title: Histopathology of intraoperatively induced linear radiofrequency ablation lesions in patients with chronic atrial fibrillation.
abstract: OBJECTIVE
  Radiofrequency (RF) energy has been extensively used in ablation of arrhythmia but so far no analysis of morphological effects in human left atria has been conducted.
  
  
  RESULTS
  We studied 59 ablation lesions from seven patients who died 2 to 22 days after open heart surgery plus intraoperative cooled-tip RF ablation to treat permanent atrial fibrillation (AF) (mean 4, 1-11 years). The ablation area was studied by macroscopy and histological analysis. RF ablation produced clearly delineated coagulation necrosis (up to a depth of 5.5 mm) bordered by an irregular zone of incomplete necrosis and fresh bleeding even 22 days post-operatively. No superficial charring, thrombotic deposition, or perforation was documented. Endocardium and subendocardium displayed oedematic loosening and microfragmentation of connective tissue fibres. Early after ablation (2-6 days), interfibrillar disseminated bleeding and necrosis without tissue removal response were found. Later after ablation (21, 22 days), mild inflammatory reaction and granulation tissue appeared. Twenty-five per cent of all studied lesions, especially in the thick region in between left pulmonary veins and mitral annulus (left atrial isthmus) (86%), were non-transmural. Nerve fibres with different degrees of thermal injury were detected in the pulmonary vein ostial region.
  
  
  CONCLUSIONS
  Intraoperative cooled-tip ablation in AF resulted in coagulation necrosis of endocardium, subendocardium, and the atrial myocardial layer to a depth of 5.5 mm bordered by an irregular zone of incomplete thermal damage. Transmurality of the lesions could only be found in 75% of intraoperatively applied lesions.
authors.affiliation: Medical Clinic II (Cardiology and Angiology), BG Kliniken Bergmannsheil, Ruhr-University Bochum, Bürkle-de-la-Camp-Platz 1, 44789 Bochum, Germany. thomas.deneke@ruhr-uni-bochum.de
authors.forename: Thomas
authors.initials: T
authors.lastname: Deneke
authors.forename: Krishna
authors.initials: K
authors.lastname: Khargi
authors.forename: Klaus-Michael
authors.initials: KM
authors.lastname: Müller
authors.forename: Bernd
authors.initials: B
authors.lastname: Lemke
authors.forename: Andreas
authors.initials: A
authors.lastname: Mügge
authors.forename: Axel
authors.initials: A
authors.lastname: Laczkovics
authors.forename: Anton E
authors.initials: AE
authors.lastname: Becker
authors.forename: Peter H
authors.initials: PH
authors.lastname: Grewe
mesh_terms: D000368:Aged; D001281:Atrial Fibrillation / Q000473:pathology / Q000601:surgery*; D017115:Catheter Ablation; D002423:Cause of Death; D002908:Chronic Disease; D004699:Endocardium / Q000473:pathology; D005260:Female; D006097:Granulation Tissue / Q000473:pathology; D006325:Heart Atria / Q000473:pathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009336:Necrosis; D011184:Postoperative Period