Retrievable IVC filters - Friend or foe

Evaluation of hemodynamic effects of different inferior vena cava filter heads using computational fluid dynamics

Inferior vena cava (IVC) filters are used to prevent pulmonary embolism in patients with deep vein thrombosis for whom anticoagulation is unresponsive. The head is a necessary structure for an Inferior vena cava filter (IVCF) in clinic use. At present, there are various head configurations for IVCFs. However, the effect of head pattern on the hemodynamics of IVCF is still a matter of unclear. In this study, computational fluid dynamics is used to simulate non-Newtonian blood flows around four IVCFs with different heads inside an IVC model, in which the Denali filter with a solid and hooked head is employed as a prototype, and three virtual variants are reconstructed either with a no-hook head or with a through-hole head for comparison. The simulation results show that the through-hole head can effectively avoid the recirculation region and weaken the blood flow stasis closely downstream the IVCF head. The shape change of the filter head has no significant effect on the blood flow acceleration inside the IVCF cone as well as little influence on the wall shear stress (WSS) distribution on the filter wire surface and IVC wall. The structure pattern of filter head greatly affects the flow resistance of its own. However, the flow drag of filter head only occupies a small proportion of the total resistance of IVCF. Therefore, to reduce the flow resistance of an IVCF should optimize its whole structure.

Success in Optional Vena Cava Filter Retrieval. An Analysis of 246 Patients

OBJECTIVE

This study assessed vena cava filter (VCF) retrieval rates and factors associated with retrieval failure in a single center cohort.

METHODS

We conducted an observational retrospective cohort study. The primary endpoint was the percentage of patients whose VCF was retrieved. We performed logistic regression to identify variables associated with retrieval failure.

RESULTS

During the study period, 246 patients received a VCF and met the eligibility requirements to be included in the study; 151 (61%) patients received a VCF due to contraindication to anticoagulation, 69 (28%) patients had venous thromboembolism (VTE) and a high risk of recurrence, and 26 (11%) patients received a filter due to recurrent VTE while on anticoagulant therapy. Of 236 patients who survived the first month after diagnosis of VTE, VCF was retrieved in 96%. Retrieval rates were significantly lower for patients with recurrent VTE while on anticoagulation, compared with patients with contraindication to anticoagulation or patients with a high risk of recurrence (79% vs. 97% vs. 100%, respectively; P<0.01). Mean time to retrieval attempt was significantly associated with retrieval failure (137.8 ± 65.3 vs. 46.3 ± 123.1 days, P<0.001).

CONCLUSIONS

In this single center study, VCF retrieval success was 96%. A delay in the attempt to retrieve the VCF correlated significantly with retrieval failure.