title: Effect of bundle branch block on microvolt T-wave alternans and electrophysiologic testing in patients with ischemic cardiomyopathy.
abstract: BACKGROUND
  T-wave alternans (TWA) and electrophysiology study (EPS) are used for risk stratification for sudden death.
  
  
  OBJECTIVE
  The purpose of the study was to determine the effect of bundle branch block or intraventricular conduction delay on TWA and EPS.
  
  
  METHODS
  386 patients with coronary artery disease, nonsustained ventricular tachycardia, and left ventricular ejection fraction < or =40% underwent TWA and EPS, and were followed for 40 +/- 19 months.
  
  
  RESULTS
  Patients with wide QRS were more likely than narrow QRS patients to have nonnegative TWA (77% vs 63%, P <.01) or positive EPS (60% vs 48%, P = .03). Nonnegative TWA predicted the combined endpoint of ventricular tachyarrhythmia or death in narrow QRS (HR = 1.64, P = .04) but not wide QRS patients (HR = 1.04, P = .91). Similarly, positive EPS predicted the combined endpoint in narrow QRS (HR = 2.28, P <.001) but not wide QRS patients (HR = 0.94, P = .84). In multivariate analysis, QRS width and TWA, as well as QRS width and EPS, were independent predictors of events. There was no TWA- or EPS-based difference in arrhythmia-free survival within any specific wide QRS morphology.
  
  
  CONCLUSIONS
  TWA and EPS are more often abnormal in patients with a wide QRS than in those with a narrow QRS. In patients with narrow QRS, both TWA and EPS stratify patients according to their risk of ventricular tachyarrhythmia or death. However, among patients with a wide QRS, regardless of specific QRS morphology, the risk is high and comparable regardless of TWA or EPS results. Therefore, the only truly low-risk group consists of those patients with negative test results and a narrow QRS.
authors.affiliation: Maurice & Corinne Greenberg Division of Cardiology, Department of Medicine, Cornell University Medical Center, New York, NY 10021, USA.
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Morin
authors.forename: Eran S
authors.initials: ES
authors.lastname: Zacks
authors.forename: Andreas C
authors.initials: AC
authors.lastname: Mauer
authors.forename: Shaun
authors.initials: S
authors.lastname: Ageno
authors.forename: Matthew
authors.initials: M
authors.lastname: Janik
authors.forename: Steven M
authors.initials: SM
authors.lastname: Markowitz
authors.forename: Suneet
authors.initials: S
authors.lastname: Mittal
authors.forename: Sei
authors.initials: S
authors.lastname: Iwai
authors.forename: Bindi K
authors.initials: BK
authors.lastname: Shah
authors.forename: Bruce B
authors.initials: BB
authors.lastname: Lerman
authors.forename: Kenneth M
authors.initials: KM
authors.lastname: Stein
mesh_terms: D000368:Aged; D002037:Bundle-Branch Block / Q000175:diagnosis / Q000401:mortality / Q000503:physiopathology*; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D022062:Electrophysiologic Techniques, Cardiac; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000503:physiopathology*