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 ( greater than or equal to 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.