Background: Intracardiac electrogram recording is influenced by the electrode size and inter-electrode spacing. Smaller electrodes with a closer inter-electrode spacing may improve the mapping resolution and outcome. Methods: Substrate mapping of the left atrium and residual pulmonary vein (PV) potentials during sinus rhythm was sequentially performed using a 3.5-mm electrode tip catheter and a 1-mm electrode multielectrode catheter in 33 patients (Group 1) that underwent repeat atrial fibrillation (AF) procedures. PV gap identification and electrophysiological characteristics were compared. Arrhythmia freedom was compared with a propensity matched (1:2) control group (66 patients, Group 2) undergoing repeat AF procedures guided by wide inter-electrode spacing catheter. Results: In the Group 1 patients, the total area of residual PV potentials measured using the 1-mm catheter was larger than that measured by the 3.5-mm catheter. Overall 1.97 ± 0.59 (1–3) and 1.49 ± 0.62 (1–3) PVs were identified by the 1-mm electrode and 3.5 mm catheters, respectively (P = 0.02). The gaps not identified by the 3.5 mm catheter had a smaller width and lower voltage. Radiofrequency catheter ablation in the areas with residual PV potentials identified by the 1-mm catheter resulted in complete electrical isolation of the PVs. Arrhythmia freedom at one year of follow-up was achieved in 26 of 33 (78.8%) patients in Group 1, which was significantly higher than the matched control group (33/66 [50%], P < 0.05). Conclusion: In the patients with a previous PV isolation, mapping with small, closely spaced electrodes can increase the detection rate of residual PV potentials and improve the outcome.
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