title: Ambulatory electrocardiographic evidence of transmural dispersion of repolarization in patients with long-QT syndrome type 1 and 2.
abstract: BACKGROUND
  Transmural dispersion of repolarization (TDR) may be related to the genesis of torsade de pointes (TdP) in patients with the long-QT (LQT) syndrome. Experimentally, LQT2 models show increased TDR compared with LQT1, and beta-adrenergic stimulation increases TDR in both models. Clinically, LQT1 patients experience symptoms at elevated heart rates, but LQT2 patients do so at lower rates. The interval from T-wave peak to T-wave end (TPE interval) is the clinical counterpart of TDR. We explored the relationship of TPE interval to heart rate and to the presence of symptoms in patients with LQT1 and LQT2.
  
  
  RESULTS
  We reviewed Holter recordings from 90 genotyped subjects, 31 with LQT1, 28 with LQT2, and 31 from unaffected family members, to record TPE intervals by use of an automated computerized program. The median TPE interval was greater in LQT2 (112+/-5 ms) than LQT1 (91+/-2 ms) or unaffected (86+/-3 ms) patients (P<0.001 for all group comparisons), and the maximal TPE values differed as well. LQT1 patients showed abrupt increases in TPE values at RR intervals from 600 to 900 ms, but LQT2 patients did so at RR intervals from 600 to 1400 ms (longest RR studied). Asymptomatic and symptomatic patients showed similar TDRs.
  
  
  CONCLUSIONS
  TDR is greater in LQT2 than in LQT1 patients. LQT1 patients showed a capacity to increase TDR at elevated heart rates, but LQT2 patients did so at a much wider rate range. The magnitude of TDR is not related to a history of TdP.
authors.affiliation: Department of Medicine, Cardiac Electrophysiology, University of California, San Francisco, USA. matti.viitasalo@hus.fi
authors.forename: Matti
authors.initials: M
authors.lastname: Viitasalo
authors.forename: Lasse
authors.initials: L
authors.lastname: Oikarinen
authors.forename: Heikki
authors.initials: H
authors.lastname: Swan
authors.forename: Heikki
authors.initials: H
authors.lastname: Väänänen
authors.forename: Kathy
authors.initials: K
authors.lastname: Glatter
authors.forename: Päivi J
authors.initials: PJ
authors.lastname: Laitinen
authors.forename: Kimmo
authors.initials: K
authors.lastname: Kontula
authors.forename: Hal V
authors.initials: HV
authors.lastname: Barron
authors.forename: Lauri
authors.initials: L
authors.lastname: Toivonen
authors.forename: Melvin M
authors.initials: MM
authors.lastname: Scheinman
mesh_terms: D000328:Adult; D015716:Electrocardiography, Ambulatory / Q000706:statistics & numerical data; D005260:Female; D005838:Genotype; D006339:Heart Rate; D006801:Humans; D008133:Long QT Syndrome / Q000145:classification / Q000175:diagnosis* / Q000503:physiopathology*; D008297:Male; D011237:Predictive Value of Tests; D012307:Risk Factors; D029597:Romano-Ward Syndrome / Q000175:diagnosis / Q000503:physiopathology; D012815:Signal Processing, Computer-Assisted; D016171:Torsades de Pointes / Q000503:physiopathology