Findings include Absence of P waves Presence of f (fibrillatory) waves between QRS complexes; f waves are irregular in timing, irregular in morphology; baseline undulations at rates > 300 / minute, usually best seen in lead V1 and not always apparent in all leads Irregularly irregular R-R intervals Atrial fibrillation Other irregular rhythms may resemble atrial fibrillation on ECG but can be distinguished by the presence of discrete P or flutter waves, which can sometimes be made more visible with vagal maneuvers.