Transition from normal sinus rhythm to atrial fibrillation in a patient with atrial fibrillation recurrence. Heart rate and step count as recorded by a photoplethysmography and accelerometer-enabled wrist-worn device demonstrate a period of variable rate tachycardia and increased beat-to-beat variability, which correlates with implantable loop recorder-confirmed paroxysmal atrial fibrillation. (A) Implantable loop recorder electrogram showing atrial fibrillation and (B) implantable loop recorder electrogram showing normal sinus rhythm.