Ablation protocol
Radiofrequency ablation was performed using open-tip irrigated catheters (IntellaNav MIFI, Boston Scientific Inc.; Thermocool SmartTouch, Biosense Webster Inc.; TactiCath, Abbott Medical Inc.; or TactiCath, Sensor Enabled, Abbott Medical Inc.). A power of 30-35 W was used for posterior wall lesions, 35-40 W for anterior or free wall lesions, and 25-30 W inside the coronary sinus.
First, focal ablation of the identified rotors were performed with 1-4 adjacent lesions. If rotor ablation was unsuccessful, sites with STD were targeted using the same focal approach.
Rotor ablation success was defined, for each patient, as conversion to sinus rhythm or a stable AT using the aforementioned strategy. If rotors were present within the pulmonary veins antra, circumferential pulmonary vein isolation of that vein or pair of veins was performed including the rotor within the line. If rotor ablation was performed <1 cm from a scar or another radiofrequency application, an ablation line between them was performed. If rotor ablation was not successful, electrical cardioversion and empirical pulmonary vein isolation plus CTI ablation was performed.
All stable ATs were mapped using local activation time mapping, propagation mapping and entrainment, and subsequently ablated (focal ablation for small reentries or focal ATs; lines for macroreentries). In the case of conversion to another AT, the new AT was mapped and ablated. After conversion to sinus rhythm, bidirectional block at the ablation lines was checked with differential pacing or with activation mapping, and absence of capture at focal ablation sites was tested. If the patient had undergone previous ablation procedures, bidirectional block of the previously performed lines was checked, and ablation was performed if gaps were present. Pulmonary vein isolation was not performed in all patients, but it was routinely completed in those with previously documented atrial fibrillation.
Finally, programmed atrial stimulation was used to test arrhythmia inducibility; if other sustained ATs were induced, they were mapped and ablated. Procedural success was defined as the successful ablation of all inducible ATs, without requiring electrical cardioversion, with final sinus rhythm and non-inducibility at the end of the procedure.