title: Transcatheter non-contact microwave ablation may enable circumferential renal artery denervation while sparing the vessel intima and media.
abstract: OBJECTIVE
  Trials of transcatheter renal artery denervation (RDN) have failed to show consistent antihypertensive efficacy. Procedural factors and limitations of radiofrequency ablation can lead to incomplete denervation. The aim of the study was to show that non-contact microwave catheter ablation could produce deep circumferential perivascular heating while avoiding injury to the renal artery intima and media.
  
  
  RESULTS
  A novel microwave catheter was designed and tested in a renal artery model consisting of layers of phantom materials embedded with a thermochromic liquid crystal sheet, colour range 50-78°C. Ablations were performed at 140 W for 180 sec and 120 W for 210 sec, delivering 25,200 J with renal arterial flow at 0.5 L/min and 0.1 L/min. Transcatheter microwave ablations 100-160 W for 180 sec were then performed in the renal arteries of five sheep. In vitro, ablations at 140 W and 0.5 L/min flow produced circumferential lesions 5.9±0.2 mm deep and 19.2±1.5 mm long with subendothelial sparing depth of 1.0±0.1 mm. In vivo, transcatheter microwave ablation was feasible with no collateral visceral thermal injury. There was histological evidence of preferential outer media and adventitial ablation.
  
  
  CONCLUSIONS
  Transcatheter microwave ablation for RDN appears feasible and provides a heating pattern that may enable more complete denervation while sparing the renal arterial intima and media.
authors.affiliation: Cardiology Department, Westmead Hospital, Sydney, Australia.
authors.forename: Pierre C
authors.initials: PC
authors.lastname: Qian
authors.forename: Michael A
authors.initials: MA
authors.lastname: Barry
authors.forename: Sara
authors.initials: S
authors.lastname: Al-Raisi
authors.forename: Pramesh
authors.initials: P
authors.lastname: Kovoor
authors.forename: Jim
authors.initials: J
authors.lastname: Pouliopoulos
authors.forename: Chrishan J
authors.initials: CJ
authors.lastname: Nalliah
authors.forename: Abhishek
authors.initials: A
authors.lastname: Bhaskaran
authors.forename: William
authors.initials: W
authors.lastname: Chik
authors.forename: Rahul
authors.initials: R
authors.lastname: Kurup
authors.forename: Virginia
authors.initials: V
authors.lastname: James
authors.forename: Winny
authors.initials: W
authors.lastname: Varikatt
authors.forename: Alistair
authors.initials: A
authors.lastname: McEwan
authors.forename: Aravinda
authors.initials: A
authors.lastname: Thiagalingam
authors.forename: Stuart P
authors.initials: SP
authors.lastname: Thomas
mesh_terms: D000818:Animals; D000959:Antihypertensive Agents / Q000627:therapeutic use; D001794:Blood Pressure / Q000187:drug effects; D017115:Catheter Ablation / Q000379:methods; D057785:Catheters; D004867:Equipment Design; D007668:Kidney / Q000098:blood supply / Q000601:surgery*; D008872:Microwaves / Q000627:therapeutic use; D012077:Renal Artery / Q000601:surgery*; D012756:Sheep; D013562:Sympathectomy / Q000295:instrumentation* / Q000379:methods
chemical_list: D000959:Antihypertensive Agents