Optically Pumped Magnetometers for Fetal Arrhythmia Evaluation: Clinical Evidence and Implications for Health Technology Assessment

Fetal magnetocardiography (fMCG) provides direct non-invasive assessment of fetal cardiac electrophysiology and can resolve atrial and ventricular activation, conduction intervals, and ventricular repolarization. Optically pumped magnetometers (OPMs) offer a cryogen-free platform for fMCG, but evidence for their use in fetal arrhythmia remains limited to a few clinical studies. This perspective examines four reports directly relevant to arrhythmia evaluation with OPM-fMCG. Clinical OPM recordings have demonstrated long QT syndrome, T-wave alternans, Torsades de Pointes, atrial flutter, atrial ectopic tachycardia, blocked atrial bigeminy, atrioventricular block, ventricular tachycardia, and ectopy, with close agreement for PR, QTc, and RR intervals in the direct OPM–SQUID comparison. Further developments have enabled simultaneous magnetic and echocardiographic assessment and improved visualization of the low-amplitude P and T waves central to rhythm and repolarization analysis. Collectively, the available reports establish clinical feasibility and show the additional electrophysiological information that OPM-fMCG can provide beyond fetal echocardiography, but they do not yet establish diagnostic sensitivity and specificity for fetal arrhythmia diagnosis. Prospective multicenter validation in larger arrhythmia cohorts is the key next step.