What is the appropriate anticoagulation regimen and duration after mechanical thrombectomy and iliac vein stent placement for May‑Thurner syndrome?

Anticoagulation Following Thrombectomy and Stent Placement for May-Thurner Syndrome

After mechanical thrombectomy and iliac vein stent placement for May-Thurner syndrome, continue therapeutic anticoagulation for a minimum of 3 months using the same dosing and monitoring as for iliofemoral DVT without stents; in young, otherwise healthy patients with patent stents and no prior VTE, discontinuation at 3–12 months is safe, whereas patients with unprovoked DVT or high-risk features should receive indefinite anticoagulation. 1, 2

Immediate Post-Procedure Anticoagulation Strategy

Direct oral anticoagulants (DOACs) are the preferred first-line agents because they eliminate the need for parenteral bridging, have comparable efficacy to warfarin, lower bleeding risk, and enable outpatient management. 3 Specifically:

• Rivaroxaban: 15 mg twice daily for 21 days, then 20 mg once daily 3, 4
• Apixaban: 10 mg twice daily for 7 days, then 5 mg twice daily 3
• Low-molecular-weight heparin (LMWH) such as enoxaparin 1 mg/kg subcutaneously every 12 hours is an acceptable alternative if DOACs are contraindicated 3

The anticoagulation regimen after stent placement should mirror the dosing, monitoring, and initial duration used for iliofemoral DVT patients without stents. 5, 1

Duration of Anticoagulation: Risk-Stratified Approach

Young, Low-Risk Patients with May-Thurner Syndrome (3–12 Months)

In selected patients—particularly younger individuals with May-Thurner syndrome, no prior VTE, and patent venous stents—discontinuing anticoagulation at 3–12 months is safe. 1, 2 A prospective study of 58 patients with acute iliofemoral DVT treated with thrombectomy and stenting showed:

• 98% remained free from post-thrombotic syndrome at 2 years after stopping anticoagulation 2
• VTE recurrence rate was only 3.5 per 100 patient-years after cessation 2
• Primary and secondary stent patency at 24 months were 80% and 95%, respectively, with no difference between limited-duration (3–12 months) and extended-duration (>12 months) anticoagulation groups 2

Key characteristics of patients suitable for limited-duration therapy: younger age (mean 38 years), female sex, no prior VTE, and confirmed May-Thurner anatomy. 2

Unprovoked DVT or High-Risk Features (Indefinite Anticoagulation)

Patients with unprovoked DVT should receive a minimum of 3 months of anticoagulation followed by reassessment; indefinite therapy is recommended for those with low-to-moderate bleeding risk. 5, 3 High-risk features warranting extended therapy include:

• Prior unprovoked VTE 2
• Recurrent thrombosis despite anticoagulation 5
• Suboptimal stent result or poor inflow vein quality 5
• Older age or multiple comorbidities 2

Anticoagulation should stop at 3 months only if bleeding risk is high. 3

Provoked DVT (Fixed 3-Month Course)

For provoked DVT (e.g., surgery, transient risk factor), a fixed 3-month anticoagulation course is sufficient. 5, 3

Adjunctive Antiplatelet Therapy

Adding antiplatelet therapy to therapeutic anticoagulation is reasonable in patients at particularly high risk of rethrombosis (e.g., poor inflow vein quality, imperfect anatomic result after stenting) after individualized bleeding-risk assessment. 5, 1 This dual therapy should be reserved for select cases because it increases bleeding risk. 5

Compression Stockings

Prescribe 30–40 mm Hg knee-high elastic compression stockings for at least 2 years to reduce the risk of post-thrombotic syndrome by approximately 50%. 5, 1 Although recent randomized trials found no specific benefit in preventing post-thrombotic syndrome, 5 compression therapy remains reasonable for symptom management and patient comfort. 5

Monitoring and Follow-Up

Verify stent patency with duplex ultrasound at regular intervals (e.g., 1 month, 6 months, 12 months, then annually) to detect early thrombosis. 1, 2 Most recurrent VTE events (82%) manifest as thrombotic stent occlusions, and 76% occur while patients are still on anticoagulation, 2 underscoring the importance of surveillance imaging rather than relying solely on clinical symptoms.

Reassess the need for continued anticoagulation at 3 months in all patients, weighing recurrence risk against bleeding risk. 3

Critical Pitfalls to Avoid

• Do not rely on anticoagulation alone when May-Thurner syndrome is identified; the persistent anatomic compression predisposes to recurrent VTE despite therapeutic anticoagulation. 5, 1, 6, 7
• Do not discontinue anticoagulation prematurely in patients with unprovoked DVT or high-risk features, as this markedly increases recurrence risk. 3
• Do not assume all patients require indefinite anticoagulation; young, healthy patients with May-Thurner syndrome and patent stents can safely stop at 3–12 months. 1, 2
• Do not add routine antiplatelet therapy to all patients; reserve dual therapy for high-risk cases after bleeding-risk assessment. 5
• Stent fracture is rare (~1% of cases) and can usually be managed by implanting a second stent without long-term sequelae. 5, 1

Special Populations

Pregnancy

In pregnant patients with prior iliac vein stents, mechanical stent deformation may occur late in pregnancy but typically resolves spontaneously postpartum without clinical consequences. 5, 1 Among 62 women with left iliac vein stents who became pregnant and received LMWH prophylaxis, none experienced recurrent VTE during pregnancy or the postpartum period. 5, 1

Cancer-Associated DVT

Extend anticoagulation for at least 3–6 months and continue while cancer is active; LMWH is preferred over warfarin or DOACs. 3

Evidence Quality and Consensus

Major vascular imaging societies endorse routine iliac vein stenting in addition to anticoagulation for May-Thurner syndrome, despite the absence of randomized controlled trials. 5, 1 Observational data consistently demonstrate that recurrent VTE occurs more frequently with anticoagulation alone compared with thrombectomy followed by iliac vein stenting in patients with obstructive iliac vein lesions. 5, 1 The anatomic compression persists despite anticoagulation, making mechanical relief of the obstruction essential. 1, 7

The 12-month stent patency rate ranges from 60% to 100%, with stent occlusion or recurrent DVT rates of 0% to 40% depending on patient selection and anticoagulation duration. 8 However, the published evidence regarding optimal antithrombotic treatment duration is limited to retrospective studies without comparator groups, 8 necessitating individualized decision-making based on patient age, VTE history, stent patency, and bleeding risk.