Abstract 5665: Assessment of Noninducibility after Catheter Ablation for Atrial Fibrillation: High Dose Isoproterenol vs Rapid Atrial Pacing

Abstract

Background: Noninducibility of atrial fibrillation (AF) after catheter ablation of paroxysmal AF (PAF) identifies patients who are more likely to remain in sinus rhythm (SR). However, it is not clear whether assessment of noninducibility by rapid atrial pacing (RAP) is incremental to high dose isoproterenol (ISO) infusion. Methods and Results: There were 65 patients (age=56±13 years) with PAF who presented in sinus rhythm for catheter ablation. ISO was administered in escalating doses of 5/10/15/20 μg/min every 2 minutes prior to ablation. AF (or frequent PACs in 4) was inducible in 61/65 patients (94%) at a mean dose of 15±6 μg/min. Antral pulmonary vein (PV) isolation (APVI) was performed in all patients with complete isolation of all PVs. If AF did not terminate during APVI, complex fractionated atrial electrograms (CFAEs) were targeted in the left atrium (16) or coronary sinus (2) until AF terminated or all target sites were ablated. AF terminated during ablation in 41/65 (63%). Following conversion to sinus rhythm, 54 of the 61 patients (89%) who were initially inducible with ISO became noninducible during ISO re-challenge. Among these 54 patients who were noninducible by ISO, rapid atrial pacing (RAP) down to a cycle length of 180 ms (≥5 times) induced sustained AF (>60 seconds) in 17 patients (31%). At a mean follow-up of 9±4 months after a single ablation procedure, 35/54 patients (65%) who were noninducible by ISO and 2/7 patients (29%) who were inducible were in sinus rhythm without antiarrhythmic drugs. However, 11/17 patients (65%) who were inducible by RAP and 26/37 (70%) who were noninducible by RAP were in sinus rhythm without antiarrhyhtmic drug therapy (P=0.8). Conclusions: Noninducibility of AF in response to high dose isoproterenol infusion identifies patients who are more likely to remain in sinus rhythm after catheter ablation. Rapid atrial pacing may still result in induction of AF in 30% of patients who are noninducible by isoproterenol. However, inducibility of AF by rapid atrial pacing in patients who are noninducible by isoproterenol appears to be a nonspecific observation.