Direct or coincidental elimination of stable rotors or focal sources may explain successful atrial fibrillation ablation: on-treatment analysis of the CONFIRM trial (Conventional ablation for AF with or without focal impulse and rotor modulation)

Abstract

Objectives: This study sought to determine whether ablation of recently described stable atrial fibrillation (AF) sources, either directly by Focal Impulse and Rotor Modulation (FIRM) or coincidentally when anatomic ablation passes through AF sources, may explain long-term freedom from AF.

Background: It is unclear why conventional anatomic AF ablation can be effective in some patients yet ineffective in others with similar profiles.

Methods: The CONFIRM (Conventional Ablation for AF With or Without Focal Impulse and Rotor Modulation) trial prospectively revealed stable AF rotors or focal sources in 98 of 101 subjects with AF at 107 consecutive ablation cases. In 1:2 fashion, subjects received targeted source ablation (FIRM) followed by conventional ablation, or conventional ablation alone. We determined whether ablation lesions on electroanatomic maps passed through AF sources on FIRM maps.

Results: Subjects who completed follow-up (n = 94; 71.2% with persistent AF) showed 2.3 ± 1.1 concurrent AF rotors or focal sources that lay near pulmonary veins (22.8%), left atrial roof (16.0%), and elsewhere in the left (28.2%) and right (33.0%) atria. AF sources were ablated directly in 100% of FIRM cases and coincidentally (e.g., left atrial roof) in 45% of conventional cases (p < 0.05). During a median (interquartile range) of 273 days (138 to 636 days) after one procedure, AF was absent in 80.3% of patients if sources were ablated but in only 18.2% of patients if sources were missed (p < 0.001). Freedom from AF was highest if all sources were ablated, intermediate if some sources were ablated, and lowest if no sources were ablated (p < 0.001).

Conclusions: Elimination of stable AF rotors and focal sources may explain freedom from AF after diverse approaches to ablation. Patient-specific AF source distributions are consistent with the reported success of specific anatomic lesion sets and of widespread ablation. These results support targeting AF sources to reduce unnecessary ablation, and motivate studies on FIRM-only ablation.

Trial registration: ClinicalTrials.gov NCT01008722.

Figure 1. Focal Impulse and Rotor Mapping (FIRM) of AF Sources

(A) Fluoroscopy of Biatrial 128 electrode wide-field of view mapping in AF (Right Atrial Oblique projection). An implantable continuous ECG recorder, diagnostic catheter in the coronary sinus, ablation catheter in the left atrium and esophageal temperature probe are also seen. (B) FIRM Maps Show Two Independent Sources: an AF Rotor in an unconventional lateral right atrial location and a concurrent left atrial focal source. Orientation right atrium: Top, superior vena cava; Left, lateral tricuspid. Left atrium: Top, superior mitral annulus; Left, septal. (C) AF Rotor in Lateral RA on Patient-Specific Electroanatomic shell (same patient as figure 1B).

Figure 2. AF Sources Remote from Conventional Ablation Sites

(A) AF rotor (clockwise, 3.2 cm²) in Inferior Left atrium in an 85 year old with paroxysmal AF. (B) AF focal source (2.0 cm²) in mid-posterior left atrium in a 64 year old with PAF. (C) AF focal source (1.8 cm²) in anterior left atrium (anterior to typical roof line) in a 48 year old with persistent AF. All cases received FIRM-guided ablation, and are AF-free on implanted cardiac monitoring at > 1 year. Orientations for FIRM maps as in figure 1B.

Figure 3. AF Focal Impulse and Rotor Locations in the CONFIRM trial, as a % of all sources for each AF type: (A) Paroxysmal AF; (B) Persistent AF

Focal impulses indicated by stars, rotors by circles. Key: IVC, SVC = inferior, superior vena cavae; LAA, RAA = left, right atrial appendages; LSPV=Left Superior Pulmonary vein; LIPV = Left Inferior Pulmonary vein; RSPV=right superior pulmonary vein; RIPV=right inferior pulmonary vein.

Figure 4. AF Rotors Near Conventional Ablation Targets

(A) Left atrial AF rotor successfully ablated by FIRM, that was then incorporated into left wide-area circumferential PV ablation. (B) Two left atrial AF rotors, each successfully ablated by FIRM. The superior rotor was incorporated into the left wide-area circumferential PV ablation, while the inferior rotor (isochrones shown) was nearby. (C) Left atrial roof AF rotor ablated coincidentally by empirical roof ablation in a man with persistent AF. AF terminated at the point indicated by a red dot. Offline FIRM analysis later revealed an AF rotor at the precise point of AF termination. All patients are AF-free. FIRM atrial orientations are as in figure 1B.

Figure 5

Cumulative freedom from Atrial Fibrillation Based on (A) Whether Ablation Did (Blue) or Did Not (Red) Pass Through AF Sources. Entire Population (solid lines) and First Ablation patients only (dashed lines). (B) Direct (FIRM-guided, Blue) or Coincidental (FIRM-blinded, Red) Source Ablation. (C) Elimination of All (Green), Some (Yellow) or No (Red) Stable AF Sources, in patients with bi-atrial baskets. p-values reflect the complete followup periods.

Figure 5

Cumulative freedom from Atrial Fibrillation Based on (A) Whether Ablation Did (Blue) or Did Not (Red) Pass Through AF Sources. Entire Population (solid lines) and First Ablation patients only (dashed lines). (B) Direct (FIRM-guided, Blue) or Coincidental (FIRM-blinded, Red) Source Ablation. (C) Elimination of All (Green), Some (Yellow) or No (Red) Stable AF Sources, in patients with bi-atrial baskets. p-values reflect the complete followup periods.

Figure 5

Cumulative freedom from Atrial Fibrillation Based on (A) Whether Ablation Did (Blue) or Did Not (Red) Pass Through AF Sources. Entire Population (solid lines) and First Ablation patients only (dashed lines). (B) Direct (FIRM-guided, Blue) or Coincidental (FIRM-blinded, Red) Source Ablation. (C) Elimination of All (Green), Some (Yellow) or No (Red) Stable AF Sources, in patients with bi-atrial baskets. p-values reflect the complete followup periods.