Persistent Atrial Fibrillation Ablation beyond Pulmonary Vein Isolation – A Case-Report

AUTHORS: Decebal Gabriel Laţcu, MD, Ahmed Mostfa Wedn, MD, Fatima Benaich, MD, Karim Wasni, MD, Bogdan Enache, MD, Sok-Sithikun Bun, MD, Nadir Saoudi, MD, FHRS

Authors’ institution: Centre Hospitalier Princesse Grace, Monaco

Corresponding author and/or reprint requests:

Dr. Decebal Gabriel Latcu
Cardiologie, Centre Hospitalier Princesse Grace
Avenue Pasteur
98000, MONACO
Phone: +377 97 98 97 71
Fax: +377 97 98 97 32
Email: dglatcu@yahoo.com

Abstract.

We report a case of longstanding persistent atrial fibrillation ablation using the ultra-high density mapping system (Rhythmia^TM). Activation mapping in case of atrial fibrillation is mainly reported with panoramic mapping systems. Beyond circumferential pulmonary vein isolation, selection of appropriates targets for ablation is performed by sequential activation mapping. Potential drivers of atrial fibrillation are identified with successful ablation.

Keywords: ultra-high density mapping, persistent atrial fibrillation, drivers

Case report.

A 69-year-old woman was admitted for catheter ablation of highly symptomatic, drug refractory, longstanding atrial fibrillation (AF). AF has been diagnosed 5 years ago, and after the first year AF became persistent. The patient refused rhythm control until 6 months before the procedure, when her symptoms became uncontrolled by the rate-lowering medication. A cardioversion briefly restored, for less than 24 hours, the sinus rhythm, but AF immediately recurred despite amiodarone (200 mg daily after a loading dose of 30 mg/kg). The patient had a previous medical history of transient ischemic attack and was treated for hypertension. Thus her CHA₂DS₂-VASc score was 5. Her weight was normal (body mass index 24 kg/m²) and she didn’t have sleep apnoea. Preoperative imaging (CT-scan) revealed important left atrial (LA) dilation: 163 ml (91.6 ml/m²), but her left ventricular function was normal.

Under general anaesthesia, by right femoral vein access, a decapolar catheter was inserted in the coronary sinus; by transseptal puncture were inserted in the LA: an Orion IntellaMap catheter (Boston Scientific, Cambridge, MA) and a Tacticath Quartz 65 catheter (St Jude Medical). In the beginning of the procedure, the patient was in AF (figure 1A); the mean cycle length of the left atrial appendage (LAA) activation was 160 ms.

Figure 1. A. Surface ECG and LAA EGM in the beginning of the procedure. B. LA map performed in AF with the Orion catheter. Black dots represent the sites with CFAE EGM’s and red tags correspond to ablation sites for CPVI. C. Surface ECG and LAA EGM after CPVI, showing organization of AF and LAA CL prolongation. LAA: left atrial appendage; EGM: electrograms; LA: left atrium; AF: atrial fibrillation; CFAE: fragmented bipolar EGM; CPVI: circumferential antral pulmonary vein isolation. CL: cycle length; AP: antero-posterior; PA: postero-anterior.

Mapping of the LA (figure 1B) was performed in AF with the Orion catheter. All the sites with visually fragmented bipolar electrograms (EGM; > 3 deflections; CFAE) were manually tagged (black dots, figure 1B). Completeness of the mapping was ensured by merging the map with the 3D CT-scan reconstruction. Circumferential antral pulmonary vein isolation (CPVI) was performed in a point-by-point manner with contiguous lesions (25 to 35 W, figure 1B) encompassing, when possible, the CFAE sites previously tagged. The catheter-tissue contact was optimized for each site and the target force-time integral was 400 gs. At the end of the antral CPVI, a significant prolongation of the mean CL was obtained, with a more organized AF on the surface ECG (figure 1C).

