Uterine Artery Embolization in Sheep: Comparison of Acute Effects with Polyvinyl Alcohol Particles and Calibrated Microspheres

Abstract

To compare the effects on the myometrium of polyvinyl alcohol (PVA) particles and calibrated microspheres (MS) in embolization of the uterine arteries in sheep. Superselective and bilateral embolization of the uterine arteries was performed with PVA particles and calibrated MS within 24 hours after artificial ovulation in 26 adult nonpregnant sheep. PVA particles of four diameters, 150-250, 250-400, 400-600, and 600-1,000 microm, were compared with calibrated MS of similar diameters, 100-300, 300-500, 500-700, and 700-900 microm, in eight groups of sheep. Evaluation was based on histopathologic study of uterus, ovaries, and vascular pedicles after sacrifice 5 days after embolization. The scores of necrosis, the diameter of occluded arteries, and the number of particles were determined. The scores of uterine necrosis were compared by using nonparametric tests (Mann-Whitney U and Kruskal-Wallis). Spearman rank test was used for correlations. PVA particles clumped more readily than did MS. Small particles had a higher score (P =.02) of uterine necrosis than did large particles. PVA particles produced more necrosis than did MS. Size of MS and diameter of occluded arteries showed significant correlation (rho = 0.762, P <.001). Size of PVA particles and diameter of occluded arteries showed no correlation. PVA particles occluded vessels of a wider range of size than did calibrated MS. PVA particles are associated with intense uterine necrosis and extensive arterial occlusion regardless of size. Calibrated MS, which are associated with less uterine necrosis, permit a segmental arterial occlusion correlated with size.