title: A new experimentally validated formula to calculate the QT interval in the presence of left bundle branch block holds true in the clinical setting.
abstract: BACKGROUND
  The evaluation of the QT interval in the presence of left bundle branch block (LBBB) is associated with the challenge to discriminate native QT interval from the prolongation due to the increase in QRS duration. The newest formula to evaluate QT interval in the presence of LBBB suggests: modified QT during LBBB = measured QT interval minus 50% of LBBB duration. The purpose of this study is therefore to validate the abovementioned formula in the clinical setting.
  
  
  METHODS
  Validation in two separate groups of patients: Patients who alternated between narrow QRS and intermittent LBBB and patients with narrow QRS who developed LBBB after transcatheter aortic valve implantation (TAVI).
  
  
  RESULTS
  The acquired mean native QTc intervals and those calculated by the presented formula displayed no significant differences (p > .99 and p > .75).
  
  
  CONCLUSIONS
  In this study we proved for the first time the validity and applicability of the experimentally acquired formula for the evaluation of the QT interval in the presence of LBBB in a clinical setting.
authors: Märkische Kliniken GmbH, Department of Cardiology and Angiology, Klinikum Lüdenscheid, Lüdenscheid, Germany.|Department of Cardiology, University Witten/Herdecke, Witten, Germany.
authors: Harilaos
authors: H
authors: Bogossian
authors: Division of Electrophysiology, Department of Cardiovascular Medicine, University of Münster, Münster, Germany.
authors: Gerrit
authors: G
authors: Frommeyer
authors: Märkische Kliniken GmbH, Department of Cardiology and Angiology, Klinikum Lüdenscheid, Lüdenscheid, Germany.
authors: Ilias
authors: I
authors: Ninios
authors: Märkische Kliniken GmbH, Department of Cardiology and Angiology, Klinikum Lüdenscheid, Lüdenscheid, Germany.
authors: Eleni
authors: E
authors: Pechlivanidou
authors: Märkische Kliniken GmbH, Department of Cardiology and Angiology, Klinikum Lüdenscheid, Lüdenscheid, Germany.
authors: Fuad
authors: F
authors: Hasan
authors: Märkische Kliniken GmbH, Department of Cardiology and Angiology, Klinikum Lüdenscheid, Lüdenscheid, Germany.
authors: Quy Suu
authors: QS
authors: Nguyen
authors: Märkische Kliniken GmbH, Department of Cardiology and Angiology, Klinikum Lüdenscheid, Lüdenscheid, Germany.
authors: Dejan
authors: D
authors: Mijic
authors: Märkische Kliniken GmbH, Department of Cardiology and Angiology, Klinikum Lüdenscheid, Lüdenscheid, Germany.
authors: Axel
authors: A
authors: Kloppe
authors: Märkische Kliniken GmbH, Department of Cardiology and Angiology, Klinikum Lüdenscheid, Lüdenscheid, Germany.
authors: Zana
authors: Z
authors: Karosiene
authors: Märkische Kliniken GmbH, Department of Cardiology and Angiology, Klinikum Lüdenscheid, Lüdenscheid, Germany.
authors: Artak
authors: A
authors: Margkarian
authors: Märkische Kliniken GmbH, Department of Cardiology and Angiology, Klinikum Lüdenscheid, Lüdenscheid, Germany.
authors: Dirk
authors: D
authors: Bandorski
authors: Märkische Kliniken GmbH, Department of Cardiology and Angiology, Klinikum Lüdenscheid, Lüdenscheid, Germany.
authors: Dominik
authors: D
authors: Schultes
authors: Medical Clinic I, Department of Cardiology, Justus-Liebig University of Giessen, Giessen, Germany.
authors: Damir
authors: D
authors: Erkapic
authors: Department of Cardiology, University Witten/Herdecke, Witten, Germany.|Department of Cardiology, Helios Klinikum Wuppertal, Wuppertal, Germany.
authors: Melchior
authors: M
authors: Seyfarth
authors: Märkische Kliniken GmbH, Department of Cardiology and Angiology, Klinikum Lüdenscheid, Lüdenscheid, Germany.
authors: Bernd
authors: B
authors: Lemke
authors: Division of Electrophysiology, Department of Cardiovascular Medicine, University of Münster, Münster, Germany.
authors: Lars
authors: L
authors: Eckardt
authors: Märkische Kliniken GmbH, Department of Cardiology and Angiology, Klinikum Lüdenscheid, Lüdenscheid, Germany.|Department of Cardiology, University Witten/Herdecke, Witten, Germany.
authors: Markus
authors: M
authors: Zarse
mesh_terms: D002036:Bundle of His / Q000503:physiopathology; D002037:Bundle-Branch Block / Q000503:physiopathology*; D004562:Electrocardiography / Q000379:methods*; D006801:Humans; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012307:Risk Factors; D016896:Treatment Outcome
keywords: JT interval; QT formula; QT interval; QT prolongation; left bundle brunch block; long QT