P-wave pseudonormalization after iatrogenic coronary sinus isolation.

We report a case of a 58 year old gentleman with prior history of catheter ablation for persistent atrial fibrillation (AF). His baseline ECG showed sinus rhythm with a broad and notched P-wave in lead II and biphasic P-wave (positive/negative) in leads III and aVF previously described as advanced interatrial block. A redo ablation procedure was performed due to AF recurrence. An iatrogenic isolation of the coronary sinus (CS) was observed during ablation with marked narrowing and loss of the terminal negative component of the P-wave on the surface ECG.