The early detection and treatment of atrial fibrillation is a high priority for patients and physicians. Atrial fibrillation is the most common cardiac arrhythmia in the world, affecting over 25% of the population over age 70. Patients with atrial fibrillation are at an increased risk of a number of complications, including stroke, cognitive impairment, dementia, paralysis and heart failure. There are currently no established biomarkers to guide the clinical management of patients with atrial fibrillation. This project will develop and validate a diagnostic biomarker panel for atrial fibrillation that will enable the early detection of atrial fibrillation and predict the risk of complications. It will also improve the care of patients with this condition by predicting best treatments and outcomes. The results of the improved decision making in atrial fibrillation is expected to save over $200 million per year in health care costs in Canada alone.