Verapamil Placental Transfer and Effects on Maternal and Fetal Hemodynamics and Atrioventricular Conduction in the Pregnant Ewe

Advances in the field of maternal/ fetal medicine have produced more and more attempts at direct in utero therapy of the fetus. Initial steps toward human fetal surgery have already been taken in the treatment of hydrocephalus. Murad and co-workers have nicely added to our knowledge regarding potential in utero therapy of fetal tachyarrhythmias with this study.Several investigators have explored the role of calcium channel blockers in many areas of the perinatal period. Promising results have emerged demonstrating their potential effectiveness as tocolytic agents and in combatting elevated blood pressure in ewes rendered hypertensive by the infusion of norepinephrine. Murad et al. have documented that verapamil lowers maternal diastolic blood pressure and prolongs atrioventricular conduction in the pregnant ewe. Although placental transfer is limited, enough verapamil crosses the uteroplacental barrier to reach the fetus in effective amounts. Fetal hepatic extraction appears to filter out more than half of the drug reaching the umbilical vein. Still the remaining verapamil prolonged fetal PR intervals 78% at 3 min while the maternal PR interval was increased by 41% at 5 min. The results of this study seem to warrant further investigation of verapamil as a therapeutic modality of fetal tachyarrhythmias in humans.