title: Facilitating assessment of QT interval duration during ventricular pacing.
abstract: OBJECTIVE
  We aimed to facilitate the assessment of the QT interval duration during conventional right ventricular pacing (VP) by uncovering relationships with the underlying QT interval during intrinsic atrioventricular conduction (IC).
  
  
  RESULTS
  The study patients (n = 122, age 68 ± 11 years) were dual-chamber device recipients with preserved IC and narrow QRS complexes. Patients were classified into either 'normal-QT' (n = 70) or 'prolonged-QT' (n = 52) group. Incremental atrial pacing rates were exercised to record serial QT/JT intervals over 5 min periods in IC mode and then in VP mode. Six different QT correction methods for heart rate were applied to assess the effect (i) of pacing mode (IC vs. VP) and (ii) of heart rate on the derived QT(c)/JT(c) intervals by mixed-effects linear models. Following VP, the uncorrected QT/JT intervals as well as the JTc intervals shortened (P < 0.001), whereas the QTc intervals prolonged (P < 0.001). In both patient groups, the Framingham and Nomogram methods demonstrated the optimal balance to assess QTc, with low heart rate dependence during VP and minimal interaction between pacing mode and heart rate. The Rautaharju formula provided excellent correction for the QT changes induced by VP, but the QTc interval responded differently to rate changes in IC vs. VP mode. Bazett's formula exaggerated QTc/JTc rate dependency during VP.
  
  
  CONCLUSIONS
  The Framingham and Nomogram correction methods perform most reliably in assessing the underlying QT interval during IC from the ventricular paced QT interval.
authors.affiliation: Cardiology Department, Patras University Hospital, Agias Lavras, 26504 Platani-Patra, Greece. chil@otenet.gr
authors.forename: John A
authors.initials: JA
authors.lastname: Chiladakis
authors.forename: Andreas
authors.initials: A
authors.lastname: Kalogeropoulos
authors.forename: Fani
authors.initials: F
authors.lastname: Zagkli
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Koutsogiannis
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Chouchoulis
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Alexopoulos
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D058406:Cardiac Resynchronization Therapy / Q000706:statistics & numerical data*; D003936:Diagnosis, Computer-Assisted / Q000379:methods* / Q000639:trends*; D004562:Electrocardiography / Q000379:methods* / Q000706:statistics & numerical data*; D005260:Female; D006115:Greece / Q000453:epidemiology; D006801:Humans; D008133:Long QT Syndrome / Q000175:diagnosis* / Q000453:epidemiology / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D015203:Reproducibility of Results; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D016896:Treatment Outcome
keywords: QT interval; Ventricular pacing