The dynamic analysis of the implantation process of a new vena cava filter was carried out by finite element analysis method to reveal the influence of the angle, length, width and thickness of the filter rod on its mechanical properties and the inner wall of the blood vessel. The results showed that the high-stress and high-strain areas of the filter were mainly concentrated in the connection between the filter rod and the filter wire. With the increase of the angle of the filter rod, the maximum equivalent stress and the maximum elastic strain on the filter wall decreased, while the maximum equivalent stress on the vascular wall increased. With the increase of the length of the filter rod, the maximum equivalent stress and strain peak of the filter wall increased, but the maximum equivalent stress of the vessel wall decreased. With the increase of the width and thickness of the filter rod, the maximum equivalent stress of the filter wall, the maximum elastic strain and the maximum equivalent stress of the vessel wall all showed an upward trend. The static safety factor of all filter models was greater than 1, and the structure after implantation was safe and reliable. The results of this study are expected to provide a theoretical basis for the structural optimization and deformation mechanism of the new type vena cava filter.
The mechanical properties of nitinol iliac vein stent (NIVS) have been studied by many scholars at home and abroad, but the study on the mechanical properties of iliac vein stent under different release scales has not been reported yet. Based on the finite element analysis method, the mechanical properties of three self-developed NIVS were studied to reveal the influence of stent diameters (12, 14, 16 mm) and different release scales (80%, 90%) on its strength, fatigue life and vein wall biomechanical properties. With an increases in the release scales, the equivalent elastic strain, fatigue strength safety factors, and vessel wall equivalent stress exhibited a downward trend, while the most stressed cross-section coincided with the arc of stent-connecting rods. Through 30, 60 and 90 days’ animal test, a narrowed vascular model was established in the iliac veins of 12 pigs, and the developed iliac vein stents were implanted to comprehensively evaluate the safety and effectiveness of the stent, and at the same time the mechanical properties of stents were verified to provide important reference for the type inspection and clinical trials of follow-up products.
Objective To summarize selection of therapeutic method for isolated iliac aneurysms and analyze its advantages and disadvantages. Method The clinical data of 21 patients with isolated iliac aneurysms from January 2006 to January 2017 in this hospital were analyzed retrospectively. Results Four patients were treated with an open surgery such as the unilateral iliac prosthetic graft interposition, aorto-biiliac or aorto-bifemoral arterial bypass graft, ligation of internal iliac artery, etc.. Seventeen patients were treated with an endovascular treatment such as the unilateral iliac stent-grafts, bifurcated aortic stent-grafts, or coil embolization alone, etc.. One patient with ruptured isolated iliac aneurysms died during the endovascular repair, and the rest patients were cured after the operation. The average operative time was 2.83 h and 1.58 h, the average hospital stay was 17.5 d and 7.7 d respectively for the patients with the open surgery and the endovascular treatment. Except 1 case of type Ⅰ and 1 case of type Ⅱ endoleaks were found in the patients with the endovascular treatment, no complications such as the ureteral and intestinal injuries, the gluteal muscle claudication, and the sigmoid ischemia were found in all the patients. Seventeen cases were followed-up. The following-up rate was 85%. The following-up time was 1–60 months with an average of 22 months. During the following-up period, the grafts and stent grafts were patent and the aneurysm sac diameter was unchanged. The abscess of the iliac fossa occurred in 1 patient with systemic lupus erythematosus and improved after the symptomatic treatment. Two patients died of other diseases during the following-up period, and the rest had no obvious clinical symptoms. Conclusions Preliminary results of limited cases in this study show that endovascular repair and open surgery in treatment of appropriately selected patients with isolated iliac artery aneurysms is safe and effective. But in special situation, technical controllability of open surgery might be better than endovascular repair, treatment should be selected according to patient’s general condition and anatomy of aneurysm.
Vena cava filter is a filter device designed to prevent pulmonary embolism caused by thrombus detached from lower limbs and pelvis. A new retrievable vena cava filter was designed in this study. To evaluate hemodynamic performance and thrombus capture efficiency after transplanting vena cava filter, numerical simulation of computational fluid dynamics was used to simulate hemodynamics and compare it with the commercialized Denali and Aegisy filters, and in vitro experimental test was performed to compare the thrombus capture effect. In this paper, the two-phase flow model of computational fluid dynamics software was used to analyze the outlet blood flow velocity, inlet-outlet pressure difference, wall shear stress on the wall of the filter, the area ratio of the high and low wall shear stress area and thrombus capture efficiency when the thrombus diameter was 5 mm, 10 mm, 15 mm and thrombus content was 10%, 20%, 30%, respectively. Meanwhile, the thrombus capture effects of the above three filters were also compared and evaluated by in vitro experimental data. The results showed that the Denali filter has minimal interference to blood flow after implantation, but has the worst capture effect on 5 mm small diameter thrombus; the Aegisy filter has the best effect on the trapping of thrombus with different diameters and concentrations, but the low wall shear stress area ratio is the largest; the new filter designed in this study has a good filtering and capture efficiency on small-diameter thrombus, and the area ratio of low wall shear stress which is prone to thrombosis is small. The low wall shear stress area of the Denali and Aegisy filters is relatively large, and the risk of thrombosis is high. Based on the above results, it is expected that the new vena cava filter designed in this paper can provide a reference for the design and clinical selection of new filters.
ObjectiveTo investigate the effect of distal tears on postoperative aortic remodeling after Thoracic Endovascular Aortic Repair (TEVAR) for the patients with subacute stage of Stanford type B aortic dissection.MethodsForty three cases with Stanford type B aortic dissection, admitted in Anhui Provincial Hospital from July 2011 to April 2015, who underwent TEVAR to repair the proximal aortic entrance tear, after which the blood reflex from distal tears were still observed were analyzed retrospectively. According to the number of heart volume required to fill the two groups, group A (≤2 heart rate) group B （>2 heart rate）, We then assessed the changes of the true and false lumen area and analyzed the effects of direction of blood flow and the number of heart rate to fill the false lumen on formation of false lumen thrombosis in the period of 3–24 months.ResultsAll the stents were successful implanted. There was a statistically significant difference in lumen area between the two groups before and after surgery, and univariate analysis showed that the direction of distal rupture of blood flow into the false lumen had no effect on postoperative aortic remodeling (P<0.05), but postoperative hypertension (≥140/90 mmHg) slows down the formation of false lumen thrombosis.ConclusionPatients had entrance tear in the distal of aortic, still broken and faster flow after TEVAR stent-graft implantation in the proximal closed entrance tear. Blood pressure should be strictly controlled and close follow-up also needed, meanwhile, the distal entrances can be closed the same period if there is a faster flow from them.