Acute termination of human atrial fibrillation by identification and catheter ablation of localized rotors and sources: first multicenter experience of focal impulse and rotor modulation (FIRM) ablation

Abstract

Introduction: Catheter ablation of atrial fibrillation (AF) currently relies on eliminating triggers, and no reliable method exists to map the arrhythmia itself to identify ablation targets. The aim of this multicenter study was to define the use of Focal Impulse and Rotor Modulation (FIRM) for identifying ablation targets.

Methods: We prospectively enrolled the first (n = 14, 11 males) consecutive patients undergoing FIRM-guided ablation for persistent (n = 11) and paroxysmal AF at 5 centers. A 64-pole basket catheter was used for panoramic right and left atrial mapping during AF. AF electrograms were analyzed using a novel system to identify sustained rotors (spiral waves), or focal beats (centrifugal activation to surrounding atrium). Ablation was performed first at identified sources. The primary endpoints were acute AF termination or organization (>10% cycle length prolongation). Conventional ablation was performed only after FIRM-guided ablation.

Results: Twelve out of 14 cases were mapped. AF sources were demonstrated in all patients (average of 1.9 ± 0.8 per patient). Sources were left atrial in 18 cases, and right atrial in 5 cases, and 21/23 were rotors. FIRM-guided ablation achieved the acute endpoint in all patients, consisting of AF termination in n = 8 (4.9 ± 3.9 minutes at the primary source), and organization in n = 4. Total FIRM time for all patients was 12.3 ± 8.6 minutes.

Conclusions: FIRM-guided ablation revealed localized AF rotors/focal sources in patients with paroxysmal, persistent and longstanding persistent AF. Brief targeted FIRM-guided ablation at a priori identified sites terminated or substantially organized AF in all cases prior to any other ablation.

© 2012 Wiley Periodicals, Inc.

Figures

Figure 1

FIRM Guided Ablation Work Flow (in lab)

Figure 2. Fluoroscopic Views of Basket Data Acquisition in

(A) Right Atrium, RAO 30° projection with circular catheter in left atrium, multipolar catheters in the coronary sinus and the His position. (B) Left atrium, LAO 30° projection

Figure 3. FIRM at Left Atrial Rotor Terminates Paroxysmal AF To Sinus Rhythm in 4 minutes (patient 5)

(A) AF with CL 180 ms, illustrating sequential activation at electrode locations spanning the rotor center. (B) Left atrial roof rotor represented in this isochronal snapshot by clockwise activation sequence (red to blue). Clinical mapping was guided by the propagation movie (Supplemental movie 1) that shows this spiral wave with slight movement (precession) of its center of rotation bounded by 1–2 electrodes. (C) FIRM at Rotor alone terminates AF to Sinus Rhythm in 4 minutes, prior to any other ablation. AF was now noninducible despite burst pacing and high dose isoproterenol.

Figure 4. Left Atrial Rotor During Human Atrial Fibrillation, Where FIRM Ablation Terminates AF to Sinus Rhythm (patient 9)

(A) Isochrones show AF Rotor with activation sequence from red to blue (CL 160 ms, clockwise). Note wavebreak and collision within the left atrium indicating breakdown of 1:1 activation from rotor (double white lines). (B) AF Termination to sinus rhythm by FIRM ablation (10 minutes). Panels C (Ablation catheter and basket in left atrium) and D (circular PV catheter and ablation catheter) LAO view

Figure 5. FIRM Terminates AF to sinus rhythm (patient 13)

(A) Isochrones show 2 small rotors in the left atrium during AF, both with small space constants in the superior and inferior septal left atrium. (B) FIRM Ablation at the inferoseptal LA rotor, posteroinferior to the right inferior pulmonary vein, at 40W rapidly terminated AF to sinus rhythm in less than one minute. AF was now non-inducible.

Figure 6. FIRM Terminates AF (CL 178 ms) in this patient with persistent AF and LA diameter 75 mm (patient 14)

(A) Isochrones show 2 rotors in the left atrium and one focal source (indicated). Supplemental movie 2 illustrates these complex dynamics, and was used to guide FIRM ablation. FIRM at each rotor prolonged AF CL from 178 to 220 ms. (B) FIRM Ablation at the focal beat terminated AF to atrial tachycardia (CL 240 ms). Total FIRM time was 10 minutes, prior to pulmonary vein or any other ablation.

Figure 7. Schematic showing locations of Rotors and Focal sources in 12 patients

Key: RA, LA, right and left atria; MV, mitral valve; TV, tricuspid valve; RAA, LAA, right and left atrial appendages; LSPV, LIPV, left superior and inferior pulmonary veins; RSPV, RIPV, right superior and inferior pulmonary veins; SVC, superior vena cava; IVC, inferior vena cava. Rotors were defined as areas where activation completed multiple clockwise or counterclockwise rotations. Focal beats were identified as sites with centrifugal activation to surrounding atrium, and their origins identified at the electrodes where activation initiated. For both definitions the pattern needed to be sustained over multiple 4–8 second epochs.