WASHINGTON – On the basis of a large randomized trial called ATTRACT, many clinicians have concluded that pharmacomechanical intervention is ineffective for preventing postthrombotic syndrome (PTS) in patients with deep venous thrombosis (DVT). But weaknesses in the study design challenge this conclusion, according to several experts in a DVT symposium at the 2018 Cardiovascular Research Technologies (CRT) meeting.
“The diagnosis and evaluation of DVT must be performed with IVUS [intravascular ultrasound], not with venography,” said Peter A. Soukas, MD, director of vascular medicine at Miriam Hospital in Providence, R.I. “You cannot know whether you successfully treated the clot if you cannot see it.”
The ATTRACT (Acute Venous Thrombosis: Thrombus Removal With Adjunctive Catheter-Directed Thrombolysis) trial was a recently published phase 3 multicenter trial that randomized 692 patients with acute proximal DVT to pharmacomechanical thrombolysis or anticoagulation alone (Vedantham S et al. N Engl J Med. 2017 Dec 7;377(23):2240-52). The results of the trial, sponsored by the National Heart, Lung, and Blood Institute, were negative for the primary outcome of a difference in the rate of PTS within 24 months of follow-up, but Dr. Soukas said the study does not resolve the issue.
“There were lots of limitations to that study. Here are some,” said Dr. Soukas, who then listed on a list of several considerations, including the fact that venograms – rather than IVUS, which Dr. Soukas labeled the “current gold standard” – were taken to evaluate procedure success. Another was that only half of patients had a moderate to severe DVT based on a Villalta score.
“If you look at the subgroup with a Villalta score of 10 or greater, the benefit [of pharmacomechanical intervention] was statistically significant,” he said.
In addition, the study enrolled a substantial number of patients with femoral-popliteal DVTs even though iliofemoral DVTs pose the greatest risk of postthrombotic syndrome. Dr. Soukas suggested these would have been a more appropriate focus of a study exploring the benefits of an intervention.
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