317. Do Calcium channel blockers modulate fetoplacental blood flow? A study using parallel wire myography

Abstract

Introduction Calcium channel blockers treat maternal hypertension in pregnancy. The effect of newer calcium channel blockers on placental vascular function remains unknown. This study aimed to determine the effect of calcium channel blockers on placental chorionic plate proximal resistance arteries in comparison to maternal omental arteries. Methods Chorionic plate and omental arteries from healthy term pregnancies delivered by caesarean section were studied using parallel wire myography (n = 80; N = 10). Arteries were normalised at 0.9 of L5.1 kPa in 5% O2 and L13.3 kPa in 20% O2 respectively, approximating physiologic vascular pressure and oxygen tension. Arteries were contracted with thromboxane-mimetic U46619 to determine and maintain optimal physiologic vascular tone (EC80). Nifedipine, Nicardipine and Clevidipine were added in incremental doses from 10–10 M to 10–5 M to create dose-dependent relaxation curves. Omental arteries were incubated for 30 min at the highest dose (10–5 M) to further evaluate full effect (n = 16; N = 4). Results Omental arteries demonstrated similar contractility to chorionic plate arteries (8.90 kPa ± 0.681 vs 8.85 kPa ± 0.603). Chorionic plate arteries did not relax with Nifedipine, Nicardipine or Clevidipine (110.73%± 7.518 vs 118.88%±9.379 vs 113.16%±5.163). Omental arteries demonstrated a trend towards larger relaxation with all calcium channel blockers at the highest dose of drug concentration. This was confirmed with highest dose incubation of omental arteries, that showed Nifedipine, Nicardipine and Clevidipine relaxed omental arteries (52.31%±16.294 vs 57.12%±8.621 vs 79.95%±14.862; One-way ANOVA, p Conclusion Chorionic plate arteries demonstrated reduced vasodilatory responses to calcium channel blockers compared to omental arteries. This suggests calcium channel blockers show limited effect on placental blood flow through proximal resistance arteries.