Background: Atrial fibrillation (Afib) is an independent risk factor for acute ischemic stroke (AIS). Studies have shown that patients with Afib on admission for AIS have poorer long-term prognoses compared to patients who do not present with pre-morbid Afib, but it is not clear whether stroke severity and outcome are associated with therapeutic anticoagulation. We aimed to determine whether patients with Afib and INR≥2.0 or who are anticoagulated prior to admission (Afib+/C+) have better outcomes following AIS compared to patients with Afib and INR<2.0 and who are not anticoagulated (Afib+/C-).
Methods: Patients who presented to our center with AIS between 07/2008-07/2014 were included if pertinent past medical history, home medication status, and INR lab values were obtained at admission. Logistic regression was used to assess differences in baseline, in-hospital, and outcome variables in the Afib+/C+ and Afib+/C- groups as compared to patients with no atrial fibrillation (Afib-). The primary outcome measure was poor functional outcome (modified Rankin Scale > 2) on discharge.
Results: A total of 1,406 cases were analyzed; 1,262 patients (89.8%) in the Afib- group, 90 patients (6.4%) in the Afib+/C- group, and 54 patients (3.8%) in the Afib+/C+ group. Afib- patients were significantly less likely to experience poor functional outcome (OR=0.40, 95% CI 0.21-0.74, p<0.0001). However, significance was lost after adjusting for age, NIHSS score at baseline, and tPA administration. There was no significant difference in the likelihood of poor functional outcome (OR=0.78, 95% CI 0.37-1.67, p=0.4331) between patients in the Afib+/C- and Afib+/C+ groups in the unadjusted model.
Conclusions: The absence of atrial fibrillation in the setting of AIS is associated with less likelihood of poor functional outcome, but this is driven by imbalances in covariates. While therapeutic anticoagulation reduces stroke occurrence, this did not protect against higher baseline stroke severity and worse functional outcome amongst patients with Afib.