Permanent IVC filter strut penetration into an abdominal aortic aneurysm

Abstract

An 85-year-old man with a known history of abdominal aortic aneurysm (AAA) presented to a vascular surgery clinic with a severely swollen, tender and erythematous left leg. An urgent CT angiogram demonstrated a left-sided, proximal deep vein thrombosis, and a permanent, Bird’s Nest inferior vena cava (IVC) filter (Cook, Inc., Bloomington, Ind.) penetrating his AAA. The patient was treated with a course of apixaban 5 mg two times per day and the decision was made to closely observe his IVC filter and AAA, given his numerous comorbidities and age. This case highlights the unique considerations associated with an approach to permanent IVC filter complications among patients with AAAs.

Background

Venous thromboembolism (VTE)—deep vein thrombosis or pulmonary emboli—is a common disease with an incidence rate of 0.001%–0.01%, respectively, in community and hospital settings.¹ Pharmacological anticoagulation is widely accepted as first line treatment.² Inferior vena cava (IVC) filters, small devices that prevent the propagation of deep vein thrombosis into the pulmonary vasculature, are an alternative therapeutic option considered in select patients.^{3 4}

The indications for IVC filters fall into three categories: absolute, relative and prophylactic. The absolute indications for IVC filters include patients with VTE who have demonstrated contraindications to, complications from or failure of pharmacological anticoagulation therapy.^{3 5} Relative indications, vary among guidelines, include those patients (a) considered to be at elevated risk for pulmonary embolism (PE) despite primary therapy, (b) have increased risk of complications from anticoagulation, (c) are non-compliant with medications or (d) have limited cardiopulmonary reserves.^{3 5} Prophylactic indications of IVC filters are controversial and encompass trauma and surgical patients at high risk of developing VTE.⁵ The most recent guidelines from the Society of Interventional Radiology recommend against IVC filter prophylaxis, given the lack of studies demonstrating supporting evidence.³

There are two types of IVC filters—permanent (pIVC) and retrievable (rIVC).⁵ Permanent filters are indicated for patients with a long-term need for mechanical prophylaxis against PE and absolute contraindications to anticoagulation.⁵ Retrievable filters are designed to be retrieved after the temporary risk of PE or contraindication to anticoagulation has been resolved. They offer greater flexibility and thus are considered as the new standard of care.⁵

A marked increase in filter insertions was reported following the introduction of retrievable filters. This may have been due to the subsequent expansion of filter indications afforded by their flexibility. rIVC filters provide the same benefit with fewer complications than pIVC filters.^5–7 Concerns regarding the low retrieval rate of rIVC filters were raised, with research reporting rates as low as 8.5% and a 34% mean retrieval rate.⁷ This was a concerning finding given the increased risk of complications associated with longer filter indwelling times.

As a result, the US Food and Drug Administration (FDA)⁸ and Health Canada⁹ issued device safety warnings in 2010 and 2016, recommending clinicians to follow-up and remove rIVC filters as soon as clinically appropriate. The National Institute for Health and Care Excellence guidelines also emphasise the importance of having a strategy to remove temporary IVC filters as soon as it is clinically advisable and that this plan should be clearly documented in clinical notes.¹⁰ In light of these recommendation, recent studies demonstrated decreased rates of IVC filter placements¹¹ and increased rate of rIVC retrievals following FDA advisory in 2010.¹²

Less is known about the removal of pIVC filters.³ Recent guidelines recommended against routine removal of pIVC filters.³

Case presentation

An 85-year-old man presented to a local vascular surgery clinic with a multi-week history of a severely swollen, erythematous and tender left leg.

The patient’s medical history was significant for a known infrarenal abdominal aortic aneurysm (AAA), hyperlipidemia, hypertension, multiple falls history, motor vehicle accident 2 years ago, osteoarthritis of bilateral hips, hypothyroidism, prostate cancer (treated with brachytherapy), coronary artery disease (inducible right ventricle ischaemia in the circumflex arteries), stage 3 chronic kidney disease and a 20 pack-year smoking history.

Investigations

A venous duplex scan at the time of visit could not rule out deep vein thrombsis (DVT) due to significant leg oedema. The arterial duplex scan was unremarkable. An urgent CT angiogram (CTA) revealed changes consistent with a left-sided proximal DVT with markedly dilated left external iliac artery, femoral and deep veins, secondary to the compression of the left external iliac vein by a tortuous left internal iliac artery. The CTA additionally revealed a 5.5 cm infrarenal aortic aneurysm (5.2 cm in July 2020) and permanent Bird’s Nest IVC filter (Cook, Inc., Bloomington, Ind.), with a strut penetrating into the aneurysm (figures 1–3). There was no periaortic haematoma, and the patient could not recall the reason for his IVC filter implantation and nor were clinical notes available.

Figure 1.

Axial view of permanent Bird’s Nest IVC filter (arrow) penetrating infrarenal abdominal aortic aneurysm. IVC, inferior vena cava.

Figure 2.

Coronal view of permanent Bird’s Nest IVC filter (arrow) penetrating infrarenal abdominal aortic aneurysm. IVC, inferior vena cava.

Figure 3.

Three-dimensional reconstruction of permanent Bird’s Nest IVC filter (arrow) penetrating infrarenal abdominal aortic aneurysm. IVC, inferior vena cava.

Treatment

The patient was managed on apixaban 5 mg two times per day for treatment of his DVT. While thrombolysis was considered,¹³ given patient’s chronic DVT, numerous comorbidities and high bleeding risk, the decision was made to manage the patient with oral anticoagulation.

Given that the patient was asymptomatic, we decided to closely observe and monitor the patient’s filter and AAA without intervention.

Outcome and follow-up

A decision was made for medical management of the DVT and follow-up on the AAA.

