IDF and AF 
Some reports have assessed the efficacy and safety of transvenous internal atrial cardioversion performed in patients with persistent AF.14, 15 The IDF is an effective procedure for restoring SR in patients with AF.6 Further, there are few complications with IDF. Boriani G etc. reported myocardial injury following repeated internal atrial defibrillations.16Although, minor elevations in the troponin I level were detected, it suggested minor asymptomatic myocardial injury. There was no relationship between an elevated troponin I level and the number of shocks or amount of energy delivered. Therefore, the BeeAT catheter and dedicated defibrillator could be used multiple times for IDF, and because of that they are useful for checking triggers. The maximum energy output of this system was 30 J. Although the mean number of IDFs was 9.1 ± 7.5 times (max 28 times) per RFCA procedure, there were no complications associated with the IDF in our study. All patients were restored to sinus rhythm by the IDF with an output of less than 30 J.
The electrode position for the outcome of the IDF was very important. Thus, low-energy biphasic shocks positioned between the RA and CS were effective for cardioverting AF. The distal 8 poles of the BeeAT catheter were positioned in the distal CS and the middle 8 poles along the lateral wall of the RA. We selected the different catheter sizes (S, M, and L) to fit the LA and RA size of the patients. Therefore, an appropriate IDF could be performed in this study. Furthermore, the IDF was less affected by the LA size than by an external defibrillation catheter that fit the LA size.6