Background: Fetal magnetocardiography is a noninvasive technique capable of identifying fetal arrhythmias and can simultaneously characterize the cardiac rhythm of the mother and fetus.
Cases: Three patients, two singleton pregnancies and one twin pregnancy, were admitted for evidence of fetal supraventricular tachycardia. Fetal magnetocardiography was used to monitor the effects of flecainide therapy on the fetus and mother. Two singleton pregnancy fetuses showed improved heart rate and cardiac rhythm within 1 week of the initial dosing. Maintenance dosages controlled the conditions thereafter. Flecainide slowed the supraventricular tachycardia in the twin subject, but magnetocardiography revealed maternal adverse effects necessitating termination of flecainide therapy.
Conclusion: Magnetocardiography is a valuable tool for rhythm diagnosis and for monitoring the maternal and fetal cardiac rhythms in a patient undergoing flecainide therapy for fetal supraventricular tachycardia.