Characteristics of atrial tachycardia due to small vs large reentrant circuits after ablation of persistent atrial fibrillation.

While macroreentrant atrial tachycardias (ATs) have been reasonably well described, little is known about small reentrant circuits.To compare characteristics of large and small reentrant circuits after ablation of persistent atrial fibrillation.Seventy-seven patients (age 61±10 years; left atrium 46±6 mm; ejection fraction 0.52±0.13) underwent a procedure for postablation AT. The p-wave duration, circuit size, electrogram characteristics, and conduction velocity were determined.AT was due to macroreentry in 62 (80%) patients, a small reentrant circuit in 13 (17%), and a focal mechanism in 2 (3%). The p-wave duration during small reentrant ATs was shorter than that during macroreentry (174±12 ms vs 226±22 ms; P<.0001). The duration of fractionated electrograms at the critical site was longer in small vs large circuits (167±43 ms vs 98±38 ms, respectively; P<.0001) and accounted for a greater percentage of the tachycardia cycle length (59%±18% vs 38%±14%, respectively; P<.0001). The mean diameters of macroreentrant and small reentrant circuits were 44±7 and 26±11 mm, respectively (P<.0001). The mean conduction velocity along the small circuits was lower (0.5±0.2 m/s vs 1.2±0.3 m/s; P<.0001). Catheter ablation eliminated the AT in all 77 patients.AT due to a small reentrant circuit after ablation of atrial fibrillation may be distinguished from macroreentry by a shorter p-wave duration and the presence of long-duration electrograms at the critical site owing to extremely slow conduction. These features may aid the clinician in the mapping of postablation ATs.