Hemodynamic changes in intracranial aneurysms due to stent-induced vascular remodeling
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Data
2018-08-31
Autores
Santos, Gabriel Bertacco dos
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Universidade Estadual Paulista (Unesp)
Resumo
Originalmente, stents foram projetados para agir como barreiras mecânicas, impedindo a herniação de coils para a artéria-mãe. Recentemente, estudos mostraram que a atual geração de stents intracranianos auto-expansíveis altera a geometria local das artérias: um fenômeno com efeitos hemodinâmicos em parte incompreendidos. Nós realizamos simulações numéricas para avaliar a influência da remodelagem arterial induzida por stent sobre a hemodinâmica em aneurismas intracranianos. As simulações foram realizadas utilizando o software open-source OpenFOAM. O sangue foi modelado como fluido Newtoniano incompressível e as paredes arteriais foram consideradas rígidas. Para quantificar as alterações hemodinâmicas, avaliamos os parâmetros wall shear stress, WSS, e oscillatory shear index, OSI. Quatro geometrias reais de aneurismas intracranianos em bifurcações foram utilizadas. Em um aneurisma na bifurcação da artéria comunicante anterior (ACoA), um stent foi implantando, levando ao endireitamento das artérias que o receberam. Após o procedimento, os níveis de WSS e OSI aumentaram aproximadamente 60% e 25%, respectivamente. Em dois aneurismas em bifurcações da artéria cerebral média (MCA), dois stents foram implantados em uma configuração em “Y”, resultando em um endireitamento de ambas as artérias-filhas. O WSS máximo na superfície do aneurisma aumentou aproximadamente 5% em um dos casos e 22% no outro. Em outro aneurisma em uma bifurcação da MCA, um stent foi implantado, resultando no endireitamento das artérias que o receberam. Após o procedimento, valores de WSS e OSI sofreram uma redução de aproximadamente 13% e 50%, respectivamente. Os resultados mostram que alterações hemodinâmicas de fato ocorrem em aneurismas intracranianos em bifurcações devido à remodelagem arterial induzida por stents. Em contraste com suspeitas anteriores, os efeitos da remodelagem arterial induzida por stents sobre a hemodinâmica de aneurisma apresentam um comportamento variável e nem sempre benéfico. Concluímos, portanto, que a remodelagem arterial induzida por stents pode beneficiar tratamentos de aneurismas intracranianos, como o procedimento em dois tempos de “Y-stent coiling”, através do implante de um único stent em uma etapa prévia. No entanto, procedimentos em dois tempos não seriam recomendado para aneurismas na bifurcação da ACoA, onde o endireitamento das artérias pode causar uma resposta hemodinâmica adversa e aumentar o risco de ruptura do aneurisma.
Stents were first designed to act as mechanical barriers, preventing coil herniation into the parent artery. The current generation of self-expanding intracranial stents has recently been shown to change the local vascular geometry, a phenomenon with unclear hemodynamic effects. We carried out numerical simulations to assess the role of stent-induced vascular remodeling in modifying intraaneurysmal hemodynamics. Simulations were performed using the open-source software OpenFOAM. Blood was assumed to behave as an incompressible Newtonian fluid; vessel walls were assumed to be rigid. Wall shear stress, WSS, and oscillatory shear index, OSI, were evaluated to quantify the hemodynamic changes in the aneurysm sac. Four pre- and post-stent patient-specific geometries of intracranial bifurcation aneurysm were used. In one aneurysm at the anterior communicating artery (ACoA) bifurcation, a single stent was deployed, resulting in straightening of the host vessels. After stenting, WSS and OSI increased by approximately 60% and 25%, respectively. In two aneurysms at middle cerebral artery (MCA) bifurcations, two stents in a “Y” configuration were deployed, resulting in straightening of both daughter arteries. The maximum WSS on the aneurysm surface increased by approximately 5% in one case and 22% in the other. In another aneurysm at a bifurcation of the MCA, a single stent was deployed, resulting in straightening of the host vessels. After stenting, WSS and OSI reduced by approximately 13% and 50%, respectively. The results show that hemodynamic changes do occur in intracranial bifurcation aneurysms due to stent-induced vascular remodeling. Contrary to previous suspicions, the effects of stent-induced vascular remodeling in modifying the intraaneurysmal hemodynamics are variable and not always beneficial. In conclusion, stent-assisted treatments of bifurcation aneurysm such as two-step Y-stent coiling may benefit from the novel vascular geometry by placing a single stent in an earlier step. However, a two-step procedure would not be recommended for aneurysms at the ACoA bifurcation, where straightening of the host vessels may cause an adverse hemodynamic environment and increase the risk of rupture.
Stents were first designed to act as mechanical barriers, preventing coil herniation into the parent artery. The current generation of self-expanding intracranial stents has recently been shown to change the local vascular geometry, a phenomenon with unclear hemodynamic effects. We carried out numerical simulations to assess the role of stent-induced vascular remodeling in modifying intraaneurysmal hemodynamics. Simulations were performed using the open-source software OpenFOAM. Blood was assumed to behave as an incompressible Newtonian fluid; vessel walls were assumed to be rigid. Wall shear stress, WSS, and oscillatory shear index, OSI, were evaluated to quantify the hemodynamic changes in the aneurysm sac. Four pre- and post-stent patient-specific geometries of intracranial bifurcation aneurysm were used. In one aneurysm at the anterior communicating artery (ACoA) bifurcation, a single stent was deployed, resulting in straightening of the host vessels. After stenting, WSS and OSI increased by approximately 60% and 25%, respectively. In two aneurysms at middle cerebral artery (MCA) bifurcations, two stents in a “Y” configuration were deployed, resulting in straightening of both daughter arteries. The maximum WSS on the aneurysm surface increased by approximately 5% in one case and 22% in the other. In another aneurysm at a bifurcation of the MCA, a single stent was deployed, resulting in straightening of the host vessels. After stenting, WSS and OSI reduced by approximately 13% and 50%, respectively. The results show that hemodynamic changes do occur in intracranial bifurcation aneurysms due to stent-induced vascular remodeling. Contrary to previous suspicions, the effects of stent-induced vascular remodeling in modifying the intraaneurysmal hemodynamics are variable and not always beneficial. In conclusion, stent-assisted treatments of bifurcation aneurysm such as two-step Y-stent coiling may benefit from the novel vascular geometry by placing a single stent in an earlier step. However, a two-step procedure would not be recommended for aneurysms at the ACoA bifurcation, where straightening of the host vessels may cause an adverse hemodynamic environment and increase the risk of rupture.
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Palavras-chave
Aneurismas intracranianos, Stents, Remodelagem arterial, Mecânica dos fluidos computacional, Hemodinâmica, Intracranial aneurysms, Vascular remodeling, Computational fluid dynamics, Hemodynamics