New insights into fetal atrioventricular block using fetal magnetocardiography.

outine fetal arrhythmia assessment typically involves the se of echocardiographic modalities that demonstrate mehanical events from which electrophysiological events are nferred (1). While M-mode and Doppler-based techniques ave been used successfully to diagnose third-degree atrioentricular block (AVB), second-degree AVB, and, more ecently, first-degree AVB, our evaluation has been limited o atrial and ventricular rates (2–4), gross P-R interval stimates using atrial-ventricular activity time intervals (5), nd rarely detected ventricular ectopy. Although fetal elecrocardiogram (ECG) has been shown to be more sensitive han echocardiogram-based techniques in detecting firstegree AVB in anti–Ro-positive pregnancies (6), it has imited use in the evaluation of fetal heart rates out of the ormal range, is more difficult to acquire at 28 to 32 weeks, nd involves signal averaging, all limiting its clinical pplication.