Background: Minimally invasive pulmonary vein isolation was developed as a treatment of lone atrial fibrillation. Until recently, electrophysiological studies in patients with recurrent arrhythmias had not been described. Methods: One hundred thirty patients underwent mini-maze pulmonary vein isolation. We performed catheter ablation guided by CARTO mapping in 8 recurrent patients (mean 61.8 ± 12.7 years old, male:female ratio, 5:3) 5.0 ± 14 months after the original surgical procedure. Results: Recurrent atrial fibrillation occurred in 4 patients, atrial tachycardia occurred in 1 patient, and atrial flutter was present in 3 patients. CARTO mapping revealed that in 3 atrial fibrillation patients, gaps in the lesion were present at the roof and the bottom of the pulmonary vein. One of these patients was also found to have microreentry around the base of the left atrial appendage. The fourth recurrent atrial fibrillation patient was found to have a gap in the pulmonary vein isolation ring. One patient with atrial tachycardia was documented to have ectopic focus between the left atrial appendage and left superior pulmonary vein. In the 3 patients with atrial flutter, it was found to be localized to the mitral valve annulus in 2 patients, and to the left atrial roof of the remaining patient. All 8 patients underwent ablation successfully. At the latest follow-up, all patients were free of arrhythmias and independent of antiarrhythmic drugs. Conclusions: Pulmonary vein conduction at the roof and the bottom of the pulmonary vein after pulmonary vein isolation is the dominant factor responsible for recurrent atrial tachyarrhythmia. Left atrial-related flutter is a common form of arrhythmia. © 2010 The Society of Thoracic Surgeons.