title: Assessment of ventricular repolarization variability with the DeltaT50 method improves identification of patients with congenital long QT syndromes.
abstract: BACKGROUND
  We analyzed ventricular repolarization variability in genotyped long QT syndrome (LQTS) patients and in healthy volunteers (HV).
  
  
  METHODS
  The deltaT50, that is, the temporal variability of ventricular repolarization at 50% of the T-wave downslope, was analyzed every 15th minute on 175 and 390 Holter electrocardiogram (ECG) recordings from HV and genotyped LQTS patients, respectively. The average deltaT50 and QTcF were calculated in each subject.
  
  
  RESULTS
  DeltaT50 was 2.26 ± 0.71 ms (mean ± SD) in the HV and 5.74 ± 2.30 ms in the LQTS population (P < 0.0001). The sensitivity and specificity of QTcF (cutoff value 450 ms) to discriminate between the LQTS patients and the HV were 51.5% and 98.9%, and for deltaT50 (cutoff value 3 ms) 93.9% and 88.6%, respectively. The combination of both variables improved the diagnosis of the LQTS patients even further. Subgroups of LQTS patients at higher risk of cardiac events (with LQTS3, JLN, QTc > 500 ms or symptoms) had higher deltaT50 than subgroups at lower risk (with LQTS1, QTc < 450 ms or without symptoms). The variation in deltaT50 between day and night was concordant with the risk of symptoms; patients with LQTS1 had higher deltaT50 in the daytime and patients with LQTS3 had higher deltaT50 during the night.
  
  
  CONCLUSIONS
  DeltaT50 more accurately distinguished between LQTS patients and HV than QTcF and was higher in LQTS patients with a higher risk of cardiac events. DeltaT50 can be used together with QTcF to improve the diagnosis in patients with the LQTS phenotype and tentatively also be of value for risk assessment in such patients.
authors.affiliation: AstraZeneca R&D, Mölndal, Sweden. christina.abrahamsson@astrazeneca.com
authors.forename: Christina
authors.initials: C
authors.lastname: Abrahamsson
authors.forename: Corina
authors.initials: C
authors.lastname: Dota
authors.forename: Bo
authors.initials: B
authors.lastname: Skallefell
authors.forename: Leif
authors.initials: L
authors.lastname: Carlsson
authors.forename: Lars
authors.initials: L
authors.lastname: Frison
authors.forename: Anders
authors.initials: A
authors.lastname: Berggren
authors.forename: Nils
authors.initials: N
authors.lastname: Edvardsson
authors.forename: Göran
authors.initials: G
authors.lastname: Duker
mesh_terms: D000293:Adolescent; D000319:Adrenergic beta-Antagonists / Q000627:therapeutic use; D000328:Adult; D000368:Aged; D000465:Algorithms; D002648:Child; D002675:Child, Preschool; D015716:Electrocardiography, Ambulatory / Q000379:methods*; D005260:Female; D005838:Genotype; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D007223:Infant; D008133:Long QT Syndrome / Q000175:diagnosis* / Q000188:drug therapy / Q000235:genetics / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D018570:Risk Assessment; D012984:Software
chemical_list: D000319:Adrenergic beta-Antagonists