title: Clinical histopathology and ultrastructural analysis of myocardium following microwave energy ablation.
abstract: OBJECTIVE
  Due to weaknesses of conventional modes for treating atrial fibrillation (AF), surgical energy ablation methods and tools to cure AF have been under rapid development. One of these methods, microwave energy, is beginning to be applied clinically. The purpose of this study was to examine histology and ultrastructure of lesions produced by microwave energy in the myocardium.
  
  
  METHODS
  Fifteen consecutive patients underwent surgical microwave energy ablation (Microwave Ablation System with FLEX 4 probe, AFx Inc., Fremont, CA) concomitant to a valve procedure. Epicardial ablation was carried out on the beating normothermic heart prior to performing the valve procedure. Two tissue specimens (1cm(2)) were obtained from each patient; one from the lesion site (right appendage) and the other from an adjacent, non-ablated site, which was used as control. Tissue samples were fixed and stained as appropriate for histological and ultrastructural analysis.
  
  
  RESULTS
  All ablated samples revealed observable microscopic alteration, including loss of nuclei, foci of coagulative necrosis or induced irregular bands of contraction. Ultrastructurally, ablated cells demonstrated architectural disarray, loss of contractile filaments, mitochondrial swelling and focal interruption of plasma membrane.
  
  
  CONCLUSIONS
  Histologic appearance of lesions created by epicardial microwave energy ablation was consistent over tissue samples, although acute findings demonstrated differences from cryoablation. In most of the cases, lesions were transmural, as was demonstrated by loss of cellular viability throughout the depth of tissue specimens.
authors.affiliation: Cardiac Surgery Department, Istituto Clinico Humanitas, University of Milan School of Medicine, Rozzano, Milan, Italy. emanasse@inwind.it
authors.forename: E
authors.initials: E
authors.lastname: Manasse
authors.forename: P G
authors.initials: PG
authors.lastname: Colombo
authors.forename: A
authors.initials: A
authors.lastname: Barbone
authors.forename: P
authors.initials: P
authors.lastname: Braidotti
authors.forename: G
authors.initials: G
authors.lastname: Bulfamante
authors.forename: M
authors.initials: M
authors.lastname: Roincalli
authors.forename: R
authors.initials: R
authors.lastname: Gallotti
mesh_terms: D001281:Atrial Fibrillation / Q000473:pathology / Q000601:surgery*; D017115:Catheter Ablation / Q000379:methods*; D006801:Humans; D008854:Microscopy, Electron; D008872:Microwaves / Q000627:therapeutic use*; D009206:Myocardium / Q000473:pathology / Q000648:ultrastructure; D010496:Pericardium / Q000601:surgery*