More Concern Over Fractures in Vena Cava Filters

November 29, 2011

November 29, 2011 (Hamamatsu, Japan) — More concern about the safety of inferior vena cava filters (IVCFs), which are used to prevent pulmonary embolism in patients with deep vein thrombosis, has been expressed in a report from Japan of a high fracture rate with the TrapEase (Cordis) device [1].

In a letter to the Archives of Internal Medicine, published November 28, 2011, a group led by Dr Masaki Sano (Hamamatsu University School of Medicine, Japan) describes a study in which the filter was fractured in 10 out of 20 patients (50%) at an average follow-up of 50 months. And nine of the 14 filters (64%) that had been inserted for longer than 14 months showed fractures. Among the 10 fractured filters, eight had a single fractured strut, while two had multiple fractured struts. Thrombus inside the filter was detected in two cases.

Although no filter-related life-threatening events occurred in this study, the authors note that several reports have previously warned of potentially fatal complications, such as cardiac tamponade or ventricular tachycardia, caused by rupture of the struts. "Therefore, the permanent IVCFs should be used with caution and followed closely," they say.

They report that use of retrievable filters such as the OptEase IVCF (Cordis) as prophylaxis in trauma patients at high risk of pulmonary embolism has been dramatically increasing, but only around 20% of these devices are actually ever retrieved. They call for further outcome studies of the retrievable devices and say that removal should be encouraged.

Commenting on this report for heartwire , Dr William Nicholson (York Hospital, PA), who has also conducted a study in this area, said this work "again demonstrates that as dwell times of these devices inside the body increase, the likelihood of device fracture increases."

He added: "The CT imaging done by the authors does a beautiful job of demonstrating how a filter’s placement in the inferior vena cava may expose it to moving neighboring structures. The pulsatile activity of a tortuous aorta or the compression forces of vertebral bodies may be the culprits for the repeated stress on the device leading to eventual fracture."

Class Effect

Nicholson pointed out that evidence is mounting to suggest that filter fractures may be a class effect and not limited to a specific design. But the effects of such fractures may vary. For example, in the TrapEase device, the structure is anchored together at both the top and bottom, so an isolated fracture will leave the two remaining fragments attached to the device. However, with other designs such as the Bard retrievable filters, the radially distributed arms are connected only at a single point, so a single fracture would result in a free fragment capable of embolization and "potentially dangerous sequelae."

Nicholson does not recommend trying to remove permanent filters, saying that they are not suited to percutaneous removal and the risk of surgical removal likely outweighs the risks of leaving the fractured device in place. But he says the removal of retrievable filters via catheters after prolonged implantation may be safe in experienced hands, even if the device has already fractured. "We have counseled our patients with removable filters to have the device retrieved as soon as possible following implantation."

Nicholson concludes: "Clearly, the mounting data have shown that filter fracture occurs at a much higher frequency than previously appreciated," and "these findings again emphasize that the use of filters, while clearly necessary in some patients, should be used judiciously." He added that patients who have had venous thromboemboli and cannot tolerate anticoagulation may still benefit from such protection, but patients should be made aware of this potential complication, and it is important to choose a proven durable permanent device for patients at long-term risk of pulmonary embolism.

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