On the fetal magnetocardiogram

Fetal magnetocardiography is a non-invasive technique for studying the elec trical activity of the fetal heart. Fetal magnetocardiograms (fMCG) can be used to diagnose and classify fetal cardiac arrhythmias reliably: An averag ed fMCG shows a QRS-complex, a P-wave, and a T-wave. However, it is still u nknown if the currents in the tissues surrounding the fetal heart disturb t hese features. Furthermore, the measuring technique is not yet optimised fo r fMCG registrations. Simulation studies may provide guidelines for the des ign of an appropriate magnetometer system. Therefore, finite-element and bo undary-element models were constructed in order to study the possible influ ence of the volume conductor. Especially, the influence of the layer of ver nix caseosa, a fatty layer that covers the fetus, was investigated. The com putations showed that the layer of vernix caseosa will affect the waveform of the fMCG. The signal processing procedure used is also discussed. It tur ned out to be difficult to deduce the onset and offset of the T-wave from t he resulting averaged signals. Possibly, the QRS-complex does not provide a correct trigger to obtain a distinguishable T-wave in the averaged signal, because the RT-interval may be variable. (C) 1998 Elsevier Science S.A. Al l rights-reserved.