Volume 38, Issue 1, Pages 7-18 (January 2007)

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ABSTRACT

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Safety and efficacy of vena cava filters in trauma patients

Accepted 17 August 2006.

Summary

Pulmonary embolism (PE), due to its sudden onset, notoriously difficult diagnosis, unpredictable nature and often fatal outcome, remains one of the most feared complications in surgical practice. Trauma patients with multisystem injuries, extremity or pelvic fractures and head or spinal cord injuries often pose a significant dilemma for the surgeon because of the inability to use conventional measures such as anticoagulation therapy and compression devices. On the other hand, the incidence of deep vein thrombosis (DVT) is high among trauma patients and the attendant risk of PE is an important cause of morbidity and mortality. Inferior vena cava (IVC) interruption by placement of diverse filtering devices has evolved over the past three decades. With the use of these devices, the risk of PE has been reduced dramatically. However, variable rates of complications are reported from their use. In this study, we review all the available data on IVC filter placement in trauma patients and we discuss the potential complications of IVC filters in order to understand better the risk/benefit ratio of their use.

Keywords: Pulmonary embolism, Inferior vena cava, Trauma

Article Outline

• Summary

• Introduction

• Available filters

• Permanent filters

• Temporary

• Retrievable

• IVC filters: indications, criteria and contraindications

• Complications

• Efficacy

• Conclusion

• Acknowledgment

• References

• Copyright

Introduction

The relationship between trauma, deep venous thrombosis (DVT) and the potential development of pulmonary embolism (PE) is well established. Virchow, in mid-19th century, first proposed that pulmonary thrombi are primary emboli originating from the veins of lower extremities as a result of venous stasis, hypercoagulability and endothelial injury.117, 118 Subsequently, Sevitt and Gallagher in 1961 reported that among trauma patients the incidence of DVT and PE was 65 and 20.3%, respectively, and judged that the cause of death was PE in a large number of non-survivors.101 These data indicated that new ways of prevention of PE, especially in high risk trauma patients, should be established.

Numerous surgical techniques have been described to date for the prevention of PE, including femoral vein ligation,38, 40 inferior vena cava (IVC) ligation,1, 74 IVC occlusion with transvenous Hunter-Sessions balloon occluder,109 and partial interruption of the IVC using plastic clips,24, 55 plication56, 104 or mechanical staplers.82 Despite these measures, little improvement in the outcome of patients with PE was observed.1

The poor outcomes from these ‘traditional’ surgical methods stimulated the development of new approaches to filter the vena cava. In the early 1980s, Mobin-Uddin introduced the first percutaneously inserted caval filter, the Mobin-Uddin umbrella filter.17 Although this filter had a high complication rate,102 it reduced the mortality rate from 24 to 10%.23

Since then, a large number of IVC filters have been developed with lower rates of complication and lower mortality rates.124 Recently, their use has increased markedly, with 30,000–40,000 filters deployed annually in the USA alone.42, 108

Available filters

Caval filters can be divided into permanent and non-permanent filters. Once inserted, a permanent filter cannot be removed percutaneously. Non-permanent filters are either temporary, being attached to a wire or catheter and, therefore, must be removed, or retrievable, with the option of removal within a specified time frame if the patient's clinical status permits. The latter can be left in situ as a permanent filter.48, 64

Caval filters are generally placed via the femoral or internal jugular approach. Insertion via the basilic vein at the antecubital fossa is also possible with some designs. Filters are ideally placed in the infrarenal IVC to prevent renal vein thrombosis in the event of IVC occlusion. However, in the presence of IVC thrombus, a suprarenal position may be required.43, 106

Permanent filters

The Bird's Nest filter (BNF) was introduced in 1982 (Fig. 1).22, 87, 88 It has a unique structure comprising four stainless steel wires folded and attached to two V-shaped struts which fix to the vena cava wall via hooks. Its design provides an advantage because it can be placed in patients with large caval diameters (up to 40mm).84 The BNF can be placed from either the jugular or the femoral approach. Disadvantages of the BNF include its deployed length which limits its use in patients with a short infrarenal IVC and its MRI incompatibility as it generates large MR artifacts.120

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Figure 1. (A) Gunther Tulip filter, (B) TrapEase filter, (C) ALN filter, (D) the Recovery nitinol filter, (E) VenaTech filter, (F) Tempofilter and (G) Bird's Nest filter.

