Electrophysiological assessment of atrial tachycardia substrates in patients with repaired tetralogy of Fallot

Abstract

Abstract Introduction Adults with repaired tetralogy of Fallot (rToF) are most often referred to Adult Congenital Heart Disease centers for atrial tachycardia (AT) and radiofrequency catheter ablation (RFCA) is often required. A systematic evaluation of the mechanisms and recurrences of arrhythmias in these patients is lacking. Methods 28 patients with rToF referred for catheter ablation to the Interventional Electrophysiology Unit of our center between January 2013 and January 2023 were evaluated. Pts underwent electrophysiologic study (EPS) with 3D electroanatomic high density mapping. Evaluation of right atrial bipolar voltage and activation mapping of the AT was performed. Intra-atrial re-entrant tachycardias (IART), focal AT (FAT), other. Activation mapping was performed to identify the critical isthmus for IART. FATs were localized according to the earliest unipolar signal. Whenever possible, all the induced tachycardias were treated besides the arrhythmia which represented the clinical indication to EPS. RFCA was aimed at the earliest activation point for FAT and at the critical isthmus for IART, anchoring lesion to fixed obstacles (valve annuli or atriotomy scar). All patients provided written informed consent for participating in the study. Results Among 28 adult (age 47±13 years) patients (females n=14, 50%), 53 AT were documented: 34 (64%) IART, 11 (21%) FAT and 8 (15%) atrial fibrillation (AF). Mean tachycardia cycle length (excluding AF) was 307±95 ms. At least 2 ATs were induced in 12 pts during index EPS. Among IARTs, incisional IART (IARTinc, atriotomy and superior and inferior vena cava orifices, SVC and IVC, respectively) was the prevalent critical part of the circuit (n=22, 52%), while CTI was the second mechanism (n=20, 48%). In three pts, due to non-inducibility, a pre-emptive lesion set comprising in one case CTI and in two cases CTI+SVC-atriotomy-IVC line was performed. 2 patient underwent scheduled pulmonary veins isolation and CTI ablation. Among FAT, in 3 cases the AT was mapped in the coronary sinus, in two at the tricuspid annulus, in the remaining at the crista terminalis, at the right appendage base, at the posterolateral incision scar or between atriotomy and SVC. In 6 patients AF was induced but not ablated. During a median follow up of 23 months (interquartile range, 6-37) recurrence occurred in 8 pts (18% of pts, 15% of tachycardias). Patients with recurrences were younger (43±7 vs. 48±17 y, p=0.04); no differences were found according to critical isthmus location (4 CTI and 4 IARTinc, 50%, p=ns). Conclusions Among rToF pts with AT, IART is the prevalent mechanism and atriotomy scar is the prevalent critical isthmus. FAT location is much more variable. Atrial fibrillation burden is not negligible. Long-term freedom from AT in this clinical setting is encouraging.