ALTERATION OF HUMAN PLACENTAL VASCULAR TONE BY ANTIARRHYTHMIC MEDICATIONS IN-VITRO

Introduction: Antiarrhythmic medications are commonly used during preg nancy for treatment of maternal or fetal arrhythmias, but little is kn own about their effect on human placental vascular tone and, consequen tly, placental blood flow. The objective of this study was to evaluate the tone responses caused by antiarrhythmic medications in human plac ental vessels from normal term pregnancies in vitro. Methods and Resul ts: Isolated human placental arteries and veins from uncomplicated ter m pregnancies incubated in Krebs'-bicarbonate under 5% oxygen/5% carbo n dioxide/balance nitrogen (PO2 35 to 38 torr) were exposed to cumulat ive doses of quinidine, procainamide, lidocaine, flecainide, propranol ol, amiodarone, verapamil, digoxin, and adenosine after submaximal con traction with 5-hydroxytryptamine. The study was conducted both in the presence and absence of endothelium. The addition of the tested medic ations caused a significant, dose-dependent relaxation of human placen tal arteries and veins except for adenosine, which induced a sustained , dose-dependent contraction of human placental vessels regardless of the presence or absence of tone. Removal of the endothelium did not al ter these responses. Conclusions: Based on these results, the medicati ons tested should have no decremental effect on placental blood flow, with the possible exception of adenosine, which causes significant, do se-dependent contraction of human placental vessels in vitro. Should s imilar contraction be present in vivo, it may have an adverse effect o n the fetus when administering adenosine to pregnant women at term or during labor.