Residency · Residency · Interventional Radiology

Deep Venous Thrombosis: Catheter-Directed Therapy

DVT Fundamentals

Deep venous thrombosis affects approximately 1-2 per 1,000 persons per year. Iliofemoral DVT, involving the iliac and/or common femoral veins, carries the highest risk of post-thrombotic syndrome (PTS). PTS is a form of chronic venous insufficiency resulting from venous obstruction and valvular incompetence that affects 20-50% of patients with proximal DVT, manifesting as leg swelling, pain, skin changes, and ulceration. Phlegmasia cerulea dolens represents the most severe form: massive iliofemoral DVT with venous congestion severe enough to compromise arterial inflow, constituting a limb-threatening emergency.

Rationale for Catheter-Directed Therapy

Standard anticoagulation treats ongoing thrombosis but does not actively remove existing clot. Early thrombus removal may preserve venous valve function, reduce venous obstruction, and lower the incidence and severity of PTS. The central debate in this field is whether active thrombus removal actually improves long-term outcomes compared with anticoagulation alone.

Patient Selection

The best candidates are those with acute iliofemoral DVT (less than 14-21 days old), low bleeding risk, good functional status, and long life expectancy. Strong indications include phlegmasia cerulea dolens, limb-threatening venous congestion, and massive iliofemoral DVT with severe symptoms. Relative contraindications include infrapopliteal DVT alone, chronic DVT (beyond 21-28 days), high bleeding risk, limited life expectancy, and poor functional status. Age, symptom severity, and extent of thrombus should guide decision-making.

Techniques

Catheter-Directed Thrombolysis (CDT)

A multi-sidehole infusion catheter is embedded within the thrombus and tPA is infused at 0.5-1.0 mg/hr for 12-48 hours, with concurrent low-dose heparin administered via the sheath. ICU monitoring is required, tracking fibrinogen levels (with infusion held if levels fall below 150 mg/dL), clinical assessment, and access site checks. Venograms are obtained at 12-24 hour intervals to assess progress. The advantages include effective clot dissolution with potential valve preservation. The disadvantages include prolonged infusion time, ICU stay requirement, and a major bleeding risk of 5-11%.

Pharmacomechanical Thrombectomy (PMT)

PMT combines mechanical thrombus removal with lytic agents to reduce treatment time. The AngioJet system (Boston Scientific) uses rheolytic thrombectomy, spraying lytic into the thrombus at high velocity followed by aspiration, and is capable of single-session treatment. Run time must be limited due to the risk of hemolysis and hemoglobinuria, and operators should be aware of rare bradycardia from adenosine release. The EKOS/EkoSonic system (Boston Scientific) uses ultrasound-accelerated thrombolysis, with ultrasound energy opening fibrin structure and enhancing lytic penetration; while it still requires infusion, it may reduce dose and duration. The ClotTriever (Inari Medical) is a mechanical thrombectomy device specifically designed for venous clot that requires no lytic agent. Its large-bore funnel captures and removes thrombus in a single-session procedure, thereby avoiding the bleeding risk of lytic agents.

Aspiration Thrombectomy

Large-bore catheter aspiration of fresh thrombus can be performed using the Indigo system, AngioVac, or manual aspiration through a large sheath. This can be combined with lytic infusion for residual thrombus.

Key Clinical Trials

ATTRACT Trial (2017)

This was the largest randomized controlled trial in the field, enrolling 692 patients with proximal DVT randomized to anticoagulation alone versus anticoagulation plus pharmacomechanical CDT. The primary endpoint was PTS at 24 months measured by Villalta score greater than 4. The result showed no significant difference in PTS incidence (47% in the CDT group vs. 48% in controls), while the CDT group had more major bleeding (1.7% vs. 0.3%). Subgroup analysis showed a trend toward reduced moderate-to-severe PTS with CDT in the iliofemoral DVT subgroup (18% vs. 28%). The trial was criticized for including femoropopliteal DVT that may not benefit from CDT, heterogeneous techniques, and the fact that only 25% had isolated iliofemoral DVT.

CaVenT Trial (2012, 5-year follow-up 2016)

This trial randomized 209 patients with iliofemoral DVT to CDT plus anticoagulation versus anticoagulation alone. CDT reduced PTS at 2 years (41% vs. 56%, an absolute risk reduction of 14.4%), with benefit maintained at 5 years. There was a higher bleeding rate in the CDT group. This was a smaller, single-country European trial.

CAVA Trial (2020)

This trial enrolled 184 patients with iliofemoral DVT comparing ultrasound-accelerated CDT versus anticoagulation. No significant reduction in PTS was found at 12 months, though the study was underpowered.

Interpretation

The evidence does not support routine CDT for all proximal DVT. There may be benefit in selected patients with extensive iliofemoral DVT and severe symptoms. Single-session mechanical thrombectomy devices like the ClotTriever may change the risk-benefit calculus by avoiding lytic-related bleeding, with CLOUT registry data promising but not yet proven in randomized trials.

