title: Ventricular repolarization duration and dispersion adaptation after atropine induced rapid heart rate increase in healthy adults.
abstract: Proper adaptation of ventricular repolarization (VR) to rapid heart rate (HR) increase is crucial for cardiac electro-mechanical function. The pattern and temporal aspects of this adaptation and its components (duration and dispersion) during normal conduction are, however, incompletely known in humans and were the topic of this study.
  
  
  
  The VR duration (QT & QTpeak) and dispersion (Tamplitude, Tarea & ventricular gradient; VG) responses were studied by continuous vectorcardiogram after a bolus injection of atropine 0.04mg/kg b.w. in 31 healthy young adults (16 men). The primary measure (T90 End) was the time to reach 90% change from baseline to end value 300s later. Mean (SD) of T90 End was 23 (9) s for a 41% RR decrease, 130 (35) s for a 16% QTend decrease and 110 (36) s for a 19% QTpeak decrease; the response was single-exponential for these measures. For 35-43% decreases of Tamplitude, Tarea & VG, mean (SD) of T90 End were 21 (10), 38 (20) and 40 (23) s and the response pattern was double-exponential with varying overshoot.
  
  
  
  VR duration and dispersion responses to a very rapid HR increase during normal conduction differed substantially. In contrast to the well-known single-exponential delay in VR duration adaptation the responses of VR dispersion measures were double-exponential and much more rapid. We describe a new and completely non-invasive phenotypic characterization of different components of VR adaptation.
authors.affiliation: Dept. of Molecular & Clinical Medicine/Cardiology, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden; Dept. of Cardiology, Sahlgrenska University Hospital, Gothenburg, Sweden. Electronic address: lennart.bergfeldt@hjl.gu.se.
authors.forename: Lennart
authors.initials: L
authors.lastname: Bergfeldt
authors.affiliation: Dept. of Molecular & Clinical Medicine/Cardiology, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden; Dept. of Cardiology, Sahlgrenska University Hospital, Gothenburg, Sweden.
authors.forename: Gunilla
authors.initials: G
authors.lastname: Lundahl
authors.affiliation: Dept. of Molecular & Clinical Medicine/Cardiology, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden; Dept. of Cardiology, Sahlgrenska University Hospital, Gothenburg, Sweden.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Bergqvist
authors.affiliation: Dept. of Molecular & Clinical Medicine/Cardiology, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden; Dept. of Cardiology, Sahlgrenska University Hospital, Gothenburg, Sweden.
authors.forename: Farzad
authors.initials: F
authors.lastname: Vahedi
authors.affiliation: Dept. of Molecular & Clinical Medicine/Cardiology, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden; Dept. of Cardiology, Sahlgrenska University Hospital, Gothenburg, Sweden.
authors.forename: Lennart
authors.initials: L
authors.lastname: Gransberg
mesh_terms: D000222:Adaptation, Physiological / Q000187:drug effects*; D000328:Adult; D001285:Atropine / Q000008:administration & dosage*; D005260:Female; D064368:Healthy Volunteers; D006329:Heart Conduction System / Q000187:drug effects* / Q000502:physiology*; D006339:Heart Rate / Q000187:drug effects*; D006352:Heart Ventricles / Q000187:drug effects*; D006801:Humans; D008297:Male; D010276:Parasympatholytics / Q000008:administration & dosage*; D014672:Vectorcardiography
chemical_list: D010276:Parasympatholytics; D001285:Atropine
keywords: Atropine; Hysteresis; Restitution; Vectorcardiography; Ventricular repolarization