Pseudo Sinus Rhythm Originating from the Left Superior Pulmonary Vein in a Patient with Paroxysmal Atrial Fibrillation

Pseudo Sinus Rhythm Originating from a Pulmonary Vein. We report the case of a patient with paroxysmal atrial fibrillation in whom the background cardiac rhythm falsely mimicked sinus rhythm but actually originated from the left superior pulmonary vein. P waves during the ectopic rhythm were flat in lead I, negative in lead aVL, and without a typical “dome‐and‐dart” feature in precordial leads. Radiofrequency applications inside the left superior pulmonary vein eliminated both atrial fibrillation and the ectopic pacemaker.