A study published June 26 in the Journal of the American Medical Association (JAMA) found that among patients with ischemic stroke, the use of intravenous tissue plasminogen activator (tPA) among warfarin-treated patients if their international normalized ration (INR) was 1.7 or lower, was not associated with increased symptomatic intracranial hemorrhage (sICH) risk compared with non-warfarin-treated patients.

"Intravenous tPA is currently the only effective treatment to improve outcomes for acute ischemic stroke; however, treatment with intravenous tPA carries the risk of sICH." The authors note that "warfarin-treated patients may be at an increased risk of sICH, but the true absolute risk of sICH in this population remains a matter of significant debate, because warfarin-treated patients were excluded from major trials of tPA."

The observational study "represents the largest clinical experience of the safety of intravenous tPA in warfarin-treated patients who met clinical guideline eligibility criteria." The study took data from the American Heart Association's Get With the Guidelines-Stroke Registry and used 23,437 patients with ischemic stroke and with INR of 1.7 or lower, treated with intravenous tPA in 1,203 registry hospitals from April 2009 – June 2011.

The authors found that out of the patients with stroke treated with tPA, 1,802 were receiving warfarin. "Warfarin-treated patients were older, had more comorbid conditions, and had more severe strokes. The unadjusted sICH rate in warfarin-treated patients was higher than in non-warfarin patients, but these differences were not significantly different after adjustment for baseline clinical factors. Similarly, there were no significant differences between warfarin-treated and non-warfarin-treated patients for serious systemic hemorrhage, any tPA complications, or in-hospital mortality."

"Among warfarin-treated patients with INRs of 1.7 or lower, the degree of anticoagulation was not statistically significantly associated with sICH risk," add the authors.

The authors observe that "further study is needed to provide guidance on thrombolytic therapy for patients who develop ischemic stroke while taking new oral anticoagulants."

There is also "the potential for substantial undertreatment, because up to 50 percent of warfarin-treated patients who might have been eligible for reperfusion therapy did not receive intravenous tPA," note the authors. "These data provide empirical support of the current American Heart Association/American Stroke Association guideline recommendations and may help support future stroke quality improvements efforts."

In an editorial comment, Mark Alberts, MD, notes that "the results of the current study provide another chance to treat a serious and potentially disabling disease that has very few effective medical therapies."

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