title: Histopathology of Bipolar Radiofrequency Ablation in the Human Atrium.
abstract: BACKGROUND
  The Cox maze IV operation has become the preferred surgical treatment for atrial fibrillation, as it is associated with less morbidity and complexity than the Cox maze III procedure, yet is still highly effective. Numerous studies have been conducted in animals to examine the histopathology of this operation on the heart but studies on human hearts that have undergone the Cox maze IV operation have not been performed.
  
  
  METHODS
  We report the histopathologic findings in 3 patients from whom tissue was available for histologic study. In 2 patients it was obtained at autopsy within a month after undergoing a Cox maze IV operation, and in the remaining patient, atrial tissue was obtained immediately after ablation.
  
  
  RESULTS
  The lesions were clearly visible on the atria at day 6 and day 18. Microscopic examination showed that the hearts were in different stages of healing. We also found that, compared with animal models, human myocardium had significant preexisting underlying damage with myocyte hypertrophy and fibrosis. Although most of the ablative lesions were transmural, not all spanned from the epicardium to the endocardium. The chronic changes present in these hearts may have prevented transmurality by impeding energy delivery from fully penetrating the tissue.
  
  
  CONCLUSIONS
  The atrial myocardial substrate studied in experimental conditions is markedly different from the human hearts that frequently express histopathologic changes secondary to the underlying disease process. That may prevent creating true transmural lesions and impact final efficacy of the procedure.
authors.affiliation: Division of Cardiothoracic Surgery, Pauley Heart Center, Richmond, Virginia. Electronic address: vkasirajan@mcvh-vcu.edu.
authors.forename: Vigneshwar
authors.initials: V
authors.lastname: Kasirajan
authors.affiliation: Department of Pathology, Virginia Commonwealth University Health System, Richmond, Virginia.
authors.forename: Sadia
authors.initials: S
authors.lastname: Sayeed
authors.affiliation: Division of Cardiothoracic Surgery, Pauley Heart Center, Richmond, Virginia.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Filler
authors.affiliation: Department of Pathology, Virginia Commonwealth University Health System, Richmond, Virginia.
authors.forename: Arkun
authors.initials: A
authors.lastname: Knarik
authors.affiliation: Division of Cardiology, Pauley Heart Center, Richmond, Virginia.
authors.forename: Jayanthi N
authors.initials: JN
authors.lastname: Koneru
authors.affiliation: Division of Cardiology, Pauley Heart Center, Richmond, Virginia.
authors.forename: Kenneth A
authors.initials: KA
authors.lastname: Ellenbogen
mesh_terms: D000368:Aged; D001281:Atrial Fibrillation / Q000175:diagnosis / Q000601:surgery*; D017115:Catheter Ablation / Q000379:methods*; D005500:Follow-Up Studies; D006325:Heart Atria / Q000473:pathology* / Q000601:surgery; D006329:Heart Conduction System / Q000473:pathology / Q000601:surgery*; D006801:Humans; D008297:Male; D009206:Myocardium / Q000473:pathology*; D011379:Prognosis