Unshielded magnetic source imaging of fetal cardiac activity for electrophysiologic follow-up during pregnancy

Aim: to evaluate the feasibility of follow−up monitoring of pregnancies with fetal magnetic source imaging (FMSI) Methods: FMSI with 36−channel system providing 1) fetal MCG (FMCG) analysis in real−time with FastICA to separate maternal and fetal signals; 2) MF reconstruction and source localization with the EMD model (after adaptive 50 Hz digital filtering, signal averaging triggered by fetal QRS peak). Ten normal pregnancies (21st to 40th gestational week) studied, five more than once, at different gestational ages. In one comparison between FMSI and neonatal cardiac MF recordings was also performed. Results: unshielded FMCG was visible only after the 26th gestational week. FMSI showed a dipolar MF distribution at the QRS peak. EMD localization of ventricular sources, localized three-dimensionally the anatomical position of the fetal heart (comparison with echography). FastICA provided quality of beat−to−beat FMCG adequate for rhythm analysis and quantitative assessment of Heart Rate Variability parameters. Conclusions: FMSI is feasible in unshielded environment for ambulatory follow−up of fetal cardiac electrophysiology since the 26th gestational week. A good agreement was found between fetal and neonatal cardiac MSI in the same subject.