title: In vivo evaluation of virtual electrode mapping and ablation utilizing a direct endocardial visualization ablation catheter.
abstract: BACKGROUND
  Radiofrequency (RF) ablation utilizing direct endocardial visualization (DEV) requires a "virtual electrode" to deliver RF energy while preserving visualization. This study aimed to: (1) examine the virtual electrode RF ablation efficacy; (2) determine the optimal power and duration settings; and (3) evaluate the utility of virtual electrode unipolar electrograms.
  
  
  RESULTS
  The DEV catheter lesions were compared to lesions formed using a 3.5 mm open irrigated tip catheter within the right atria of 12 sheep. Generator power settings for DEV were titrated from 12W, 14W and 16W for 20, 30 and 40 seconds duration with 25 mL/min saline irrigation. Standard irrigated tip catheter settings of 30W, 50°C for 30 seconds and 30 mL/min were used. The DEV lesions were significantly greater in surface area and both major and minor axes compared to irrigated tip lesions (surface area 19.43 ± 9.09 vs 10.88 ± 4.72 mm, P<0.01) with no difference in transmurality (93/94 vs 46/47) or depth (1.86 ± 0.75 vs 1.85 ± 0.57 mm). Absolute electrogram amplitude reduction was greater for DEV lesions (1.89 ± 1.31 vs 1.49 ± 0.78 mV, P = 0.04), but no difference in percentage reduction. Pre-ablation pacing thresholds were not different between DEV (0.79 ± 0.36 mA) and irrigated tip (0.73 ± 0.25 mA) lesions. There were no complications noted during ablation with either catheter.
  
  
  CONCLUSIONS
  Virtual electrode ablation consistently created wider lesions at lower power compared to irrigated tip ablation. Virtual electrode electrograms showed a comparable pacing and sensing efficacy in detecting local myocardial electrophysiological changes.
authors.affiliation: Cardiology Department, Westmead Hospital, Sydney, Australia.
authors.forename: William W B
authors.initials: WW
authors.lastname: Chik
authors.forename: M A
authors.initials: MA
authors.lastname: Barry
authors.forename: Zach
authors.initials: Z
authors.lastname: Malchano
authors.forename: Bryan
authors.initials: B
authors.lastname: Wylie
authors.forename: Jim
authors.initials: J
authors.lastname: Pouliopoulos
authors.forename: Kaimin
authors.initials: K
authors.lastname: Huang
authors.forename: Juntang
authors.initials: J
authors.lastname: Lu
authors.forename: Sujitha
authors.initials: S
authors.lastname: Thavapalachandran
authors.forename: David
authors.initials: D
authors.lastname: Robinson
authors.forename: Vahid
authors.initials: V
authors.lastname: Saadat
authors.forename: Stuart P
authors.initials: SP
authors.lastname: Thomas
authors.forename: David L
authors.initials: DL
authors.lastname: Ross
authors.forename: Pramesh
authors.initials: P
authors.lastname: Kovoor
authors.forename: Aravinda
authors.initials: A
authors.lastname: Thiagalingam
mesh_terms: D000200:Action Potentials; D000818:Animals; D002304:Cardiac Pacing, Artificial; D017115:Catheter Ablation / Q000009:adverse effects / Q000295:instrumentation*; D057785:Catheters; D004566:Electrodes; D022062:Electrophysiologic Techniques, Cardiac; D004699:Endocardium / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D004867:Equipment Design; D005471:Fluoroscopy; D006325:Heart Atria / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D023421:Models, Animal; D015641:Radiography, Interventional / Q000379:methods; D012756:Sheep; D013997:Time Factors