Abstract
The use of endovascular treatment in the thoracic aorta has revolutionized the clinical approach for treating Stanford type B aortic dissection. The endograft procedure is a minimally invasive alternative to traditional surgery for the management of complicated type-B patients. The endograft is first deployed to exclude the proximal entry tear to redirect blood flow toward the true lumen and then a stent graft is used to push the intimal flap against the false lumen (FL) wall such that the aorta is reconstituted by sealing the FL. Although endovascular treatment has reduced the mortality rate in patients compared to those undergoing surgical repair, more than 30% of patients who were initially successfully treated require a new endovascular or surgical intervention in the aortic segments distal to the endograft. One reason for failure of the repair is persistent FL perfusion from distal entry tears. This creates a patent FL channel which can be associated with FL growth. Thus, it is necessary to develop stents that can promote full re-apposition of the flap leading to complete closure of the FL. In the current study, we determine the radial pressures required to re-appose the mid and distal ends of a dissected porcine thoracic aorta using a balloon catheter under static inflation pressure. The same analysis is simulated using finite element analysis (FEA) models by incorporating the hyperelastic properties of porcine aortic tissues. It is shown that the FEA models capture the change in the radial pressures required to re-appose the intimal flap as a function of pressure. The predictions from the simulation models match closely the results from the bench experiments. The use of validated computational models can support development of better stents by calculating the proper radial pressures required for complete re-apposition of the intimal flap.
Highlights
The incidence of aortic dissection (AD) in the United States is approximately 2,000 cases per year and early mortality is as high as 1% per hour if untreated (Vecht et al, 1980; Roberts, 1981)
The endograft is first deployed to exclude the proximal entry tear to redirect blood flow toward the true lumen (TL) and a stent or graft is used to push the intimal flap against the false lumen (FL) wall such that the aorta is reconstituted by sealing the FL
During In the case of simulations, the aorta vessel was loaded with experiments, the static pressure was homogenously applied to a pressure equal to that applied during bench testing, but the expansion member was unloaded
Summary
The incidence of aortic dissection (AD) in the United States is approximately 2,000 cases per year and early mortality is as high as 1% per hour if untreated (Vecht et al, 1980; Roberts, 1981). There are three modes of treating patients suffering from type-B acute AD: medical management, open surgery, or endovascular treatment. Clinicians recommend the minimally invasive endovascular grafting procedure over open surgery for complicated type-B patients suffering from impending or actual complicated dissections because surgical methods have approximately a 13% higher mortality rate at 5-year follow-up as compared to endovascular grafting (Moulakakis et al, 2014). Stent grafting has been largely successful in closing the initial entry tear (Kato et al, 2002; Song et al, 2006; Marcheix et al, 2008; Sayer et al, 2008; Alves et al, 2009; Manning et al, 2009; Czerny et al, 2010), patients may still undergo re-interventions in the form of multiple stent-grafts or open surgery due to ongoing complications (Thrumurthy et al, 2011; Fattori et al, 2013; Andersen et al, 2014; Faure et al, 2014). A significant enlargement of the aortic diameter above the stent graft has been observed during deployment, which is important because this may reflect increased strain and stress on the aorta in the segments adjacent to the stent graft (Trimarchi and Eagle, 2016)
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