Magnetocardiography in a Fetus With Long-QT Syndrome
A woman had experienced multiple syncopal attacks of unknown origin in her life. During her first pregnancy, fetal bradycardia was detected at 36 weeks of gestation. Fetal distress was assumed at that time, and consequently, premature delivery was performed by cesarean section. The ECGs of the neonate and his mother showed prolonged QT intervals, which resulted in the diagnosis of Romano-Ward Syndrome and in β-blocker treatment. Molecular genetic testing in the mother and her offspring revealed identical mutations within the LQT1 locus. The present report is about the second pregnancy of that woman, when she was referred to our institution at 31 and again at 34 weeks of gestation because of persistent fetal bradycardia observed during scheduled prenatal check-up.
Fetal magnetocardiography (FMCG) was performed with a 16-SQUID magnetometer in a magnetically shielded environment (Figure). By independent component analysis, fetal and maternal signals could be distinguished and treated separately. The FMCG showed sinus bradycardia at heart rates of 103 and 104 bpm, respectively, and prolonged QTc intervals of 0.58 s and 0.59 s, respectively. Maternal magnetocardiography showed heart rates of 73 and 69 bpm, respectively, and a QTc interval of 0.46 s at both instants, which corresponded well with the QTc of 0.45 s in her ECG. An ECG from the neonate taken immediately after term delivery confirmed the diagnosis of Romano-Ward syndrome with an initial QTc of 0.57 s. QTc shortened to 0.48 s one week after the introduction of β-blocker therapy. FMCG produces signals similar to those known from common surface ECG. As far as it concerns rhythm disorders and time intervals, the same diagnostic criteria can be applied for magnetocardiography as for ECG. In contrast to the ECG, the FMCG can be obtained contact free and without harm from ≈15 weeks of gestation on throughout pregnancy. As has been demonstrated, FMCG can help to distinguish fetal distress reactions from disorders like the prolonged-QT syndrome as one of the less common causes of low heart rates in the fetus.
We thank Wolfgang Mueller, Allard Schnabel, and Florian Thiel for their technical assistance.