Open-loop, clockwise QT-RR hysteresis immediately before the onset of torsades de pointes in type 2 long QT syndrome.
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.
Nakaji
Gen
G
Department of Medicine and Biosystemic Science, Kyushu University Graduate School of Medical Sciences, Fukuoka, Japan.
Fujiwara
Masahiko
M
Fukata
Mitsuhiro
M
Yasuda
Shioto
S
Odashiro
Keita
K
Maruyama
Toru
T
Akashi
Koichi
K
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*