (UFH), or any of their excipients. * Requirement for intensive care admission for conditions unrelated to the index PE; * Duration of symptoms attributable to the index PE \> 14 days at presentation, as defined in contemporary trial criteria; * Known severe thrombocytopenia (e.g., platelet count \< 100 × 10⁹/L) or coagulopathy precluding safe catheter access; * Life expectancy \< 6 months due to advanced comorbid disease unrelated to acute PE; * Pregnancy.