title: Risk prediction of cardiovascular death based on the QTc interval: evaluating age and gender differences in a large primary care population.
abstract: OBJECTIVE
  Using a large, contemporary primary care population we aimed to provide absolute long-term risks of cardiovascular death (CVD) based on the QTc interval and to test whether the QTc interval is of value in risk prediction of CVD on an individual level.
  
  
  RESULTS
  Digital electrocardiograms from 173 529 primary care patients aged 50-90 years were collected during 2001-11. The Framingham formula was used for heart rate-correction of the QT interval. Data on medication, comorbidity, and outcomes were retrieved from administrative registries. During a median follow-up period of 6.1 years, 6647 persons died from cardiovascular causes. Long-term risks of CVD were estimated for subgroups defined by age, gender, cardiovascular disease, and QTc interval categories. In general, we observed an increased risk of CVD for both very short and long QTc intervals. Prolongation of the QTc interval resulted in the worst prognosis for men whereas in women, a very short QTc interval was equivalent in risk to a borderline prolonged QTc interval. The effect of the QTc interval on the absolute risk of CVD was most pronounced in the elderly and in those with cardiovascular disease whereas the effect was negligible for middle-aged women without cardiovascular disease. The most important improvement in prediction accuracy was noted for women aged 70-90 years. In this subgroup, a total of 9.5% were reclassified (7.2% more accurately vs. 2.3% more inaccurately) within clinically relevant 5-year risk groups when the QTc interval was added to a conventional risk model for CVD.
  
  
  CONCLUSIONS
  Important differences were observed across subgroups when the absolute long-term risk of CVD was estimated based on QTc interval duration. The accuracy of the personalized CVD prognosis can be improved when the QTc interval is introduced to a conventional risk model for CVD.
authors.affiliation: Danish National Research Foundation Centre for Cardiac Arrhythmia (DARC), Copenhagen, Denmark Laboratory for Molecular Cardiology, The Heart Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark jonas.bille.nielsen@gmail.com.
authors.forename: Jonas B
authors.initials: JB
authors.lastname: Nielsen
authors.affiliation: Department of Health Science and Technology, Aalborg University, Aalborg, Denmark.
authors.forename: Claus
authors.initials: C
authors.lastname: Graff
authors.affiliation: Danish National Research Foundation Centre for Cardiac Arrhythmia (DARC), Copenhagen, Denmark Laboratory for Molecular Cardiology, The Heart Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Peter V
authors.initials: PV
authors.lastname: Rasmussen
authors.affiliation: Copenhagen General Practitioners' Laboratory, Copenhagen, Denmark.
authors.forename: Adrian
authors.initials: A
authors.lastname: Pietersen
authors.affiliation: Copenhagen General Practitioners' Laboratory, Copenhagen, Denmark.
authors.forename: Bent
authors.initials: B
authors.lastname: Lind
authors.affiliation: Danish National Research Foundation Centre for Cardiac Arrhythmia (DARC), Copenhagen, Denmark Laboratory for Molecular Cardiology, The Heart Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Morten S
authors.initials: MS
authors.lastname: Olesen
authors.affiliation: Department of Health Science and Technology, Aalborg University, Aalborg, Denmark.
authors.forename: Johannes J
authors.initials: JJ
authors.lastname: Struijk
authors.affiliation: Danish National Research Foundation Centre for Cardiac Arrhythmia (DARC), Copenhagen, Denmark Laboratory for Molecular Cardiology, The Heart Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Stig
authors.initials: S
authors.lastname: Haunsø
authors.affiliation: Danish National Research Foundation Centre for Cardiac Arrhythmia (DARC), Copenhagen, Denmark Laboratory for Molecular Cardiology, The Heart Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Jesper H
authors.initials: JH
authors.lastname: Svendsen
authors.affiliation: Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Lars
authors.initials: L
authors.lastname: Køber
authors.affiliation: Department of Biostatistics, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Gerds
authors.affiliation: Danish National Research Foundation Centre for Cardiac Arrhythmia (DARC), Copenhagen, Denmark Laboratory for Molecular Cardiology, The Heart Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Anders G
authors.initials: AG
authors.lastname: Holst
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D002318:Cardiovascular Diseases / Q000401:mortality* / Q000503:physiopathology; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D018570:Risk Assessment / Q000379:methods; D012737:Sex Factors
keywords: Cardiovascular death; Gender; Marquette 12SL validation; QTc interval; Risk prediction