What's wrong with the atrium in patients with atrial fibrillation?
D001281:Atrial Fibrillation / Q000209:etiology* / Q000503:physiopathology; D004594:Electrophysiology; D006321:Heart / Q000503:physiopathology*; D006325:Heart Atria / Q000503:physiopathology; D006801:Humans; D012032:Refractory Period, Electrophysiological