title: Characterization of the arrhythmogenic substrate in ischemic and nonischemic cardiomyopathy implications for catheter ablation of hemodynamically unstable ventricular tachycardia.
abstract: OBJECTIVE
  The purpose of this study was to compare the characteristics and prevalence of late potentials (LP) in patients with nonischemic cardiomyopathy (NICM) and ischemic cardiomyopathy (ICM) etiologies and evaluate their value as targets for catheter ablation.
  
  
  BACKGROUND
  LP are frequently found in post-myocardial infarction scars and are useful ablation targets. The relative prevalence and characteristics of LP in patients with NICM is not well understood.
  
  
  METHODS
  Thirty-three patients with structural heart disease (NICM, n = 16; ICM, n = 17) referred for catheter ablation of ventricular tachycardia were studied. Electroanatomic mapping was performed endocardially (n = 33) and epicardially (n = 19). The LP were defined as low voltage electrograms (<1.5 mV) with onset after the QRS interval. Very late potentials (vLP) were defined as electrograms with onset >100 ms after the QRS.
  
  
  RESULTS
  We sampled an average of 564 +/- 449 points and 726 +/- 483 points in the left ventricle endocardium and epicardium, respectively. Mean total low voltage area in patients with ICM was 101 +/- 55 cm(2) and 56 +/- 33 cm(2), endocardial and epicardial, respectively, compared with NICM of 55 +/- 41 cm(2) and 53 +/- 28 cm(2), respectively. Within the total low voltage area, vLP were observed more frequently in ICM than in NICM in endocardium (4.1% vs. 1.3%; p = 0.0003) and epicardium (4.3% vs. 2.1%, p = 0.035). An LP-targeted ablation strategy was effective in ICM patients (82% nonrecurrence at 12 +/- 10 months of follow-up), whereas NICM patients had less favorable outcomes (50% at 15 +/- 13 months of follow-up).
  
  
  CONCLUSIONS
  The contribution of scar to the electrophysiological abnormalities targeted for ablation of unstable ventricular tachycardia differs between ICM and NICM. An approach incorporating LP ablation and pace-mapping had limited success in patients with NICM compared with ICM, and alternative ablation strategies should be considered.
authors.affiliation: University of California, Los Angeles, Cardiac Arrhythmia Center, David Geffen School of Medicine, Los Angeles, California, USA.
authors.forename: Shiro
authors.initials: S
authors.lastname: Nakahara
authors.forename: Roderick
authors.initials: R
authors.lastname: Tung
authors.forename: Rafael J
authors.initials: RJ
authors.lastname: Ramirez
authors.forename: Yoav
authors.initials: Y
authors.lastname: Michowitz
authors.forename: Marmar
authors.initials: M
authors.lastname: Vaseghi
authors.forename: Eric
authors.initials: E
authors.lastname: Buch
authors.forename: Jean
authors.initials: J
authors.lastname: Gima
authors.forename: Isaac
authors.initials: I
authors.lastname: Wiener
authors.forename: Aman
authors.initials: A
authors.lastname: Mahajan
authors.forename: Noel G
authors.initials: NG
authors.lastname: Boyle
authors.forename: Kalyanam
authors.initials: K
authors.lastname: Shivkumar
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019571:Arrhythmogenic Right Ventricular Dysplasia / Q000150:complications / Q000175:diagnosis* / Q000601:surgery; D018780:Body Surface Potential Mapping / Q000379:methods; D009202:Cardiomyopathies / Q000150:complications / Q000473:pathology / Q000601:surgery; D017115:Catheter Ablation / Q000009:adverse effects / Q000379:methods*; D015331:Cohort Studies; D004562:Electrocardiography; D056149:Epicardial Mapping; D005260:Female; D005500:Follow-Up Studies; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000150:complications / Q000175:diagnosis / Q000601:surgery; D018570:Risk Assessment; D012720:Severity of Illness Index; D017180:Tachycardia, Ventricular / Q000175:diagnosis / Q000601:surgery*; D013997:Time Factors; D016896:Treatment Outcome