What are the options for interventional radiology (IR) intervention in patients with pulmonary embolism (PE)?

Interventional Radiology Options for Pulmonary Embolism

For patients with pulmonary embolism, interventional radiology offers two main categories of catheter-based therapies: catheter-directed thrombolysis (CDL) and catheter-based embolectomy, with selection based on PE severity, hemodynamic status, bleeding risk, and institutional expertise. 1

Primary IR Intervention Categories

Catheter-Directed Thrombolysis (CDL)

CDL delivers thrombolytic drugs directly into the pulmonary artery circulation through a multi-sidehole infusion catheter, aiming to achieve similar effectiveness to systemic thrombolysis while reducing bleeding risk by using approximately one-fourth the standard systemic dose (typically 20-24 mg alteplase versus 100 mg systemically). 1

Available CDL devices include:

• Standard CDL catheters (Unifuse, Cragg-McNamara): 4F-5F catheters with 5-10 cm infusion length, FDA-cleared for peripheral vasculature 1

• Ultrasound-assisted thrombolysis (USAT) with EKOSonic system: 5F catheter with dual lumens—one housing ultrasound transducers emitting high-frequency, low-energy ultrasound to facilitate fibrin dissociation, the other delivering thrombolytics through multiple ports; FDA-cleared specifically for PE treatment 1

• Pharmacomechanical CDL (Bashir Endovascular Catheter): 7F catheter with nitinol-supported infusion basket expanded within thrombus, FDA-cleared for peripheral vasculature 1

The USAT approach typically involves gradual infusion over 12 hours, though recent data suggest 2-4 hours may have comparable effectiveness. 1 The ULTIMA trial (n=59) demonstrated that USAT with 20 mg alteplase reduced RV/LV ratio from 1.28±0.19 to 0.99±0.17 at 24 hours (P<0.001) with zero major bleeds. 1 The larger SEATTLE II trial (n=150) showed RV/LV ratio reduction from 1.55 to 1.13 at 48 hours with 24 mg alteplase, with only 1 GUSTO major bleed and no intracranial hemorrhage. 1

Catheter-Based Embolectomy

These devices mechanically remove thrombus from the pulmonary vasculature without requiring thrombolytics, offering immediate mechanical relief of pulmonary obstruction. 1

Available embolectomy devices include:

• FlowTriever system: Large-bore device (20F catheter) with three self-expanding nitinol disks that mechanically engage thrombus; FDA-cleared specifically for PE treatment 1

  • The FLARE trial (n=106) demonstrated RV/LV ratio reduction from 1.53 to 1.15 at 48 hours with minimal complications (1 death, 1 hemoptysis, 1 cardiogenic shock) 1

• Indigo System: 8F catheter with mechanical clot engagement and mechanized aspiration; FDA-cleared for peripheral artery and venous systems, though large proximal PE may be difficult to aspirate en bloc with 8F device 1

• AngioVac: Veno-venous bypass system with funnel-shaped inflow tip (26F inflow access, 16F-20F outflow); requires perfusion team; FDA-cleared for removal of undesirable intravascular material 1

• Aspire Max: Suction thrombectomy with specialized handheld aspirator (5F-6F catheters); FDA-cleared for removal of fresh, soft thrombi from peripheral and coronary vasculature 1

Important caveat: The AngioJet rheolytic thrombectomy device (6F-8F catheters) carries an FDA black-box warning against use in pulmonary arteries due to risks of hypotension and bradycardia. 1

Clinical Decision-Making Algorithm

High-Risk PE (Massive PE with Shock/Hypotension)

For patients with systolic blood pressure <90 mmHg or requiring inotropic support:

• First-line therapy remains systemic thrombolysis (alteplase 100 mg over 2 hours, or 50 mg bolus for cardiac arrest) unless absolute contraindications exist 2

• When systemic thrombolysis is contraindicated or has failed, surgical embolectomy is preferred, but catheter-based embolectomy or CDL may be considered as alternatives 1

• Unfractionated heparin should be the preferred anticoagulation mode in hemodynamically unstable patients, as LMWH and fondaparinux have not been tested in shock settings 1

Intermediate-Risk PE (Submassive PE)

For normotensive patients with RV dysfunction (by imaging) and/or elevated cardiac biomarkers:

• The evidence for IR intervention versus anticoagulation alone remains controversial and closely counterbalanced 1

• CDL or catheter-based embolectomy may be considered when patients have severely compromised RV function, high cardiac biomarkers (troponin, BNP), and contraindications to full-dose systemic thrombolysis 1, 2

• The decision should account for bleeding risk, thrombus burden and location, and institutional expertise 1

• Approximately 10% of intermediate-risk patients will decompensate hemodynamically despite anticoagulation, though identifying these specific patients prospectively remains challenging 3

Comparative Safety Profile

The theoretical advantage of catheter-based interventions over systemic thrombolysis is reduced bleeding risk:

• Systemic thrombolysis carries 2% intracranial hemorrhage risk in clinical trials (3-5% outside trials) and 6.3% major extracranial bleeding risk 1

• CDL studies report significantly lower bleeding rates: ULTIMA (0 major bleeds), SEATTLE II (1 GUSTO major bleed, 0 ICH), PERFECT (0 major hemorrhages or strokes) 1

• The OPTALYSE PE trial (n=101) using 8-24 mg alteplase via USAT reported 4 major bleeds, 1 recurrent PE, and 1 death at 30 days 1

Critical Limitations and Caveats

The evidence supporting catheter-based interventions is substantially less robust than that for systemic thrombolysis. 1 Key limitations include:

• No completed randomized trials have demonstrated mortality benefit for catheter-based interventions over anticoagulation alone 1

• Most trials focus on surrogate endpoints (RV/LV ratio, pulmonary artery systolic pressure) rather than mortality or quality of life 1

• No randomized comparison trials exist between standard CDL and USAT in the pulmonary circulation 1

• The optimal dosing strategy for catheter-directed thrombolysis remains unknown 1

• Risk stratification models may not accurately reflect individual patient mortality risk, as approximately half of deaths at 90 days are from causes other than PE 1

Common pitfall: Relying solely on risk category assignment without comprehensive clinical assessment of the individual patient's bleeding risk, comorbidities, and trajectory. 1

Procedural Considerations

• CDL catheter placement typically requires only preprocedural CT angiography for guidance 1

• Embolectomy cases typically require selective pulmonary angiograms to assess thrombus location, choose appropriate device, and optimize catheter navigation 1

• Embolectomy may be performed concurrently or sequentially with CDL in selected cases 1

• Treatment plans may appropriately be modified after accessing the pulmonary arteries based on findings 1