What are the indications, technique, and post‑procedure management for venous stenting in patients with symptomatic chronic venous outflow obstruction such as iliac vein compression (May‑Thurner syndrome), post‑thrombotic stenosis, or central venous stenosis refractory to conservative therapy?

Venous Stenting for Chronic Venous Outflow Obstruction

Iliac vein stenting combined with catheter-directed thrombolysis or pharmacomechanical thrombectomy is the definitive treatment for symptomatic chronic venous outflow obstruction in patients who have failed conservative therapy, particularly for May-Thurner syndrome, post-thrombotic stenosis, and central venous obstruction. 1, 2

Clinical Indications

Primary Indications

• Iliac vein obstruction between the clavicles and inguinal ligaments with symptomatic chronic venous insufficiency refractory to compression therapy 2
• May-Thurner syndrome (iliac vein compression) presenting with acute iliofemoral DVT or chronic symptoms 1, 2
• Post-thrombotic syndrome with documented iliac vein obstruction causing quality-of-life-impairing symptoms 3, 2
• Persistent venous ulcers with duplex ultrasound evidence of iliocaval obstruction 3

Urgent/Emergent Indications

• Phlegmasia cerulea dolens (limb-threatening venous gangrene) requires immediate thrombus removal followed by stenting 1, 2
• Rapid thrombus extension despite therapeutic anticoagulation 3, 1
• Symptomatic deterioration on anticoagulation alone 3, 1

Key Clinical Pearl

Young patients (<50 years) presenting with left-sided iliofemoral DVT should immediately raise suspicion for May-Thurner syndrome, as anatomic compression persists despite anticoagulation and predisposes to recurrent VTE if treated with anticoagulation alone. 1

Pre-Procedure Diagnostic Algorithm

Step 1: Initial Screening

• Duplex ultrasound is the mandatory first-line examination 3
• Look for: nonphasic common femoral vein velocity waveforms, reduced flow augmentation with distal compression, and diffuse venous reflux 3

Step 2: Anatomic Characterization

• CT venography (CTV) or MR venography (MRV) of abdomen/pelvis is required before intervention to characterize stenosis location, collaterals, and anatomic variants 3
• This step is critical because 15-35% of patients experience recurrence at 2 years, often due to unrecognized anatomic variants 3
• CTV/MRV identifies: stenosis, occlusion, venous atresia, collaterals, webs, trabeculations, and vein wall thickening 3

Step 3: Intraprocedural Confirmation

• Catheter venography with intravascular ultrasound (IVUS) is performed immediately before stenting 3
• IVUS is the most sensitive modality for deep vein obstructive disease, though 10% of stenoses require trial balloon angioplasty to unmask 3
• Venous manometry must confirm pressure gradient before stenting and document gradient resolution after stenting 2

Procedural Technique

Acute DVT (<14 days old)

1. Initiate therapeutic anticoagulation immediately upon diagnosis 1
2. Perform catheter-directed thrombolysis (CDT) or pharmacomechanical thrombectomy (PMT) first to remove thrombus burden 3, 1, 2
   • PMT reduces thrombolytic drug dose by 40-50% and shortens infusion time compared to CDT alone 1
3. After thrombus removal, perform balloon angioplasty followed by self-expanding stent placement 3, 1
   • Angioplasty alone typically fails and requires stenting 3

Chronic Obstruction (>21 days) or Non-Thrombotic Lesions

• Stent recanalization without prior thrombolysis achieves 83-98% anatomic success 3, 1
• Proceed directly to balloon angioplasty and stent placement after venography/IVUS confirmation 4

Stent Positioning Guidelines

• Confine stents to the iliac vein whenever feasible for optimal patency 3, 1, 2
• If lesion extends into common femoral vein, caudal stent extension is reasonable but expect modestly lower patency (90% vs 84%) 3, 1, 2
• For isolated common femoral vein stenosis, attempt percutaneous transluminal angioplasty without stenting first 3, 2
• Never place stents in peripheral veins subject to bending/flexing (neck, axilla, groin below inguinal ligament) due to high collapse risk 2

