Characterization of pressure reduction mechanism in treatment of intracranial aneurysm

Abstract

Intracranial aneurysm can be treated endoluminally without major surgery by placing embolization coils into the aneurysm or flow diverters across the aneurysm's neck. With these placements, blood flow into the aneurysm is immediately reduced and the aneurysm is occluded in long term. However, clinical studies showed that recurrence risk of aneurysm treated by coils is high and aneurysm is known to rupture after deployment of flow diverters. The rupture risk due to tensional wall stress can be reduced if aneurysmal pressure is reduced with device deployment. In this study, four kinds of mechanisms were hypothesized to affect pressure: flow diverting effect and coagulation effect by flow diverter, and intra-aneurysmal flow reduction effect and coagulation effect with coils. Pressures inside rubber-model aneurysms were characterized with flowing anti-coagulated blood. The analysis showed that the pressure inside aneurysm was only marginally affected when flow diverters were deployed across the aneurysm necks. When blood coagulation capability was restored in the same setup, >10% pressure reductions were induced in 60 minutes or less. The results showed that coagulation in aneurysm is essential for reduction of aneurysmal pressure and rupture risk. Further experiments with packed coils in model aneurysm confirmed that coagulation in aneurysm is essential for aneurysmal pressure reduction. These characterization studies have led to better understanding on pressure behavior within aneurysm after deployment of different treatment device. In clinical practice and treatments, anti-coagulants such as heparin are routinely administered into patient's bloodstream as a means to prevent arterial stenosis. Aneurysmal pressure reduction cannot be effected unless coagulation can be selectively restored in the aneurysm without significantly affecting the heparin's anti-coagulating action in the parent vessel. To meet this need, novel coils coated with a bio-soluble polymer matrix have been developed. Local coagulation is restored inside aneurysm by loading the coating matrix with reversal drugs for anti-coagulants. The effect of the biosoluble drug-loaded coils on the pressure profile was experimentally studied using the aneurysm model with flowing heparinized human blood. Platinum coils were used as control for comparison. The results showed that aneurysmal pressure was reduced by >10% within an hour while only minor reduction was observed in the platinum coil case. These results confirmed that the coagulation-inducing coils can effectively reduce local aneurysmal pressure better than platinum coils. This suggests that risk of re-rupture can be better managed with the new drug-loaded coils when used in combination with flow diverters and stents in the acute treatment of ruptured intracranial aneurysms. This new coil device should address the anti-platelet medication problem as well and be adapted in-vivo for testing in the future.

Date of Award	2014
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology