Localized reentry within the left atrial appendage: arrhythmogenic role in patients undergoing ablation of persistent atrial fibrillation

Abstract

Background: Left atrial appendage (LAA) is implicated in maintenance of atrial fibrillation (AF) and atrial tachycardia (AT) associated with persistent AF (PsAF) ablation, although little is known about the incidence and mechanism of LAA AT.

Objective: The purpose of this study was to characterize LAA ATs associated with PsAF ablation.

Methods: In 74 consecutive patients undergoing stepwise PsAF ablation, 142 ATs were encountered during index and repeat procedures. Out of 78 focal-source ATs diagnosed by activation and entrainment mapping, 15 (19%) arose from the base of LAA. Using a 20-pole catheter, high-density maps were constructed (n = 10; age 57 ± 6 years) to characterize the mechanism of LAA-AT. The LAA orifice was divided into the posterior ridge and anterior-superior and inferior segments to characterize the location of AT.

Results: Fifteen patients with LAA AT had symptomatic PsAF for 17 ± 15 months before ablation. LAA AT (cycle length [CL] 283 ± 30 ms) occurred during the index procedure in four and after 9 ± 7 months in 11 patients. We could map 89% ± 8% AT CLs locally with favorable entrainment from within the LAA, which is suggestive of localized reentry with centrifugal atrial activation. ATs were localized to inferior segment (n = 4), anterior-superior segment (n = 5), and posterior ridge (n = 6) with 1:1 conduction to the atria. Ablation targeting long fractionated or mid-diastolic electrogram within the LAA resulted in tachycardia termination. Postablation, selective contrast radiography demonstrated atrial synchronous LAA contraction in all but one patient. At 18 ± 7 months, 13/15 (87%) patients remained in sinus rhythm without antiarrhythmic drugs.

Conclusion: LAA is an important source of localized reentrant AT in patients with PsAF at index and repeat ablation procedures. Ablation targeting the site with long fractionated or mid-diastolic LAA electrogram is highly effective in acute and medium-term elimination of the arrhythmia.

Figure 1

A: Location of LAA AT. In this posteroanterior fluroscopic view of the LA with contrast opacified LAA, the location of each AT is marked with an asterisk on the segment of LAA involved. All the ATs are located at the base of the LAA: four at the inferior segment, six at the posterior ridge, and five at the anterior-superior segment. B: P-wave morphology of LAA AT. Typical P-wave morphology of LAA AT from three patients, showing positive polarity in lead V1 and an inferior axis in the frontal leads.

Figure 2

Ablation of LAA AT. Fluroscopic views of the ablation catheter and transseptal sheath to reach the posterior ridge are demonstrated. Ablation was typically commenced along the collar of the LAA either by (1) entering directly into the LAA along its long axis, turning the catheter with a clockwise rotation, and pulling back the catheter to the base (A); or (2) rotating both the sheath and the catheter posteriorly (perpendicular; B). PA: posteroanterior; LAO: left anterior oblique; RAO: right anterior oblique.

Figure 3

Electroanatomical isochronal maps demonstrating centrifugal activation of the LA from the LAA AT. The numbers against PPI show the difference between PPI and TCL at the local site of entrainment mapping. PPI: postpacing interval; TCL: tachycardia CL; LPV: left superior pulmonary vein; LAT: local activation time.

Figure 4

At the site of successful ablation of AT, marked conduction abnormality with low-amplitude, fractionated, and multicomponent electrograms was recorded during sinus rhythm (pacing).

Figure 5

Mapping and ablation of localized reentry from the LAA. A: A long fractionated signal can be seen on bipole C11-12, representing >70% of the tachycardia CL. The ablation catheter was then moved to this area (B), and ablation terminated the tachycardia within few seconds (C).

Figure 6

Two examples of entrainment from the LAA. Tachycardia entrainment from the LAA site demonstrates that the postpacing interval (PPI) = tachycardia CL (TCL), with the same activation sequence during pacing and tachycardia.

Figure 7

Left-hand panel intracardiac tracings on the PentaRay catheter show >70% of tachycardia CL recorded on bipole Ap. Right-hand panel: fluoroscopic image demonstrating the relative positions of the PentaRay catheter and the ablation catheter in the LAA. The roving ablation catheter is mapping the localized reentrant circuit to find the critical isthmus (long fractionated signal) located at the bipole Ap for ablation.