Application to biomedical signals - Practical Biomedical Signal Analysis Using MATLAB - page 190

FIGURE 4.38: Three-dimensional images of RR interval return maps calculated
from 24-h Holter ECG recordings. a) and b) data from the same subject before car-
diac arrest and 1y after, respectively; plot b) is very similar to plots obtained for
healthy subjects; c) example plot for a ventricular arrhythmia; d) example plot for
atrial fibrillation. Adapted from [ Zebrowski et al., 1994].
the North American Society of Electrophysiology [Malik, 1996]. Since 1996 consid-
erable progress has been achieved in the field of applications of non-linear methods
to HRV, but at present the standards are still lacking and none of these methods is in
widespread clinical use. For validation of non-linear methods the studies involving
application of both linear and non-linear approaches applied for the same data are
needed.
4.2.3 Fetal ECG
The fetal electrocardiogram is the electrical activity of a fetus heart, which con-
tains valuable information about the physiological state of a fetus and is an important
tool in monitoring its well being. For instance pathological conditions like hypoxia
or acidemia may be detected by means of fECG. The amplitude of fECG is in the
range from 10 to 100 μV , whereas the maternal ECG (mECG) can be as high as: