Significant reduction of atrial defibrillation threshold and inducibility by catheter ablation of atrial fibrillation

Background: Radiofrequency catheter ablation (RFCA) of atrial fibrillation (AF) has antiarrhythmic effects by multiple mechanisms. We hypothesized that RFCA curtails atrial defibrillation threshold (A-DFT) and postablation induction pacing cycle length (iPCL), making critical mass reduction one potential mechanism by which antiarrhythmic effect is achieved. Methods: We included 289 patients with AF (male 77.9%, 55.7 ± 10.8 years old; 197 paroxysmal AF: 92 persistent AF) who underwent RFCA. A-DFT (serial internal cardioversion 2, 3, 5, 7, and 10 J) and iPCL (serial 10 mA 10-second atrial pacing with pacing cycle length 250, 200, 190, 180, 170, 160, and 150 ms) were evaluated before and after RFCA. Results: (1) RFCA of AF reduced the A-DFT from 6.7 ± 3.7 J to 3.0 ± 3.0 J (P < 0.001). (2) AF ablation reduced AF inducibility from 95.4% before the procedure to 56.3% after the procedure (P < 0.001), and the iPCL from 194.8 ± 32.6 to 160.9 ± 26.2 ms (P < 0.001). (3) In patients who underwent a greater number of ablation lines, the post-RFCA A-DFT (P < 0.001) was lower, and %ΔA-DFT (P = 0.003) and proportion of atrial tachycardia (P = 0.022) were higher than those with a lower number of ablation lines. Conclusion: AF ablation significantly reduced A-DFT, AF inducibility, and iPCL, and the degree of their reduction was related to the number of ablation lines. (PACE 2012;35:1428-1435)