Abstract
Electric heart activity of fetuses can be measured noninvasively not with electrocardiography but with magnetocardiography, which can measure faint magnetic fields generated by the fetal heart. Recently, intervals between peaks on magnetocardiograms have been mainly investigated, especially for the diagnosis of fetal arrhythmia; however, the amplitudes of each peak (P, QRS, and T waves) of the magnetocardiogram have not yet fully studied. In this study, the amplitude of the P wave on a fetal magnetocardiogram was investigated to examine whether P wave amplitude may directly relate to atrial load and fetal prognosis. Magnetocardiograms of 36 fetuses (14 normal fetuses and 22 fetuses with congenital heart diseases) were recorded using 64-channel SQUID (superconducting quantum interference device) magnetocardiography. By averaging the magnetocardiogram triggering R peaks, we obtained an averaged magnetocardiogram and measured the peak amplitudes of the P. In cases of monophasic P waves, the absolute amplitude of the P wave was measured. In cases of biphasic P wave, the amplitude between positive and negative peaks was measured. The peak amplitudes of P waves with atrial load such as pulmonary atresia, pulmonary stenosis, Ebstein disease were significantly larger than those in normal fetuses and were related to poor prognosis, indicating that excess atrial load resulted in a large P wave even on a fetal magnetocardiogram. [J Physiol Sci. 2007;57 Suppl:S206]
