Author Affiliations: Division of Vascular Surgery (Drs Sano, Unno, Yamamoto, and Tanaka), and Second Department of Surgery (Drs Sano, Unno, Yamamoto, Tanaka, and Konno), Hamamatsu University School of Medicine, Hamamatsu, Japan.
Pulmonary thromboembolism (PTE) is one of the most significant complications of deep vein thrombosis (DVT) of the lower extremities. To prevent PTE, an inferior vena cava filter (IVCF) is often used.1 The TrapEase IVCF (Cordis Endovascular, Johnson & Johnson) is one of the most popular permanent IVCFs today. Previous studies have reported that the TrapEase IVCF is safe, effective, and resistant to fracture.2,3 However, these studies were performed over a short-term follow-up period, and their evaluation methods seemed to be insufficient to adequately assess IVCF fractures. In the present study, we created 3-dimensional (3-D) images from computed tomographic (CT) images to accurately evaluate the presence of TrapEase IVCF fractures after long-term follow-up.
Between November 2002 and July 2006, 20 TrapEase IVCFs were inserted in 20 patients (7 men and 13 women; mean age, 64 years; range, 39-84 years) (eTable). Six other patients, who had undergone TrapEase IVCF insertion in this period but died from malignant disease within 6 months, were not included. Of the 20 patients, 14 were diagnosed as having PTE by CT or lung perfusion scintigraphy before the placement of the filter. In all cases, filter insertion was performed uneventfully. The follow-up study was performed retrospectively at our outpatient clinic after the placement of the filter. Radiographic examination in 2 projections (anteroposterior view and lateral view) and an abdominal CT were performed on each patient to assess IVCF fractures. For more detailed assessment of the fracture site, 3-D images were created by the Volume Analyzer SYNAPSE VINCENT 3D image analysis system (Fujifilm Medical). The mean follow-up time was 60 months (range, 9-94 months).
The devices were evaluated at an average of 50.0 months after implantation. Among the 20 patients (20 TrapEase IVCFs), 10 TrapEase IVCFs (50%) were fractured. Remarkably, 9 of the 14 filters (64%) that had been inserted for longer than 4 years revealed fractures. Straight struts were fractured in all cases. Among the 10 fractured IVCFs, 8 had a single fractured strut, while 2 had multiple fractured struts (Figure, C and E). Radiographic and 3-D CT images revealed the geometrical relationships between the fracture sites and the neighboring structures. Among the fractured filters, the straight struts of the TrapEase IVCF seemed to be fractured by the compression of the vertebral bodies, particularly the vertebral osteophytes (9 cases) and the compression of the tortuous aorta (3 cases) (Figure). Thrombus inside the filter was detected in 2 cases. None of the patients presented filter-related life-threatening adverse events such as cardiac tamponade or retroperitoneal hematoma. All patients continued follow-up examination at our outpatient clinic. In the 10 cases with no filter fracture, neither the vertebral bodies nor the aorta compressed the filters.
Figure. Radiographic examinations and 3-dimensional images of filter fracture cases. A, Case 6; B, case 7; C, case 8; D, case 9; E, case 10; F, case 15; G, case 16; H, case 18; I, case 19; and J, case 20 (eTable). Arrows show the fractured struts. In cases A, B, D, F, G, H, and I, a single strut was fractured because of the compression of the vertebral body. In case J, a single strut was fractured because of the compression of the tortuous aorta. In cases C and E, 2 struts were fractured because of the compression of the body and tortuous aorta.
The use of IVCFs for the prevention of fatal PTE has been increasing in recent times. In this study, we showed that patients undergoing permanent TrapEase IVCF insertion are at extremely high risk of strut fractures as early as 2 to 3 years after IVCF placement. Although no filter-related life-threatening events were registered in our study, several reports have previously warned of potentially fatal complications, such as cardiac tamponade or ventricular tachycardia, caused by rupture of the struts.4,5 Therefore, the permanent IVCFs should be used with caution and followed closely. Moreover, the indication of retrievable IVCFs such as the OptEase IVCF (Cordis Endovascular), which has a structure similar to that of TrapEase IVCF, as prophylaxis in trauma patients at high risk of PTE has been dramatically increasing.6 However, the rate of the filter removal has remained as low as around 20%.7 The remaining cases of retrievable IVCF placement are considered permanent IVCF placements owing to technical difficulties during retrieval or loss to follow-up. The outcomes of re- trievable IVCF placement should be studied and removal should be encouraged.
Correspondence: Dr Unno, Division of Vascular Surgery, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu 431-3192, Japan (firstname.lastname@example.org).
Published Online: November 28, 2011. doi:10.1001/archinternmed.2011.548
Author Contributions: Dr Unno had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. Study concept and design: Sano, Unno, and Yamamoto. Acquisition of data: Sano, Yamamoto, and Tanaka. Analysis and interpretation of data: Sano, Unno, Yamamoto, Tanaka, and Konno. Drafting of the manuscript: Sano and Unno. Critical revision of the manuscript for important intellectual content: Unno, Yamamoto, Tanaka, and Konno. Statistical analysis: Sano and Unno. Administrative, technical, and material support: Unno, Yamamoto, and Tanaka. Study supervision: Unno and Konno.
Financial Disclosure: None reported.
Funding/Support: We acknowledge the cooperation and support of the staff in the Second Department of Surgery, Hamamatsu University School of Medicine. They did not receive additional compensation for their contributions.
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