Anticoagulation regimes and their influence on the occlusion rate of aneurysms: an experimental study in rabbits.

OBJECTIVE: Our purpose was to determine whether anticoagulation has an influence on the occlusion rate and thromboembolic occurrence in saccular aneurysms treated with Guglielmi detachable coils.
METHODS: Aneurysms in the right CCA were created in rabbits. Group 1 served as a control group (n = 6) without embolization or anticoagulation. In Groups 2 to 5, aneurysms were embolized. In Group 2, no anticoagulation was given (n = 5). Group 3 received heparin before the placement of the first coil, then low molecular weight heparin (LMWH) for the next 2 days (n = 7). In Group 4, additional aspirin was administered after 2 days until sacrifice (n = 10). Group 5 received heparin before the placement of the first coil, then a LMHW was administered daily until sacrifice (n = 5). Angiography was performed 3 months after coiling, followed by a histological examination.
RESULTS: Histopathological evaluation showed thrombus formation with neovascularization, regardless of the anticoagulation regime used. Only in the group with LMWH over 3 months was the thrombus not focally, properly organized, especially in the dome. The coils in the neck showed, however, the same fibrous scar tissue as in the other groups.
CONCLUSION: Anticoagulation with heparin during the first days, followed by aspirin, appears unlikely to affect the occlusion rate in aneurysms. LMWH over a long period, however, could impair thrombus organization. Therefore, in regard to thrombus organization, an anticoagulation regime with aspirin seems to be superior to LMWH. This could play an important role in the prevention of thromboembolic events in humans treated with Guglielmi detachable coils.