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 (≥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.