title: Scar voltage threshold determination using ex vivo magnetic resonance imaging integration in a porcine infarct model: Influence of interelectrode distances and three-dimensional spatial effects of scar.
abstract: Studies analyzing optimal voltage thresholds for scar detection with electroanatomic mapping frequently lack a gold standard for comparison.
  
  
  
  The purpose of this study was to use a porcine infarct model with ex vivo magnetic resonance imaging (MRI) integration to characterize the relationship between interelectrode spacing and bipolar voltage thresholds and examine the influence of 3-dimensional scar on unipolar voltages.
  
  
  
  Thirty-two combined endocardial-epicardial electroanatomic maps were created in 8 postinfarct porcine subjects (bipolar 2-mm, 5-mm, and 8-mm interelectrode spacing and unipolar) for comparison with ex vivo MRI. Two thresholds were compared: (1) 95% normal distribution and (2) best fit to MRI. Direct electrogram analysis was performed in regions across from MRI-defined scar and adjacent to scar border zone.
  
  
  
  A linear increase in optimal thresholds was observed with wider bipole spacing. The 95% thresholds for scar were lower than MRI-matched thresholds with moderate sensitivity for nontransmural scar (54% endo, 63% epi). Unipolar endocardial scar area exceeded MRI-defined scar, resulting in mismatched false scar in 5 of 8 (63%). Endocardial and epicardial unipolar voltages were lower than normal in regions adjacent and across from scar.
  
  
  
  Variations in interelectrode spacing necessitate tailored bipolar voltage thresholds to optimize scar detection. Statistical 95% thresholds appear to be conservative and not fully sensitive for the detection of scar defined by high-resolution ex vivo MRI. In the presence of endocardial scar, unipolar mapping to quantitatively characterize epicardial scar may be overly sensitive due to 3-dimensional spatial averaging.
authors.affiliation: UCLA Cardiac Arrhythmia Center, UCLA Health System, Los Angeles, California. Electronic address: rodericktung@uchicago.edu.
authors.forename: Roderick
authors.initials: R
authors.lastname: Tung
authors.affiliation: St. Jude Medical, Minneapolis, Minnesota.
authors.forename: Steve
authors.initials: S
authors.lastname: Kim
authors.affiliation: UCLA Cardiac Arrhythmia Center, UCLA Health System, Los Angeles, California.
authors.forename: Daigo
authors.initials: D
authors.lastname: Yagishita
authors.affiliation: UCLA Cardiac Arrhythmia Center, UCLA Health System, Los Angeles, California.
authors.forename: Marmar
authors.initials: M
authors.lastname: Vaseghi
authors.affiliation: Department of Radiological Sciences, University of California, Los Angeles, California,; Department of Bioengineering, University of California, Los Angeles, California.
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Ennis
authors.affiliation: Department of Bioengineering, University of California, Los Angeles, California.
authors.forename: Sarah
authors.initials: S
authors.lastname: Ouadah
authors.affiliation: UCLA Cardiac Arrhythmia Center, UCLA Health System, Los Angeles, California.
authors.forename: Olujimi A
authors.initials: OA
authors.lastname: Ajijola
authors.affiliation: UCLA Cardiac Arrhythmia Center, UCLA Health System, Los Angeles, California.
authors.forename: Jason S
authors.initials: JS
authors.lastname: Bradfield
authors.affiliation: St. Jude Medical, Minneapolis, Minnesota.
authors.forename: Srijoy
authors.initials: S
authors.lastname: Mahapatra
authors.affiliation: Department of Radiological Sciences, University of California, Los Angeles, California.
authors.forename: Paul
authors.initials: P
authors.lastname: Finn
authors.affiliation: UCLA Cardiac Arrhythmia Center, UCLA Health System, Los Angeles, California; Department of Radiological Sciences, University of California, Los Angeles, California,; Department of Bioengineering, University of California, Los Angeles, California.
authors.forename: Kalyanam
authors.initials: K
authors.lastname: Shivkumar
mesh_terms: D000818:Animals; D002921:Cicatrix / Q000000981:diagnostic imaging* / Q000209:etiology / Q000503:physiopathology; D004195:Disease Models, Animal; D022062:Electrophysiologic Techniques, Cardiac / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009203:Myocardial Infarction / Q000150:complications*; D009206:Myocardium / Q000473:pathology*; D013552:Swine; D017180:Tachycardia, Ventricular / Q000209:etiology / Q000517:prevention & control
keywords: Bipolar; Electroanatomic mapping; Infarct; Magnetic resonance imaging; Porcine; Unipolar; Ventricular scar; Voltage threshold