Characterization of fetal arrhythmias by means of fetal magnetocardiography in three cases of maternal obesity, fetal prone position, and oligohydramnios

Clinical detection of fetal arrhythmias is generally performed by means of M-mode and pulsed Doppler echocardiography (fECHO), although this method is far from being ideal because it detects the mechanical activity, not the electrophysiological events. Several studies have shown the ability of fetal magnetocardiography (fMCG) to detect fetal arrhythmias directly. Method: we report fMCG of three patients (pts), respectively studied at the 37th, 32nd and 36th, 30th gestational week. In all patients fECHO had shown evidence of irregular fetal heart rhythm, but a satisfying cardiac visualization was impossible because of maternal obesity, or fetus in a constant prone position, or intra-uterine growth retardation and oligohydramnios. In the third patient fECHO had evidenced minor pericardial effusion and digoxin therapy was given. fMCG was recorded for 5 minutes with the flat 77-channel magnetometer (sensitivity 5 fT/Hz½) working in shielded room at ITAB (Chieti University). Independent Component Analysis (FastICA algorithm) was used to extract the fetal signal from fMCG raw data. Smoothing of the extracted fetal traces was performed, if necessary, to improve the S/N ratio Results: The quality of all reconstructed fetal traces allowed real-time beat-to-beat detection of supraventricular extrasystoles (SVE), with/or without aberrant ventricular conduction and/or atrio-ventricular block. Selective averaging of sinus and SVE helped the accurate estimate of QRS duration. Heart rate variability parameters were also computed in time and frequency domains. Conclusions: Reliable reconstruction of fetal cardiac signals allowed the non-invasive beat-to-beat detection of, even transient, fetal arrhythmias and the monitoring of antiarrhythmic therapy effects during pregnancy.