Interatrial Septal Tachycardias Following Atrial Fibrillation Ablation or Cardiac Surgery: Electrophysiologic Features and Ablation Outcomes.

Abstract

BACKGROUND\nInteratrial septal tachycardias (IAS-AT) following atrial fibrillation (AF) ablation or cardiac surgery are rare and their management is challenging.\n\n\nOBJECTIVE\nTo investigate the electrophysiologic features and outcomes associated with catheter ablation of IAS-AT.\n\n\nMETHODS\nWe screened 338 patients undergoing catheter ablation of ATs following AF ablation or cardiac surgery. Diagnosis of IAS-AT was based on activation mapping and analysis of response to atrial overdrive pacing.\n\n\nRESULTS\n29 (9%) patients had IAS-AT (CL 311+/-104 ms); 16 (55%) had prior AF ablation procedures (median 3, range 1-5), 3 (10%) had prior surgical MAZE and 12 (41%) had prior cardiac surgery (including ASD surgical repair in 5 and LA myxoma resection in 1). IAS substrate abnormalities were documented in all patients. Activation mapping always demonstrated a diffuse early IAS breakout with centrifugal biatrial activation, and atrial overdrive pacing showed a good PPI (equal or within 25 ms of the AT CL) only at one or two anatomically opposite IAS sites in all cases. Ablation was acutely successful in 27 (93%) patients (from only the right IAS in 2, only the left IAS in 9, both IAS sides with sequential ablation in 13, and both IAS sides with bipolar ablation in 3). After a median follow-up of 15 months (6-52 months), 17 patients (59%) remained free from recurrent arrhythmias.\n\n\nCONCLUSION\nIAS-AT are rare and typically occur in patients with evidence of IAS substrate abnormalities and prior cardiac surgery. Catheter ablation can be challenging and may require sequential unipolar ablation or bipolar ablation.