title: A Novel Microwave Catheter Can Perform Noncontact Circumferential Endocardial Ablation in a Model of Pulmonary Vein Isolation.
abstract: BACKGROUND
  Pulmonary vein isolation is an effective treatment for atrial fibrillation. Current endocardial ablation techniques require catheter contact for lesion formation. Inadequate or inconsistent catheter contact results in difficulty with achieving acute and long-term isolation and consequent atrial arrhythmia recurrence. Microwave energy produces radiant heating and therefore can be used for noncontact catheter ablation. We hypothesized that it is possible to design a microwave catheter to produce a circumferential transmural thermal lesion in an in vitro model of a pulmonary vein antrum.
  
  
  RESULTS
  A monopole microwave catheter with a sideways firing axially symmetrical heating pattern was designed. Noncontact ablations were performed in a perfused pulmonary vein model constructed from microwave myocardial phantom embedded with a sheet of thermochromic liquid crystal to permit visualization and measurement of thermal lesions from color changes. 1200 J ablations were performed at 150 W for 80 seconds and 120 W for 100 seconds at high (0.8 L/min) and low (0.06 L/min) flow through the modeled pulmonary vein. Myocardial tissue was substituted for the phantom material and ablations repeated at 150 W for 180 seconds and stained with nitro-blue tetrazolium. The catheter was able to induce deep circumferential antral lesions in myocardial phantom and myocardial tissue. Higher power and shorter ablations delivering the same amount of microwave energy resulted in larger lesions with less surface sparing.
  
  
  CONCLUSIONS
  A microwave catheter can be designed to produce a circumferential thermal lesion on noncontact ablation and may have possible applications for pulmonary vein isolation.
authors: Cardiology Department, Westmead Hospital, Sydney, Australia.
authors: Pierre
authors: P
authors: Qian
authors: Cardiology Department, Westmead Hospital, Sydney, Australia.
authors: Michael Anthony
authors: MA
authors: Barry
authors: Cardiology Department, Westmead Hospital, Sydney, Australia.|School of Electrical and Information Engineering, University of Sydney, Sydney, Australia.
authors: Trang
authors: T
authors: Nguyen
authors: Cardiology Department, Westmead Hospital, Sydney, Australia.|Sydney Medical School, University of Sydney, Sydney, Australia.
authors: David
authors: D
authors: Ross
authors: Cardiology Department, Westmead Hospital, Sydney, Australia.|Sydney Medical School, University of Sydney, Sydney, Australia.
authors: Pramesh
authors: P
authors: Kovoor
authors: Cardiology Department, Westmead Hospital, Sydney, Australia.|School of Electrical and Information Engineering, University of Sydney, Sydney, Australia.
authors: Alistair
authors: A
authors: McEwan
authors: Cardiology Department, Westmead Hospital, Sydney, Australia.|Sydney Medical School, University of Sydney, Sydney, Australia.
authors: Stuart
authors: S
authors: Thomas
authors: Cardiology Department, Westmead Hospital, Sydney, Australia.|Sydney Medical School, University of Sydney, Sydney, Australia.
authors: Aravinda
authors: A
authors: Thiagalingam
mesh_terms: D000818:Animals; D006328:Cardiac Catheterization / Q000295:instrumentation*; D062906:Cardiac Catheters; D017115:Catheter Ablation / Q000295:instrumentation*; D002417:Cattle; D004699:Endocardium / Q000473:pathology / Q000601:surgery*; D004867:Equipment Design; D008872:Microwaves; D008953:Models, Anatomic; D008955:Models, Cardiovascular; D011667:Pulmonary Veins / Q000601:surgery*; D013997:Time Factors
keywords: atrial fibrillation; endocardial sparing; microwave catheter ablation; noncontact ablation; pulmonary vein isolation