title: Optimal QT interval correction formula in sinus tachycardia for identifying cardiovascular and mortality risk: Findings from the Penn Atrial Fibrillation Free study.
abstract: BACKGROUND
  The QT interval measures cardiac repolarization, and prolongation is associated with adverse cardiovascular outcomes and death. The exponential Bazett correction formula overestimates the QT interval during tachycardia.
  
  
  OBJECTIVE
  We evaluated 4 formulas of QT interval correction in individuals with sinus tachycardia for the identification of coronary artery disease, heart failure, and mortality.
  
  
  METHODS
  The Penn Atrial Fibrillation Free study is a large cohort study of patients without atrial fibrillation. The present study examined 6723 Penn Atrial Fibrillation Free study patients without a history of heart failure and with baseline sinus rate ≥100 beats/min. Medical records were queried for index clinical parameters, incident cardiovascular events, and all-cause mortality. The QT interval was corrected by using Bazett (QT/RR(0.5)), Fridericia (QT/RR(0.33)), Framingham [QT + 0.154 * (1000 - RR)], and Hodges (QT + 105 * (1/RR - 1)) formulas.
  
  
  RESULTS
  In 6723 patients with a median follow-up of 4.5 years (interquartile range 1.9-6.4 years), the annualized cardiovascular event rate was 2.3% and the annualized mortality rate was 2.2%. QT prolongation was diagnosed in 39% of the cohort using the Bazett formula, 6.2% using the Fridericia formula, 3.7% using the Framingham formula, and 8.7% using the Hodges formula. Only the Hodges formula was an independent risk marker for death across the range of QT values (highest tertile: hazard ratio 1.26; 95% confidence interval 1.03-1.55).
  
  
  CONCLUSIONS
  Although all correction formulas demonstrated an association between QTc values and cardiovascular events, only the Hodges formula identified one-third of individuals with tachycardia that are at higher risk of all-cause mortality. Furthermore, the Bazett correction formula overestimates the number of patients with a prolonged QT interval and was not associated with mortality. Future work may validate these findings and result in changes to automated algorithms for QT interval assessment.
authors.affiliation: St. Vincent Medical Group, Division of Cardiology, Indianapolis, Indiana; Section of Electrophysiology, Division of Cardiovascular Medicine, University of Pennsylvania, Philadelphia, Pennsylvania. Electronic address: parin.patel@post.harvard.edu.
authors.forename: Parin J
authors.initials: PJ
authors.lastname: Patel
authors.affiliation: Section of Electrophysiology, Division of Cardiovascular Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: Yuliya
authors.initials: Y
authors.lastname: Borovskiy
authors.affiliation: Section of Electrophysiology, Division of Cardiovascular Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: Anthony
authors.initials: A
authors.lastname: Killian
authors.affiliation: Section of Electrophysiology, Division of Cardiovascular Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: Ralph J
authors.initials: RJ
authors.lastname: Verdino
authors.affiliation: Section of Electrophysiology, Division of Cardiovascular Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: Andrew E
authors.initials: AE
authors.lastname: Epstein
authors.affiliation: Section of Electrophysiology, Division of Cardiovascular Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: David J
authors.initials: DJ
authors.lastname: Callans
authors.affiliation: Section of Electrophysiology, Division of Cardiovascular Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: Francis E
authors.initials: FE
authors.lastname: Marchlinski
authors.affiliation: Section of Electrophysiology, Division of Cardiovascular Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: Rajat
authors.initials: R
authors.lastname: Deo
mesh_terms: D000328:Adult; D015331:Cohort Studies; D003324:Coronary Artery Disease / Q000401:mortality*; D004562:Electrocardiography / Q000379:methods; D022062:Electrophysiologic Techniques, Cardiac / Q000379:methods / Q000706:statistics & numerical data; D005260:Female; D005500:Follow-Up Studies; D006333:Heart Failure / Q000401:mortality*; D006801:Humans; D008297:Male; D008875:Middle Aged; D018570:Risk Assessment / Q000379:methods; D013616:Tachycardia, Sinus / Q000175:diagnosis / Q000453:epidemiology / Q000503:physiopathology; D014481:United States / Q000453:epidemiology
keywords: Cardiovascular disease; Mortality; QT interval; Tachycardia