Pseudo sinus rhythm originating from the left superior pulmonary vein in apatient with paroxysmal atrial fibrillation

Pseudo Sinus Rhythm Originating from a Pulmonary Vein. We report the case o f a patient with paroxysmal atrial fibrillation in whom the background card iac rhythm falsely mimicked sinus rhythm but actually originated from the l eft 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" featur e in precordial leads. Radiofrequency applications inside the left superior pulmonary vein eliminated both atrial fibrillation and the ectopic pacemak er.