Baseline electrophysiological study
The procedure was performed in fasting state, under general anesthesia in 5 patients (standard procedure in one center) for which propofol and atracurium were used during the study. In the remaining procedures, patients were under conscious sedation with propofol and remifentanil and monitored with bispectral index (BIS®). Three right femoral vein punctures allowed introduction of a 7F diagnostic decapolar catheter in the coronary sinus, a 6F diagnostic quadripolar catheter at His location and one 8.5F SL1® sheath (Abbot Inc.) Baseline electrophysiological study was performed using a multichannel cardiac recorder for bipolar intracardiac electrograms with filtered signals at 30-300 Hz (EP WorkMate Claris System®, Abbott Medical and LabSystem Pro®, Boston Scientific), displaying 3 surface ECG leads (DII, aVF and V1) and with programmed digital stimulation (EP-4® Cardiac Stimulator, Abbott Medical and Qubic Stim, Biotronik). Baseline intervals were measured, and sinoatrial node function was evaluated by measuring RR intervals and AV node function was assessed by measuring Wenckebach cycle length (WBCL) (atrial decremental stimulation at which Wenckebach AV block occurs).