A global study led in part by Dell Med’s Steven Warach shows that starting blood thinners just days after a stroke is not only safe — it significantly lowers the chance of another stroke. Findings could help change how doctors treat stroke patients worldwide.
AUSTIN, Texas — A new global study published in The Lancet finds that starting blood thinners within four days of an ischemic stroke caused by atrial fibrillation can significantly lower the risk of a second stroke — without increasing the risk of brain bleeding.
The findings offer the most definitive evidence to date on a question that has long challenged clinicians: How soon is too soon to begin blood-thinning therapy after stroke?
The study, called CATALYST, analyzed data from more than 5,400 patients across four major randomized clinical trials. Steven Warach, M.D., Ph.D., professor of neurology at Dell Medical School at The University of Texas at Austin, served as the U.S. principal investigator and co-author of the study. He also led the U.S.-based START trial, one of the four studies included in the meta-analysis, which was published earlier this year in JAMA Neurology.
“For decades, clinicians have been uncertain when to safely start anticoagulation after stroke,” said Warach. “This study provides the clearest evidence yet that in most cases, it’s not only safe to start earlier — it’s better for patients.”
Atrial fibrillation, an irregular heartbeat that increases stroke risk, causes about 1 in 3 ischemic strokes. Although direct oral anticoagulants (DOACs) are highly effective in preventing future strokes, the best time to start them after an initial stroke has remained controversial, with many physicians waiting one to two weeks to begin treatment.
By pooling individual patient data from all high-quality trials available, the CATALYST analysis offers a more reliable answer.
Key Findings: Evidence That Could Change Stroke Care Worldwide
- Starting DOACs within four days of stroke onset cut the risk of a second stroke by nearly one-third.
- No added risk of brain bleeding or other major complications.
- Benefits observed across a broad range of patients, regardless of stroke severity or prior treatment.
- Suggests earlier DOAC use should become the new standard of care.
- Potential to shorten hospital stays and improve global outcomes.
“This gives clinicians the clarity they’ve been waiting for — and gives patients a better chance at recovery,” said Warach. “It’s a major step forward in evidence-based stroke care.”
Led by University College London, the study reflects a broad international collaboration with investigators from the U.S., Sweden, Switzerland, Austria and Japan.