Rotors of truly atypical atrial flutters visualized by FIRM mapping and 3D-MRI overlay on live fluoroscopy
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Rotors of two different left atrial flutters were mapped using focal impulse and rotor modulation and 3D-MRI overlayed on live fluoroscopy and were successfully ablated in a patient with two prior left-atrium ablation procedures for recurrent atrial fibrillation.
KeywordsFocal Impulse and Rotor Modulation Atrial Flutter MRI Overlay Mapping Ablation
A common sequel to atrial fibrillation (AF) ablation is atypical atrial flutters which frequently require lengthy ablations. A 61-year-old male presented with recurrent persistent AF after two prior ablation procedures (pulmonary vein isolation and roof line) and underwent a repeat ablation of two atypical atrial flutters. Both arrhythmias, induced from the left atrium (LA) through rapid atrial pacing, were mapped and ablated using the focal impulse and rotor modulation (FIRM) method. A multipolar basket and standard ablation catheters were positioned under X-ray guidance and 3D-MRI LA shell overlaid on live fluoroscopy (figure panel A, Online Resource 1). Simultaneous activation mapping of 64 points in the LA during the first induced atrial flutter (cycle length (CL) 220 ms) demonstrated a pattern of atypical roof-dependent reentry around the previously created roof line (figure panel C, Online Resource 2) with two breakthrough points at splines CD23 (lateral gap, red asterisk) and CD67 (medial gap, yellow asterisk; figure panels C and D). The wave front moved from the interatrial septum at the posterior LA wall and in the opposite direction on the anterior wall using two gaps in the previously created roof ablation line. Conventional activation mapping showed high-to-low activation of both anterior and posterior LA walls proving a truly atypical mechanism of this flutter. Entrainment mapping was considered likely to terminate the arrhythmia and was thus not performed. Ablation at the lateral gap modified the first flutter (CL lengthened to 280 ms and the activation sequence changed). This arrhythmia terminated after ablation at the medial gap (figure panel B). A second flutter (CL 200 ms) was induced by rapid atrial pacing, and FIRM mapping demonstrated a separate rotor on the posterior wall with centrifugal activation (green spiral—figure panel D; white arrows—figure panel E, Online Resource 3). Ablation at the second rotor (figure panels D and E) terminated that arrhythmia. Repeat attempts to re-induce the arrhythmia were unsuccessful. FIRM and total ablation times were 13.0 and 15.3 min.
In conclusion, two different LA flutters were mapped using FIRM and 3D-MRI overlayed on live fluoroscopy and were successfully ablated in a patient with two prior LA ablation procedures for recurrent persistent AF.
Dr. Michael Orlov has received research grant support and is on the advisory board of Philips Healthcare.
Conflict of interest
The authors do not have any financial relationship with the organization that sponsored the research (Topera Inc., San Diego, CA).
Basket mapping catheter deployment into the LA under the guidance of a 3D-MRI of the LA (blue shell) overlayed on live fluoroscopy in AP view. The ablation catheter and transseptal sheath are seen in the LA via a single transseptal approach. The CS catheter is also shown. Registration of the LA shell on live fluoroscopy is performed using the bronchial carina (yellow) as an anatomic reference. The LA appendage is shown in light blue. (MPG 3942 kb)
Dynamic FIRM map of the truly atypical roof dependent atrial flutter shows a reentry circuit around the LA roof line (as indicated) with two gaps: lateral (sector CD2-3) and septal (sector CD7-8). The activation wavefront direction is counterclock-wise. Sept – septal LA, lat – lateral LA. (MPG 2310 kb)
Dynamic FIRM map of the second atypical atrial flutter shows a rotor (as indicated) in sector E2. The activation wavefront direction is clock-wise. (MPG 2149 kb)