Kwok M. Ho, Sudhakar Rao, Stephen Honeybul Whereet el published results of a multicenter randomized trial of early prophylactic IVC filters in severely injured patients with contraindication to anticoagulation in NEJM.
Venous thromboembolism is very common after major trauma and leads to major morbidity and mortality. In the prospective study of trauma patients who were not given prophylactic anticoagulation, incidence of proximal deep vein thrombosis and pulmonary embolism was 18 and 11% respectively. It accounts for 12% of all deaths after major trauma. Many of these patients have contraindication to prophylactic anticoagulation, as it has been shown to be associated with progressive enlargement of hematoma in patients with traumatic brain injury.
To deal with this issue, retrievable inferior vena cava filters have been developed and are now widely used in many trauma centers as a primary means to prevent pulmonary embolism, though without high quality evidence.
In this multi Center randomized controlled trial, conducted in Australia and new Zealand, 240 severely injured adult patients (injury severity score of more than 15) who had contraindication to anticoagulation, was randomized to have inferior vena caval filter within the first 72 hours or not. Trial was funded by medical research foundation of Royal Perth hospital.
Anticoagulation was initiated within 7 days after severe injury in 67% of the patients.
Following patient’s were excluded- imminent death, conformed pulmonary embolism, systemic anticoagulation treatment before injury, pregnancy, unavailability of interventional radiologist to insert the filter within 72 hours.
Primary endpoint was a composite of symptomatic pulmonary embolism or death from any cause at 90 days after enrollment.
Secondary end points were complications related to vena cava filters data at 90 days and major and non major bleeding at 90 days, DVT at 2 weeks.
Early placement of a vena caval filter did not result in significantly lower incidence of symptomatic pulmonary embolism or death at 90 days (13.9% in the venacaval group and 14.4% in the control group, P=0.98).
The incidence of major and nonmajor bleeding, the incidence of deep-vein thrombosis in a leg (which occurred in 11.4% of patients in the vena cava filter group and in 10.1% in the control group; relative risk, 1.1; 95% CI, 0.6 to 2.3), and transfusion requirements did not differ significantly between the two groups.
In the patients who did not receive prophylactic anticoagulation within 7 days after injury(46 in vena caval group and 34 in the control group), none of the patient in the venacaval group had pulmonary embolism, where as 5 patient’s in the control group had asymptomatic pulmonary embolism.
Vena caval filters were left in situ for median duration of 27 days. Entrapped thrombus within the filter was noted at the first attempt to remove the filter in 6 of the 122 patients. In 1 patient the filter was adhered to venacaval wall and was removed surgically. More than 1 attempt was needed in 7 patients to remove the filter. In 34 patients, filter was not removed because of technical regions are because of lost to follow-up.
As this well conducted randomized controlled trial demonstrates that there is no difference in incidence of pulmonary embolism as well as death at 90 days in trauma patients with or without use of IVC filter, prophylactic IVC filter has no role in management of trauma patients.
OVERVIEW OF IVC FILTERS
Parenteral anticoagulation is standard therapy for treatment of venous thromboembolism. Approximately 400000- 650,000 patients develop PE annually, leading to up to 240000 deaths.
In patients who have contraindications to anticoagulation, initially surgical interpretation of inferior vena cava was attempted to prevent pulmonary embolism. Mobin-Uddin filter was first introduced in 1967. Due to high incidence of thrombosis and occlusion, Greenfield filter quickly became the preferred choice, which was first described in 1973.
In the late 1990s, the PREPIC study was conducted to determine the safety and efficacy of IVC filters in the setting of proximal DVT. The landmark study found initial benefit of IVC filters in preventing PE, but this was offset by an increase in recurrent DVT in patients with an IVC filter. The PREPIC 2 study, however, failed to show a similar short term benefit of reduced PE recurrence with the use of retrievable IVC filters.
On average, 29% of patients with IVC filters suffer complications. Complications from IVC filter insertion
include improper anatomic placement of the filter (7%), migration (2%-3%), angulation of the filter (2%), caval
stenosis or filter narrowing (2%), caval occlusion (2%- 9%), air embolism (1%), penetration of the caval wall
(1%), lower extremity edema (13%-26%), and sequelae of venous stasis (27%).
IMPROVED TECHNOLOGY in the fabrication of inferior vena cava (IVC) filters has made them less thrombogenic,
smaller, easier to insert percutaneously, safer, and retrievable. Greenfield stainless steel filter and another permanent Bird’s Nest filter are MRI incompatible. Other permanent IVC filters available are Simon Nitinol,
TrapEase, and VenaTech, which are all MRI compatible
Trial of DENALI IVC filter showed that Filter placement was technically successful in 199 patients (99.5%). Filters were clinically successful in190 patients (95%). The rate of PE was 3% (n 6), with 5 patients having a small subsegmental PE and 1 having a lobar PE. New or worsening DVT was noted in 26 patients (13%). Filter retrieval was attempted 125 times in 124 patients and was technically successful in 121 patients (97.6%).
Although most of the filters are placed in infrarenal portion of IVC, there are few exceptions where they are placed above the renal veins. Indications for suprarenal placement of IVC filters include IVC thrombus, intrinsic and/or extrinsic narrowing of the infrarenal IVC, renal and/or gonadal vein thrombus, congenital IVC anomalies, pelvic mass, and pregnancy.
Please see the picture below for various retrievable filters.
In a cohort of patients with inferior vena cava filters in stable pulmonary embolism as well as heart failure showed In-hospital all-cause mortality was 102 of 2,423 (4.2%) with IVC filter compared with 686 of 14,063 (4.9%) without an IVC filter (p = 0.16). Only patients aged >80 years showed a lower in-hospital all-cause mortality with IVC filters, 38 of 933 (4.1%) with an IVC filter compared with 307 of 4,486 (6.8%) without an IVC filter (p = 0.0012).
In the same study, several subcategories of patients with acute pulmonary embolism were identified who would benefit from insertion of Inferior vena cava filters. These subcategories are those who underwent pulmonary embolectomy, receiving thrombolytic therapy, suffering recurrent pulmonary embolism while on treatment,
hospitalized with solid malignant tumors if aged >60 years, hospitalized with chronic obstructive pulmonary disease (COPD) if aged >50 years, and very elderly (aged >80 years).
In 2010, and again in 2014, the FDA issued a safety communication urging all physicians who place IVC filters to take an active role in ensuring proper follow-up for patients who have received an IVC filter. The goal is to ensure that patients who no longer have an indication for IVC filtration have their filters evaluated for removal in a timely
Because of the complications associated with IVCF placement, physicians are prone to Malpractice litigation. Jury verdict reviews from the Westlaw database from the year 2000 -2015 showed That physicians were sued for failure to place IVC filter (41%), implantation failure such as misplacement and/or misaligned implant (24%), erosion of IVC/retroperitoneal bleed (6%), and discontinuation of anticoagulation prematurely (6%). The most frequent defendants were internal medicine physicians (38%), vascular surgeons (19%), and cardiothoracic surgeons (12%). Seventeen cases (35%) were found for the plaintiff, with median awards worth of $1,092,500.
The American College of Radiology (ACR)/Society of Interventional Radiology (SIR), American College of Chest Physicians (ACCP), and American Heart Association (AHA) agree that IVC filters are indicated for patients with venous thromboembolism (VTE) who have an absolute contraindication to anticoagulation or in patients whom anticoagulation has failed (recurrent VTE).