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.

Copyright © 2013 Canadian Cardiovascular Society. Published by Elsevier Inc. All rights reserved.

Figures

Figure 1. Focal Impulse and Rotor Mapping (FIRM) of Atrial Fibrillation, Using Contact Electrodes Widely Covering Both Atria

Fluoroscopy also shows a coronary sinus catheter, an ablation catheter, an intracardiac ultrasound catheter and an esophageal temperature probe. A subcutaneous ECG monitor, to stringently document AF recurrence, is also visible.

Figure 2. Multiple AF Sources in “Difficult to Treat” AF Patients

(A) Concurrent rotor and focal sources, including 2 in the LA, in a 49-year-old patient with OSA. (B) Right atrium showing 2 concurrent rotors in a 63 year old morbidly obese patient (BMI 41.9 kg/m2), that were successfully ablated by FIRM but would not have been targeted by conventional ablation near the PVs.

Figure 2. Multiple AF Sources in “Difficult to Treat” AF Patients

(A) Concurrent rotor and focal sources, including 2 in the LA, in a 49-year-old patient with OSA. (B) Right atrium showing 2 concurrent rotors in a 63 year old morbidly obese patient (BMI 41.9 kg/m2), that were successfully ablated by FIRM but would not have been targeted by conventional ablation near the PVs.

Figure 3. Cumulative Single Procedure Freedom from Atrial Fibrillation for FIRM-Guided versus Conventional Ablation for prespecified high risk subgroups

FIRM-guided provided higher freedom from AF than FIRM-blinded ablation for patients with (A) Obesity or Morbid Obesity (BMI>30), (B) Obstructive Sleep Apnea Syndrome; (C) Right Atrial Sources; (D) LA Enlargement (diameter >40 mm); (E) Hypertension.

Figure 3. Cumulative Single Procedure Freedom from Atrial Fibrillation for FIRM-Guided versus Conventional Ablation for prespecified high risk subgroups

FIRM-guided provided higher freedom from AF than FIRM-blinded ablation for patients with (A) Obesity or Morbid Obesity (BMI>30), (B) Obstructive Sleep Apnea Syndrome; (C) Right Atrial Sources; (D) LA Enlargement (diameter >40 mm); (E) Hypertension.

Figure 3. Cumulative Single Procedure Freedom from Atrial Fibrillation for FIRM-Guided versus Conventional Ablation for prespecified high risk subgroups

FIRM-guided provided higher freedom from AF than FIRM-blinded ablation for patients with (A) Obesity or Morbid Obesity (BMI>30), (B) Obstructive Sleep Apnea Syndrome; (C) Right Atrial Sources; (D) LA Enlargement (diameter >40 mm); (E) Hypertension.

Figure 3. Cumulative Single Procedure Freedom from Atrial Fibrillation for FIRM-Guided versus Conventional Ablation for prespecified high risk subgroups

FIRM-guided provided higher freedom from AF than FIRM-blinded ablation for patients with (A) Obesity or Morbid Obesity (BMI>30), (B) Obstructive Sleep Apnea Syndrome; (C) Right Atrial Sources; (D) LA Enlargement (diameter >40 mm); (E) Hypertension.

Figure 3. Cumulative Single Procedure Freedom from Atrial Fibrillation for FIRM-Guided versus Conventional Ablation for prespecified high risk subgroups

FIRM-guided provided higher freedom from AF than FIRM-blinded ablation for patients with (A) Obesity or Morbid Obesity (BMI>30), (B) Obstructive Sleep Apnea Syndrome; (C) Right Atrial Sources; (D) LA Enlargement (diameter >40 mm); (E) Hypertension.