title: Ratio of late to early T-wave peak amplitude in 24-h electrocardiographic recordings as indicator of symptom history in patients with long-QT Syndrome types 1 and 2.
abstract: We reviewed 24-h electrocardiographic recordings from 214 genotyped subjects--97 with long-QT syndrome type 1 (LQT1), 62 with LQT2, and 55 unaffected--to record maximal diurnal amplitude ratios between late and early T-wave peaks. Maximal amplitude ratios between late and early T-wave peaks were higher in symptomatic than in asymptomatic patients both in LQT1 (3.2 +/- 1.0 vs. 2.3 +/- 0.8; p < 0.001) and in LQT2 patients (2.6 +/- 1.0 vs. 1.7 +/- 0.5; p < 0.001). The maximal amplitude ratio between late and early T-wave peaks was independently associated with symptom history in both LQT1 and LQT2 patients.
  
  
  OBJECTIVE
  We tested the hypothesis that in long-QT syndrome types 1 (LQT1) and 2 (LQT2), the diurnal maximal ratio between late and early T-wave peak amplitudes correlates with a history of symptoms better than QT interval durations.
  
  
  BACKGROUND
  Genotype and phenotype studies have delineated clinical profiles of the most prevalent LQT1 and LQT2 subtypes of inherited LQT, but prediction of arrhythmia risk remains uncertain, the baseline QTc interval being the best predictor. In experimental long-QT syndrome models, the ratio between late and early T-wave peak amplitude predicts onset of torsade de pointes.
  
  
  METHODS
  We reviewed 24-h electrocardiographic recordings from 214 genotyped subjects--97 with LQT1, 62 with LQT2, and 55 unaffected-to record maximal amplitude ratios between late and early T-wave peaks by use of a computer-assisted program.
  
  
  RESULTS
  Maximal amplitude ratios between late and early T-wave peaks were higher in symptomatic than in asymptomatic patients both in LQT1 (3.2 +/- 1.0 vs. 2.3 +/- 0.8; p < 0.001) and LQT2 patients (2.6 +/- 1.0 vs. 1.7 +/- 0.5; p < 0.001). Although the QTc interval also was longer in symptomatic patients, only the maximal amplitude ratio between late and early T-wave peaks was independently associated with symptoms in both LQT1 and LQT2 patients.
  
  
  CONCLUSIONS
  Maximal diurnal ratio between late and early T-wave peak amplitude improves noninvasive risk assessment both in LQT1 and LQT2 syndromes. We propose this new indicator in clinical evaluation of arrhythmia risk in LQT1 and LQT2.
authors.affiliation: Department of Cardiology, Helsinki University Central Hospital, Helsinki, Finland. 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: Kathryn A
authors.initials: KA
authors.lastname: Glatter
authors.forename: Heikki
authors.initials: H
authors.lastname: Väänänen
authors.forename: Heidi
authors.initials: H
authors.lastname: Fodstad
authors.forename: Nipavan
authors.initials: N
authors.lastname: Chiamvimonvat
authors.forename: Kimmo
authors.initials: K
authors.lastname: Kontula
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; D005260:Female; D005838:Genotype; D006801:Humans; D008133:Long QT Syndrome / Q000175:diagnosis* / Q000235:genetics; D008297:Male; D029597:Romano-Ward Syndrome / Q000175:diagnosis / Q000235:genetics