title: Large radiofrequency ablation lesions can be created with a retractable infusion-needle catheter.
abstract: BACKGROUND
  Radiofrequency (RF) catheter ablation of ventricular tachycardia is sometimes limited by inadequate lesion depth. We report the use of a novel retractable needle-tipped electrode catheter with intramyocardial (IM) saline infusion and IM RF energy delivery to create large myocardial ablation lesions.
  
  
  METHODS
  The left ventricle was entered via the femoral artery in 6 and 11 anesthetized goats and swine (32-90 kg) with an 8-F electrode catheter with an extendable 27-gauge needle at the tip (modified for RF ablation by making the needle electrically active). The needle was advanced 5-7 mm intramyocardially and 0.9% saline was infused 1 mL/min x 60 seconds prior to, and throughout a 120-second application of RF via the active needle, with power titrated to 12 W for 9 lesions, and 30-40 W for 37 lesions, followed by a 120-second RF application using the 4-mm-tip electrode, with power titrated to achieve a 10-Omega decrease in impedance. Needle/saline lesions were compared to 18 standard 4-mm-tip control lesions (power titrated to < or =50 W, to achieve a 10-Omega impedance decrease or limited to 60 degrees Celsius) and to 17 irrigated 3.5-mm-tip lesions (power titrated to < or =50 W, temperature limited to 50 degrees Celsius, 30 mL/min infusion rate). Lesions were identified in the excised heart, fixed, serially sectioned from the endocardium, and digitally analyzed to calculate volume.
  
  
  RESULTS
  Lesions were homogeneous and had distinct borders. Compared to 4-mm-tip and irrigated-tip lesions, high-power needle/saline lesions were significantly deeper (13 +/- 2 vs 5 +/- 1 and 8 +/- 3 mm, P < 0.001), had significantly larger volumes (1,700 +/- 750 vs 240 +/- 170 and 750 +/- 650 mm(3), P < 0.001), and had larger cross-sectional area at each millimeter depth beyond the 1 mm (P < 0.01).
  
  
  CONCLUSIONS
  IM saline infusion and IM RF energy delivery markedly increase RF lesion size as compared to standard RF ablation and is feasible with a percutaneous catheter. This method warrants further investigation because of its potential clinical utility.
authors.affiliation: Dalhousie University, Queen Elizabeth II Health Sciences Centre, Halifax, Nova Scotia, Canada. john.sapp@cdha.nshealth.ca
authors.forename: John L
authors.initials: JL
authors.lastname: Sapp
authors.forename: Joshua M
authors.initials: JM
authors.lastname: Cooper
authors.forename: Paul
authors.initials: P
authors.lastname: Zei
authors.forename: William G
authors.initials: WG
authors.lastname: Stevenson
mesh_terms: D000818:Animals; D017115:Catheter Ablation / Q000295:instrumentation / Q000379:methods*; D005240:Feasibility Studies; D006041:Goats; D009206:Myocardium / Q000473:pathology*; D009339:Needles; D012965:Sodium Chloride / Q000008:administration & dosage; D013552:Swine; D017180:Tachycardia, Ventricular / Q000628:therapy
chemical_list: D012965:Sodium Chloride