title: Early repolarization is associated with symptoms in patients with type 1 and type 2 long QT syndrome.
abstract: BACKGROUND
  Early repolarization (ER) is associated with an increased risk for death from cardiac causes. Recent evidence supports ER's role as a modifier and/or predictor of risk in many cardiac conditions.
  
  
  OBJECTIVE
  The purpose of this study was to determine the prevalence of ER among genotype-positive patients with long QT syndrome (LQTS) and evaluate its utility in predicting the risk of symptoms.
  
  
  METHODS
  ER was defined as QRS slurring and/or notching associated with ≥1-mV QRS-ST junction (J-point) elevation in at least 2 contiguous leads, excluding the anterior precordial leads. The ECG with the most prominent ER was used for analysis. Major ER was defined as ≥ 2-mm J-point elevation. Symptoms of LQTS included cardiac syncope, documented polymorphic ventricular tachycardia (VT), and resuscitated cardiac arrest.
  
  
  RESULTS
  One hundred thirteen patients (mean age 41 ± 19 years; 63 female) were reviewed, among whom 414 (mean 3.7 ± 1.5) ECGs were analyzed. Of these, 30 patients (27%) with a history of symptoms. Fifty patients (44%) had ER, and 19 patients (17%) had major ER. Patients with major ER were not different from patients without major ER with respect to age, sex, long QT type, longest QTc recorded, number of patients with QTc >500 ms, or use of beta-blockade. Univariate and independent predictors of symptom status included the presence of major ER, longest QTc recorded >500 ms, and female sex.
  
  
  CONCLUSIONS
  ER ≥2 mm was the strongest independent predictor of symptom status related to LQTS, along with female sex and QTc >500 ms.
authors.affiliation: Division of Cardiology, University of Western Ontario, London, Ontario, Canada.
authors.forename: Zachary W M
authors.initials: ZW
authors.lastname: Laksman
authors.affiliation: Division of Cardiology, University of Western Ontario, London, Ontario, Canada.
authors.forename: Lorne J
authors.initials: LJ
authors.lastname: Gula
authors.affiliation: Division of Cardiology, University of Western Ontario, London, Ontario, Canada.
authors.forename: Pradyot
authors.initials: P
authors.lastname: Saklani
authors.affiliation: Division of Cardiology, University of Western Ontario, London, Ontario, Canada.
authors.forename: Romain
authors.initials: R
authors.lastname: Cassagneau
authors.affiliation: Division of Cardiology, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Christian
authors.initials: C
authors.lastname: Steinberg
authors.affiliation: Division of Cardiology, University of Western Ontario, London, Ontario, Canada.
authors.forename: Susan
authors.initials: S
authors.lastname: Conacher
authors.affiliation: Division of Cardiology, University of Western Ontario, London, Ontario, Canada.
authors.forename: Raymond
authors.initials: R
authors.lastname: Yee
authors.affiliation: Division of Cardiology, University of Western Ontario, London, Ontario, Canada.
authors.forename: Allan
authors.initials: A
authors.lastname: Skanes
authors.affiliation: Division of Cardiology, University of Western Ontario, London, Ontario, Canada.
authors.forename: Peter
authors.initials: P
authors.lastname: Leong-Sit
authors.affiliation: Division of Cardiology, University of Western Ontario, London, Ontario, Canada.
authors.forename: Jaimie
authors.initials: J
authors.lastname: Manlucu
authors.affiliation: Division of Cardiology, University of Western Ontario, London, Ontario, Canada.
authors.forename: George J
authors.initials: GJ
authors.lastname: Klein
authors.affiliation: Division of Cardiology, University of British Columbia, Vancouver, British Columbia, Canada. Electronic address: akrahn@mail.ubc.ca.
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Krahn
mesh_terms: D000328:Adult; D004247:DNA / Q000235:genetics; D004252:DNA Mutational Analysis; D004562:Electrocardiography; D005260:Female; D005500:Follow-Up Studies; D005838:Genotype; D006329:Heart Conduction System / Q000503:physiopathology*; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D015994:Incidence; D051657:KCNQ1 Potassium Channel / Q000235:genetics; D051658:KCNQ2 Potassium Channel / Q000235:genetics; D008131:London / Q000453:epidemiology; D008133:Long QT Syndrome / Q000453:epidemiology* / Q000235:genetics / Q000503:physiopathology; D008297:Male; D009154:Mutation; D016017:Odds Ratio; D012189:Retrospective Studies; D018570:Risk Assessment / Q000379:methods*; D029597:Romano-Ward Syndrome / Q000235:genetics* / Q000503:physiopathology; D013997:Time Factors
chemical_list: D051657:KCNQ1 Potassium Channel; C496909:KCNQ1 protein, human; D051658:KCNQ2 Potassium Channel; C496914:KCNQ2 protein, human; D004247:DNA
keywords: Arrhythmia; Early repolarization; Long QT syndrome; Risk stratification; Syncope