Discussion
To the best of our knowledge this is the first observational prospective study that monitored closely the QTc interval following CV in patients with persistent AF using 7-day Holter monitoring. The main finding of this study include 1) significant QTc prolongation that was detected in 47% of patients following CV, 2) the maximal median QTc prolongation occurred during the second day (44 hours following CV), 3) there was a substantial increase in detection rates of clinically significant QTc prolongation using prolonged Holter monitoring compared with standard monitoring, and 4) chronic beta blocker use was the only predictor associated with significant QTc prolongation.