The stainless steel Greenfield filter (GF) was originally introduced in 1972.15 The original Greenfield filter was placed through a venotomy and a 29 F (outer diameter) catheter. Since then smaller introduction devices were produced decreasing the incidence of femoral vein thrombosis. The stainless steel over the wire Greenfield filter was introduced in 1994. It has conical shape and better hook design compared with the previous Greenfield filters decreasing the incidence of migration. It can be used in vena cavae sized up to 28mm in diameter but creates a significant artifact on the MR image.

The titanium Greenfield filter (TGF) was introduced in 1988.30, 33 It has a conical design and consists of six struts with terminal hooks for fixation to the vessel wall. It can be compressed into a smaller diameter system allowing percutaneous delivery through a 14.3Fr sheath. High rates of migration were reported and the filter's hooks were modified.31 The titanium Greenfield filter is MRI compatible producing only a minor MR artifact.114

The Simon Nitinol filter (SNF)29, 59, 103 is made of nitinol, a non-ferromagnetic nickel–titanium alloy which has thermal memory (at low temperatures, the filter is presented as a set of straight wires which unfold to form a predetermined umbrella shape at body temperature). It is anchored to the wall of vena cava through six hooked struts. This filter can be inserted through the femoral, jugular or antecubital vein. It is designed for insertion into IVCs of diameter less than 28mm.

The LGM VenaTech filter18, 63, 85, 113 was introduced in 1989 and modified in 1991. It has a conical shape and is attached to the walls of the vena cava through six struts with side rails. It is MR-compatible and can be placed in vena cavae up to 28mm in size.

The VenaTech low profile filter is a modified version of LGM VenaTech filter introduced in 2001 (Fig. 1).51 It is composed of eight Phynol wires fused in pairs making side rails which secure the filter through hooks to the caval walls. The filter was designed for insertion into IVCs of diameter less than 28mm but it may be used for larger vena cavae.

The TrapEase filter is made from nitinol and consists of two conical filter baskets connected together to create a six-pointed star configuration (Fig. 1).97, 100 It is a permanent filter and can be deployed through a low profile 6Fr introducer sheath via the femoral, internal jugular or antecubital vein.99 This filter can be placed in vena cavae with diameter less than 30mm.

Temporary

Temporary IVC filters61 were developed as a short-term prophylaxis against PE which can be easily removed when no longer required. These include the Gunther temporary filter,119 Filcard,66 Protect Infusion Catheter,41 Amplatz,20 Prolyser,57 Tempofilter (Fig. 1),10 DIP,69, 78 Lysofilter,78 Cook,128 Angiocor128 and Antheor filter.57 Since they are anchored to the skin via a catheter or wire, they have the risk of becoming infected. Another disadvantage is that the filter may prove difficult to remove if there is thrombus trapped within it.

Retrievable

Retrievable filters are essentially permanent filters which have design features which allow them to be removed after a specified period. The retrieval mechanism differs with the different filter designs, but they all require a jugular approach for removal.

The Gunther Tulip filter was introduced in Europe in 1992 (Fig. 1).61, 62, 68, 71 It is composed of four struts interconnected and stabilised by wire loops. It can be deployed via a femoral or jugular route in IVCs up to 30mm and has a hook at its apex which allows it to be retrieved. It was originally approved for retrieval up to 14 days post-insertion, but has been retrieved beyond this period,67 and has recently been approved for indefinite retrieval.

The Optease filter was introduced in 2002.48 Its shape resembles a TrapEase filter with slight modifications including a caudal hook which allows the filter to be retrieved.

The Recovery nitinol filter was introduced in 2003 as a permanent retrievable filter (Fig. 1).4 It has a hub with 12 nitinol wires extending from it providing two layers of filtration. It measures 4cm in height and can accommodate in a vena cava up to 28mm.

