Effects of a mixture of a low concentration of n-butylcyanoacrylate and ethiodol on tissue reactions and the permanence of arterial occlusion after embolization

OBJECTIVE: Cyanoacrylates are the most commonly used liquid embolic agents. For embolization of arteriovenous malformations, a mixture of a low concen tration of n-butylcyanoacrylate (NBCA) and Ethiodol (Savage Laboratories, M elville, NY) has been recommended for deeper penetration of the nidus. Dilu tion of NBCA, however, might result in different degrees of tissue reaction and might influence the permanence of vessel occlusion, with an increased risk of vessel recanalization. We compared tissue reactions induced by diff erent NBCA/Ethiodol mixtures and analyzed the permanence of their embolic e ffects. METHODS: NBCA was diluted with Ethiodol to prepare the following standard s olutions: Mixture A, low concentration (NBCA/Ethiodol ratio of 20:80); Mixt ure B, high concentration (50:50). The study was designed in two parts, bec ause tissue reactions after embolization are considered to be a combination of foreign body reactions to solidified material and reactions to the inju red blood vessel. Foreign body reactions were studied by intramuscularly in jecting both glue mixtures into the backs of 18 rats. Specimens were obtain ed at various times after implantation. Immunohistochemical analysis and es terase staining were used to detect macrophages and neutrophils, respective ly. The densities of these inflammatory cells were calculated and statistic ally compared. To study the degree of vascular wall injury and the permanen ce of embolic effects, the renal arteries in 48 rabbits were embolized with NBCA Mixture A or B. Six specimens for each group were obtained at various times after embolization. RESULTS: There was no significant difference in foreign body reactions betw een groups treated with Mixtures A and B, at any time. However, the macroph age density was larger for both groups at 3 months versus 3 days and for th e group treated with Mixture B at 3 months versus 2 weeks. There was no dif ference in the degree of vessel wall injury. None of the embolized vessels demonstrated evidence of recanalization. CONCLUSION: The low concentration of NBCA induced a tissue response similar to that of the high-concentration form. Embolized vessels exhibited no gre ater incidence of recanalization. Therefore, embolization of arteriovenous malformations with diluted NBCA may be safe.