How to prevent thrombosis in venous ectatic aneurysms after treatment of a Type 4 Cognard (Cognard classification) dural arteriovenous fistula (DAVF)?

From the Guidelines

To avoid venous ectatic aneurysms from thrombosis after treatment of a type 4 Cognard dural arteriovenous fistula, anticoagulation therapy with a direct oral anticoagulant such as rivaroxaban (10 mg daily) or apixaban (2.5 mg twice daily) should be initiated immediately after the endovascular or surgical intervention, as these lower doses have been shown to be effective in preventing venous thromboembolism with a reduced risk of bleeding 1.

Key Considerations

• The American Society of Hematology 2020 guidelines suggest that the standard dose or the lower dose of rivaroxaban or apixaban may be used for the secondary prevention of venous thromboembolism, with a conditional recommendation due to moderate certainty in the evidence of effects 1.
• Anticoagulation therapy is preferred over antiplatelet therapy with aspirin for secondary prevention of venous thromboembolism, as it has been shown to be more effective in preventing recurrent events without an increased risk of bleeding 1.
• Close monitoring with serial imaging (MRI/MRV or CT venography) at 1,3, and 6 months is essential to assess venous remodeling and determine the need for continued anticoagulation.

Treatment Regimen

• Initiate anticoagulation therapy with a direct oral anticoagulant such as rivaroxaban (10 mg daily) or apixaban (2.5 mg twice daily) immediately after the endovascular or surgical intervention.
• Continue anticoagulation therapy for at least 3-6 months, with close monitoring of venous remodeling and adaptation.
• Consider alternative anticoagulation regimens, such as warfarin (target INR 2.0-3.0), in patients with contraindications to direct oral anticoagulants.

Rationale

• Type 4 Cognard DAVFs have direct perimedullary venous drainage with ectatic venous components that are prone to thrombosis after treatment due to altered hemodynamics.
• Sudden thrombosis of these dilated venous structures can lead to venous infarction, hemorrhage, or neurological deterioration.
• Maintaining venous patency during the remodeling period allows for gradual adaptation of the venous system and reduces the risk of these potentially devastating complications.

From the Research

Prevention of Venous Ectatic Aneurysms from Thrombosis

To avoid venous ectatic aneurysms from thrombosis after treatment of a type 4 Cognard dural arteriovenous fistula, several strategies can be considered:

• Identification of patients at risk of developing venous thromboembolism (VTE) enables appropriate thromboprophylaxis to be implemented 2
• The use of guidelines and risk assessment tools to identify patients at risk of VTE, and the implementation of decision making tools based on risk factor assessment improves the prescription of appropriate VTE prophylaxis 2
• Pharmacological thromboprophylaxis, such as low dose unfractionated heparin, low molecular weight heparin, fondaparinux, warfarin, or aspirin, can be effective in preventing VTE 2
• Novel, single-target oral anticoagulants have been developed that appear to fulfill many of the requirements for optimal anticoagulant therapy, including oral administration, wide therapeutic window, rapid onset of action, and predictable pharmacodynamics and pharmacokinetics 2

Management of Dural Arteriovenous Fistulae

In the context of dural arteriovenous fistulae (DAVFs), the following points are relevant:

• DAVFs can be associated with venous aneurysms, which can rupture and cause hemorrhage 3
• The development of venous aneurysms in patients with DAVFs may not require preceding venous hypertension or venous ectasia 3
• A careful review of draining vein features, including tortuosity or stenosis, is needed to identify patients at risk of developing venous aneurysms 3
• Anticoagulation therapy may be restricted in some cases of DAVFs, especially when they are associated with retrograde venous flow, due to the increased risk of hemorrhage 4

Prevention of Post-Thrombotic Syndrome

To prevent post-thrombotic syndrome (PTS), which can occur after deep vein thrombosis (DVT), the following strategies can be considered:

• Optimal anticoagulation is key for PTS prevention, and low-molecular-weight heparins have anti-inflammatory properties and a particularly attractive profile 5
• Elastic compression stockings (ECS) may be helpful for treating acute DVT symptoms, but their benefits for PTS prevention are debated 5
• Catheter-directed techniques may reduce the risk of moderate-severe PTS in the long term in patients with ilio-femoral DVT at low risk of bleeding 5
• Statins may decrease the risk of PTS, but current evidence is lacking 5