title: QTc compared to JTc for monitoring drug-induced repolarization changes in the setting of ventricular pacing.
abstract: BACKGROUND
  QT prolongation is a risk factor for proarrhythmia when beginning antiarrhythmic drug therapy (AAD). However, there are no data regarding monitoring repolarization changes during a ventricular paced (VP) rhythm.
  
  
  OBJECTIVE
  The purpose of this study was to compare serial changes in corrected QT and JT intervals, during native conduction (NC) and VP rhythms when initiating Class III AADs.
  
  
  METHODS
  Twenty-two patients (73% men; mean age 65 ± 11 years) with an implantable device and with <10% VP were monitored during AAD initiation (16 sotalol, 6 dofetilide). QTc and JTc were measured from ECGs obtained during NC and VP at baseline (pre-AAD) and then after each AAD dose.
  
  
  RESULTS
  During AAD loading, mean QTc increased significantly during NC (431 ± 28 ms to 463 ± 33 ms, P = .002) but not with VP (520 ± 48 ms to 538 ± 45 ms, P = .07). Mean percent increase in peak QTc during NC was significantly greater than during VP (12% vs 7%, P = .003). In contrast, peak JTc during AAD loading was not significantly different between NC and VP (P = .67).
  
  
  CONCLUSIONS
  When initiating AAD, the change in QTc during VP does not correlate with the change in QTc during NC; thus, the VP QTc is inadequate for monitoring repolarization changes. However, VP JTc correlates well with JTc during NC. When initiating Class III AADs in patients with VP rhythms, the JTc, and not the QTc, interval is the useful marker for assessing repolarization.
authors.affiliation: Section of Electrophysiology, Division of Cardiology, Ross Heart Hospital, Wexner Medical Center at The Ohio State University, Columbus, Ohio.
authors.forename: Shane F
authors.initials: SF
authors.lastname: Tsai
authors.affiliation: Section of Electrophysiology, Division of Cardiology, Ross Heart Hospital, Wexner Medical Center at The Ohio State University, Columbus, Ohio.
authors.forename: Mahmoud
authors.initials: M
authors.lastname: Houmsse
authors.affiliation: Section of Electrophysiology, Division of Cardiology, Ross Heart Hospital, Wexner Medical Center at The Ohio State University, Columbus, Ohio.
authors.forename: Barrah
authors.initials: B
authors.lastname: Dakhil
authors.affiliation: Section of Electrophysiology, Division of Cardiology, Ross Heart Hospital, Wexner Medical Center at The Ohio State University, Columbus, Ohio.
authors.forename: Ralph
authors.initials: R
authors.lastname: Augostini
authors.affiliation: Section of Electrophysiology, Division of Cardiology, Ross Heart Hospital, Wexner Medical Center at The Ohio State University, Columbus, Ohio.
authors.forename: John D
authors.initials: JD
authors.lastname: Hummel
authors.affiliation: Section of Electrophysiology, Division of Cardiology, Ross Heart Hospital, Wexner Medical Center at The Ohio State University, Columbus, Ohio.
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Kalbfleisch
authors.affiliation: Section of Electrophysiology, Division of Cardiology, Ross Heart Hospital, Wexner Medical Center at The Ohio State University, Columbus, Ohio.
authors.forename: Zhengou
authors.initials: Z
authors.lastname: Liu
authors.affiliation: Section of Electrophysiology, Division of Cardiology, Ross Heart Hospital, Wexner Medical Center at The Ohio State University, Columbus, Ohio.
authors.forename: Charles
authors.initials: C
authors.lastname: Love
authors.affiliation: Section of Electrophysiology, Division of Cardiology, Ross Heart Hospital, Wexner Medical Center at The Ohio State University, Columbus, Ohio.
authors.forename: Troy
authors.initials: T
authors.lastname: Rhodes
authors.affiliation: Section of Electrophysiology, Division of Cardiology, Ross Heart Hospital, Wexner Medical Center at The Ohio State University, Columbus, Ohio.
authors.forename: Jaret
authors.initials: J
authors.lastname: Tyler
authors.affiliation: Section of Electrophysiology, Division of Cardiology, Ross Heart Hospital, Wexner Medical Center at The Ohio State University, Columbus, Ohio.
authors.forename: Raul
authors.initials: R
authors.lastname: Weiss
authors.affiliation: Section of Electrophysiology, Division of Cardiology, Ross Heart Hospital, Wexner Medical Center at The Ohio State University, Columbus, Ohio.
authors.forename: Ismail
authors.initials: I
authors.lastname: Hamam
authors.affiliation: Section of Electrophysiology, Division of Cardiology, Ross Heart Hospital, Wexner Medical Center at The Ohio State University, Columbus, Ohio.
authors.forename: Marshall
authors.initials: M
authors.lastname: Winner
authors.affiliation: Section of Electrophysiology, Division of Cardiology, Ross Heart Hospital, Wexner Medical Center at The Ohio State University, Columbus, Ohio. Electronic address: emile.daoud@osumc.edu.
authors.forename: Emile G
authors.initials: EG
authors.lastname: Daoud
mesh_terms: D000368:Aged; D000889:Anti-Arrhythmia Agents / Q000627:therapeutic use*; D004562:Electrocardiography; D005260:Female; D006329:Heart Conduction System / Q000187:drug effects*; D006801:Humans; D008297:Male; D010138:Pacemaker, Artificial; D010627:Phenethylamines / Q000627:therapeutic use*; D013015:Sotalol / Q000627:therapeutic use*; D013449:Sulfonamides / Q000627:therapeutic use*
chemical_list: D000889:Anti-Arrhythmia Agents; D010627:Phenethylamines; D013449:Sulfonamides; D013015:Sotalol; C063533:dofetilide
keywords: Antiarrhythmic drug; Electrocardiography; JT interval; Pacing; QT interval; Repolarization