title: Electrophysiologic Scar Substrate in Relation to VT: Noninvasive High-Resolution Mapping and Risk Assessment with ECGI.
abstract: BACKGROUND
  Ischemic cardiomyopathy (ICM) can provide the substrate for ventricular tachycardia (VT).
  
  
  OBJECTIVE
  To map noninvasively with high resolution the electrophysiologic (EP) scar substrate, identify its relationship to reentry circuits during VT, and stratify VT risk in ICM patients.
  
  
  METHODS
  Noninvasive high-resolution epicardial mapping with electrocardiographic imaging (ECGI) was performed in 32 ICM patients (17 with clinical VT, 15 without VT). Abnormal scar EP substrate was determined based on electrogram (EGM) amplitude (as percentage of maximal peak-to-peak voltage over the entire ventricular epicardium; total scar [TS] < 30%; dense scar [DS] < 15%), fractionation, and presence of late potentials (LPs). Scar burden was defined as the ratio of the scar size to the total epicardial surface area. The VT activation pattern was mapped and correlated with the EP substrate to identify components of the reentry circuit.
  
  
  RESULTS
  Patients with VT had higher scar burden (TS: 51.0 ± 9.3% vs 36.5 ± 5.4%, P < 0.05; DS: 29.5 ± 7.3% vs 16.8 ± 6.8%, P < 0.05) with lower normalized unipolar EGM voltage (TS: 0.107 ± 0.027 vs 0.153 ± 0.031, P < 0.05; DS: 0.073 ± 0.023 vs 0.098 ± 0.026, P < 0.05), greater prevalence of fractionated EGMs (TS: 44.1 ± 10.6% vs 26.8 ± 6.3%, P < 0.05; DS: 50.8 ± 10.8% vs 30.9 ± 7.0%, P < 0.05), and LPs (TS: 26.8 ± 10.7% vs 15.8 ± 5.3, P < 0.05). VTs were mapped in eight patients; the reentry circuits were closely related to the EP substrate.
  
  
  CONCLUSIONS
  ECGI noninvasively identified scar EP substrate that underlies abnormal conduction in ICM patients. It identified regions within the scar that aligned with critical elements of the reentry circuit during VT. ECGI can potentially be used for VT risk stratification in ICM patients.
authors.affiliation: Cardiac Bioelectricity and Arrhythmia Center, Washington University, St. Louis, Missouri.|Department of Biomedical Engineering, Washington University, St. Louis, Missouri.
authors.forename: Junjie
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Cardiac Bioelectricity and Arrhythmia Center, Washington University, St. Louis, Missouri.|School of Medicine, Washington University, St. Louis, Missouri.
authors.forename: Daniel H
authors.initials: DH
authors.lastname: Cooper
authors.affiliation: Cardiac Bioelectricity and Arrhythmia Center, Washington University, St. Louis, Missouri.
authors.forename: Kavit A
authors.initials: KA
authors.lastname: Desouza
authors.affiliation: Cardiac Bioelectricity and Arrhythmia Center, Washington University, St. Louis, Missouri.|School of Medicine, Washington University, St. Louis, Missouri.
authors.forename: Phillip S
authors.initials: PS
authors.lastname: Cuculich
authors.affiliation: Cardiac Bioelectricity and Arrhythmia Center, Washington University, St. Louis, Missouri.|Department of Biomedical Engineering, Washington University, St. Louis, Missouri.|School of Medicine, Washington University, St. Louis, Missouri.
authors.forename: Pamela K
authors.initials: PK
authors.lastname: Woodard
authors.affiliation: Cardiac Bioelectricity and Arrhythmia Center, Washington University, St. Louis, Missouri.|School of Medicine, Washington University, St. Louis, Missouri.
authors.forename: Timothy W
authors.initials: TW
authors.lastname: Smith
authors.affiliation: Cardiac Bioelectricity and Arrhythmia Center, Washington University, St. Louis, Missouri.|Department of Biomedical Engineering, Washington University, St. Louis, Missouri.|School of Medicine, Washington University, St. Louis, Missouri.
authors.forename: Yoram
authors.initials: Y
authors.lastname: Rudy
mesh_terms: D000368:Aged; D018780:Body Surface Potential Mapping / Q000379:methods*; D002921:Cicatrix / Q000175:diagnosis / Q000503:physiopathology; D004562:Electrocardiography / Q000379:methods*; D005260:Female; D005355:Fibrosis; D006329:Heart Conduction System / Q000473:pathology* / Q000503:physiopathology*; D006801:Humans; D008297:Male; D015203:Reproducibility of Results; D018570:Risk Assessment / Q000379:methods; D012680:Sensitivity and Specificity; D017180:Tachycardia, Ventricular / Q000175:diagnosis* / Q000503:physiopathology*
keywords: arrhythmias; electrophysiology; mapping; myocardial infarction