Key Words:
venous thromboembolism , prophylaxis , filter , indications , complications
Filters and Terminology
A variety of inferior vena cava (IVC) filters are available on the market today and these are summarized in Table 21-1 ; the more commonly used devices are shown in Figure 21-1 . Vena cava filters may be divided in to two groups: those that are permanent and those that are potentially retrievable, the latter being the most frequently utilized in clinical practice today. In addition, filters may be inserted for either “therapeutic” or “prophylactic” indications based on the presence or absence of pulmonary embolism (PE) and/or deep venous thrombosis (DVT). In this context, the term “therapeutic” is somewhat of a misnomer as the filter itself does not treat the thrombus or thromboembolism (i.e., it does not decrease the amount of thrombus). However, as the filter is placed to treat the natural history of the condition, the term “therapeutic” is commonplace. Therapeutic filters are those that are placed in patients with a confirmed clinical event (i.e., diagnoses of DVT and/or PE) to prevent subsequent thromboembolic sequelae. In contrast, prophylactic filters are those that are placed without the diagnosis of a clinical event (i.e., DVT or venous thromboembolism [VTE]). In the case of prophylactic filters, the device is most commonly used in patients who are deemed to be at a high risk for future VTE and/or those who are not suitable for anticoagulation (prophylactic or therapeutic). Prophylactic filter placement has seen the largest growth in filter use.
| Device | Size of Introducer | Insertion Site (Jugular/Femoral) | MRI Compatibility |
|---|---|---|---|
| Permanent Filters | |||
| Bird’s Nest | 14 Fr | Either (separate kits) | No |
| Greenfield (stainless steel) | 14 Fr | Either (separate kits) | No |
| Simon Nitinol | 9 Fr | Either (separate kits) | Yes |
| TrapEase | 8 Fr | Either (1 kit for both) | Yes |
| VenaTech | 14.6 Fr | Either (one kit) | Yes |
| Retrievable Filters | |||
| Gunther Tulip | 12 Fr | Either (separate kits) | Yes |
| OptEase | 8 Fr | Either | Yes |
| Recovery Filter | 9 Fr | Femoral | Yes |
Indications
There has been an exponential increase in the use of IVC filters over the last 2 decades, driven by their increasing availability, relative ease of insertion, good safety profile, and use for prophylactic indications. Despite their popularity, there is a surprising paucity of robust clinical evidence supporting their efficacy with only two randomized controlled trials (RCTs) being conducted and examining their outcomes. Indications for IVC filter insertion may be broadly divided into the following two subgroups: recommended use (based on evidence-based guidelines) and expanded use (referring to indications beyond those specified in evidence-based guidelines). These indications are summarized in Box 21-1 .
Recommended use (based on evidence-based guidelines)
- •
Proven VTE with contraindication for anticoagulation
- •
Proven VTE with complications of anticoagulation treatment
- •
Recurrent VTE despite anticoagulation treatment (failure of anticoagulation)
Expanded use (indications beyond those specified in evidence-based guidelines)
- •
Recurrent PE complicated by pulmonary hypertension
- •
Patients with DVT and limited cardiopulmonary reserve or chronic obstructive pulmonary disease (COPD)
- •
Patients with large, free-floating iliofemoral thrombus
- •
Following and during thrombectomy, embolectomy, or thrombolysis of DVT
- •
Trauma patients with a high risk of DVT (head and spinal cord injury, pelvic or lower extremity fractures) with a contraindication for anticoagulation
- •
High-risk surgical patients with a contraindication for anticoagulation
- •
Patients with DVT who have cancer, who have burns, or who are pregnant
Contraindications for filter placement
- •
Uncorrectable coagulopathy
- •
Chronically thrombosed IVC
- •
Sepsis or bacteremia
- •
Mega IVC (3.5 cm)
Recommended Indications
IVC filter placement is recommended in those patients with proven VTE and with one or more of the following: (1) a contraindication to anticoagulation, (2) a current or previous complication from anticoagulation, or (3) a recurrent VTE despite full or adequate anticoagulation. In patients in whom a filter was inserted as an alternative to anticoagulation, conventional pharmacological anticoagulation should be started once bleeding risk resolves; and the filter should be removed thereafter.
Expanded Indications
IVC filters may be used for a range of indications beyond those specified in evidence-based guidelines. Typically, the use of a filter in this category involves a high-risk clinical scenario, including patients with hypercoagulable conditions for which limited evidence exists to guide the practice. Examples include patients with cancer, those who are pregnant with an established DVT, high-risk surgical or trauma patients, and patients with chronic thromboembolic disease or cardiorespiratory frailty in the presence of DVT. The use of filters as a prophylactic measure in the high-risk trauma patient has been the subject of interest in the literature recently. The lack of randomized data to support the use of IVC filters in this group of patients must again be reiterated. However, it is up to individual institutions and clinicians to decide on best practice for their patients in this category on a case-by-case basis.