Procedural Technique

Access

Popliteal vein access in the prone position is the most common approach for iliofemoral DVT, performed under ultrasound guidance. Posterior tibial vein access is used for more distal thrombus extension. Internal jugular vein access is employed for IVC or bilateral iliofemoral thrombosis.

Procedure Steps

After obtaining venous access under ultrasound guidance, ascending venography defines the thrombus extent. The thrombus is crossed with a guidewire, and PMT is performed or an infusion catheter is placed spanning the entire thrombus. For CDT, lytic infusion is initiated and the patient is transferred to the ICU. Venograms are checked at intervals, and residual thrombus is aspirated or macerated. Any underlying venous stenosis such as May-Thurner syndrome or extrinsic compression is treated with venous stenting. Completion venography confirms restored flow.

Post-Procedure

Anticoagulation is continued for at least 3-6 months, with longer duration for unprovoked DVT. Compression stockings are traditionally prescribed, though the OCTAVIA trial questioned their benefit. Surveillance duplex ultrasound is performed for stent patency if stenting was performed, and evaluation for underlying thrombophilia is considered if the DVT was unprovoked.

Complications

Major hemorrhage occurs in 5-11% with CDT and is lower with PMT alone. Intracranial hemorrhage occurs in less than 1%. Pulmonary embolism during thrombus manipulation is rare, particularly with IVC filter protection, though routine filter placement is controversial. Other complications include access site hematoma, hemolysis with AngioJet, and vessel perforation or dissection.

<image>Illustration of catheter-directed thrombolysis for acute iliofemoral deep venous thrombosis. Sequential panels: (1) Pre-treatment venogram showing extensive thrombus filling the common femoral and external iliac veins with no flow into the IVC; (2) Popliteal vein access with a multi-sidehole infusion catheter advanced through the thrombus, spanning from the popliteal vein to the common iliac vein, with tPA infusing through the sideholes; (3) 24-hour check venogram showing significant thrombus dissolution revealing an underlying compression of the left common iliac vein (May-Thurner lesion); (4) Final result after iliac vein stenting with restored flow into the IVC. Labels indicate the infusion catheter, residual thrombus, May-Thurner compression, and the deployed venous stent.</image>

<image>Comparison diagram of pharmacomechanical thrombectomy devices for DVT. Three panels: (1) AngioJet rheolytic system showing high-velocity saline jets creating a Venturi effect to fragment and aspirate thrombus, with an inset showing the power pulse spray mode delivering lytic agent; (2) EKOS ultrasound-accelerated catheter with ultrasound transducers along the infusion catheter emitting energy to loosen fibrin cross-links; (3) ClotTriever mechanical thrombectomy device showing the self-expanding nitinol coring element capturing thrombus and the collection bag. Each panel includes advantages and disadvantages listed below.</image>

<image>Bar graph summarizing key trial results for catheter-directed therapy in DVT. Three grouped columns for ATTRACT, CaVenT, and CAVA trials. Each column shows: PTS rate in the intervention group vs. control group, major bleeding rate in each group, and the iliofemoral subgroup PTS rate where available. Annotations highlight the key finding from each trial: ATTRACT (no overall PTS benefit, trend in iliofemoral subgroup), CaVenT (PTS benefit at 2 and 5 years), CAVA (no benefit, underpowered). A legend indicates statistical significance.</image>

Clinical Pearls

ATTRACT showed no overall benefit of CDT for all proximal DVT, making patient selection critical with focus on extensive iliofemoral DVT with severe symptoms. After thrombus clearance, always look for an underlying venous stenosis such as May-Thurner syndrome, because untreated compression leads to rethrombosis. Phlegmasia cerulea dolens is an emergency indication for thrombus removal and should not be delayed. Single-session mechanical thrombectomy devices like the ClotTriever are changing the field by avoiding the bleeding risks of prolonged lytic infusion. During CDT, fibrinogen must be monitored closely, with values below 150 mg/dL mandating cessation of the lytic agent. Compression stockings after DVT were standard practice, but recent evidence from the SOX trial has questioned their efficacy in preventing PTS.

References

• Vedantham S et al. Pharmacomechanical catheter-directed thrombolysis for deep-vein thrombosis (ATTRACT trial). N Engl J Med 2017
• Enden T et al. Long-term outcome after additional catheter-directed thrombolysis versus standard treatment for acute iliofemoral DVT (CaVenT trial). Lancet 2012
• Notten P et al. Ultrasound-accelerated catheter-directed thrombolysis versus anticoagulation for acute iliofemoral DVT (CAVA trial). Lancet Haematol 2020
• Defined by the SIR/AVF Position Statement on Catheter-Directed Therapy for DVT. J Vasc Interv Radiol 2019

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