title: Effect of electrode orientation on lesion sizes produced by irrigated radiofrequency ablation catheters.
abstract: BACKGROUND
  Irrigated radiofrequency (RF) ablation catheters may produce different lesion sizes dependent upon the electrode orientation to the tissue. This study examined the effect of irrigated electrode orientation on the lesion size and explores a potential mechanism for this effect.
  
  
  RESULTS
  Lesions were created in isolated porcine myocardium using an open irrigation, closed irrigation, and nonirrigated RF catheter (all 3.5-4 mm tips). Lesions were created with the electrodes with all permutations of electrode orientation (vertical or horizontal), contact pressure (6 or 20 g), and saline superfusate flow (0.2 or 0.4 m/sec) over tissue interface. The effect of electrode irrigation without RF delivery on tissue temperature was assessed with intramyocardial temperature probes and infrared thermal imaging. For both irrigated catheters, the horizontal orientation produced 25-30% smaller lesion volumes than the vertical orientation despite equal or greater power deliveries. The horizontal orientation produced larger lesion volumes for the nonirrigated catheter. Higher superfusate flow rates were associated with decreased lesion volumes for the irrigated catheters but greater lesion volumes for the nonirrigated catheter. Catheter irrigation alone without RF delivery reduced intramyocardial temperatures up to 4.9 degrees C and the horizontal orientation produced a 2-fold greater area of tissue cooling than the vertical orientation.
  
  
  CONCLUSIONS
  Horizontal electrode orientations reduce lesion volumes for irrigated RF catheters. This effect may be in part due to greater areas of active tissue cooling in the horizontal orientation.
authors: Virginia Commonwealth University Medical Center, Richmond, Virginia, USA. mwoodmd@pol.net
authors: Mark A
authors: MA
authors: Wood
authors: Scott M
authors: SM
authors: Goldberg
authors: Babar
authors: B
authors: Parvez
authors: Vishesh
authors: V
authors: Pathak
authors: Kristen
authors: K
authors: Holland
authors: Amy L
authors: AL
authors: Ellenbogen
authors: Frederick T
authors: FT
authors: Han
authors: Daniel
authors: D
authors: Alexander
authors: Melissa
authors: M
authors: Lau
authors: Leonid
authors: L
authors: Reshko
authors: Aneesh
authors: A
authors: Goel
mesh_terms: D000818:Animals; D006328:Cardiac Catheterization / Q000295:instrumentation*; D017115:Catheter Ablation / Q000295:instrumentation*; D004566:Electrodes; D006352:Heart Ventricles / Q000473:pathology / Q000601:surgery*; D007036:Hypothermia, Induced / Q000295:instrumentation*; D013552:Swine; D007507:Therapeutic Irrigation / Q000295:instrumentation*; D016896:Treatment Outcome