title: Investigation into causes of abnormal cerebral MRI findings following PVAC duty-cycled, phased RF ablation of atrial fibrillation.
abstract: BACKGROUND
  Left atrial catheter ablation of the pulmonary veins (PVs) is an established option for patients with atrial fibrillation (AF). Asymptomatic cerebral emboli (ACE) detected by diffusion weighted MRI (DW-MRI) following AF ablation has been reported at varying rates. This variability may be linked to procedural variables and demographic risk factors. Animal studies with the multielectrode pulmonary vein ablation catheter (PVAC) have identified potential sources of emboli, including air introduced during PVAC introduction, inadequate anticoagulation, and high current densities when the distal (E1) and proximal (E10) electrodes are in contact. We sought to evaluate the incidence, size, and number of DW-MRI findings with procedural modifications that potentially reduce the embolic load.
  
  
  METHODS
  Thirty-seven AF patients (59 ± 10 years, 73% male, all with paroxysmal AF, left atrial [LA] diameter 44 ± 7 mm, left ventricular ejection fraction 57 ± 7%) underwent MRI sequences preceding ablation, within 24 hours postablation, and at 4-6 weeks. During the procedure all patients were on uninterrupted phenprocoumon, an attempted activated clotting time (ACT) level >300 seconds, had the PVAC introduced under saline, and antral ablation was started with a 2:1 bipolar/unipolar mode. Files from the ablation unit (GENius v14.4) were retrospectively analyzed to determine the relationship between E1 and E10 in close proximity and DW-MRI findings.
  
  
  RESULTS
  Post procedure, 10/37 patients (27%) were positive for new DWI cerebral lesions. Nine of 10 patients had a single lesion, and 1/10 patient had 2 lesions. Average lesion size was 3.1 ± 3.9 mm (2-14 mm). One of 10 (10%) had lesions at MRI follow-up. No neurological symptoms were observed. Eighteen of 37 (49%) of procedures had evidence of E1/E10 interaction. In the subgroup of patients with and without E1 and E10 in close proximity, the DW-MRI rate was 8/18 (44%) and 2/19 (11%), respectively (P = 0.029).
  
  
  CONCLUSIONS
  The source of positive DW-MRI findings in LA ablation involves several factors. Controlling anticoagulation and careful sheath management helps to reduce the number and size of DW-MRI lesions. With the PVAC catheter, an ablation with the E1 and E10 in close proximity increases the risk of a DW-MRI finding. In the future, electrodes E1 and E10 should be kept apart to help reduce the incidence of acute ACE.
authors.affiliation: Department of Electrophysiology, Witten/Herdecke University, School of Medicine, St. Agnes-Hospital, Bocholt, Germany. drmwieczorek@t-online.de
authors.forename: Marcus
authors.initials: M
authors.lastname: Wieczorek
authors.forename: Michael
authors.initials: M
authors.lastname: Lukat
authors.forename: Reinhard
authors.initials: R
authors.lastname: Hoeltgen
authors.forename: Cathy
authors.initials: C
authors.lastname: Condie
authors.forename: Thomas
authors.initials: T
authors.lastname: Hilje
authors.forename: Ulrich
authors.initials: U
authors.lastname: Missler
authors.forename: Jessica
authors.initials: J
authors.lastname: Hirsch
authors.forename: Christoph
authors.initials: C
authors.lastname: Scharf
mesh_terms: D001281:Atrial Fibrillation / Q000150:complications / Q000473:pathology* / Q000601:surgery*; D017115:Catheter Ablation / Q000009:adverse effects*; D005260:Female; D006801:Humans; D020766:Intracranial Embolism / Q000209:etiology* / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D011651:Pulmonary Artery / Q000473:pathology* / Q000601:surgery*; D016896:Treatment Outcome