GLOSSARY OF TERMS USED IN TIME SERIES ANALYSIS OF CARDIOVASCULAR DATA

|LEVEL 0| |HOMEPAGE|

Procedure which allows to describe particular frequency components of a time series as a function of time.

Complex demodulation consists of multiplying the signal x(t) by . In this way a new complex function y(t) is obtained where the frequency band of x(t) centered at f₀ has been shifted to a frequency band centered at 0 Hz, and where the 0-Hz band of x(t) has been shifted simultaneously to a frequency band centered at 2f₀. Thus it is possible to remove components of x(t) with frequency higher and lower than the band centered at f₀ by low-pass filtering y(t), obtaining the complex signal y_LP(t). The modulus 2|y_LP(t)| gives the time-varying amplitude of the x(t) components centered at f₀, while remodulation y_LP(t) gives their time courses.
Complex demodulation of cardiovascular signals has been applied to quantify the amplitude of specific oscillations and to investigate the baroreceptors control on the heart.

References:
Orr WC, Hoffman HJ (1974) A 90-min cardiac biorhythm: metodology and data analysis using modified periodograms and complex demodulation. IEEE Trans Biomed Eng 21, 130-143
Kim SY (1997) Baroreflex sensitivity assessed by complex demodulation of cardiovascular variability Hypertension
Lipsitz LA (1998)  Complex demodulation of cardiorespiratory dynamics preceding vasovagal syncope. Circulation
Burguera M et al (1995) Continuous heart rate variability monitoring through complex demodulation implemented with the fast Fourier transform and its inverse. Pacing Clin Electrophysiol.
Hayano J et al (1994) Assessment of frequency shifts in R-R interval variability and respiration with complex demodulation. J Appl Physiol.
Hayano J et al (1993) Continuous assessment of hemodynamic control by complex demodulation of cardiovascular variability. Am J Physiol.
Shin SJ et al (1989) Assessment of autonomic regulation of heart rate variability by the method of complex demodulation. IEEE Trans Biomed Eng.