Abstract 3373: The Mechanism of Left Atrial Tachycardia Occurring During Circumferential Pulmonary Vein and Linear Ablation of the Left Atrial Roof in Patients with Atrial Fibrillation: A study with the use of a Noncontact Mapping System

Abstract

Introduction: Radiofrequency (RF) ablation during atrial fibrillation (AF) has been reported to be effective in eliminating AF, but the AF sometimes converts to drug-refractory left atrial tachycardia (AT). The present study aimed to examine the mechanism of the AT with the use of a noncontact mapping system (NCM).

Methods: Forty five patients with drug-refractory AF (male 38, 57 ± 10 years) who underwent AF ablation were included in this study (paroxysmal AF in 30 and persistent AF in 15 patients). Under navigation using NCM, RF energy (30–50W) was delivered during on-going AF circumferentially around the ipsilateral PVs and along the LA roof with a non-irrigated 8 mm-tip ablation catheter. The end-point of this study was the complete electrical isolation of the PVs and a line of conduction block along the LA roof, and if residual LA-PV conduction occurred, additional RF energy was delivered to that site under guidance with a circular catheter placed around each PV ostium.

Results: Among the 45 patients, the AF was directly converted to sinus rhythm in 10, spontaneously terminated in 8, persisted and required cardioversion for termination in 7. AT (217 ± 41 msec) was observed in the remaining 20 patients (44%), and the mechanisms revealed by dynamic wavefront maps using NCM were perimitral flutter (PMF) in 10, macro-reentrant AT rotating around the LA appendage in 3, that involving an electrical gap on the LA roof in 2, and focal AT originating from peri-PV ostia in 5. Other than for the PMF, additional RF energy applications were delivered to the critical site of the reentry circuit, conduction gap, or AT focus, and resulted in conversion to sinus rhythm in 5 patients and PMF in another 5. In a total of 15 patients with PMF, RF ablation to the mitral isthmus was performed and converted the PMF to sinus rhythm in 2 and was left untreated in the remaining 13. During a follow-up period of 160 ± 130 days, 39 of 45 (87%) patients were free from any symptoms. Those with untreated PMF (n=3), spontaneous termination to sinus rhythm (n=1), and persistent AF (n=2) during the RF ablation had an AF or AT recurrence.

Conclusions: The mechanisms of the LA-ATs occurring during the RF ablation while AF is on-going are diverse, and adequate treatment based on the AT mechanism is required to deal with each AT.