title: Beat-to-beat QT interval variability associated with acute myocardial ischemia.
abstract: Beat-to-beat QT interval variability (QTV) quantifies lability in ventricular repolarization. We hypothesized that myocardial ischemia destabilizes ventricular repolarization and increases QTV. We analyzed 2-hour 2-lead digitized electrocardiogram records of 68 patients in the European ST-T Database. All patients had ischemic episodes during the 2-hour record, annotated by the developers of the database. We determined the normalized QTV (QTVnorm), QT variability index (QTVI), and normalized heart rate variability (HRVnorm) for each 5-minute epoch by automated analysis. QTVnorm was greater during ischemic episodes than during nonischemic episodes (1.41 +/- 0.77 vs. 0.88 +/- 0.23, P <.0001). There was no significant difference in HRVnorm between ischemic and nonischemic episodes (1.22 +/- 0.63 vs. 0.94 +/- 0.18, not significant). The QTVI was higher during ischemic episodes than during nonischemic episodes (0.14 +/- 0.31 vs. -0.051 +/- 0.12, P <.0001). Acute ischemia is associated with labile ventricular repolarization, which manifests as enhanced beat-to-beat QT interval variability. The association between ischemic repolarization liability and arrhythmic risk deserves further study.
authors.affiliation: Cardiology Division, Department of Medicine, Johns Hopkins School of Medicine, Baltimore, MD, USA.
authors.forename: Taizo
authors.initials: T
authors.lastname: Murabayashi
authors.forename: Barry
authors.initials: B
authors.lastname: Fetics
authors.forename: David
authors.initials: D
authors.lastname: Kass
authors.forename: Erez
authors.initials: E
authors.lastname: Nevo
authors.forename: Boris
authors.initials: B
authors.lastname: Gramatikov
authors.forename: Ronald D
authors.initials: RD
authors.lastname: Berger
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015716:Electrocardiography, Ambulatory; D022062:Electrophysiologic Techniques, Cardiac; D005060:Europe / Q000453:epidemiology; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006352:Heart Ventricles / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000175:diagnosis / Q000453:epidemiology* / Q000503:physiopathology*; D015588:Observer Variation; D012680:Sensitivity and Specificity; D013997:Time Factors