Abstract WP74: Intravenous Thrombolysis for Acute Ischemic Stroke in Patients Taking Warfarin with Subtherapeutic INR

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Introduction: AHA/ASA guidelines allow use of IV rtPA in warfarin-treated acute ischemic stroke (AIS) patients with INR ≤1.7. Concerns remain regarding safety of IV rtPA, as value of 1.7 was not determined through randomized trials, and available data is controversial.

Objectives: To evaluate symptomatic intracranial hemorrhage (sICH) rate and outcome of IV rtPA treated AIS patients taking warfarin with INR ≤ 1.7, and compare with non-warfarin patients. Also, to evaluate rate of sICH and outcome in different INR ranges in warfarin-treated AIS patients who received IV rtPA.

Methods: Retrospective chart review was performed on patients who received IV rtPA for AIS from the beginning of January 200 till the end of August 2015 (n=834), with 55 patients (6.5%) identified to be on Warfarin prior to AIS. One of these patients was excluded because of INR being greater than 1.7. Due to differences in sample size (54 vs 779), Warfarin group was matched in case-control manner with 54 non-warfarin patients with similar sICH risk factors (age, admission NIHSS, history of diabetes, history of atrial fibrillation), eliminating need to adjust for covariates. Good outcome was defined as mRS of 0-2 on discharge, and sICH was defined as an increase in NIHSS ≥4. Frequencies of good outcome and sICH were calculated for each group and compared. Warfarin group was also dichotomized based on INR (1-1.3 vs 1.31-1.7), and safety and outcome measures of the two groups were compared.

Results: In the Warfarin group, 2 patients (3.7 %) developed sICH post IV rtPA . Fifteen patients in this group (27.8%) had good outcome on discharge. After case-control matching, no significant difference was found in the frequency of patients with good outcome on discharge or occurrence of sICH between warfarin and non-warfarin groups (P=0.270 and P=0.874 respectively). Also, there were no between group differences in frequency of patients with good outcome and rate of sICH between subjects on Warfarin with an INR 1.31-1.7 ( 0 % with sICH; 26.7% with good outcome) and those with INR < 1.3 (5.1% with sICH ; 28.2 % with good outcome) (p=0.910 and p=0. 371 respectively)

Conclusion: Our results suggest that IV rtPA does not increase the risk of sICH in Warfarin treated patients with INR≤1.7.

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