The ALN filter was originally introduced in 1990 as a permanent filter later becoming a retrievable filter following development of an extraction kit in 1999 (Fig. 1). It is manufactured from stainless steel43, 79 and has six short legs that adhere to the caval wall with three long legs that assure the centralization along the main caval axis. It can be introduced through a femoral, jugular or antecubital approach.

Today, retrievable filters are the most commonly used as they pose several advantages over the other types. Orthopaedic and trauma patients could benefit from their aptitude to be used in the high-risk period for developing PE while avoiding the long-term sequelae.96, 99 In cases where there is significant clot found within the filter at the time of intended retrieval, it can be left in situ, either permanently, or could be retrieved at a later date once the clot has lysed. These properties together with their low rate of complications make them the best candidates for short-term prophylaxis against PE.2, 39

IVC filters: indications, criteria and contraindications

There are a number of ‘accepted’ indications for the use of IVC filters. These are patients with PE in whom anticoagulants are contraindicated, with recurrent PE despite adequate anticoagulation and those where there has been a complication from anticoagulant therapy. With the development of lower profile percutaneously inserted and retrievable devices, the use of filters has been extended to include more contentious ‘prophylactic’ indications, including patients with free-floating iliofemoral or caval thrombus and in patients at high risk of venous thromboembolic disease (Table 1).51, 107, 112

Table 1.

Indications and contraindications of IVC filters

	A. Accepted indications
	1. PE with contraindication to anticoagulation, failure of/or complication from anticoagulant therapy51

	Prophylactic indications
	2. Free-floating iliofemoral or caval thrombus51, 107
	3. Deep vein thrombosis107
	4. Cancer6, 81
	5. Prophylactic placement in high risk patients:
	• Spinal cord injury39, 73, 95
	• Severe head injury39, 73, 95
	• Pelvic fractures39, 73, 95
	• Multiple long bone fractures39, 73, 95
	• Iliofemoral venous injuries112
	• Hip or knee replacement patients with prior deep venous thrombosis16, 66

	B. Contraindications
	1. Lack of route to IVC7, 107
	2. Chronically thrombosed IVC7, 107
	3. Adolescence patients7, 107

In trauma patients, the criteria for placing an IVC filter are diverse and vary according to individual physician preference and local practice. Specific risk factors which are associated with increase incidence of DVT and subsequently PE are used as criteria for the insertion of an IVC filter. These include severe head injury, multiple long bone fractures, spinal cord injury, abdominal or pelvic penetrating venous injury, paraplegia or quadriplegia and severe pelvic fractures. Patients over 45 years of age with an ISS greater than 16 and Glasgow Coma Scale less than 8 complete the criteria used for IVC filter application.49, 89, 91 The Eastern Association for the Surgery of Trauma has issued guidelines for prophylactic vena caval filter insertion.76, 126 According to these guidelines, patients who are unable to receive anticoagulants and have poor cardiopulmonary function or are over 45 years of age and suffering from spinal cord injury with paraplegia/quadriplegia, have complex pelvic fractures together with long-bone fractures, have multiple long-bone fractures or have head trauma with GCS<8 are candidates to receive an IVC filter.76, 124

There are a number of contraindications to the placement of IVC filters (Table 1). These include patients in whom there is a lack of route to the IVC and those where the IVC is chronically thrombosed.107 Filters should also be used with caution in paediatric and adolescent patients due to the lack of long-term follow-up data on the currently available implants.7, 107

Complications

Complications can occur during any stage of IVC filter placement, varying from complications occurring at the time of filter insertion to late complications which can develop after several months or years (Table 2).

Table 2.

