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Interventional Radiology |
1 Both authors: Department of Radiology, Hospital of Saint Raphael, 1540 Chapel St., New Haven, CT 06511.
Received August 12, 2003;
accepted after revision May 17, 2004.
Address correspondence to R. Urena
(rurena{at}srhs.org).
Introduction
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Although clinically efficacious, filters are not exempt from complications. Major complications associated with inferior vena cava filters include intravascular or extravascular migration, thrombosis of the filter itself or of the inferior vena cava, and recurrent pulmonary emboli [2, 3].
Filter migration has been reported with all filters [4–9] but is rare with the bird's nest device. Although conventional radiographs can be used to diagnose filter migration, this case shows the importance of CT in confirming the diagnosis of migration. Moreover, we show how CT can be used to determine the clinical significance of the migration and the type of intervention needed to retrieve the device. We present a case of a bird's nest filter migration to the right atrium with cardiac tamponade.
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A chest CT scan obtained after pulmonary embolism protocol showed a large, partially obstructing embolus in the left lower lobe pulmonary artery branch and a large embolus in the right lower lobe pulmonary artery.
Considering the history of hyperhomocystinemia, noncompliance with the medication, and recurrent pulmonary embolism, we decided to place an inferior vena cava filter.
The left femoral vein was punctured as a result of right leg deep vein thrombosis. A 5-French pigtail catheter was placed within the low inferior vena cava and venography was performed. The inferior vena cava was noted to be free of filling defects. The renal veins were located at the L1 level. Measurement of the inferior vena cava was done electronically by using a 24-mm standard applied to the patient; this was also confirmed by direct measurement of the visualized inferior vena cava on the initial CT scan (lower images of chest CT). The inferior vena cava diameter was 34.7 mm, placing it beyond the range of a Greenfield vena cava filter in size. After the diagnostic study, a bird's nest filter (Cook) was successfully deployed below the renal veins. Injection of contrast material after filter placement showed no extravasation and good filter alignment (Fig. 1A). The patient tolerated the procedure well and received anticoagulation afterward to reduce further venous thrombosis.
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Five days after placement of the inferior vena cava filter, the patient returned to the emergency department with chest pain and shortness of breath. A chest radiograph showed filter struts projecting over the right heart area (Fig. 1B). A chest CT scan showed new filling defects in the main pulmonary arteries, and the inferior vena cava bird's nest filter was seen in the right atrium. One of the struts appeared at the edge of the right atrium wall anteriorly, and pericardial effusion was present, suggestive of myocardial perforation (Fig. 1C). The patient was taken immediately to thoracic surgery for removal of the foreign body.
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An intraoperative transesophageal echocardiogram showed a concentric pericardial effusion. The tricuspid valve function was normal. A standard median sternotomy was performed, and the pericardium was opened, relieving the acute tamponade and evacuating a significant amount of blood. A perforation site in the right atrium was found where one of the struts of the bird's nest filter had penetrated the atrial wall. The filter was engulfed by a significant clot that was intertwined in the wire nest of the filter. No other cardiac injury was found.
The patient tolerated the procedure well and was taken to the cardiothoracic intensive care unit in stable condition. The patient was advised to have another inferior vena cava filter placed or possibly even bilateral iliac vein filters, but he refused further treatment. Several days later the patient suddenly died at the hospital, and an autopsy revealed massive pulmonary embolism as the cause of death.
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Complications reported with the bird's nest filter include insertion site thrombosis, filter migration, strut erosion through the inferior vena cava wall, recurrent pulmonary embolism, inferior vena cava obstruction, lower extremity venous insufficiency, and fracture of the bird's nest filter strut [12, 13].
Filter migration with the bird's nest filter is rare compared with other filters [4]. Since the modification of the filter in 1986, approximately five cases of migration have been reported. In 1992, Rogoff et al. [7] reported the first two cases of cephalic migration associated with massive thromboembolism. In 1996, White and McLean [8] reported a case of inferior strut migration with massive thromboembolization. Additionally, two unreported cases in 1994 were obtained from the manufacturer's registry [7, 8].
In all cases, the migration has been discovered in the first 7 days after the filter placement. The cases described by Rogoff et al. occured at 1 and 7 days, by White and McLean at 7 days, and by the Cook filter registry at 1 and 3 days. Our case presented at 5 days after filter placement.
The exact time of migration is unknown. Previous reported cases have been related to massive embolization, suggesting that at times a large migrating clot overwhelms the filter. We are not sure in our patient what came first, the massive clot or the filter migration; however, the deep imbedding of the clot in the filter suggests to us that the filter migration was the result of a large thromboembolism impacting the filter.
Studies with animals have shown that strut and wire-mesh endothelization in the caval wall does not occur until 2 weeks after placement [14, 15], which suggests that the first 2 weeks after filter placement is the most critical time for possible migration.
Our case is similar to one described by Rogoff et al. [7] in which a patient presented with clinical cardiac tamponade and required emergent surgery; however, we performed chest CT before surgical intervention. Although some cases of filter migration can be treated with percutaneous foreign body retrieval, this is inherently more difficult with the large amorphous bird's nest device and, as in our patient, the atrial wall was perforated by the rigid struts of the device.
Surgery was considered the best means of removal in our patient and must be strongly considered in cases of bird's nest filter migration. In our case, chest CT was important in helping us decide the best approach for safe retrieval of the patient's migrated filter. CT not only enabled the diagnosis of the filter migration, but it also clearly showed the pericardial effusion and pinpointed the exact strut responsible for the perforation. In a case report of a TrapEase (Cordis Europa NV) filter migration to the heart, CT was also helpful in assessing the position, the amount of clot, and the need for surgical treatment instead of percutaneous retrieval [9].
Because the bird's nest filter migration has been associated with massive thromboembolism, perhaps it may not be the best filter option in patients with a large clot. Theoretically, a filter with side struts and extra hooks on the strut may offer an added advantage. In patients with an oversized vena cava, however, the filter options are limited. These options include the bird's nest filter and the Vena Tech LGM (Braun), both of which accommodate larger venae cavae. Additionally, bilateral iliac vein filters have been successfully used [16, 17].
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  C. A. Owens, J. T. Bui, M-G. Knuttinen, R. C. Gaba, T. C. Carrillo, N. Hoefling, and J. E. Layden-Almer Intracardiac Migration of Inferior Vena Cava Filters: Review of Published Data Chest, September 1, 2009; 136(3): 877 - 887. [Abstract] [Full Text] [PDF]
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 J. O. F. Roehm Jr. Bird's Nest Filter Migration to the Right Atrium Am. J. Roentgenol., August 1, 2005; 185(2): 555 - 556. [Full Text] [PDF]
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