Warfarin, a blood-thinning medication, has long been the standard treatment for preventing life-threatening blood clots. Although warfarin is highly effective as an anticoagulant, it is burdened with unpleasant and inconvenient side effects, making its usage quite challenging.

Warfarin, a recognized bleeding risk factor, may pose potential harm rather than benefit for individuals who take it regularly. The drug’s association with an increased risk of death from a dangerous brain bleed is a growing concern.

A recent study conducted by researchers at UT Southwestern Medical Center reveals that the majority of stroke patients who are prescribed the anticoagulant warfarin do not face an increased risk of brain bleeding when undergoing lifesaving clot-removal surgery.

The study, published in JAMA, provides valuable insights that could help doctors in assessing the risk associated with endovascular thrombectomy (EVT), thereby potentially widening the scope of eligible patients for this crucial stroke treatment.

Warfarin, a widely prescribed blood thinner, is often utilized for stroke prevention in individuals with heart conditions like atrial fibrillation. While relatively rare, patients on warfarin can still encounter strokes. Unfortunately, in clinical settings, some physicians may refrain from recommending an endovascular thrombectomy for patients who have previously received warfarin treatment prior to their strokes.

“Our study could increase the number of patients for whom this lifesaving and function-saving surgery would be appropriate,” comments study leader Ying Xian.

According to the Centers for Disease Control and Prevention, nearly 800,000 people in the U.S. suffer from a stroke each year, with the majority being ischemic strokes caused by a clot blocking blood flow to the brain.

The most common treatment for acute ischemic stroke is endovascular thrombectomy (EVT), a surgical procedure that removes the clot by navigating instruments through the blood vessels. However, there is a risk of symptomatic intracranial hemorrhage (sICH), a dangerous brain bleed that can be fatal, associated with EVT. It has been uncertain whether stroke patients who have been on the blood thinner warfarin are at a higher risk of sICH following EVT, even though warfarin is known to increase the risk of bleeding.

To address this question, Dr. Xian and his colleagues, including Dr. Eric Peterson from UTSW and researchers from other medical institutions, collected data from the largest registry of stroke patients in the world, the American Heart Association’s Get with the Guidelines-Stroke registry. They analyzed information from 32,715 stroke patients who underwent EVT within six hours of experiencing stroke symptoms between 2015 and 2020.

The researchers compared outcomes between the 3,087 patients who had been taking warfarin before their strokes and the 29,628 patients who had not taken any blood thinners. They examined whether patients experienced sICH within 36 hours of the EVT procedure, as well as other adverse outcomes such as serious systemic hemorrhage, complications requiring additional medical intervention or extended hospital stays, in-hospital deaths, and discharges to hospice care. They also considered complications arising from additional therapies that restored blood flow in the brain.

After adjusting for inherent differences between the two patient groups, the researchers found no significant difference in the overall risk of sICH or other adverse outcomes. However, patients with an international normalized ratio (INR) greater than 1.7, which indicates a higher clotting tendency in patients taking warfarin, had an increased risk of experiencing sICH by approximately 4%.

Dr. Peterson noted that it remains unclear whether this increased risk translates into worse outcomes for patients. Apart from the elevated risk of bleeding, patients with INRs greater than 1.7 were no more likely than those not taking warfarin to have worse functional outcomes at discharge or face higher mortality rates.

“Physicians must evaluate stroke patients on a case-by-case basis,” he added, “to determine whether EVT is appropriate, but our study suggests that taking warfarin alone should not necessarily be a limiting factor.”

Dr. Xian and Dr. Peterson have expressed their intention to conduct further research to examine whether other commonly used anticoagulants taken by patients at risk of stroke could potentially elevate the risk of symptomatic intracranial hemorrhage (sICH) or other severe complications following endovascular thrombectomy (EVT) for ischemic stroke.

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