title: Feasibility of contrast-enhanced and nonenhanced MRI for intraprocedural and postprocedural lesion visualization in interventional electrophysiology: animal studies and early delineation of isthmus ablation lesions in patients with typical atrial flutter.
abstract: BACKGROUND
  Imaging of myocardial ablation lesions during electrophysiology procedures would enable superior guidance of interventions and immediate identification of potential complications. The aim of this study was to establish clinically suitable MRI-based imaging techniques for intraprocedural lesion visualization in interventional electrophysiology.
  
  
  RESULTS
  Interventional electrophysiology was performed under magnetic resonance guidance in an animal model, using a custom setup including magnetic resonance-conditional catheters. Various pulse sequences were explored for intraprocedural lesion visualization after radiofrequency ablation. The developed visualization techniques were then used to investigate lesion formation in patients immediately after ablation of atrial flutter. The animal studies in 9 minipigs showed that gadolinium-DTPA-enhanced T1-weighted and nonenhanced T2-weighted pulse sequences are particularly suitable for lesion visualization immediately after radiofrequency ablation. MRI-derived lesion size correlated well with autopsy (R(2)=0.799/0.709 for contrast-enhanced/nonenhanced imaging). Non-contrast agent-enhanced techniques were suitable for repetitive lesion visualization during electrophysiological interventions, thus allowing for intraprocedural monitoring of ablation success. The patient studies in 24 patients with typical atrial flutter several minutes to hours after cavotricuspid isthmus ablation confirmed the results from the animal experiments. Therapeutic lesions could be visualized in all patients using contrast-enhanced and also nonenhanced MRI with high contrast-to-noise ratio (94.6±35.2/111.1±32.6 versus 48.0±29.0/68.0±37.3 for ventricular/atrial lesions and contrast-enhanced versus nonenhanced imaging).
  
  
  CONCLUSIONS
  MRI allows for precise lesion visualization in electrophysiological interventions just minutes after radiofrequency ablation. Nonenhanced T2-weighted MRI is particularly feasible for intraprocedural delineation of lesion formation as lesions are detectable within minutes after radiofrequency delivery and imaging can be repeated during interventions.
authors.affiliation: Department of Internal Medicine I-Cardiology, University Hospital Würzburg, Würzburg, Germany. nordbeck_p@medizin.uni-wuerzburg.de
authors.forename: Peter
authors.initials: P
authors.lastname: Nordbeck
authors.forename: Karl-Heinz
authors.initials: KH
authors.lastname: Hiller
authors.forename: Florian
authors.initials: F
authors.lastname: Fidler
authors.forename: Marcus
authors.initials: M
authors.lastname: Warmuth
authors.forename: Natalie
authors.initials: N
authors.lastname: Burkard
authors.forename: Matthias
authors.initials: M
authors.lastname: Nahrendorf
authors.forename: Peter M
authors.initials: PM
authors.lastname: Jakob
authors.forename: Harald H
authors.initials: HH
authors.lastname: Quick
authors.forename: Georg
authors.initials: G
authors.lastname: Ertl
authors.forename: Wolfgang R
authors.initials: WR
authors.lastname: Bauer
authors.forename: Oliver
authors.initials: O
authors.lastname: Ritter
mesh_terms: D000818:Animals; D001282:Atrial Flutter / Q000175:diagnosis / Q000601:surgery*; D017115:Catheter Ablation / Q000009:adverse effects; D003287:Contrast Media; D005240:Feasibility Studies; D019786:Gadolinium DTPA; D006801:Humans; D008279:Magnetic Resonance Imaging; D053783:Magnetic Resonance Imaging, Interventional; D009206:Myocardium / Q000473:pathology; D013552:Swine; D013556:Swine, Miniature
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA