Characteristics of catheter ablation of atrial tachycardia involving interatrial septum

Abstract

Background: Reentrant atrial tachycardia involving interatrial septum is associated with higher likelihood of recurrence. We assessd the procedural characteristics and clinical outcomes of catheter ablation for macro-reentrant atrial tachycardia involving interatrial septum (septal AT). Methods: The consecutive 49 patients with atrial tachycardia which was directly terminated during ablation were divided into 3 groups, based on the mechanism; septal AT, macro-reentrant AT which does not involve interatrial septum within the circuit (non-septal AT), or focal AT. Results: Clinical AT was septal AT in 9, non-septal AT in 21, and focal AT in 19 patients. Prevalence of underlying structural heart disease was the highest in patients with septal AT (78 vs 40 vs 7%, p<0.01). The ratio of low voltage area in left atrial-septum (<0.3 mV in the bipolar electrograms) was significantly broader in patients with septal AT than the other 2 groups (84±10 vs 51±26 vs 5±2%, p<0.01). Septal wall thickness measured by transesophageal echocardiogram or cardiac computed-tomography was significantly thicker in patients with septal AT than the other 2 groups (3.2±0.92 vs 2.3±0.60 vs 2.3±0.60 mm, p<0.01). Abrupt prolongation of tachycardia cycle length was more likely to occur during ablation without the change of tachycardia circuit, that was confirmed by repeated activation and/or entrainment mapping, in patients with septal AT than the other 2 groups (75±53 vs 30±35 vs 18±16 msec, p=0.01). Arrhythmia recurrence rate was significantly higher in patients with septal AT (56 vs 16 vs 5%, p=0.03) in the follow-up period of 19±8 months. At the redo procedure, the septum was ablated from the bi-lateral side in patients with septal AT and there was no recurrence in 9 months follow-up period. Conclusions: Macro-reentrant septal ATs were characterized by higher prevalence of structural heart disease, more scar burden and thicker inter-atrial septum. These findings may be one of reasons for higher likelihood of recurrence of septal ATs. It is possible that ablation from bi-lateral side improves the clinical outcome of catheter ablation for septal AT.