RESUMO
Introduction: Estimation of the prevalence of undiagnosed or untreated atrial fibrillation (AF) is crucial for the prevention of AF-related ischemic stroke. Objective: To assess the prevalence of undiagnosed or untreated AF in primary care. Methods: We conducted a prospective cross-sectional non-randomized study in Joinville, Brazil, among elderly individuals in primary care units (PCUs). Results: One thousand individuals were included, with a mean age of 69±7 years, and 57% women. Prevalence of AF was 3%, with 50% of AF patients being previously undiagnosed and 33% of previously diagnosed AF patients not receiving oral anticoagulation despite clinical indication. Using agestandardized prevalences, we estimated 68 and 27,342 strokes per year due to untreated or undiagnosed AF in Joinville and Brazil, respectively. Conclusion: The observation that two out of three AF patients were either undiagnosed or untreated is very alarming. Screening strategies to uncover this population are urgently needed.