Characteristics of Atrial Tachycardia due to Small versus Large Reentrant Circuits after Ablation of Persistent Atrial Fibrillation.
Division of Cardiovascular Medicine, University of Michigan, Ann Arbor, Michigan, USA.Heart rhythm: the official journal of the Heart Rhythm Society (Impact Factor: 5.08). 12/2012; 10(4). DOI: 10.1016/j.hrthm.2012.12.018
BACKGROUND: While macro-reentrant atrial tachycardias (AT) have been reasonably well described, little is known about small reentrant circuits. OBJECTIVE: The goal of the study was to compare characteristics of large and small reentrant circuits after ablation of persistent atrial fibrillation (AF). METHODS: Seventy-seven patients (age=61±10 years; LA=46±6 mm; EF=0.52±0.13) underwent a procedure for post-ablation AT. The p-wave duration, circuit size, electrogram characteristics, and conduction velocity were determined. RESULTS: AT was due to macro-reentry in 62 patients (80%), 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 macro-reentry (174±12 vs. 226±22 ms; p<0.0001). The duration of fractionated electrograms at the critical site was longer in small vs. large circuits (167±43 vs. 98±38 ms, respectively, p<0.0001), and accounted for a greater percentage of the tachycardia cycle length (59±18 vs. 38±14%, respectively, p<0.0001). The mean diameters of macro-reentrant vs. small reentrant circuits were 44±7 and 26±11 mm, respectively (p<0.0001). The mean conduction velocity along the small circuits was lower (0.5±0.2 vs. 1.2±0.3 m/s, p<0.0001). Catheter ablation eliminated the AT in all 77 patients. CONCLUSIONS: AT due to a small reentrant circuit after ablation of AF may be distinguished from macro-reentry 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 mapping of post-ablation ATs.
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ABSTRACT: Low conduction velocity (CV) in the area showing low electrogram amplitude (EA) is characteristic of reentry circuit of atypical atrial flutter (AFL). The quantitative relationship between CV and EA remains unclear. We characterized AFL reentry circuit in the right atrium (RA), focusing on the relationship between local CV and bipolar EA on the circuit. We investigated 26 RA AFL (10 with typical AFL; 10 atypical incisional AFL; 6 atypical nonincisional AFL) using CARTO system. By referring to isochronal and propagation maps delineated during AFL, points activated faster on the circuit were selected (median, 7 per circuit). At the 196 selected points obtained from all patients, local CV measured between the adjacent points and bipolar EA were analyzed. There was a highly significant correlation between local CV and natural logarithm of EA (lnEA) (R(2) = 0.809, P < 0.001). Among 26 AFL, linear regression analysis of mean CV, calculated by dividing circuit length (152.3 ± 41.7 mm) by tachycardia cycle length (TCL) (median 246 msec), and mean lnEA, calculated by dividing area under curve of lnEA during one tachycardia cycle by TCL, showed y = 0.695 + 0.191x (where: y = mean CV, x = lnEA; R(2) = 0.993, P < 0.001). Local CV estimated from EA with the use of this formula showed a highly significant linear correlation with that measured by the map (R(2) = 0.809, P < 0.001). The lnEA and estimated local CV show a highly positive linear correlation. CV is possibly estimated by EA measured by CARTO mapping.
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ABSTRACT: In the genesis of flutter as well or any reentrant tachycardia, substrate is a critical component. Reentry may result from myocardial disease or anatomical anomalies. Seminal works brought the clinical proof that partially scarred areas are localized by low-voltage and are associated with local slowing of conduction. This article is protected by copyright. All rights reserved.
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