Identification of deceleration zones during sinus rhythm for locating critical isthmuses in left atrial macroreentrant tachycardias

Abstract

Abstract Introduction Ablation of left atrial (LA) macroreentrant tachycardias (LAMT) poses considerable challenges, with issues such as tachycardia cycle length variations, multiple reentrant circuits, and tachycardia termination during entrainment maneuvers. Evaluating deceleration zones (DZ) through atrial pacing during sinus rhythm, and their correlation with potential critical conduction isthmuses (CI) in LAMT, remains unexplored. This approach may facilitate LAMT ablation. Objective To investigate the presence of DZ through atrial pacing during sinus rhythm and their association with LAMT critical conduction isthmuses (CI). Methods Patients who underwent LAMT high-density activation mapping with a 16-pole grid catheter were included. Conventional mapping (activation, voltage and entrainment mapping during tachycardia) was performed to localize the CI. Atrial pacing with three atrial extrastimuli (S2/S3/S4 with 500/500/300 ms coupling interval) was performed during sinus rhythm from the distal coronary sinus (CS). Isochronal late activation mapping (ILAM) of the S3 and S4 cycles was compared. Deceleration zones (DZ) were defined as an offset in the color scale of the activation map in an area with at least a radius of 10 mm. ILAMs were evaluated blindly, and DZs were compared with CIs defined by conventional mapping during tachycardia and validated by radiofrequency application termination. Results 18 p (60.50 ± 11.63 yo, 11 male) and 21 procedures were included. LAMT termination was successful in 18 out of 21 procedures (85.71%) and failed in 3 due to the epicardial component of the reentrant circuit. ILAM during CS pacing was achieved in 13 patients and was not possible in 5 p due to multiple LAMTs leading to empiric linear ablation in 1 and to recurrent induction of LAMT or AF during the pacing protocol. A DZ was identified in 13 out of 16 maps (81.25%) in the S3 map, which was more pronounced in the S4 map. In all these 13 maps, the final ablation site was within the DZ in the S4 map, terminating the tachycardia with focal RF applications in 11 and with extended in 2. Conclusions Deceleration zones identified through atrial pacing during sinus rhythm are prevalent in LAMT patients. These zones generally correspond to the critical conduction isthmus and offer a valuable method for mapping the reentrant circuit when mapping during stable LAMT is not feasible.