The use of inferior vena cava filters in patients with venous thromboembolism and problems with anticoagulation is a relatively safe and effective method for preventing pulmonary embolus, according to the results of the Predicting the Safety and Effectiveness of Inferior Vena Cava Filters (PRESERVE) study.
The 12-month outcomes of PRESERVE will be presented as a Featured Abstract on Wednesday, March 8, 3:36–3:45 p.m., Room 225AB of the Phoenix Convention Center. The findings will also be discussed today during The SIR/SVS PRESERVE Trial Study—Real World Use and Outcomes of IVC Filters, 3–4:30 p.m., in Plenary hall 6.
PRESERVE, a multicenter, prospective, open-label, nonrandomized longitudinal evaluation of the commercially available inferior vena cava (IVC) filters, collected data indicating the current practices of IVC use and retrieval, as well as safety and effectiveness.
The study, which was initiated by SIR and the Society for Vascular Surgery in response to a directive from the FDA, was a response to concerns regarding the safety and long-term impact of IVC filter placement, according to lead investigator Matthews S. Johnson, MD, FSIR.
“There is a real hole in our understanding of IVC filters,” said Dr. Johnson. “Hundreds of thousands of people die every year from pulmonary embolus. It’s a huge health issue. And while most of the time patients are treated with anticoagulation, many cannot receive that standard of care. Which is why IVC filters became a popular alternative.”
According to Dr. Johnson, IVC filters are often used for patients with large clots or those with increased clot risk scheduled for surgery. Physicians saw very low instance of pulmonary embolism (PE) as a result.
“For many years, IVC filters were placed upon request, but there was very little follow up,” said Dr. Johnson. The physicians placing filters were rarely the primary physician or not even intimately involved in the patient’s case, which made it hard to collect long-term data on IVC filters or to track patients who had them placed, he said. Combined with the lack of rigorous data and emerging reports of fractures and thrombosis, concerns were raised.
However, Dr. Johnson and others who are active in the deep vein thrombosis (DVT) space did not feel it was accurate to say that IVC filters are inherently dangerous or ineffective. “We’ve always thought they were of value based upon comparisons to cohorts,” he said. “But in light of these very real concerns, representatives from SIR and SVS approached the FDA to see how to best evaluate the safety and effectiveness of IVC filters.”
This posed its own problems, due to the health concerns and disease states of the population in question.
“Due to ethical reasons, we didn’t have any substantial randomized controlled trials regarding the efficacy of IVC filters," Dr. Johnson said. “If you believe a person with a pulmonary embolus who can’t be anticoagulated needs a filter, you cannot ethically choose to do a randomized control trial with that person and not give them a filter.”
Researchers decided to conduct a real-world study of patients who had filters placed, beginning enrollment in October 2015. Between then and 2019, PRESERVE enrolled 1,428 patients and placed filters in 1,421. Of those, 71.7% had DVT or PE. 81.6% were not eligible for anticoagulation, and 126 filters were placed prophylactically.
The primary safety endpoint (89.4%) and primary effectiveness endpoint (96.4%) were both achieved, and clinical significant IVC filter-related adverse events were rare.
“I believe these findings are impressive because this population was very sick,” Dr. Johnson said. “All but 107 patients had either current or past history of PE, and our prophylactic population didn’t have a clot, but were deemed at risk.”
After filter placement, 93 patients experienced events: 5.2% experienced DVT, 1.6% had a PE, and 1.1% had caval thrombotic occlusions. None of these were fatal, and no PE occurred in the prophylactic patients.
“As for filter-related complications, only one embolized,” Dr. Johnson said. Some (15.4% at one year per the core lab) filters did perforate, however, according to Dr. Johnson.
“These are metal devices inside a flimsy vena cava, and it doesn’t surprise me that some may perforate. However, it depends on how you define a clinically significant perforation,” he said. “We talk about perforation as a complication in the same paragraph we talk about embolization and filter-related thrombus, but perforation that occurs may or may not have clinical relevance in terms of pain or location. The sites reported only 3 cases of clinically significant perforation.”
According to Dr. Johnson, filters were removed from 44.5% of patients with a 99.2% success rate for retrieval.
“Filters were placed and removed at 54 centers with varied practices,” Dr. Johnson said. “This success rate, combined with the low event rate and low incidence of filter-related complications, indicates to me that if you follow your patients and have a plan for retrieval at the time of placement, IVC filters can play a safe and effective role in helping these patients.”
Next year, PRESERVE researchers will release the 24-month patient follow-up data, as well as further data by subpopulation.
