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Long or short postpacing interval response to ventricular tachycardia entrainment: What is the mechanism?

  • Takuro Nishimura
    Affiliations
    Center for Arrhythmia Care, Section of Cardiology, Department of Medicine, Pritzker School of Medicine, University of Chicago Medicine, Chicago, Illinois
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  • Roderick Tung
    Correspondence
    Address reprint requests and correspondence: Dr Roderick Tung, Center for Arrhythmia Care, Section of Cardiology, Department of Medicine, Pritzker School of Medicine, University of Chicago Medicine, 5841 S Maryland Avenue, MC 6080, Chicago, IL 60637.
    Affiliations
    Center for Arrhythmia Care, Section of Cardiology, Department of Medicine, Pritzker School of Medicine, University of Chicago Medicine, Chicago, Illinois
    Search for articles by this author
Published:August 11, 2020DOI:https://doi.org/10.1016/j.hrthm.2020.08.004
      A 58-year-old man with nonischemic cardiomyopathy and an ejection fraction of 25% presented with ventricular tachycardia (VT) storm. Epicardial mapping revealed an inferolateral scar, and during tolerated VT with right bundle branch superior axis morphology with V3 transition (tachycardia cycle length [TCL] 325 ms), overdrive pacing was performed. What is the response to entrainment and why (Figure 1A )?
      Figure thumbnail gr1
      Figure 1A: Overdrive pacing during ventricular tachycardia. B: Determination of postpacing interval (PPI) measurement annotated either to far-field (FF) large amplitude and near-field (NF) lower amplitude components or to an electrogram (EGM) not visualized on left ventricle (LV) 9,10 that matches the S-QRS interval (?). The PPI is long for both scenarios involving the local EGM, and the PPI would be 15 ms shorter than the tachycardia cycle length on the basis of the assumption that the S-QRS interval reflects an unseen EGM-QRS component (?).

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