title: ECG quantification of myocardial scar in cardiomyopathy patients with or without conduction defects: correlation with cardiac magnetic resonance and arrhythmogenesis.
abstract: BACKGROUND
  Myocardial scarring from infarction or nonischemic fibrosis forms an arrhythmogenic substrate. The Selvester QRS score has been extensively validated for estimating myocardial infarction scar size in the absence of ECG confounders, but has not been tested to quantify scar in patients with hypertrophy, bundle branch/fascicular blocks, or nonischemic cardiomyopathy. We assessed the hypotheses that (1) QRS scores (modified for each ECG confounder) correctly identify and quantify scar in ischemic and nonischemic patients when compared with the reference standard of cardiac magnetic resonance using late-gadolinium enhancement, and (2) QRS-estimated scar size predicts inducible sustained monomorphic ventricular tachycardia during electrophysiological testing.
  
  
  RESULTS
  One hundred sixty-two patients with left ventricular ejection fraction < or =35% (95 ischemic, 67 nonischemic) received 12-lead ECG and cardiac magnetic resonance using late-gadolinium enhancement before implantable cardioverter defibrillator placement for primary prevention of sudden cardiac death. QRS scores correctly diagnosed cardiovascular magnetic resonance scar presence with receiver operating characteristics area under the curve of 0.91 and correlation for scar quantification of r=0.74 (P<0.0001) for all patients. Performance within hypertrophy, conduction defect, and nonischemic subgroups ranged from area under the curve of 0.81 to 0.94 and r=0.60 to 0.80 (P<0.001 for all). Among the 137 patients undergoing electrophysiological or device testing, each 3-point QRS-score increase (9% left ventricular scarring) was associated with an odds ratio for inducing monomorphic ventricular tachycardia of 2.2 (95% CI, 1.5 to 3.2; P<0.001) for all patients, 1.7 (1.0 to 2.7, P=0.04) for ischemics, and 2.2 (1.0 to 5.0, P=0.05) for nonischemics.
  
  
  CONCLUSIONS
  QRS scores identify and quantify scar in ischemic and nonischemic cardiomyopathy patients despite ECG confounders. Higher QRS-estimated scar size is associated with increased arrhythmogenesis and warrants further study as a risk-stratifying tool.
authors.affiliation: Division of Cardiology, Department of Medicine, Johns Hopkins Medical Institutions, Baltimore, MD 21287, USA.
authors.forename: David G
authors.initials: DG
authors.lastname: Strauss
authors.forename: Ronald H
authors.initials: RH
authors.lastname: Selvester
authors.forename: João A C
authors.initials: JA
authors.lastname: Lima
authors.forename: Håkan
authors.initials: H
authors.lastname: Arheden
authors.forename: Julie M
authors.initials: JM
authors.lastname: Miller
authors.forename: Gary
authors.initials: G
authors.lastname: Gerstenblith
authors.forename: Eduardo
authors.initials: E
authors.lastname: Marbán
authors.forename: Robert G
authors.initials: RG
authors.lastname: Weiss
authors.forename: Gordon F
authors.initials: GF
authors.lastname: Tomaselli
authors.forename: Galen S
authors.initials: GS
authors.lastname: Wagner
authors.forename: Katherine C
authors.initials: KC
authors.lastname: Wu
mesh_terms: D000328:Adult; D000368:Aged; D009202:Cardiomyopathies / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology / Q000628:therapy; D002921:Cicatrix; D003287:Contrast Media; D016757:Death, Sudden, Cardiac / Q000209:etiology* / Q000473:pathology / Q000517:prevention & control; D017147:Defibrillators, Implantable; D004562:Electrocardiography; D005260:Female; D005355:Fibrosis; D005682:Gadolinium; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D016015:Logistic Models; D019028:Magnetic Resonance Imaging, Cine; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000150:complications* / Q000473:pathology / Q000503:physiopathology; D009206:Myocardium / Q000473:pathology*; D015588:Observer Variation; D016017:Odds Ratio; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012372:ROC Curve; D015203:Reproducibility of Results; D018570:Risk Assessment; D012307:Risk Factors; D013318:Stroke Volume; D017180:Tachycardia, Ventricular / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology / Q000517:prevention & control; D018487:Ventricular Dysfunction, Left / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology / Q000628:therapy; D016277:Ventricular Function, Left
chemical_list: D003287:Contrast Media; D005682:Gadolinium