A Dual-Loop Figure-8 Reentry Left Atrial Flutter

Introduction

Typical right atrial isthmus-dependent flutter (Type 1 atrial flutter) has been extensively studied, but little data is available on the mapping of atypical left atrial (LA) flutters. Atypical LA flutters are commonly seen after catheter ablation for atrial fibrillation (AF). A dual-loop figure-8 macro-reentry atrial flutter (AFL) is an atypical AFL, which consists of two re-entry circuit loops in left atrium connected via an isthmus.

Case Report

A 65-year-old male was admitted to our hospital for elective catheter ablation for persistent refractory atypical AFL. He had a history of coronary artery disease (CAD), hypertension, and dyslipidemia. He was a former smoker with more than a 50-pack/year smoking history. For more than three years, he had severely symptomatic persistent AF refractory to antiarrhythmic drugs (AAD) including amiodarone and DC cardioversion. The patient underwent successful radiofrequency (RF) ablation for AF, including pulmonary vein isolation (PVI) and ablation of Type 1 AFL. Post procedure, he developed persistent atypical AFL. The patient was severely symptomatic with this atypical AFL, and it was resistant to treatment with chemical and electrical cardioversion. Amiodarone was restarted, but he continued to be very symptomatic and developed significant limiting side effects from the amiodarone therapy. Prior to the procedure, an echocardiogram showed a moderately increased left atrial volume index of 33–39 ml/m².

The procedure was performed under the guidance of a three-dimensional mapping system (EnSite, St. Jude Medical). Prior to entering the LA, the right atrium (RA) was mapped using EnSite, showing early activation at the septum. The RA points accounted for 60% of the flutter cycle length. Transseptal access, EnSite, and a circular catheter were used to map the LA flutter. The propagation map after 100 activation points demonstrated figure-8 reentry with an isthmus anteriorly near the right superior pulmonary vein (RSPV). One loop encircled the mitral valve and the other encircled the right pulmonary veins (Figure 1). Entrainment mapping was performed during the procedure. The longer post-pacing intervals (PPI) in the RA led to mapping in the LA. The shortest PPIs were obtained in the region anterior to the RSPV (Figure 2). Focal RF ablation at the isthmus of the two circuits initially slowed and organized the flutter (Figure 3). A second lesion terminated the flutter, restoring sinus rhythm (Figure 4). Burst pacing from the LA failed to induce any atrial arrhythmia afterwards. Since the procedure was successful, amiodarone was discontinued. Warfarin therapy was continued for three months. The patient has been asymptomatic and has stayed in sinus rhythm on follow-up evaluation. 

Discussion

Dual-loop reentry AFL is defined as concomitance of two simultaneously documented loops, each meeting the definition of reentry.¹ Double-loop reentry AFL was reported to be frequent late after open-heart correction of congenital heart disease, or post-AF ablation patients.^2,3

Pulmonary vein isolation is the cornerstone for catheter ablation of AF.⁴ In a worldwide survey, catheter ablation proved curative in 52.0% of patients in the absence of any AAD and in an additional 23.9% of patients with the use of formerly ineffective AADs. Up to 27.3% of patients had recurrent arrhythmia requiring redo ablation.⁵ A recent report focusing on PV electrical disconnection has shown that up to 80% of disconnected PVs may have reconnected some months after the first procedure.⁷ However, LA flutter is another mechanism of recurrent atrial arrhythmia in these patients. A new-onset atypical atrial flutter was reported in 3.9% of patients.⁵ The occurrence of this arrhythmia late after ablation may be associated with very symptomatic palpitations and represent a difficult challenge for curative treatment.⁶ Jaïs et al described different types of circuits in atypical left AFLs in 22 patients. Only 1 out of 22 patients had a figure-8 macro-reentrant circuit that required extensive ablation lesions to break the circuit. In our case, the patient had undergone RF ablation for AF, but the dual-loop figure-8 reentry loop was found distinct from the previous lesions. The figure-8 loops had an isthmus anteriorly near the RSPV. The unique aspect about this case is the detailed mapping, which allowed specific localization of the culprit focus, i.e. the isthmus between the two loops. Focal RF ablation of the isthmus terminated the flutter, thus minimizing the large areas of atrial damage that occur during conventional ablation. We propose that it is important to map and identify the circuits for atypical left AFLs. It requires more time relative to conventional mapping, but once the culprit focus is accurately identified, limited lesions can successfully terminate these symptomatic and resistant flutters.

Conclusion

Atypical left atrial flutters are common after catheter ablation for AF. They can be very symptomatic and resistant to AADs. These should be extensively mapped, as limited lesion sets placed at the isthmus of the loops can terminate the flutter.  

Disclosure: Drs. Kumar and Kocheril have no conflicts of interest to report. 

References

1. Shah D, Jaïs P, Takahashi A, et al. Dual-loop intra-atrial reentry in humans. Circulation. 2000;101(6):631-639.
2. Chae S, Oral H, Good E, et al. Atrial tachycardia after circumferential pulmonary vein ablation of atrial fibrillation: mechanistic insights, results of catheter ablation, and risk factors for recurrence. J Am Coll Cardiol. 2007;50(18):1781-1787.
3. Szili-Torok T, Kornyei L, Jordaens LJ. Transcatheter ablation of arrhythmias associated with congenital heart disease. J Interv Card Electrophysiol. 2008;22:161-166.
4. Calkins H, Kuck KH, Cappato R, et al. 2012 HRS/EHRA/ECAS Expert Consensus Statement on Catheter and Surgical Ablation of Atrial Fibrillation: recommendations for patient selection, procedural techniques, patient management and follow-up, definitions, endpoints, and research trial design. Europace. 2012;14(4):528-606. 
5. Cappato R, Calkins H, Chen SA, et al. Worldwide survey on the methods, efficacy, and safety of catheter ablation for human atrial fibrillation. Circulation. 2005;111(9):1100-1105.
6. Jaïs P, Shah DC, Haïssaguerre M, et al. Mapping and ablation of left atrial flutters. Circulation. 2000;101:2928-2934.
7. Cappato R, Negroni S, Pecora D, et al. Prospective assessment of late conduction recurrence across radiofrequency lesions producing electrical disconnection at the pulmonary vein ostium in patients with atrial fibrillation. Circulation. 2003;108:1599-1604.