Abstract 2102: Mechanism of Atrial Tachycardias Following Left Atrial Ablation of Atrial Fibrillation
Background: Patients who undergo left atrial (LA) ablation of atrial fibrillation (AF) may develop organized atrial tachycardia (AT) during follow up. The mechanism of AT is not well described.
Objective: To determine the mechanism of AT following LA ablation of AF.
Methods: Fifty four patients (Age=56±9; Males=42; paroxysmal AF=37; EF=52±10 years; LA=43±5 mm) who had previously undergone LA ablation of AF were referred for a repeat ablation procedure for AT. The initial procedure for AF involved creation of circular lesions around the left- and right-sided pulmonary veins (PV), a posterior/roof line connecting the two circular lesions, and a mitral isthmus line. AT was mapped by activation and entrainment mapping. The 3-D maps from the AF and AT procedures were compared in multiple views to determine whether AT arose from a prior ablation line.
Results: A total of 91 ATs were mapped in the 54 patients. Of the 91 ATs, the mechanism was due to macroreentry in 74 (81%), small reentrant circuits in 6 (7%), and focal tachycardias in 11 (12%) of the cases. The critical isthmus of the 74 macroreentrant ATs was localized to the mitral isthmus in 32 (43%), LA roof in 12 (16%), LA septum in 9 (12%), coronary sinus in 4 (5%), LA anterior wall in 2 (3%), and the cavotricuspid isthmus (CTI) in 15 (20%) of the ATs. The target site of the 6 ATs due to a small reentrant circuit was determined to be the periostial region of the left superior PV in 3 (50%), LA anterior wall in 2 (33%), and the proximal coronary sinus in 1 (17%) of the ATs. All of the 11 focal ATs originated from the left or right PVs. Fifty nine of the 65 (91%) reentrant left atrial tachycardias (after excluding the 15 ATs from the CTI) originated from prior ablation lines.
Conclusions: The vast majority of ATs that occur following LA ablation of AF are due to a reentrant mechanism. Approximately 90% of the LA reentrant ATs arose from previously ablated areas, and therefore, were most likely due to gaps in the prior ablation lines. Prior LA ablation may have unmasked focal ATs originating from the PVs by elimination of fibrillatory conduction. Although demonstration of linear block may be challenging in some patients, it may have reduced the prevalence of gap-related ATs.