Interventricular dispersion in repolarization causes bifid T waves in dogs with dofetilide-induced long QT syndrome

Veronique M F Meijborg, Samuel Chauveau, Michiel J Janse, Evgeny P Anyukhovsky, Peter R Danilo, Michael R Rosen, Tobias Opthof, Ruben Coronel

Research output: Contribution to journalArticleAcademicpeer-review


BACKGROUND: Long QT2 (LQT2) syndrome is characterized by bifid (or notched) T waves, whose mechanism is not understood.

OBJECTIVE: The purpose of this study was to test whether increased interventricular dispersion of repolarization induces bifid T waves.

METHODS: We simultaneously recorded surface ECG and unipolar electrograms at baseline and after dofetilide in a canine model of dofetilide-induced LQT2 (6 male mongrel dogs). Standard ECG variables, T-wave duration, and moments of peaks of bifid T waves (Tp1 and Tp2) were correlated with moments of local repolarization. Epicardial electrograms were recorded over the left ventricular (LV) and right ventricular (RV) anterior walls (11 × 11 electrode grid, 5-mm interelectrode distance). In 5 of the 6 hearts, we also recorded intramural unipolar electrograms (n = 4-7 needles per heart). In each unipolar recording, we determined activation time, repolarization time (RTs), and activation-recovery interval. In addition, we studied RT response to heart rate changes.

RESULTS: Dofetilide prolonged QT and QTc, induced bifid T waves in 4 of 6 animals, and prolonged RT heterogeneously in LV and RV, resulting in increased interventricular and LV intraventricular RT dispersion. Dofetilide did not induce a disparate response in activation-recovery interval across the transmural axis. Dofetilide-induced separation of RT across the RV-LV interface concurred with the moments of T-wave peaks. Dofetilide-induced steepening of restitution slopes was larger in LV than RV.

CONCLUSION: Dofetilide-induced bifid T waves result from interventricular RT dispersion.

Original languageEnglish
Pages (from-to)1343-51
Number of pages9
JournalHeart Rhythm
Issue number6
Publication statusPublished - Jun 2015


  • Bifid Twave
  • Long QT syndrome type 2
  • Repolarization
  • Dog


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