title: The Complex QT/RR Relationship in Mice.
abstract: The QT interval reflects the time between the depolarization of ventricles until their repolarization and is usually used as a predictive marker for the occurrence of arrhythmias. This parameter varies with the heart rate, expressed as the RR interval (time between two successive ventricular depolarizations). To calculate the QT independently of the RR, correction formulae are currently used. In mice, the QT-RR relationship as such has never been studied in conscious animals, and correction formulas are mainly empirical. In the present paper we studied how QT varies when the RR changes physiologically (comparison of nocturnal and diurnal periods) or after dosing mice with tachycardic agents (norepinephrine or nitroprusside). Our results show that there is significant variability of QT and RR in a given condition, resulting in the need to average at least 200 consecutive complexes to accurately compare the QT. Even following this method, no obvious shortening of the QT was observed with increased heart rate, regardless of whether or not this change occurs abruptly. In conclusion, the relationship between QT and RR in mice is weak, which renders the use of correction formulae inappropriate and misleading in this species.
authors.affiliation: Inserm U1046, UMR CNRS 9214, Université de Montpellier, 34295 Montpellier France.
authors.forename: Julien
authors.initials: J
authors.lastname: Roussel
authors.affiliation: CERB, Chemin de Montifault, 18800 Baugy France.
authors.forename: Pascal
authors.initials: P
authors.lastname: Champeroux
authors.affiliation: Inserm U1046, UMR CNRS 9214, Université de Montpellier, 34295 Montpellier France.
authors.forename: Jérôme
authors.initials: J
authors.lastname: Roy
authors.affiliation: Inserm U1046, UMR CNRS 9214, Université de Montpellier, 34295 Montpellier France.
authors.forename: Sylvain
authors.initials: S
authors.lastname: Richard
authors.affiliation: Inserm U1046, UMR CNRS 9214, Université de Montpellier, 34295 Montpellier France.
authors.forename: Jérémy
authors.initials: J
authors.lastname: Fauconnier
authors.affiliation: Inserm U1046, UMR CNRS 9214, Université de Montpellier, 34295 Montpellier France.
authors.forename: Jean-Yves
authors.initials: JY
authors.lastname: Le Guennec
authors.affiliation: Inserm U1046, UMR CNRS 9214, Université de Montpellier, 34295 Montpellier France.
authors.forename: Jérôme
authors.initials: J
authors.lastname: Thireau
mesh_terms: D000818:Animals; D001145:Arrhythmias, Cardiac / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000503:physiopathology*; D004562:Electrocardiography / Q000379:methods*; D006339:Heart Rate / Q000187:drug effects; D006352:Heart Ventricles / Q000000981:diagnostic imaging / Q000187:drug effects / Q000503:physiopathology*; D006801:Humans; D051379:Mice; D009599:Nitroprusside / Q000008:administration & dosage; D009638:Norepinephrine / Q000008:administration & dosage
chemical_list: D009599:Nitroprusside; D009638:Norepinephrine