Time-frequency analysis of heart rate variability during head-up tilt

AIM To study the time-frequency analysis of heart rate variability. METHODS Four time-frequency methods were applied to heart rate variability analysis during head-up tilt, which were short-time Fourier transform, Choi-Williams distribution, cone-kernel representation and continuous wavelet transform. RESULTS Low frequency component increased while high frequency component decreased. Each component was under dynamic modulation during supine and head-up tilt. CONCLUSION Time-frequency methods can be applied to studying the dynamic change of heart rate variability, which could be potential in clinical monitoring.