A major multi-site clinical trial co-led by researchers at Washington University School of Medicine in St. Louis has shown that post-thrombotic syndrome — a common and often painful complication suffered by many people who have experienced blockages of major veins due to blood clots — can be effectively treated with a minimally invasive procedure. The study found that placing a stent to open and strengthen the affected vein reduced the severity of the post-thrombotic syndrome and improved venous symptoms and overall quality of life in affected patients.
The results are published April 13 in the New England Journal of Medicine and presented at the Society of Interventional Radiology's 2026 Annual Scientific Meeting in Toronto.
Lead author Suresh Vedantham, MD , an interventional radiologist and professor of radiology in Mallinckrodt Institute of Radiology at WashU Medicine and national principal investigator of the clinical trial, said the study was driven by the need to find effective ways to help a large and growing patient population for whom physicians did not previously have many well-tested options.
"We see a lot of patients who have moderate or severe post-thrombotic syndrome and have a tough time conducting their daily activities and maintaining a good quality of life. Many patients are unable to walk without pain or work productively," said Vedantham. "The condition has been undertreated, in part because there have not been evidence-based options available. This study is the first large randomized trial to show that this is a treatable condition, giving patients meaningful relief from this disease."
Opening the way to relief
More than 300,000 people in the U.S. each year are diagnosed with deep vein thrombosis, a blockage within one or more of the deep veins within the body, often in the leg. Deep vein thrombosis often increases the risk of pulmonary embolism, a life-threatening condition in which a blood clot travels to one of the lungs. Together, the two conditions cause as many as 100,000 deaths in the U.S. each year.
An estimated 40% of survivors of deep vein thrombosis will subsequently experience post-thrombotic syndrome, which can cause leg pain, swelling, skin discoloration, impaired mobility and reduced quality of life. In severe cases, open sores (ulcers) that are difficult to heal may develop in the leg below the blocked vein.
Vedantham said the primary goal for doctors treating deep vein thrombosis is to prevent the formation of new clots using blood-thinning medications. However, the blockages leave residual damage in the vein that can turn into scar tissue and restrict blood flow. This is a major underlying cause of post-thrombotic syndrome, which is often treated with compression (such as with specialty stockings) to reduce leg swelling, along with blood-thinning medications to prevent new clotting. Vedantham noted that neither of these treatments addresses the underlying blockage of blood flow in the vein nor provides consistent long-term relief from the symptoms and disability.
The Chronic Venous Thrombosis: Relief with Adjunctive Catheter-Directed Therapy (C-TRACT) Trial, sponsored by the National Institutes of Health (NIH), tested whether re-opening the blocked vein and restoring blood flow would reduce symptoms of post-thrombotic syndrome.
The study enrolled 225 patients at 29 sites across the U.S. who had been treated for deep vein thrombosis for at least 3 months and had blockage of the iliac vein (a major vein in the pelvis) causing substantial disability. Patients were chosen at random to receive either a stent — a mesh tube inserted into the vein to reinforce and expand it — plus standard treatment with compression and blood-thinning medications, or standard treatment alone. A stent is placed in a two-to-three-hour operation that requires only tiny incisions.
At the start of the study, 93% of participants met the clinical criteria for severe post-thrombotic syndrome. Six months after treatment, just 40% of patients who received the stent still experienced severe post-thrombotic syndrome, compared to 61% in the standard care group.
Patients with stents also reported improved symptoms in the veins of their legs and overall quality of life following the procedure compared with those on standard treatment. On a 100-point quality of life scale, those who received the stent scored 14 points higher, a large improvement.
"Post-thrombotic syndrome can be life‑altering, yet we've had very few effective treatment options," said Sameer Parpia, PhD, senior author and data coordinating center principal investigator of the study and an associate professor in the departments of Oncology and Health Research Methods, Evidence, & Impact at McMaster University. "This trial provides clear evidence that targeted therapy can make a meaningful difference for patients living with this condition."
Vedantham said the trial will provide a foundation for improving patient care for post-thrombotic syndrome and help physicians to better understand options that they can recommend for their patients seeking treatment for the condition.
Vedantham S, Kahn S, Marston W, Weinberg I, Sista A, Magnuson E, Cohen D, Wasan S, Razavi M, Goldhaber S, Sanfilippo K, Comerota A, Azene E, Ochoa C, Cassius I, Leung D, Kolli K, Kalva S, Rostambeigi N, Desai A, Desai K, Tafur A, Khalsa B, Majerus E, Wang B, Wang Y, Nieters P, Derfler M, Oliver A, Hardy C, Bashir R, Winokur R, Weger N, Khaja M, Sharma A, Mani N, Kavali P, Thukral S, Lake L, Mikkelsen K, Parpia S. Endovascular therapy for post-thrombotic syndrome: A randomized trial. New England Journal of Medicine. April 13, 2026. DOI: 10.1056/NEJMoa2519001
The C-TRACT trial is sponsored by the National Heart, Lung, and Blood Institute (NHLBI) of the U.S. National Institutes of Health (NIH) via grants UH3-HL138325 (clinical coordinating center, PI Dr. Suresh Vedantham) and U24-HL137835 (data coordinating center, PI Dr. Sameer Parpia). Study development was supported by NHLBI grants U34-HL123831 and UG3-HL138325 to Dr. Vedantham. Additional support was obtained from the Institute for Clinical and Translational Sciences at Washington University in St. Louis which is funded by National Center for Advancing Translational Sciences (NCATS) via grant Ul1-TR002345 to Dr. William Powderly. Medi USA donated compression garments to study patients. Dr. Kahn is a Tier 1 Canada Research Chair and receives support from the Canadian Institutes of Health Research. The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH.
About WashU Medicine
WashU Medicine is a global leader in academic medicine, including biomedical research, patient care and educational programs with more than 3,000 faculty. Its National Institutes of Health (NIH) research funding portfolio is the second largest among U.S. medical schools and has grown 83% since 2016. Together with institutional investment, WashU Medicine commits well over $1 billion annually to basic and clinical research innovation and training. Its faculty practice is consistently among the top five in the country, with more than 2,000 faculty physicians practicing at 130 locations. WashU Medicine physicians exclusively staff Barnes-Jewish and St. Louis Children's hospitals — the academic hospitals of BJC HealthCare — and Siteman Cancer Center , a partnership between BJC HealthCare and WashU Medicine and the only National Cancer Institute-designated comprehensive cancer center in Missouri. WashU Medicine physicians also treat patients at BJC's community hospitals in our region. With a storied history in MD/PhD training, WashU Medicine recently dedicated $100 million to scholarships and curriculum renewal for its medical students, and is home to top-notch training programs in every medical subspecialty as well as physical therapy, occupational therapy, and audiology and communications sciences.