Discussion

Decisions regarding implantation and retrieval of IVC filters are important as increased filter indwelling times is associated with increased risk of complications. IVC filter-related complications are divided into two categories: procedural and delayed.¹⁴ Procedural complications include access site complications (0%–25%), insertion difficulties (5%–23%) and defective filter deployment (1%–9%).¹⁴ Delayed IVC filter complications include filter migration (0%–18%), thrombosis (2%–30%), fracture (2%–10%), recurrent PE (0.5%–6%) and IVC penetration and perforation (0%–41%). Strut penetration may lead to additional complications such as perforation of nearby structures (eg, aorta or duodenum) resulting in infection or aortic pseudoaneurysms.¹⁴ As seen in our case, most complications including IVC penetration are often asymptomatic, and few require intervention.¹⁵

Recognising the complications of rIVC filters, there is a clear consensus among various guidelines regarding their removal: to do so as soon as safely possible (ie, once the patient is no longer at high risk of PE or adequate anticoagulation can be safely achieved³). In contrast, recent guidelines³ advise against the removal of permanent filters even after the risk of PE is mitigated; the retrieval of pIVC filters can be challenging with potentially higher rates of retrieval-related complications.

For patients with complications as a result of their pIVC filters, guidelines emphasise the importance of weighing the filter versus procedure-related risks when considering filter removal, while acknowledging the lack of research exploring the indications that may prompt a clinician to remove a permanent filter.³ Previous case reports suggest considering pIVC filter removal in patients with symptomatic filter complications, such as perforations of nearby structures causing pain¹⁶ or filter thrombosis leading to recurrent DVT.¹⁷

These case reports have reported both endovascular and open approaches to pIVC filter removals. Endovascular procedures include the standard loop and snare technique,¹⁸ the double guidewire snare technique using both the femoral and jugular access^{17 19–21} and the laser thermal dissection technique.²² In contrast, open repair approaches involve cavatomy, followed by direct suturing.^{23 24} Current literature (primarily consisting of case reports) suggests that pIVC filter removal is possible and successful in carefully selected patients. We did not find any retrospective or prospective studies focusing on pIVCs. A recent study by Jaberi et al²⁵ reported on the removal of rIVC filters after extended implantation (mean time to removal at 3846.9 days) and demonstrated successful filter retrieval in 15 of 16 attempts, with no significant morbidity or mortality. While this study’s findings may not be directly generalisable to permanent filters, the study demonstrates that safe removal of chronically implanted filters is possible and feasible (despite the complications secondary to chronic indwelling times) by using advanced filter retrieval techniques, such as the hangman and the forceps technique. The extent to which the decision making for pIVC filter management is (and should be) impacted by concurrent aortic pathology (eg, AAA) in setting of filter complications (eg, aortic penetration) is unclear.

Case reports have described both the asymptomatic²⁶ and symptomatic^{16 27–30} sequelae of aortic penetration (in a non-aneurysmal aorta) by pIVC filters, providing insight into its possible consequences. These include both asymptomatic and severely symptomatic patients (eg, severe abdominal or back pain, dyspnoea or abnormal vaginal bleeding, secondary to complications such as aortic pseudoaneurysms,^{16 27 28} aortocaval fistula³⁰ and aortic mural thrombus³⁰). There were other case reports that reported specifically on IVC filter penetration into AAA. One case described the asymptomatic penetration of Greenfield filter into AAA, identified during surgery for aneurysm resection.³¹ The authors postulated that the IVC perforation into the aorta might have contributed to the aorta’s rapid enlargement, recommending careful monitoring of IVC filters and AAA via periodic CT scans to prevent complications such as rupture or dissection. Chauhan et al highlighted a rare but serious sequela of AAA penetration by pIVC filter: an infrarenal aortic dissection.³²

Since the earliest report of endovascular aortic repair in literature, endografts have been applied to repair aneurysms, traumatic dissections and anastomotic pseudoaneurysms. A number of reports in the literature document aortic pseudoaneurysm from a pIVC filter treated with an aortic endograft.^{16 28} Enhanced graft technology and expertise has been supplemented by growing reports of the effectiveness of these devices in managing complex vascular problems. As long-term complications associated with IVC filter placement become apparent, those related with the adjacent abdominal aorta may be safely treated with endovascular techniques in high-risk patients. However, open treatment still represents a more preferred option in the fitter patient, because the strut of the IVC filter is removed.

Given the rare but potentially dire consequences of pIVC filter penetration into AAA, one may postulate that (1) patients with penetrated pIVC filters in the setting of AAA should undergo close monitoring via frequent CT scan intervals and (2) removal of pIVC filter may be a viable (and even preferred) option in select patients. Current literature is lacking in providing insight and clarity regarding pIVC filter complication management due to the lack of studies comparing the outcomes of permanent filter retrieval versus non-retrieval. Thus, future research should aim to examine the safety, efficacy and cost-benefit of pIVC filter retrieval (vs non-retrieval), especially in the setting of filter complications and concurrent aortic pathology that may put the patient at higher risk of serious filter-related complications.

Learning points.

• Inferior vena cava (IVC) filters are a therapeutic option considered in select patients for preventing the propagation of deep vein thrombosis into the pulmonary vasculature.

• IVC filters are not benign. While most filter complications are asymptomatic, rare but serious complications have been reported.

• There are two types of IVC filters—retrievable and permanent. While retrievable filters should be removed as soon as clinically possible, the current literature does not provide much guidance regarding the removal of permanent filters.

• Close and careful monitoring of IVC filters with imaging studies is critical, especially among patients with concurrent pathology such as abdominal aortic aneurysm.

• Select patients with symptomatic or serious complications of permanent IVC filters may benefit from their removal.

Ethics statements

Patient consent for publication

Obtained.