title: Direct cooling of the catheter tip increases safety for CMR-guided electrophysiological procedures.
abstract: BACKGROUND
  One of the safety concerns when performing electrophysiological (EP) procedures under magnetic resonance (MR) guidance is the risk of passive tissue heating due to the EP catheter being exposed to the radiofrequency (RF) field of the RF transmitting body coil. Ablation procedures that use catheters with irrigated tips are well established therapeutic options for the treatment of cardiac arrhythmias and when used in a modified mode might offer an additional system for suppressing passive catheter heating.
  
  
  METHODS
  A two-step approach was chosen. Firstly, tests on passive catheter heating were performed in a 1.5 T Avanto system (Siemens Healthcare Sector, Erlangen, Germany) using a ASTM Phantom in order to determine a possible maximum temperature rise. Secondly, a phantom was designed for simulation of the interface between blood and the vascular wall. The MR-RF induced temperature rise was simulated by catheter tip heating via a standard ablation generator. Power levels from 1 to 6 W were selected. Ablation duration was 120 s with no tip irrigation during the first 60 s and irrigation at rates from 2 ml/min to 35 ml/min for the remaining 60 s (Biotronik Qiona Pump, Berlin, Germany). The temperature was measured with fluoroscopic sensors (Luxtron, Santa Barbara, CA, USA) at a distance of 0 mm, 2 mm, 4 mm, and 6 mm from the catheter tip.
  
  
  RESULTS
  A maximum temperature rise of 22.4°C at the catheter tip was documented in the MR scanner. This temperature rise is equivalent to the heating effect of an ablator's power output of 6 W at a contact force of the weight of 90 g (0.883 N). The catheter tip irrigation was able to limit the temperature rise to less than 2°C for the majority of examined power levels, and for all examined power levels the residual temperature rise was less than 8°C.
  
  
  CONCLUSIONS
  Up to a maximum of 22.4°C, the temperature rise at the tissue surface can be entirely suppressed by using the catheter's own irrigation system. The irrigated tip system can be used to increase MR safety of EP catheters by suppressing the effects of unwanted passive catheter heating due to RF exposure from the MR scanner.
authors.affiliation: Department of Internal Medicine I, University Hospital Wuerzburg, Wuerzburg, Germany. Reiter_T@medizin.uni-wuerzburg.de
authors.forename: Theresa
authors.initials: T
authors.lastname: Reiter
authors.forename: Daniel
authors.initials: D
authors.lastname: Gensler
authors.forename: Oliver
authors.initials: O
authors.lastname: Ritter
authors.forename: Ingo
authors.initials: I
authors.lastname: Weiss
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Geistert
authors.forename: Ralf
authors.initials: R
authors.lastname: Kaufmann
authors.forename: Sabine
authors.initials: S
authors.lastname: Hoffmeister
authors.forename: Michael T
authors.initials: MT
authors.lastname: Friedrich
authors.forename: Stefan
authors.initials: S
authors.lastname: Wintzheimer
authors.forename: Markus
authors.initials: M
authors.lastname: Düring
authors.forename: Peter
authors.initials: P
authors.lastname: Nordbeck
authors.forename: Peter M
authors.initials: PM
authors.lastname: Jakob
authors.forename: Mark E
authors.initials: ME
authors.lastname: Ladd
authors.forename: Harald H
authors.initials: HH
authors.lastname: Quick
authors.forename: Wolfgang R
authors.initials: WR
authors.lastname: Bauer
mesh_terms: D017115:Catheter Ablation / Q000009:adverse effects / Q000295:instrumentation*; D057785:Catheters; D004867:Equipment Design; D004868:Equipment Failure; D004869:Equipment Safety; D053783:Magnetic Resonance Imaging, Interventional / Q000009:adverse effects / Q000295:instrumentation*; D008422:Materials Testing; D019047:Phantoms, Imaging; D013696:Temperature; D007507:Therapeutic Irrigation