Antenatal detection of fetal A-V dissociation utilizing real-time B-mode ultrasound

Congenital heart block is an unusual cause of fetal bradycardia. Until recently, the diagnosis could be confirmed only by evaluation of the fetal cardiac electrical activity. Two cases are reported in which the diagnosis of atrio-ventricular (A-V) dissociation was confirmed in the antepartum period by real-time ultrasound evaluation of cardiac mechanical activity.