Subtherapeutic warfarin is not associated with increased hemorrhage rates in ischemic strokes treated with tissue plasminogen activator

Background and Purpose- Concern exists that preadmission warfarin use may be associated with an increased risk of intracerebral hemorrhage in patients with ischemic stroke receiving intravenous tissue plasminogen activator, even in those with an international normalized ratio <1.7. However, evidence to date has been derived from a small single-center cohort of patients. Methods- We used data from Phase 3 of the Registry of the Canadian Stroke Network. We compared the rates of post-tissue plasminogen activator hemorrhage, including any intracerebral hemorrhage, symptomatic intracerebral hemorrhage, and gastrointestinal hemorrhage in patients with and without preadmission warfarin use. For those receiving warfarin, we restricted the analysis to patients with an international normalized ratio <1.7 on presentation. Secondary outcomes included functional status and mortality. Multivariate analyses were performed to adjust for other prognostic factors. Results- Our cohort included 1739 patients with acute ischemic stroke treated with intravenous tissue plasminogen activator of whom 125 (7.2%) were receiving warfarin before admission and had an international normalized ratio <1.7. Preadmission warfarin use was not associated with any secondary intracerebral hemorrhage (OR, 1.2; 95% CI, 0.7 to 2.2), symptomatic intracerebral hemorrhage (OR, 1.1; 95% CI, 0.5 to 2.3), or gastrointestinal hemorrhage (OR, 1.1; 95% CI, 0.2 to 5.6). Multivariate analysis showed that preadmission warfarin use was independently associated with a reduced risk of poor functional outcome (OR, 0.6; 95 CI, 0.3 to 0.9), but not with in-hospital mortality (OR, 0.6; 95% CI, 0.3 to 1.0). Conclusions- The results from the present study suggest that tissue plasminogen activator treatment appears to be safe in patients with acute ischemic stroke taking warfarin with an international normalized ratio <1.7 and may reduce the risk of poor functional outcome.