Potential complications of IVC filters


	Early	Late
	• Post-procedural bleeding83	• PE46, 53, 86, 89, 91, 92, 93
	• Access site thrombosis89	• IVC thrombosis46, 86, 91
	• Delivery system complications (sheath kinking, air embolism)57	• Venous stasis and chronic venous insufficiency34, 86
	• Malposition92	• Fracture of filter111
	• Tilting89, 92	• Migration49, 54
	• Failure of opening/incomplete opening54	• Arteriovenous fistula28, 53
	• Vessel penetration12, 58
	• Duodenal perforation3, 21
	• Vertebral body penetration50
	• Renal penetration-hydronephrosis44, 105

Access site thrombosis was a common complication of filter placement with reported incidence as high as 35%.65, 102 However, more recent studies with contemporary, lower profile filter delivery systems demonstrate a much lower incidence of 1–3%.77, 95

Another important early complication is malpositioning and tilting of the filter. Filter tilt and malposition reduce its ‘clot trapping’ effectiveness and result in higher rates of recurrent PE than with optimally placed filters.47, 89, 92

Additionally, rare early complications include arterial punctures and artriovenous filstula,12, 28, 58 failure of the filter to open, air embolism and duodenal perforation.21

Recurrent PE is one of the most important and potentially fatal complications of IVC filter placement. Most filters will allow the passage of small clots.47 Recurrent PE is variable depending on the filter type and centering of the filter within the cava. Greenfield and Michna reported the highest rates of recurrent PE (4–5%).32, 37 Aside from the mortality following PE, there is an incidence of pulmonary hypertension from chronic subclinical PE's.70, 98

Vena cava occlusion secondary to trapped thrombus in the filter is both a functional success of the filter but also an important pathologic condition. The incidence of IVC occlusion is variable. Becker et al. reported a rate of 15.3% of IVC occlusion without anticoagulation therapy but this rate decreased at 7.7% with the administration of anticoagulants.8 In the event of symptomatic IVC thrombosis, mechanical thrombectomy has been used with varying success to recannalise the IVC.80

Migration of the IVC filter is another serious complication. The reported incidence of migration is 7–19% for the VenaTech filter and 8–15% for the Greenfield filter.35, 83, 125 Filter migration to the heart26, 45 and lungs26, 110 has been reported, resulting in major complication, including sudden death.11

Filter fractures are reported when forceful maneuvers are applied in order to displace and retrieve an IVC filter.111 Embolisation into the left pulmonary artery, right hepatic artery and right hepatic vein are reported from broken struts.111

Efficacy

DVT may be clinically silent following trauma and its diagnosis can, therefore, be challenging.52 Pulmonary embolism is the third most common cause of death in trauma patients who survive after the first day.25 On the other hand, 6% of trauma patients develop PE within the first day of admission.75 Since anticoagulant prophylaxis against DVT and PE is often not clinically appropriate, placement of an IVC filter in this select patient population is suggested to prevent PE. We should note here that an IVC filter does not by any means inhibit the thrombotic process and may possibly aggravate it.42

The literature on the use of prophylactic IVC filters in trauma patients is conflicting. Several authors have shown a decrease in the incidence of PE after prophylactic use of IVC filters.14, 49, 86, 90, 122 Carlin et al. demonstrated a reduction in the incidence of PE from 0.29 to 0.15% after increased use of prophylactic IVC filters in trauma patients at high risk and with contraindication to anticoagulation.14 In contrast, McMurtry et al., in a study of 299 patients having an IVC filter out of 28,227 trauma patients, concluded that the use of prophylactic filters failed to decrease the overall incidence of PE.60

Table 3 reviews the most important data presenting the application of IVC filters in the trauma population. It contains the study of 3404 patients receiving a filter, taking into account the complications encountered and the type of the filter. According to these data, 1.4% of injured patients received an IVC filter, with the Greenfield filter used in more than 70% of cases. However, the more recent studies show increased use of temporary and retrievable filters. There were 433 complications in the 3404 patients indicating a 13% complication rate in this population. The most important of these, recurrent PE, occurred in less than 1% (32 PEs), with 40% being fatal. IVC thrombosis and occlusion occurred at an average rate of 2%. Insertion site thrombosis complicated a filter insertion in 2%. Filter migration occurred in 1%, as did misplacement and filter tilt.

Table 3.

