Impact of Atrial Fibrillation on Outcome in Thrombolyzed Patients With Stroke: Evidence From the Virtual International Stroke Trials Archive (VISTA)

Background and Purpose— Atrial fibrillation has been considered a risk factor for poor outcome from acute stroke and may influence response to thrombolysis, although supporting data are limited due to potential confounding with age and stroke severity. Method— We assessed the association of atrial fibrillation and thrombolysis exposure with the modified Rankin Scale score distribution at 90 days among patients registered in a trials archive. We used an age and baseline National Institutes of Health Stroke Scale-adjusted Cochran-Mantel-Haenszel test to test significance (P) followed by proportional odds logistic regression analysis to estimate the ORs for improved modified Rankin Scale score. Results— Data were available for 7091 patients, of whom 3027 were thrombolyzed. A total of 1631 patients had a history of atrial fibrillation, of whom 639 were thrombolyzed. Among patients with atrial fibrillation, baseline severity was greater (median baseline National Institutes of Health Stroke Scale, 14 versus 12; P<0.001) and age was higher (mean age, 74.0 versus 66.5; P<0.001). An association of treatment with outcome was seen independently and was of similar magnitude within patients with atrial fibrillation (OR, 1.44; 95% CI, 1.12–1.73; P<0.001) and without atrial fibrillation (OR, 1.53; 95% CI, 1.39–1.69; P<0.001). No association of atrial fibrillation and overall stroke outcome could be found (OR, 0.93; 95% CI, 0.84–1.03; P=0.409). Conclusion— In this nonrandomized comparison, presence of atrial fibrillation had no independent impact on stroke outcome and compared with untreated comparators, the patients who received thrombolysis experienced an advantage in outcomes that was of equal magnitude whether in the presence or absence of atrial fibrillation.