- IVC filter placement is an interventional radiologic procedure to prevent the propagation of a deep venous thrombus (DVT), or “blood clot” from a vein in your legs or pelvis to your lungs.
Risk factors for a DVT:
- Inheriting a blood-clotting disorder
- Prolonged immobility
- Injury or surgery
- Pregnancy
- Oral contraceptives
- Obesity
- Smoking
- Cancer
- Family history
- Age greater than 60
Indications
Accepted:
Documented deep venous thrombus (DVT) with one or more of the following:
- Contraindication to anticoagulation
- High risk of bleeding, intracranial hemorrhage, recent surgery, allergy
- Formation or progression of DVT while on therapeutic anticoagulation
- Inability to maintain therapeutic level of anticoagulation
- Poor patient compliance with medical management
Relative:
- Prophylactic in the setting of major trauma, closed head injury, spinal cord injury, multiple long bone fractures, high-risk patients with prolonged immobilization
Contraindications
True contraindications are rare
- IVC too large or too small to safely accommodate filter
- Confirmed allergy to filter component
- Inability to gain venous access
- Total thrombosis of the IVC
Complications
- Access site thrombosis
- IVC thrombosis (<30%)
- IVC perforation (9-24%)
- Filter migration/embolization
- Filter fracture 1%
- Penetration of vena cava wall 🡪 adjacent organs, aorta, etc.
- Other: infection, air embolism, bleeding
Work-up
Ultrasound:
- Most common test. Utilizes sound waves to visualize veins within the lower extremities to assess for a visible thrombus, compressibility of the vein, and evidence of blood flow. A series of ultrasounds may be done to determine whether a blood clot is growing or to check for a new one.
- D-dimer:
- This is a blood test which can be performed. A DVT would cause an elevated D-dimer level, although many other derangements can elevate D-dimer. A negative D-dimer is highly specific to rule out a DVT.
- CT or MRI scans:
- Either can provide visual images of your veins and might show a thrombus. Often these scans performed for other reasons and incidentally reveal a thrombus. Given the radiation associated with a CT scan, and the high cost associated with MRI, these modalities are not typically first line for DVT detection.
Filter types:
Procedure/Technique:
- Access to the vena cava: Typically obtained via the internal jugular or common femoral vein.
- Venogram of the IVC: Performed to define/confirm anatomy and plan deployment location. The most common location for deployment of the IVC filter is below the level of the renal veins, although there are instances which may warrant alternate location, like placing a filter in the suprarenal segment, when there is a clot in the infrarenal segment.
- Duration: Takes about 30 – 60 minutes depending on the anatomy and technique.
- Level of risks: Minimal
Who performs the procedure:
This procedure involves using an Ultrasound and Fluoroscopic/Angiography machine to obtain images. These are safely performed by Interventional Radiologists.
Duration of Implant:
These can be permanent or retrievable. Once the reason for the DVT has been addressed and patients undergo management either medical or surgical, and are no longer considered to have risks of DVT can be referred to Interventional Radiologists, who can assist in the removal of the IVC filter.
Procedure/Technique for removal:
- Access to the vena cava: Obtained via the internal jugular.
- Venogram of the IVC: Performed to define/confirm anatomy and patency of the vessel.
- Patent or occluded: Decision would be made if it’s safe to remove or if more expertise is needed in removal based on the cavagram. Sometimes, it’s better to leave it if it’s difficult to remove which might cause more problems.
- These are better answered depending on the situation by the expert.