Neonatal outcomes following chronotropic rescue and delayed umbilical cord clamping in fetal complete atrioventricular block with low heart rate

Fetal complete atrioventricular block (f-CAVB) with ventricular bradycardia of ≤ 55 bpm is associated with increased perinatal mortality. With the goal of increasing perinatal survival of f-CAVB cases, we initiated a delivery room protocol to increase fetal heart rate (HR) and cardiac output using intramuscular and intravenous epinephrine given immediately before Cesarean delivery and prior to umbilical cord clamping. We tested the safety and efficacy of this concept of 'chronotropic rescue' in the delivery management of seven fetuses with f-CAVB meeting fetal HR criteria of ≤ 55 bpm in the 12 h prior to delivery. The combination of exogenous epinephrine and delayed umbilical cord clamping increased neonatal HR and stabilized the neonates who received an epicardial pacemaker < 24 h to 5 days after delivery. Based on the findings of this Case Series, chronotropic rescue with delayed umbilical cord clamping may improve survival and should be considered in the perinatal management of high-risk f-CAVB cases with very low fetal HR. © 2026 International Society of Ultrasound in Obstetrics and Gynecology.