title: Targeted ablation at stable atrial fibrillation sources improves success over conventional ablation in high-risk patients: a substudy of the CONFIRM Trial.
abstract: BACKGROUND
  Pulmonary vein (PV) isolation has disappointing results in patients with obesity, heart failure, obstructive sleep apnea (OSA) and enlarged left atria (LA), for unclear reasons. We hypothesized that these comorbidities may cause higher numbers or non-PV locations of atrial fibrillation (AF) sources, where targeted source ablation (focal impulse and rotor modulation [FIRM]) should improve the single-procedure success of ablation.
  
  
  METHODS
  The Conventional Ablation of AF With or Without Focal Impulse and Rotor Modulation (CONFIRM) trial prospectively enrolled 92 patients at 107 AF ablation procedures, in whom computational mapping identified AF rotors or focal sources. Patients underwent FIRM plus conventional ablation (FIRM-guided), or conventional ablation only, and were evaluated for recurrent AF quarterly with rigourous, often implanted, monitoring. We report the n = 73 patients undergoing first ablation in whom demographic information was available (n = 52 conventional, n = 21 FIRM-guided).
  
  
  RESULTS
  Stable sources for AF were found in 97.1% of patients. The numbers of concurrent sources per patient (2.1 ± 1.1) rose with LA diameter (P = 0.021), lower left ventricular ejection fraction (P = 0.039), and the presence of OSA (P = 0.002) or hypomagnesemia (P = 0.017). Right atrial sources were associated with obesity (body mass index ≥ 30; P = 0.015). In patients with obesity, hypertension, OSA, and LA diameter > 40 mm, single-procedure freedom from AF was > 80% when FIRM-guided was used vs. < 50% when conventional ablation was used (all; P < 0.05).
  
  
  CONCLUSIONS
  Patients with "difficult to treat" AF exhibit more concurrent AF sources in more widespread biatrial distributions than other patients. These mechanisms explain the disappointing results of PV isolation, and how FIRM can identify patient-specific AF sources to enable successful ablation in this population.
authors.affiliation: University of California and Veterans' Affairs Medical Centers, San Diego, California, USA.
authors.forename: Tina
authors.initials: T
authors.lastname: Baykaner
authors.forename: Paul
authors.initials: P
authors.lastname: Clopton
authors.forename: Gautam G
authors.initials: GG
authors.lastname: Lalani
authors.forename: Amir A
authors.initials: AA
authors.lastname: Schricker
authors.forename: David E
authors.initials: DE
authors.lastname: Krummen
authors.forename: Sanjiv M
authors.initials: SM
authors.lastname: Narayan
mesh_terms: D001281:Atrial Fibrillation / Q000503:physiopathology / Q000601:surgery*; D017115:Catheter Ablation / Q000379:methods*; D004562:Electrocardiography; D005260:Female; D005471:Fluoroscopy; D005500:Follow-Up Studies; D006329:Heart Conduction System / Q000503:physiopathology* / Q000601:surgery; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011667:Pulmonary Veins / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery; D012008:Recurrence; D016896:Treatment Outcome