Localized sources maintaining atrial fibrillation organized by prior ablation

• Background— Endocardial mapping of localized sources drivingatrial fibrillation (AF) in humans has not been reported.Methods and Results— Fifty patients with AF organizedby prior pulmonary vein and linear ablation were studied. AFwas considered organized if mapping during AF showed irregularbut discrete atrial complexes exhibiting consistent activationsequences for >75% of the time using a 20-pole catheter with5 radiating spines covering 3.5-cm diameter or sequential conventionalmapping. A site or region centrifugally activating the remainingatrial tissue defined a source. During AF with a cycle lengthof 211±32 ms, activation mapping identified 1 to 3 sourcesat the origin of atrial wavefronts in 38 patients (76%) predominantlyin the left atrium, including the coronary sinus region. Electrogramsat the earliest area varied from discrete centrifugal activationto an activity spanning 75% to 100% of the cycle length in 42%of cases, the latter indicating complex local conduction ora reentrant circuit. A gradient of cycle length (>20 ms)to the surrounding atrium was observed in 28%. Local radiofrequencyablation prolonged AF cycle length by 28±22 ms and eitherterminated AF or changed activation sequence to another organizedrhythm. In 4 patients, the driving source was isolated, surroundedby the atrium in sinus rhythm, and still firing at high frequency(228±31 ms) either permanently or in bursts.Conclusions— AF associated with consistent atrial activationsequences after prior ablation emanates mostly from localizedsources that can be mapped and ablated. Some sources harborelectrograms suggesting the presence of localized reentry.

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