Data presenting the effectiveness of IVC filters


Author/date	IVC filters/total trauma patients	PE among patients with IVC filter	Complications	Filters used
Jarrell/198346	21/209	1 (fatal)	• Two vena caval thrombosis	• GF (Kim–Ray)
			• Three wound hematomas

Carabasi/198713	188/n/a	2 (1 fatal)	• Three misplaced filters	• GF
			• 14 inability to pass the introducer through the jugular vein (10 placed through femoral vein, no filter placed in 4 patients)
			• One small retroperitoneal hematoma
			• Two migrated filters
			• Two struts extended outside of caval walls
			• Five thrombosis of IVC
			• Four lower extremity swelling

Rohrer/198993	21/n/a	1	• Two post-phlebitis syndrome	• GF

Webb/1992121	24/n/a	0	• Four had leg edema	• GF
			• One phlegmasia

Ferris/199322	320/n/a	11 (8 fatal)	• 26 vena cava occlusion	• 78 BN
			• 12 penetrations of IVC wall	• 30 Amplatz
			• 13 migrations	• 21 SN
			• Five filter strut or leg fracture	• 113 VT
			• 26 insertion site thrombosis	• 10 TGF
				• 72 TGF (modified hook)

Rogers/199391	34/792	0	• One vena caval thrombosis	• 32 TGF
				• Two BN

Leach/199454	201/10,948 (205 filters)	0	• One migrated to pulmonary artery	• GF
			• One misplaced filter
			• Three filters failed to flare
			• One filter tilted
			• One insertion site thrombosis

Rosental/199494	49/161	0	• One hematoma	• GF
Wilson/1994122	15/2525	0	• No complications	• TGF
Winchell/1994123	61/9721	0	• No complications	• n/a

Khansarinia/199549	108/6556	0	• One insertion site thrombosis (internal jugular)	• GF
			• One migration of IVC filter to Rt ventricle
			• Four partially opened filters

Rogers/199590	63/3151	1 (fatal)	• Two insertion site thrombosis	• n/a
			• Two vena caval occlusion

Zolfaghari/1995127	45/3005	0	• No complications	• VT

Patton/199677	110/15,526	0	• Three misplaced (renal, iliac, lumbar vein)	• TGF
			• Three insertion site thrombosis
			• One migration
			• One IVC occlusion

Rodriquez/199686	40/n/a	1	• Four vena caval thrombosis	• TGF
Gosin/199727	99/1630	0	• No complications	• n/a

Rogers/199789	35/940 (36 filters)	1	• Two insertion site thrombosis	• 32 TGF
			• One tilted (patient developed PE)	• Three BN

Nunn/199772	49/3172	0	• One tilted filter	• TGF
			• One insertion site thrombosis
			• One vena cava occlusion
			• One migrated filter

Rogers/199892	132/5280	3 (1 fatal)	• Four insertion site thrombosis	• 93 TGF
			• Six tilted filters	• 21 GF
			• 41 strut malpositions	• 10 VT
			• One vena caval thrombosis	• Eight BN

Van Natta/1998116	71/16,417	0	• One insertion site thrombosis	• 65 GF
			• One tilted filter	• Six BN
			• One migration
			• One vena cava occlusion

Lagman/199953	187/7333	1	• One misplacement in Rt common iliac vein (non-fatal PE developed in this patient)	• GF
			• One femoral arterio-venous fistula
			• One groin hematoma

McMurtry/199960	299/28,227	6	• Four IVC occlusion	Data available for 237:
			• Three misplacements	• 142 GF
			• Two insertion site hemorrhage	• 80 VT
			• Two hemorrhage from insertion site (transfusion needed)	• 11 SN
				• Four BN

Tola/1999115	21/803	0	• No complications	• n/a
Benjamin/19999	23/n/a		• One misplaced in suprarenal IVC	• TGF

Greenfield/200034	385/n/a	5	• One misplaced	• 180 GF
			• One incomplete opening	• 205 TGF
			• 75 lower extremity edema
			• Eight insertion site thrombosis
			• Two caval penetrations
			• Six migrated
			• Five tilted
			• Nine IVC occlusion
			• One incomplete opening
			• 15 asymmetry encountered

