Focal atrial tachycardia from the superior vena cava following atrial fibrillation cryoablation: a case report.

A 58-year-old woman with recurrent paroxysmal atrial fibrillation and a history of cryoablation 3 years prior underwent an electrophysiological study for an irregular narrow complex tachyarrhythmia. The electrocardiogram showed positive P' waves in all leads except aVR, with the P' waves separated by large isoelectric intervals, indicating focal atrial tachycardia rather than atypical atrial flutter. High-resolution 3D mapping revealed a focal atrial tachycardia originating from the postero-septal part of the superior vena cava (in close proximity to the right superior pulmonary vein). Three applications at the superior vena cava level terminated the tachycardia and restored sinus rhythm. There were no recurrences. This case underscores the need for high-resolution electrophysiological mapping to identify the arrhythmia origin, especially in patients with prior procedures.