We describe a case of sequential flexion, fracture, and pulmonary migration of the wires of a retrievable IVC filter. Anticoagulation has been accepted as an effective treatment for venous thrombosis and PE. IVC filters have been used for the prevention of PE in patients with contraindications to anticoagulation and in patients with progressive venous thromboembolic disease despite anticoagulation [6
IVC filters have been shown to be relatively safe. The most common complications after IVC filter placement are recurrent PE, thrombosis of the IVC, and local access site complications [6
]. Migration of the filter is a relatively rare complication [14
]. Filter fractures are extremely rare and have been reported in 1 to 2 percent of cases [15
]. There is limited data published on the long-term outcomes with the Bard Recovery filter. This filter, described in our case, was commercially available until August 2005, when it was voluntarily withdrawn from the market and replaced by the Bard G2 filter [8
]. The modified G2 filter was designed to decrease risk of perforation, migration, and fracture.
The risk of these long-term complications of indwelling filters increases with time; therefore, retrievable filters are considered beneficial to avoid possible late complications [16
]. Despite the advantages of retrieval, only a small number of patients return for filter removal [18
]. Grande et al. reported a less than 15 percent retrieval rate in all Recovery filters placed with the intention of future retrieval [20
]. An overestimation of the number of patients who need only temporary IVC filtration combined with high rates of loss to follow-up probably contribute to this low retrieval rate. The filter in our case was placed with the intent of removal, however, due to poor patient compliance, was never retrieved.
Nicholson et al. reported a 25 percent (seven of 28) prevalence of device fragmentation and embolization in patients with the Bard Recovery filter. All the fractured fragments embolized to an end organ [21
]. Another study showed filter leg fractures with migration into the right ventricle, the pulmonary artery, and the retroperitoneum in 21 percent of the patients (three of 14) [18
]. A MAUDE database search performed by Desjardins et al. demonstrated 329 reported cases of significant malfunction of the Recovery filter within a 6-year period, including 69 cases of filter migration, 149 cases of filter fragmentation, and 88 cases of filter fragment migration [22
]. The migrated fragments were reported to be lodged within the heart and lungs. The unique feature in our case is the fact that two of the filter arms underwent consecutive fracture and pulmonary migration. This highlights the increased risk for a subsequent filter fragment migration after the first event.
The mechanism of fracture may be related to tilting of the filter, continuous strain on the engaged strut resulting in repetitive flexion, and eventual fracture caused by metal fatigue. In our case, both leg fractures were preceded by leg flexion. To detect malposition, leg flexion or fracture, a plain radiograph of the abdomen is the initial screening test that will allow detection of gross changes in filter position, location, and orientation. Additionally, abdominal CT scanning can be useful in detecting filter angulation, caval perforation, and leg flexion and fracture. The fractured and migrated IVC filter struts within pulmonary arteries are difficult to distinguish from surrounding enhancing vessels on pulmonary CTA. Therefore, careful review of the plain chest X-ray film should be performed.