title: Open-loop, clockwise QT-RR hysteresis immediately before the onset of torsades de pointes in type 2 long QT syndrome.
abstract: Delay of QT interval adaptation to sudden heart rate change causes hysteresis in dynamic QT-RR relationship. We analyzed QT-RR plotting during and after exercise in a patient with genetically identified type 2 long QT syndrome before and after starting oral propranolol. Blunted QT shortening by exercise and augmented postexercise QT prolongation resulted in an open-loop, clockwise QT-RR hysteresis immediately before the onset of torsades de pointes before propranolol. However, this hysteresis was eliminated by propranolol. QT-RR analysis provided insight into the mechanisms of the onset of torsades de pointes at least in this case of type 2 long QT syndrome.
authors.affiliation: Department of Medicine and Biosystemic Science, Kyushu University Graduate School of Medical Sciences, Fukuoka, Japan.
authors.forename: Gen
authors.initials: G
authors.lastname: Nakaji
authors.forename: Masahiko
authors.initials: M
authors.lastname: Fujiwara
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Fukata
authors.forename: Shioto
authors.initials: S
authors.lastname: Yasuda
authors.forename: Keita
authors.initials: K
authors.lastname: Odashiro
authors.forename: Toru
authors.initials: T
authors.lastname: Maruyama
authors.forename: Koichi
authors.initials: K
authors.lastname: Akashi
mesh_terms: D003937:Diagnosis, Differential; D004562:Electrocardiography / Q000379:methods*; D005260:Female; D006801:Humans; D008133:Long QT Syndrome / Q000175:diagnosis*; D008875:Middle Aged; D016171:Torsades de Pointes / Q000175:diagnosis*