Post-Procedure Anticoagulation Management

Standard Regimen

• Continue therapeutic anticoagulation with the same dosing, monitoring, and duration as iliofemoral DVT patients without stents 3, 1, 2
• Minimum 3 months; indefinite therapy for unprovoked events 1, 2
• Direct oral anticoagulants are preferred over warfarin in non-cancer patients due to lower bleeding risk 1
• Target INR 2.0-3.0 if warfarin is used 2

High-Risk Patients

Add antiplatelet therapy to anticoagulation for patients at high risk of rethrombosis after individualized bleeding risk assessment 3, 1, 2:

• Poor inflow vein quality (moderate to severe femoral vein disease) 5
• Suboptimal anatomic result 3, 1
• Type IV obstruction (multiple venous outflow segments occluded) 5
• Known hypercoagulable state 5
• Continue antiplatelet therapy for at least 3-6 months 2

Critical Evidence on Anticoagulation Type

Low-molecular-weight heparin for >10 days post-stenting significantly reduces early reocclusion (odds ratio 0.012) compared to other anticoagulation regimens in patients with complete venous outflow occlusion 5. This is particularly important for type IV obstruction and hypercoagulable states, which have 4.6-fold and 3.8-fold increased odds of early thrombosis, respectively 5.

Adjunctive Therapy

• Prescribe 30-40 mmHg knee-high elastic compression stockings for at least 2 years to reduce post-thrombotic syndrome risk 1

Expected Clinical Outcomes

Patency Rates

• Primary patency: 94-95% at 1 year, 58-64% at 3 years 5, 6, 7
• Secondary patency: 93-96% at 3 months, 76-100% at 3-5 years 5, 6, 7
• Non-thrombotic iliac vein lesions have superior patency (100% at 12 months) compared to post-thrombotic obstruction (87% at 12 months) 7

Symptom Relief

• 95% experience initial reduction in pain and swelling 3, 1
• At 3 years: 79% maintain pain reduction, 66% maintain swelling reduction 3, 1
• 86% achieve substantial clinical improvement (≥2 rVCSS points) 6
• Venous ulcer healing occurs in 56% of affected patients 3, 1
• Quality-of-life scores improve significantly and are sustained long-term 3

Critical Pitfalls and How to Avoid Them

Do Not Rely on Anticoagulation Alone

Anticoagulation alone for May-Thurner syndrome leads to significantly higher recurrent VTE rates because the anatomic compression persists 1. Mechanical relief of obstruction is essential 1.

Do Not Delay Intervention

Early thrombus removal within 14 days yields optimal outcomes 1. CDT/PCDT should not be given to patients with chronic DVT symptoms >21 days unless combined with stenting 3.

Recognize High-Risk Reocclusion Scenarios

Early stent thrombosis (within 3 months) occurs in 25.5% of patients with complete venous outflow occlusion 5:

• Type IV obstruction (multiple segments): 4.6-fold increased risk 5
• Hypercoagulable state: 3.8-fold increased risk 5
• Inadequate anticoagulation duration: 83-fold increased risk if LMWH <10 days 5

Stent Fracture Management

Stent fracture is rare (~1% of cases) and can be successfully managed by implanting a second stent 3, 1. It does not cause problems beyond thrombosis of that vessel 3.

Pregnancy Considerations

In pregnant patients with prior iliac vein stents, mechanical deformation may occur late in pregnancy but typically resolves spontaneously postpartum without clinical sequelae 3, 1. Among 62 women who received LMWH prophylaxis during pregnancy, none experienced recurrent VTE 3, 1.

Contraindications

• High bleeding risk patients should not receive CDT/PCDT 3
• Chronic DVT symptoms >21 days are not suitable for thrombolysis alone 3
• Systemic fibrinolysis should never be given routinely to patients with iliofemoral DVT 3