6. Study limitations
Several limitations of the present study warrant mention. First, data analyses were not performed at independent facilities blinded to patient characteristics, which may have resulted in bias in mapping-data collection. In particular, mean regional voltage was obtained using arbitrarily selected mapping points within the region, possibly resulting in biased values. Second, the study did not investigate data from repeat procedures, and did not examine the reconnection rate of isolated pulmonary vein. Accordingly, AF recurrence does not necessarily mean that the patient had an extra-pulmonary-vein AF substrate. Third, ablation strategies were at the discretion of attending physician, possibly affecting rhythm outcomes. Fourth, AF recurrence after discharge was quantified on the basis of intermittent ECG monitoring, giving rise to the possibility that asymptomatic episodes of AF might have been missed. Finally, the study was conducted under a single-center, observational design. Confirmation awaits a prospective multicenter study.