On 3 November, Raman Uberoi, Department of Radiology, The John Radcliffe Hospital, Oxford, UK, shared vital information from the world’s largest prospective collection of data on the practice of inferior vena cava (IVC) filter placement at the annual British Society of Interventional Radiology meeting in Glasgow, UK.
“The contributors to this registry are to be congratulated for this data, which will help guide future practice in the UK,” Uberoi said.
The main recommendations from the registry were that, “When a right femoral access is not available for the placement of an IVC filter, a jugular approach should be used, when possible. Also, where a filter is placed with the intention of removal, procedures should be put in place to avoid the patient being lost to follow-up. This could be simply done by booking an appointment on the Radiology Information System,” he recommended based on the data obtained to delegates. The data also indicate that filter retrieval appears to be most successful before nine weeks have passed after placement, and patients should be booked for removal within this time-frame,” he said.
Uberoi pointed to the dearth of evidence behind the use of IVC filters; “There is only one randomised, controlled trial (PREPIC) comparing IVC filter with standard anticoagulation,” he said. Data on the utilisation of inferior vena cava filters within the UK are currently limited, including on the use of retrievable filters. “The British Society of Interventional Radiology instituted an internet-based registry in January 2008, and the data were submitted online. The primary aim of this registry was to assess current practice of IVC filter usage in theUK. The secondary aims were to examine outcomes for patients with complications from the insertion procedure; those with complications whilst the filter is in place and the success rate of retrieval.”
“Data was submitted from 68 centres between January 2008 and December 2010. This report contains analysis of data on 1,255 caval filter placements and 387 attempted retrievals. The peak age distribution, irrespective of gender is 70–74 years. There were no significant differences in age distributions between the genders. The majority of filter placements were undertaken for recognised indications according to CIRSE guidelines, with the most frequently recorded indication (30.3%) being pre-operatively for acute deep vein thrombosis (DVT)/pulmonary embolus (PE). Pulmonary embolus with contraindication to anticoagulation was the indication in 25.6% and prophylaxis in high-risk patients was the indication in 21% of cases.
IVC filter type
Uberoi noted that in the registry, over 96% of filters were deployed as intended. “The majority of filters used were of a retrievable type, even when the intention was to leave them permanently in place. Cook’s Guenther Tulip was used in 39.1% of cases, Cook’s Celect in 24.3%, Cordis’ OptEase 13.7%, Bard’s G2 in 7.6% and Cordis’ Trapease in 5.5%. “There was a significant increasing trend for using retrievable filters (2×2 analysis of trend over time; p=0.014),” said Uberoi.
“Filter complication rates are low, with an average complication rate of 3.5%. There were, however, two major complications involving surgical removal of the filter,” he noted.
Filter perforation of the caval wall
“Overall perforation rates were low, but in the absence of systematic CT follow-up, perforation is likely to be underreported. Perforation was reported most frequently with the Bard’s G2 and Recovery filters. Perforation was not reported with the Cordis filters.
A further filter (Cook, Günther Tulip) required surgical removal following penetration through the caval wall insertion,” said Uberoi.
Tilting was seen with all of the commonly used filters but most frequently with the Cook’s Günther Tulip and Celect Tulip filters. The Cook Tulip and Celect filters were associated with tilting, or apex abutting the caval wall in over 20% of placements. Tilting was less frequently reported with the Cordis’ TrapEase and OptEase and the Bard G2 device.
Tilting was more likely to occur with a left femoral deployment, than right femoral, or jugular. Tulip and Celect filters deployed via the left femoral approach were significantly less likely to be centralised than those deployed via the right femoral approach (2×2 contingency table; p=0.013) or via the right jugular approach (2×2 contingency table; p=0.021).
Tilting, to the extent of the filter head abutting the caval wall, was a frequent cause of failure to retrieve the filter, Uberoi noted.
A few cases of migration of over 10mm were reported: A total of nine migrations have been reported: Four with Bard’s G2 filter, three with the Cook’s Celect filter and one each with the Bard’s Recovery and Cordis’ OptEase filters. In one case, caudal migration was associated with failure to retrieve the filter. There was one case of migration to the intra hepatic IVC. There were no instances of cardiac migration reported and no instances of fracture or significant structural failure.
Pulmonary embolism and IVC or lower limb thrombosis during follow-up
“New lower limb deep vein thrombosis and or IVC thrombosis was reported in 88 cases after filter placement,” said Uberoi. He added that deep vein thrombosis (DVT) is a known risk of IVC filter placement. The rate identified in this series is low and this may reflect under-reporting,” he said.
There were differences between the immediate post-procedure rates of DVT for Cook’s Celect vs. Cordis’ OptEase filters (2-sided Fisher’s exact test; p=0.004) and for Cook’s Günther Tulip
Tulip vs. Cordis’ OptEase (2-sided Fisher’s exact test; p=0.002)
“There was no statistically significant difference in DVT rates between those patients who had successful filter retrieval compared to those that had their filters left in place. Pulmonary embolism was reported in 16 cases during follow-up. There were six reported cases of death due to pulmonary embolism, but on closer inspection this was not supported by objective evidence in most cases,” said Uberoi.
“Retrieval was attempted in 77.8% of cases and was technically successful in 82.3% of cases. Retreival success diminishes with the duration of implantation. Filters that have been deployed for over nine weeks or 62 days are significantly less likely to be retrieved (2×2 contingency table; p=0.001). This is most likely due to incorporation in the caval wall,” he said.
“Centralised filters were associated with a higher rate of successful retrieval, but this did not reach statistical significance. Contrary to expectation, retrieval success of Cook Celect and Tulip filters was unrelated to filter tilting, and had success rates of around 80% for all orientations,” noted Uberoi. “For the other filters in this registry, tilting was associated with a lower success rate of filter retrieval (p=0.004) but there was no major difference in retrieval success of different filter makes,” he said.
Retrieval was associated with few minor complications and no serious complications.
“The average in-hospital mortality rate was 8.1% indicating that this is overall a high-risk group. Patients who have permanent filters inserted appear to have an elevated mortality rate of 12.3%. Those patients with temporary filters inserted appear to have an elevated mortality rate of 4.3%. The difference in mortality, both in-hospital and at 30 days and between temporary and permanent placements probably reflects the severity of underlying disease. It confirms that the initial decision for temporary vs. permanent placement should be based on objective clinical criteria,” Uberoi said.
Limitations of the dataset
Uberoi said, “Inevitably, not all UK centres participated and the proportion of cases registered by participating centres is unknown. There is no independent external data monitoring, and there have been some instances of differences in interpretation of certain data items between participants.
“There was no systematic clinical or imaging follow-up regime. Thus data on long-term filter integrity, migration and caval wall perforation are derived from clinically-driven investigations. This detracts from the quality of some of the data analysis and limits ours confidence in some of the subsequent conclusions.”
Still, “This report provides interventional radiologists with an improved understanding of the technical aspects of IVC filter placement to help guide and improve future practice. Also the potential consequences of filter placement so that we are better able to advise patients and referrers.”