Remapping of the LA was than performed, by defining as timing reference the left atrial appendage (LAA) EGM. Mapping criteria used were described in detail elsewhere.¹ In brief, the stable relative timing of two reference EGM was not used, neither was the EGM stability, but electrode location stability and respiratory gating were still used (these distinguishes AF mapping from organized tachycardia mapping²). Selection of the surface EGM was based on a 3 mm “projection distance”.

Activation mapping of AF (25580 EGM, mapping time 22 minutes) showed potential drivers of AF (figure 2): rotating sites with highly-fragmented potentials in the middle of the rotation as well as focal sites with centrifugal activation. Pulmonary veins were disconnected. Radiofrequency delivery (2 to 3 applications for each site) for a total of 750 s, stopped AF by transformation into a roof-dependent atrial macro-re-entry (figure 3A). No ablation was performed at the CFAE sites for which propagation suggested wavefront collision.

Figure 2. Activation mapping of AF shows potential drivers: rotating sites with highly-fragmented potentials in the middle of the rotation as well as focal sites with centrifugal activation. AP: antero-posterior; PA: postero-anterior; EGM: electrogram.

Subsequent ablation of the roof (with a line) changed the tachycardia into a counterclockwise perimitral flutter (figure 3B). Ablation at the mitral isthmus and inside the distal coronary sinus prolonged the CL, and finally an anterior line allowed resumption of sinus rhythm. No complication occurred. Follow-up is ongoing, without AF recurrence at 3 months.

Figure 3. A. Roof-dependent atrial macro-re-entry. B. Counter clockwise perimitral flutter. AT: atrial tachycardia; CL: cycle length; MI: mitral isthmus; SR: sinus rhythm; AP: antero-posterior; PA: postero-anterior; EGM: electrogram.

Discussion.

Pulmonary vein isolation is still the cornerstone of ablation of all forms of AF^3,4. Nevertheless, experimental and clinical studies showed that stable re-entrant drivers are the key mechanism or maintenance of atrial fibrillation (AF).^5,6,7 Panoramic endocardial (simultaneous, whole chamber) ^8,9 and non-invasive body surface epicardial mapping¹⁰ have been proposed as clinical tools for rotor/driver site identification, with debatable results.^11,12,7 Local mapping of consistent radial activation sequences,¹³ of small-radius rotor-like re-entry,^14,15 or of clusters of EGM with spatiotemporal dispersion¹⁶ brought indirect proof that foci and re-entrant drivers may be visualized also with sequential techniques.

The ultra-high density (UHD) mapping system (Rhythmia^TM) is increasingly used for the mapping of organized tachycardias.¹⁷ Cardiac mapping is performed in a sequential manner using the dedicated 64-electrode basket catheter (IntellaMap Orion^TM, Boston Scientific) which incorporates very small unidirectional electrodes (0.4 mm²; 2.5 mm spacing) in order to suppress noise and farfield signals.¹⁸ Multi-electrode acquisition and highly reliable automatic annotation yield maps with a previously unattained resolution.^{18,19,20,21 We previously reported the first case of sequential UHD activation mapping of AF with Rhythmia, indicating a focal source, with successful ablation.1}

This new report shows that, beyond pulmonary vein isolation, drivers of persistent AF cans be successfully mapped and their ablation is successful for stopping AF. Subsequent atrial tachycardias can be accurately mapped and ablated with the Rhythmia system, up to the resumption of the sinus rhythm.

Conclusion.

Beyond pulmonary vein isolation, ablation of persistent AF may target extra-venous drivers. In this case, sequential ultra-high density activation mapping of AF using Rhythmia^TM revealed a limited number of rotating activation sites and foci with centrifugal activation; their ablation resulted in AF conversion to atrial tachycardia and finally restauration of sinus rhythm.

Conflict of interest: Dr. Latcu and Dr. Bun received during the last year speaking honoraria from Boston Scientific.

El contenido de este artículo es responsabilidad únicamente del autor y no representa la opinión de Boston Scientific

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