Experimental analysis of risk factors for aneurismal sac re-expansion after stent-grafting

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[Introduction] There are, in accordance with clinical use of stent graft placement, cases in which aneurysm size is not reduced despite the aneurysm being thrombosed. In addition, these cases are often reported to involve a high risk of secondary rupture. The aim of this study was to continuously measure excluded sac pressure changes in an aneurysm in which blood flow had been blocked by stent graft placement and to clarify more useful factors for successful reduction of aneurysm size and decrease of excluded sac pressure within the aneurysm in the late stages of this procedure.[Subjects and methods] Excluded sac pressure changes in an aneurysm in which blood flow was blocked after stent graft placement were continuously measured using pigs, and changes in aneurysm size were compared. An aneurysm model with no endoleaks and type I and type II endoleaks was created to indicate factors affecting internal pressure within the aneurysm. Arterial blood pressure and internal pressure within t … More he aneurysm were continuously measured simultaneously for 6 months postoperatively using a telemetric pressure sensor implanted in the body. In addition, the above experimental results allowed remediation of problems with the stent graft, and the graft was placed in an aneurysm model with no endoleaks and type I and type II endoleaks. In addition, the pigs were sacrificed, and the nature of the thrombus in the aneurysm was examined together with a pathological study of the aneurysmal wall. [Results] Systemic blood pressure and internal pressure within the aneurysm had a significant correlation to the thickness of the graft portion of the stent graft and the presence or absence of an endoleak. In addition, internal pressure within the aneurysm dropped significantly in comparison to systemic blood pressure when an endoleak was not found in angiography, regardless of the length of the landing zone. With both type I and type II endoleaks, excluded sac pressure within the aneurysm dropped significantly in comparison to systemic blood pressure in acute stages. In cases where an endoleak remained over the long-term, however, there was no significant difference in internal pressure within the aneurysm and systemic blood pressure, and a red thrombus was noted. [Discussion and Conclusion] No studies simultaneously measured systemic blood pressure and internal pressure within the aneurysm for several months after stent graft placement and reported on the relationship to aneurysm size, but this study clarified the relationship between aneurysm size and systemic blood pressure and internal pressure within the aneurysm. An endoleak did not cause internal pressure within the aneurysm to rise during acute stages, but a rise in internal pressure within the aneurysm was noted despite the lack of evidence of major changes in angiography. Treatment should be quickly converted to surgery when an endoleak continues for 6 months or longer. Less