Trauma
Complex trauma patients have the highest incidence of VTE of all hospitalized patients, with PE attributed to the third most-common cause of death in these patients who survive the first 24 hours from their injuries. VTE risk is exacerbated by factors influencing coagulopathy such as immobility, fluid depletion, inflammatory mediators, and iatrogenic factors including treatment with blood products. Pharmacological (low molecular weight heparin) and mechanical thromboprophylaxis (intermittent pneumatic compression [IPC)]) and graduated compression stockings are advocated as first-line therapies in those without significant-bleeding risk. There remains debate about optimal VTE prophylaxis in those considered to be at high risk of VTE with associated significant-bleeding risk.
Several groups have advocated the use of prophylactic IVC filters in the prevention of PE in high-risk trauma patients. Guidelines published by The Eastern Association of the Surgery in Trauma in 2002 suggested consideration of prophylactic IVC interruption for select high-risk patients. EAST developed a risk-stratification tool—the Risk Assessment Profile (RAP)—to allow stratification of trauma patients according to VTE risk. The RAP score ( Box 21-2 ) takes into account various other scoring systems such as the Glasgow Coma Scale (GCS) and the abbreviated injury score (AIS), together with 16 other patient factors. A RAP score greater than 5 signifies increased a threefold increased risk of VTE.
| Age | Weight |
| >40 but <60 | 2 |
| >60 but <75 | 3 |
| >75 | 4 |
| Injury-related factors | Weight |
| AIS >2 for the chest | 2 |
| AIS >2 for the abdomen | 2 |
| Spinal fractures | 2 |
| AIS >2 for the head | 3 |
| Coma (GCS score <8 for >4 hr) | 3 |
| Complex lower extremity fracture | 4 |
| Pelvic fracture | 4 |
| Spinal cord injury with paraplegia/quadriplegia | 4 |
| Iatrogenic factors | Weight |
| Central femoral line >24 hr | 2 |
| 4 or more transfusions during first 24 hr | 2 |
| Surgical procedures >24 hr | 2 |
| Repair or ligation of major venous injury | 3 |
| Underlying conditions | Weight |
| Obese (>120% Metropolitan Life Table) | 2 |
| Malignancy | 2 |
| Abnormal coagulation factors at admission | 2 |
| History of thromboembolism | 3 |
Contrary to this, however, the American College of Chest Physicians (ACCP) 2008 guidelines recommend against the use of IVC filters as primary thromboprophylaxis in patients with major trauma or spinal cord injuries (Grade 1C evidence). These guidelines recommend that high-risk trauma patients who are contraindicated to low molecular weight heparin due to bleeding risk should receive mechanical prophylaxis with IPS or GCS alone (Grade 1B evidence). Much variation in practice exists among national and international trauma centers; and, without any randomized controlled trials addressing the efficacy of IVC filters for trauma, this trend is likely to continue.
Recommended Indications
IVC filter placement is recommended in those patients with proven VTE and with one or more of the following: (1) a contraindication to anticoagulation, (2) a current or previous complication from anticoagulation, or (3) a recurrent VTE despite full or adequate anticoagulation. In patients in whom a filter was inserted as an alternative to anticoagulation, conventional pharmacological anticoagulation should be started once bleeding risk resolves; and the filter should be removed thereafter.
Expanded Indications
IVC filters may be used for a range of indications beyond those specified in evidence-based guidelines. Typically, the use of a filter in this category involves a high-risk clinical scenario, including patients with hypercoagulable conditions for which limited evidence exists to guide the practice. Examples include patients with cancer, those who are pregnant with an established DVT, high-risk surgical or trauma patients, and patients with chronic thromboembolic disease or cardiorespiratory frailty in the presence of DVT. The use of filters as a prophylactic measure in the high-risk trauma patient has been the subject of interest in the literature recently. The lack of randomized data to support the use of IVC filters in this group of patients must again be reiterated. However, it is up to individual institutions and clinicians to decide on best practice for their patients in this category on a case-by-case basis.
Trauma
Complex trauma patients have the highest incidence of VTE of all hospitalized patients, with PE attributed to the third most-common cause of death in these patients who survive the first 24 hours from their injuries. VTE risk is exacerbated by factors influencing coagulopathy such as immobility, fluid depletion, inflammatory mediators, and iatrogenic factors including treatment with blood products. Pharmacological (low molecular weight heparin) and mechanical thromboprophylaxis (intermittent pneumatic compression [IPC)]) and graduated compression stockings are advocated as first-line therapies in those without significant-bleeding risk. There remains debate about optimal VTE prophylaxis in those considered to be at high risk of VTE with associated significant-bleeding risk.
Several groups have advocated the use of prophylactic IVC filters in the prevention of PE in high-risk trauma patients. Guidelines published by The Eastern Association of the Surgery in Trauma in 2002 suggested consideration of prophylactic IVC interruption for select high-risk patients. EAST developed a risk-stratification tool—the Risk Assessment Profile (RAP)—to allow stratification of trauma patients according to VTE risk. The RAP score ( Box 21-2 ) takes into account various other scoring systems such as the Glasgow Coma Scale (GCS) and the abbreviated injury score (AIS), together with 16 other patient factors. A RAP score greater than 5 signifies increased a threefold increased risk of VTE.
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