Wojcik/2000126	191/7145	0	• One migrated	Available only for 105 patients:
			• One vena caval occlusion	• 72 GF
			• 11 patients with leg swelling	• 28 BN
				• Five SN

Carlin/200214	200/19,276	1 (fatal)	• Five insertion site thrombosis	• GF
			• One retroperitoneal hematoma
			• Two pericardial infusion due to a guide wire puncture

Morris/200367	55/1257	1	• No further complications	• 29 GT (the rest was GF, VT, SN, TE)
Offner/200373	44/n/a	0	• Three could not be retrieved	• GT
Duperier/200319	133/1548	1 (fatal)	• No further complications	• GF
Hoff/200439	35/1045	0	• No complications	• GT

Rosental/200495	94/n/a	0	• Three misplaced in right iliac vein	• Optease
			• Two groin hematomas
			• One insertion site thrombosis
			• One 5mm defect in the IVC wall

Allen/20052	51/2426	0	• One unsuccessful retrieval	• GT

Abbreviations: n/a, not available; GF, Greenfield filter; TGF, titanium Greenfield filter; GT, Gunther Tulip filter; BN, Bird's Nest filter; SN, Simon nitinol filter; VT, VenaTech filter; TE, TrapEase filter.

An important factor contributing to the efficacy of IVC filters is their proper placement and alignment. Malposition and misplacement of the filter will potentially make it ineffective. Tilting, on the other hand, is associated with increased incidence of recurrent PE.89, 92 Rogers et al., in 1998, had a 5.5% rate of filter tilting and 38% of strut malposition in 132 filter placements. These complications seem to have contributed to the three recurrent PE's that they reported.92 Katsamouris et al. demonstrated that eccentric filter placement resulted in the passage of large clots through it.47 It should be noted that a reduction in clot trapping efficacy is also observed as the diameter of the IVC and the downstream IVC pressure increases.36

Ultrasound guided IVC filter placement is used today as a quick bedside method for prophylaxis for PE leading to a more precise and focused placement of the filter addressing the need for proper placement and alignment.9, 72 Benjamin et al. presented a technique for placing IVC filters under duplex ultrasound.9 Despite the fact that 1 of the 23 filters was inadvertently placed in the suprarenal IVC, this technique seems to be relatively accurate and quick method of filter placement by the bed side, obviating the need for transporting the seriously injured patient out of the intensive care setting to the angiography suite. It also significantly reduces the cost of filter placement.9 Ashley et al. studied the accuracy of IVC filter placement with intravascular ultrasound and venography.5 He concluded that venography overestimates the diameter and in many cases fails to determine the ideal site for IVC filter deployment.

It is anticipated that new data will emerge in the future driving us to safer conclusions and liberalisation of their use in the trauma setting.

Conclusion

Despite the fact that the incidence of PE is low, it could be a significant cause of death among trauma patients. IVC filters are relatively safe and appear to be effective in reducing the incidence of PE. But is there an ideal filter? Some essential properties characterising an ideal filter include the clot-trapping efficacy, secure fixation to the caval wall, percutaneous insertion through a small diameter sheath, MR compatibility, low rate of complications and low cost. Clearly, currently available devices do not fulfill all these criteria. Therefore, familiarity with a range of filters is essential allowing choice of filter to be tailored to the needs of the individual patient.

Acknowledgements

This work is attributed to Departments of Trauma & Orthopaedics, School of Medicine, University of Leeds, and University of Pittsburgh, Department of Radiology, The Leeds Teaching Hospitals NHS Trust.

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a Academic Department of Trauma & Orthopaedics, School of Medicine, University of Leeds, United Kingdom

b Trauma & Orthopaedic Surgery, School of Medicine, University of Pittsburgh, United States

c Department of Radiology, St James's University Hospital, United Kingdom

Corresponding author at: Department of Trauma & Orthopaedics, St James's University Hospital, Beckett Street, Leeds LS9 7TF, United Kingdom. Tel.: +44 113 2433144; fax: +44 113 2065156.

PII: S0020-1383(06)00544-4

doi:10.1016/j.injury.2006.08.054

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