Microgravity effects on ventricular response to heart rate changes.
The effect of simulated microgravity on ventricular repolarization (VR) has been evaluated on healthy volunteers by a 5-day Head Down (-6°) Bed Rest (HDBR) maneuver. QT to RR and QT(p) (measured until the peak of the T wave) to RR hystereses have been measured during a tilt table test, and differences between them have been studied to better understand possible changes in the final part of the repolarization. To characterize the hystereses, two indices have been computed: M(90), quantifying adaptation lag in beats, and α evaluating the slope of parabolic regression fitting. Significant differences between QT and QT(p) were found before, but not after HDBR. Specifically, before HDBR was considerable lower for QT(p) than for QT, while α was significantly higher. After HDBR, M(90) and a took essentially the same values for QT and QT(p). This fact evidenced the different effect of HDBR on QT to RR and QT(p) to RR adaptations, and suggest HDBR could lead to an impairment in ventricular repolarization dispersion.
Communications Technology Group, Aragón Institute of Engineering Research (I3A), IIS Aragón, Universidad de Zaragoza, Zaragoza, Spain. jbolea@lagunaat unizar.es
Juan
J
Bolea
Enrico G
EG
Caiani
Esther
E
Pueyo
Pablo
P
Laguna
Rute
R
Almeida
D000222:Adaptation, Physiological; D000328:Adult; D018592:Cross-Over Studies; D006339:Heart Rate; D006352:Heart Ventricles; D006801:Humans; D008297:Male; D012016:Reference Values; D014893:Weightlessness; D055815:Young Adult