title: Acute and chronic effects of extensive radiofrequency lesions in the canine caval veins: implications for ablation of atrial arrhythmias.
abstract: BACKGROUND
  Although radiofrequency (RF) ablation within the caval veins has been increasingly used to treat a variety of atrial tachyarrhythmias, the consequences of RF ablation in the caval veins are unknown. We explored the acute and chronic angiographic and pathological effects of extensive RF ablation in the caval veins.
  
  
  METHODS
  Under fluoroscopy guidance, conventional (4 mm tip, 60 degrees C, 60 seconds) RF applications (n = 6-7) were delivered in each vena cava (from +/-2 cm into the vein to the veno-atrial junction) of 15 dogs (10 +/- 3 kg). Animals were killed 1 hour and 5 weeks after ablation for histological analysis. Angiography was performed before ablation (acute dogs only) and at sacrifice to assess the degree of vascular stenosis.
  
  
  RESULTS
  In acute dogs (n = 5), luminal narrowing was noted in 10/10 (100%) targeted veins (mild in two; moderate in three and severe in five, including two total occlusions). In the six chronic animals that completed the protocol (four died during follow-up), stenosis was also observed in 12/12 (100%) ablated veins (mild in six; moderate in four and severe in two). Of these, one superior vena cava was suboccluded with development of extensive collateral circulation. Histologically, acute lesions displayed typical transmural coagulative necrosis, whereas chronic lesions revealed intimal proliferation, necrotic muscle replaced with collagen, endovascular contraction, and disruption and thickening of the internal elastic lamina.
  
  
  CONCLUSIONS
  In this model, extensive RF ablation in the caval veins may result in significant vascular stenosis. These findings may have implications for catheter ablation of arrhythmias originating within the caval veins.
authors.affiliation: Department of Cardiology, Paulista School of Medicine, Federal University if São Paulo, São Paulo, SP, Brazil. guilhermefenelon@uol.com.br
authors.forename: Guilherme
authors.initials: G
authors.lastname: Fenelon
authors.forename: Marcello
authors.initials: M
authors.lastname: Franco
authors.forename: Elerson
authors.initials: E
authors.lastname: Arfelli
authors.forename: Mieko
authors.initials: M
authors.lastname: Okada
authors.forename: Sérgio
authors.initials: S
authors.lastname: De Araújo
authors.forename: Angelo A V
authors.initials: AA
authors.lastname: De Paola
mesh_terms: D000208:Acute Disease; D000818:Animals; D001281:Atrial Fibrillation / Q000473:pathology / Q000601:surgery; D017115:Catheter Ablation / Q000009:adverse effects* / Q000379:methods; D002908:Chronic Disease; D003251:Constriction, Pathologic; D004285:Dogs; D014652:Vascular Diseases / Q000209:etiology* / Q000473:pathology*; D014684:Venae Cavae / Q000473:pathology* / Q000601:surgery*