Evaluation of Multiple Embolic Agents for Embolization of the Superior Rectal Artery in an Animal Model

OBJECTIVE

To prospectively compare the safety of transcatheter embolization of superior rectal arteries in healthy pigs with multiple agents such as coils, spheres and liquids.

MATERIALS AND METHODS

Nine adult domestic pigs (three males, mean weight: 60 kg [50-70]) were randomly assigned to the embolization group: copolymer of ethylene vinyl alcohol (EVOH)-Onyx® (group 1, n = 3), microspheres 500 µ (group 2, n = 3), 2-mm micro-coils (group 3, n = 3). After a selective angiogram has been acquired, the embolic agent was infused at the distal part of rectal arteries. An angio-CT was performed before and after each embolization. After one week, angiography was repeated prior to euthanasia. At necropsy, the anorectal juncture was removed for histopathologic examination.

RESULTS

At necropsy, 100% of animals embolized with Onyx developed a significant necrosis zone of the distal part of the rectum. Histological examination revealed a mural infarction. For the micro-coil and microsphere groups, gross examination of the intestines did not reveal any evidence of ischaemia. The coils were found in the distal arterial vasculature of the meso-rectum, allowing a downstream revascularization by collaterals. The microspheres and onyx in the rectal wall, more distally.

CONCLUSION

Microspheres appear to induce fewer histologic complications than the liquid embolic agent and provide a more distal occlusion than micro-coils. These results suggest that, for superior rectal artery embolization, a super-selective embolization using spheres in human clinical conditions should be more effective and as safe as coil embolization. EVOH might be an unsafe embolization agent for haemorrhoids.

FairEmbo Concept for Arterial Embolizations: In Vivo Feasibility and Safety Study with Suture-Based Microparticles Compared with Microspheres

PURPOSE

Microspheres are effective embolic agents, especially for the management of bleeding and oncologic lesions. The first FairEmbo study reported the effectiveness of embolization using suture fragments. The effectiveness and safety of arterial embolization with suture-based microparticles (SBM) were assessed in a swine model.

MATERIALS AND METHODS

In this ethical-approved animal study, a polar artery in each kidney was embolized in four swine: one side with hand-cut non-absorbable SBM (Flexocrin 2®) and the contralateral side with Embozene® 900 for comparison. Swine were followed for 3 months (M3) to evaluate the effectiveness and the safety of SBM. Follow-up protocol included clinical monitoring, computed tomography (CT) control and digital subtraction angiography (DSA), followed by histological analyses. The SBM confection parameters were evaluated by automatic microscopic sizer. RStudio software and Mann-Whitney test (significance at P < 0.05) were used for statistics.

RESULTS

The average size of SBM was 1002 μm (SD = 258). All targets were effectively embolized by SBM with an angiogram defect estimated at 45.6% (95% CI [35.9-55.2]), compared to 40.5% (95% CI [30.6-55.5]) for Embozene® group (P = 0.342). The average duration of SBM embolization procedure was significantly increased compared to Embozene® embolization (1202 s versus 222 s, P = 0.029). There were no statistical differences in M3 DSA and CT for SBM and Embozene®, with persistence of partial arterial occlusion and atrophic embolized area. No postoperative complications were observed on clinical and CT controls.

CONCLUSION

This experimental study suggests that embolization with SBM is feasible, safe and effective in short- and medium-term follow-up as compared to microspheres.