Effect of bundle branch block on microvolt T-wave alternans and electrophysiologic testing in patients with ischemic cardiomyopathy

Heart Rhythm. 2007 Jul;4(7):904-12. doi: 10.1016/j.hrthm.2007.02.027. Epub 2007 Mar 12.


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.

Conclusion: 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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Bundle-Branch Block / diagnosis
  • Bundle-Branch Block / mortality
  • Bundle-Branch Block / physiopathology*
  • Cardiac Pacing, Artificial / methods*
  • Electrophysiologic Techniques, Cardiac*
  • Female
  • Humans
  • Male
  • Middle Aged
  • Myocardial Ischemia / physiopathology*