Changes in atrial fibrillation cycle length and inducibility during catheter ablation and their relation to outcome.

BACKGROUND: The modification of atrial fibrillation cycle length (AFCL) during catheter ablation in humans has not been evaluated.

METHODS AND RESULTS: Seventy patients undergoing ablation of prolonged episodes of AF were randomized to pulmonary vein (PV) isolation or additional ablation of the mitral isthmus. Mean AFCL was determined at a distance from the ablated area (coronary sinus) at the following intervals: before ablation, after 2- and 4-PV isolations, and after linear ablation. Inducibility of sustained AF (> or =10 minutes) was determined before and after ablation. Spontaneous sustained AF (715+/-845 minutes) was present in 30 patients and induced in 26 (AFCL, 186+/-19 ms). PV isolation terminated AF in 75%, with the number of PVs requiring isolation before termination increasing with AF duration (P=0.018). PV isolation resulted in progressive or abrupt AFCL prolongation to various extents, depending on the PV: to 214+/-24 ms (P<0.0001) when AF terminated and to 194+/-19 ms (P=0.002) when AF persisted. The increase in AFCL (30+/-17 versus 14+/-11 ms; P=0.005) and the decrease in fragmentation (30.0+/-26.8% to 10.3+/-14.5%; P<0.0001) were significantly greater in patients with AF termination. Linear ablation prolonged AFCL, with a greater prolongation in patients with AF termination (44+/-13 versus 22+/-23 ms; P=0.08). Sustained AF was noninducible in 57% after PV isolation and in 77% after linear ablation. At 7+/-3 months, 74% with PV isolation and 83% with linear ablation were arrhythmia free without antiarrhythmics, which was significantly associated with noninducibility (P=0.03) with a recurrence rate of 38% and 13% in patients with and without inducibility, respectively.

CONCLUSIONS: AF ablation results in a decline in AF frequency, with a magnitude correlating with termination of AF and prevention of inducibility that is predictive of subsequent clinical outcome.