Removal of retrievable vena cava filters in routine practice: a multicenter study

Effects of reverse deployment of cone-shaped vena cava filter on improvements in hemodynamic performance in vena cava

BACKGROUND

Cone-shaped vena cava filters (VCFs) are widely used to treat venous thromboembolism. However, in the long term, the problem of occlusion persists even after the filter is deployed. A previous study hypothesized that the reverse deployment of a cone-shaped VCFs may prevent filter blockage.

METHODS

To explore this hypothesis, a comparative study of the traditional and reverse deployments of VCFs was conducted using a computational fluid dynamics approach. The distribution of wall shear stress (WSS) and shear stress-related parameters were calculated to evaluate the differences in hemodynamic effects between both conditions. In the animal experiment, we reversely deployed a filter in the vena cava of a goat and analyzed the blood clot distribution in the filter.

RESULTS

The numerical simulation showed that the reverse deployment of a VCF resulted in a slightly higher shear rate on the thrombus, and no reductions in the oscillating shear index (OSI) and relative residence time (RRT) on the vessel wall. Comparing the traditional method with the reversely deployed cases, the shear rate values is 16.49 and 16.48 1/s, respectively; the minimal OSI values are 0.01 and 0.04, respectively; in the vicinity of the VCF, the RRT values are both approximately 5 1/Pa; and the WSS is approximately 0.3 Pa for both cases. Therefore, the reverse deployment of cone-shaped filters is not advantageous when compared with the traditional method in terms of local hemodynamics. However, it is effective in capturing thrombi in the short term, as demonstrated via animal experiments. The reversely deployed cone-shaped filter captured the thrombi at its center in the experiments.

CONCLUSIONS

Thus, the reverse deployment of cone-shaped filters is not advantageous when compared with the traditional method in terms of local hemodynamics. Therefore, we would not suggest the reverse deployment of the cone-shaped filter in the vena cava to prevent a potentially fatal pulmonary embolism.

The high-risk polytrauma patient and inferior vena cava filter use

OBJECTIVES

The aim of this study was to assess the impact on practice of vena cava filter insertion guidelines (Eastern Association for the Surgery of Trauma: practice management guidelines).

DESIGN

The study was performed at a level 1 trauma centre with data from the 'Trauma Audit and Research Network' cross-referenced to hospital data.

RESULTS

A total of 1138 specific 'high-risk' major trauma patients were identified over a 6-year period. The mean age was 46 years (18-102) and the male to female ratio was 3.3:1. The average Injury Severity Score was 23.6 (4-75). The overall DVT rate was 2.6% and the PE rate was 1.8%. A retrievable IVC filter was inserted in 42 cases (3.8%). The filter retrieval rate was 23.8% at a mean of 68.5days (4-107). Only one complication was reported of a breakthrough PE despite filter. Applying the EAST guidelines to this cohort would have suggested filter insertion in 279 (24.6%) cases. The kappa concordance value between observed practice and the 'EAST filter group' was 0.103 (poor). The PE rate in the 'EAST filter group' was 2.2% vs 1.6% in the 'no filter group' (p=0.601, no statistical difference) and the observed odds ratio was 0.814 (95% CI 0.413, 1.602).

CONCLUSION

The EAST guidelines are useful but may be overestimating the need for filter insertion.

Improvement of hemodynamic performance using novel helical flow vena cava filter design

We propose a vena cava filter in which helical flow is created in the filter’s working zone to minimize filter blockage by trapped clots and facilitate the lysis of trapped clots. To validate this new design, we compared five helical flow inducers with different thread pitches in terms of blood flow patterns in the filter. The vena cava was reconstructed based on computed tomography images. Both the numerical simulation and in vitro experiment revealed that the helical flow inducer can effectively create a helical flow in the vessel, thereby subduing the filter structure’s adverse disruption to blood flow, and increasing flow-induced shear stress in the filter center. In addition, the smaller thread pitch helical flow inducer reduced the oscillating shear index and relative residence time on the vessel wall. Moreover, we observed that the helical flow inducer in the vena cava could induce flow rotation both in clockwise and counterclockwise directions. In conclusion, the new design of the filter with the smaller thread pitch inducer is advantageous over the traditional filter in terms of improving local hemodynamics, which may reduce thrombosis build-up after deployment.

Inferior Vena Cava Filters in Trauma Patients: A National Practice Patterns Survey of U.S. Trauma Centers

Inferior vena cava filters (IVCFs) for thromboprophylaxis in trauma patients are being increasingly used despite a lack of strong clinical data in support of their efficacy and conflicting clinical practice guidelines. This national survey elucidates practice patterns of IVCF use across U.S. trauma centers. A web-based survey was administered to members of the Eastern Association for the Surgery of Trauma between September 2011 and October 2011. The survey queried: 1) background and professional practice; 2) trauma patient population; 3) IVCF placement; 4) IVCF retrieval and follow-up; and 5) pharmacologic prophylaxis. Two hundred eighty-one of 1059 eligible providers completed the survey (27%). Respondents were from a wide spectrum of training backgrounds and clinical practice settings. IVCFs were used by 98.9 per cent of respondents. IVCFs in patients without known venous thromboembolism were considered by 93.2 per cent of respondents. Indications and timing of IVCF retrieval vary. Follow-up care of patients with IVCFs was not uniform. An IVCF registry was maintained by 38 per cent of trauma programs. Adjunctive pharmacologic prophylaxis was used by 96.8 per cent of respondents. This study elucidates the gaps and variations in contemporary practices of IVCF use in trauma patients. Identification of best practices in IVCF use and retrieval awaits well-designed comparative effectiveness studies.