From the SIR Residents and Fellows Section (RFS)
Teaching Topic: Inferior Vena Cava Filters in Pregnancy: A Systematic Review
Harris SA, Velineni R, Davies AH. Inferior vena cava filters in pregnancy: a systematic review. J Vasc Interv Radiol. 2016. 27(3):354-60.
Pregnancy can cause patients to be at increased risk for venous thromboembolism and is an important cause of maternal mortality. This systematic review sought to collate the available information on the use of IVC filters in pregnancy. A total of 44 articles with 124 total pregnancies were able to be identified. The articles were case reports or case series without any randomized controlled trials. The authors argue there is currently not enough evidence to suggest that IVC filters should be routinely used in pregnancy in patients with DVT. While the use of retrievable filters is attractive in this young, healthy patient population, until further studies are carried out, their use should be considered for the same absolute indications as in the nonpregnant population or in individuals in whom there are concerns surrounding delivery. The manuscript reports complication rates that are comparable to those in the nonpregnant population. In addition, while suprarenal and infrarenal positioning can be used, there are more theoretical benefits to suprarenal placement. The authors conclude that IVC filters can be used safely, when appropriate, during pregnancy. However, as always, long-term follow-up data is lacking and further research is warranted.
What is the rate of VTE in pregnancy?
The author quotes rates of VTE in pregnancy as 0.79 in 100,000 maternities and the 3rd most common cause of maternal mortality in Great Britain, specifically. Worldwide incidence of VTE has been quoted up to 3.24 per 1000 women years accounting for 15% of maternal mortality.
What is the proposed mechanism of the increased risk of VTE?
The rate of VTE is 5 times higher during pregnancy and 60 times higher in the postpartum period. The etiology is theorized to be secondary to adaptions in the hemostatic system in preparation for the hemostatic challenge of delivery in combination with the venous stasis that occurs with a gravid uterus and increased plasma volume. Furthermore, there may be vascular endothelial damage that occurs from distention or surgical intervention, which promote thrombus formation.
What is the standard treatment in pregnancy?
Medical management is the first line treatment for VTE in pregnancy. Patients are treated with low molecular weight heparin throughout the pregnancy up until at least 6 weeks postpartum. Warfarin is avoided due to its ability to cross the placenta.
Questions to Consider
What are the Society of Interventional Radiology Guidelines (SIR) regarding the absolute indications, relative indications, and contraindications for IVC filter placement?
Absolute Indications (Proven VTE)
- Recurrent VTE (acute or chronic) despite adequate anticoagulation
- Contraindication to anticoagulation
- Complication of anticoagulation
- Inability to achieve/maintain therapeutic anticoagulation
Relative Indications (Proven VTE)
- Iliocaval DVT
- Large, free-floating proximal DVT
- Difficulty establishing therapeutic anticoagulation
- Massive PE treated with thrombolysis/thrombectomy
- Chronic PE treated with thromboendarterectomy
- Thrombolysis for iliocaval DVT VTE with limited cardiopulmonary reserve
- Recurrent PE with filter in place
- Poor compliance with anticoagulant medications
- High risk of complication of anticoagulation (eg, ataxia, frequent falls)
- Prophylactic Indications (No VTE, primary prophylaxis not feasible)
- Trauma patient with high risk of VTE
- Surgical procedure in patient at high risk of VTE
- Medical condition with high risk of VTE
Contraindications to Filter Placement
- No access route to the vena cava
- No location available in vena cava for placement of filter
What considerations are especially relevant regarding IVC filter placement in pregnancy?
An additional consideration in pregnancy is that anticoagulation is stopped during both vaginal and caesarian delivery, increasing the risk of VTE in this time period. Therefore, a filter may be placed prior to delivery. This relative indication is addressed by the above SIR guideline, “medical condition with high risk of VTE” and/or “difficulty maintaining therapeutic anticoagulation”.
SIR consensus guidelines state that some patients with indications for vena cava filters have limited periods of risk of clinically significant PE and/or contraindication to anticoagulation and may not require permanent protection from PE with a vena cava filter. This tenant applies to most pregnant patients and therefore removable filters are preferred. According to this study, rates of non-retrieval in the pregnant population (11.25%) is comparable to the non-pregnant population (12.1%).
It is thought that below the level of the renal veins, it is more likely that the IVC filter can be crushed/fractured due to compression from a gravid uterus which may lead to migration of the filter and damage to the IVC wall. Suprarenal placement may also provide additional protection from thrombus which may have developed in the ovarian veins. Finally, the increased venous flow from the renal veins may promote clot lysis of trapped thrombi.
Pomp ER, Lenselink AM, Rosendaal FR, Doggen CJ. Pregnancy, the postpartum period and prothrombotic defects: risk of venous thrombosis in the MEGA study. J Thromb Haemost. 2008 Apr. 6(4):632-7.
Kaufman JA, Kinney TB, Streiff MB, Sing RF, Proctor MC, Becker D, Cipolle M, Comerota AJ, Millward SF, Rogers FB, Sacks D, Venbrux AC. Guidelines for the use of retrievable and convertible vena cava filters: report from the Society of Interventional Radiology multidisciplinary consensus conference. J Vasc Interv Radiol. 2006 Mar;17(3):449-59.
Lindsay Karr Thornton, MD
Diagnostic Radiology Resident, PGY-4
University of Florida