Certification in Electronic Fetal Monitoring (CEFM) Practice Test

Fetal heart block disrupts conduction between the atria and ventricles, so the ventricles pace themselves at a slow, independent rate. On the tracing, this often appears as a bradycardic rhythm that is unusually regular with little beat-to-beat fluctuation in the baseline—minimal variability. The reduced variability occurs because the ventricular rhythm is driven by an intrinsic pacemaker rather than the normal, autonomic-influenced atrial-ventricular conduction. Sinusoidal patterns point to severe anemia or hypoxia, tachycardia to a tachyarrhythmia, and pure bradycardia can occur for other reasons, but the combination of slow rate with minimal variability is characteristic of heart block.