title: Determinants of lesion sizes and tissue temperatures during catheter cryoablation.
abstract: BACKGROUND
  Factors which influence lesion size from catheter-based cryoablation have not been well described. This study describes factors which influence lesion size during catheter cryoablation.
  
  
  RESULTS
  Cryoablation was delivered to porcine left ventricular myocardium in a saline bath using 4- or 8-mm electrode catheters. Ablation was delivered with the electrodes either vertical or horizontal to the tissue and both with and without superfusate flow over the electrode. The effect of electrode contact pressure was tested. Lesion dimensions were measured. All experiments were duplicated to measure tissue temperatures at 1-, 2-, 3-, and 5-mm deep to the ablation electrode. The 8-mm electrode produced lower tissue temperatures and larger lesion volumes when compared with the 4-mm electrode (all P < 0.05). Superfusate flow slowed the rate of tissue cooling, markedly warmed tissue temperatures, and reduced lesion volume when compared with no flow conditions. By linear regression modeling, lesion sizes and tissue temperatures were related to the presence of superfusate flow, electrode orientation, contact pressure and electrode size, or catheter refrigerant flow rate (r2 for models = 0.90-0.96, all P < 0.001). Electrode temperature predicted lesion size or tissue temperatures only when analyzed independent of electrode size or refrigerant flow rate.
  
  
  CONCLUSIONS
  Lesion sizes and tissue temperatures during catheter cryoablation are related to convective warming, electrode orientation, electrode contact pressure, and any of the following: electrode size, catheter refrigerant flow rate or electrode temperature. However, electrode temperature may be a poor predictor of lesion size and tissue temperature for a given catheter size.
authors.affiliation: Department of Cardiology, Virginia Commonwealth University Medical Center, Richmond, Virginia 23298-0053, USA. mwoodmd@pol.net
authors.forename: Mark A
authors.initials: MA
authors.lastname: Wood
authors.forename: Babar
authors.initials: B
authors.lastname: Parvez
authors.forename: Amy L
authors.initials: AL
authors.lastname: Ellenbogen
authors.forename: Katherine M
authors.initials: KM
authors.lastname: Shaffer
authors.forename: Scott M
authors.initials: SM
authors.lastname: Goldberg
authors.forename: Michael P
authors.initials: MP
authors.lastname: Gaspar
authors.forename: Isti
authors.initials: I
authors.lastname: Arief
authors.forename: Christine M
authors.initials: CM
authors.lastname: Schubert
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D003452:Cryosurgery / Q000379:methods*; D004566:Electrodes; D006352:Heart Ventricles / Q000473:pathology / Q000601:surgery*; D066298:In Vitro Techniques; D016014:Linear Models; D013552:Swine; D013696:Temperature