title: The high frequency relationship: implications for torsadogenic hERG blockers.
abstract: OBJECTIVE
  Ventricular arrhythmias induced by human ether-a-go-go related gene (hERG; Kv 11.1 channel) blockers are a consequence of alterations in ventricular repolarisation in association with high-frequency (HF) oscillations, which act as a primary trigger; the autonomic nervous system plays a modulatory role. In the present study, we investigated the role of β1 -adrenoceptors in the HF relationship between magnitude of heart rate and QT interval changes within discrete 10 s intervals (sorted into 5 bpm heart rate increments) and its implications for torsadogenic hERG blockers.
  
  
  METHODS
  The HF relationship was studied under conditions of autonomic blockade with atenolol (β1 -adrenoceptor blocker) in the absence or presence of five hERG blockers in beagle dogs. In total, the effects of 14 hERG blockers on the HF relationship were investigated.
  
  
  RESULTS
  All the torsadogenic hERG blockers tested caused a vertical shift in the HF relationship, while hERG blockers associated with a low risk of Torsades de Pointes did not cause any vertical shift. Atenolol completely prevented the effects four torsadogenic agents (quinidine, thioridazine, risperidone and terfenadine) on the HF relationship, but only partially reduced those of dofetilide, leading to the characterization of two types of torsadogenic agent.
  
  
  CONCLUSIONS
  Analysis of the vertical shift in the HF relationship demonstrated that signs of transient sympathetic activation during HF oscillations in the presence of torsadogenic hERG blockers are mediated by β1 -adrenoceptors. We suggest the HF relationship as a new biomarker for assessing Torsades de pointes liability, with potential implications in both preclinical studies and the clinic.
authors.affiliation: Centre de Recherches Biologiques, CERB, Chemin de Montifault, 18800, Baugy, France.
authors.forename: P
authors.initials: P
authors.lastname: Champeroux
authors.affiliation: Laboratoire PHYMEDEXP, Physiologie et Médecine Expérimentale, Cœur et Muscles, INSERM U1046, CNRS UMR 9214, Université de Montpellier, CHU Arnaud de Villeneuve, 371 Avenue du doyen G. Giraud, 34295, Montpellier cedex 05, France.
authors.forename: J Y
authors.initials: JY
authors.lastname: Le Guennec
authors.affiliation: Centre de Recherches Biologiques, CERB, Chemin de Montifault, 18800, Baugy, France.
authors.forename: S
authors.initials: S
authors.lastname: Jude
authors.affiliation: Centre de Recherches Biologiques, CERB, Chemin de Montifault, 18800, Baugy, France.
authors.forename: C
authors.initials: C
authors.lastname: Laigot
authors.affiliation: Centre de Recherches Biologiques, CERB, Chemin de Montifault, 18800, Baugy, France.
authors.forename: A
authors.initials: A
authors.lastname: Maurin
authors.affiliation: Centre de Recherches Biologiques, CERB, Chemin de Montifault, 18800, Baugy, France.
authors.forename: M L
authors.initials: ML
authors.lastname: Sola
authors.affiliation: Centre de Recherches Biologiques, CERB, Chemin de Montifault, 18800, Baugy, France.
authors.forename: J S L
authors.initials: JS
authors.lastname: Fowler
authors.affiliation: Centre de Recherches Biologiques, CERB, Chemin de Montifault, 18800, Baugy, France.
authors.forename: S
authors.initials: S
authors.lastname: Richard
authors.affiliation: Laboratoire PHYMEDEXP, Physiologie et Médecine Expérimentale, Cœur et Muscles, INSERM U1046, CNRS UMR 9214, Université de Montpellier, CHU Arnaud de Villeneuve, 371 Avenue du doyen G. Giraud, 34295, Montpellier cedex 05, France.
authors.forename: J
authors.initials: J
authors.lastname: Thireau
mesh_terms: D058671:Adrenergic beta-1 Receptor Antagonists / Q000494:pharmacology*; D000818:Animals; D001262:Atenolol / Q000494:pharmacology; D004285:Dogs; D004562:Electrocardiography; D051638:Ether-A-Go-Go Potassium Channels / Q000502:physiology*; D005260:Female; D008297:Male; D026902:Potassium Channel Blockers / Q000494:pharmacology*; D018342:Receptors, Adrenergic, beta-1 / Q000502:physiology*; D016171:Torsades de Pointes / Q000503:physiopathology*
chemical_list: D058671:Adrenergic beta-1 Receptor Antagonists; D051638:Ether-A-Go-Go Potassium Channels; D026902:Potassium Channel Blockers; D018342:Receptors, Adrenergic, beta-1; D001262:Atenolol