Secondary Versus Primary Stroke Prevention in Atrial Fibrillation : Insights from the Darlington Atrial Fibrillation Registry

Background and purpose: Although patients with atrial fibrillation (AF) who experienced an acute stroke are at high risk for recurrence, many patients are untreated or treated suboptimally for stroke prevention. The objective of this study is to compare clinical outcomes of AF patients with versus without previous stroke in relation to guideline-adherent antithrombotic treatment in a contemporary primary care population. Methods: Community cohort of 105 000 patients from 11 general practices in Darlington, England, was used to assess AF stroke prevention strategies against 2014 National Institute for Health and Care Excellence guidelines. Results: Overall, 2259 (2.15%) patients with AF were identified, of which 18.9% constituted a secondary prevention cohort. For secondary prevention, antithrombotic treatment was guideline adherent in 56.3%, 18.9% were overtreated, and 24.8% undertreated; corresponding proportions for primary prevention were 49.5%, 11.7%, and 38.8%, respectively. One-year stroke rates were 8.6% and 1.6% for secondary and primary prevention, respectively (P<0.001); corresponding all-cause mortality rates were 9.8% and 9.4%, respectively (P=0.79). On multivariable analysis, lack of antithrombotic treatment guideline adherence was associated with increased stroke risk for primary prevention (odds ratio, 2.95; 95% confidence interval, 1.26-6.90; P=0.013 for undertreatment); for secondary prevention, lack of guideline adherence was associated with increased risk of recurrent stroke (odds ratio, 2.80; 95% confidence interval, 1.25-6.27; P=0.012 for overtreatment) and all-cause death (odds ratio, 2.75; 95% confidence interval, 1.33-5.69; P=0.006 for undertreatment). Conclusions: Only approximately half of eligible patients with AF are prescribed oral anticoagulation in line with guidelines. Guideline-adherent antithrombotic treatment significantly reduces the risk of stroke among primary prevention patients and both risk of recurrent stroke and death in patients with previous stroke.