Effects of Aneurysmal Neck Angle on Stent Displacement after Endovascular Repair of Abdominal Aortic Aneurysm / 医用生物力学

Objective To study the effects of aneurysmal neck angle on stent displacement after endovascular repair of abdominal aortic aneurysm (AAA). Methods The CT images of 28 patients were selected to establish preoperative AAA model, postoperative AAA model and covered stent model respectively, and the models were divided into non-severe angulation group ( n = 14) and severe angulation group ( n = 14) according to the preoperative angle of tumor neck. The geometric shape of each model was measured, and the changes of AAA geometric parameters and postoperative stent displacements before and after surgery were analyzed. The displacement force of the model during the first follow-up was calculated by hemodynamic simulation. Results Significant differences were found in tumor length, maximum diameter, displacement force, tumor neck length and tumor volume between two groups of patients (P 0. 05). For the incidence of internal leakage, there were 2 cases in non-severe angulation group and 4 cases in severe angulation group (P>0. 05).Conclusions Severe neck angulation can lead to a significant increase in support displacement force and decrease in proximal anchorage zone, and thus increase the possibility of support displacement. It is suggested that doctors should strengthen postoperative follow-up for patients with severe neck angulation and be vigilant of the occurrence of long-term internal leakage in clinic.

Two Cases of Combined Performance of Endovascular Aortic Aneurysm Repair (EVAR) and Off-Pump Coronary Artery Bypass Grafting (OPCAB) / 日本心臓血管外科学会雑誌

Concomitant occurrence of coronary arterial disease (CAD) with abdominal aortic aneurysm (AAA) is not rare. Combined performance of open surgery (OS) of AAA repair and coronary arterial bypass grafting (CABG) has been reported to be effective as the way to avoid the risk of rupture of the aneurysm and acute coronary syndrome (ACS), while it's highly invasive. We successfully performed a combination performance of endovascular aneurysm repair (EVAR) and off-pump CABG (OPCAB) with the support of an intra-aortic balloon pump (IABP) in 2 cases with AAA and unstable angina pectoris (UAP). It was suggested that this strategy is a reasonable clinical option for the patient with UAP complicated with large AAA.

Management of concurrent thoracic and abdominal aortic aneurysms

Concurrent thoracic and abdominal aortic aneurysm is uncommon. It remains a formidable surgical challenge to vascular surgeons, as decision to treat in staged or simultaneous setting still debatable. We present, here, a case of a 62-year-old-man with asymptomatic concurrent thoracic and abdominal aortic aneurysms, which was successfully treated with two-stage hybrid endovascular repair. The aim of this case report is to discuss the treatment options available, possible associated complications and measures to prevent them.

Biomechanical research progress on abdominal aortic aneurysm enlargement after endovascular aneurysm repair / 医用生物力学

Clinically, abdominal aortic aneurysm (AAA) may continue to expand or even rupture after endovascular aneurysm repair (EVAR) due to endoleak or endotension. The existence of endoleak and endotension can significantly affect the mechanical/hemodynamic environment in AAAs, thus changing the strain and stresses on aneurysm wall, further influencing the transportation of low density lipoprotein (LDL), oxygen and nitric oxide (NO) in AAAs and aneurysm wall, which might eventually alter the biochemical environment and physiological property of aneurysm wall. This review focused on biomechanical mechanism of AAA enlargement after EVAR and its recent research progress, which indicated that reduction of the aneurysm wall strength due to deterioration of biomechanical environment (such as increase of tensile stress on aneurysm wall) and abnormity of biochemical environment (such as increase of LDL deposition, change of oxygen concentration) might be the source leading to AAA enlargement after EVAR. Based on previous studies, the authors propose that comprehensive investigations on AAA enlargement after EVAR from the perspective of biomechanics and mechanobiology have great research values and clinical significance, which will help clarify the mechanism of AAA enlargement after EVAR, as well as optimize the strategies of aneurysm repair surgery and designs of interventional medical devices.

Technique of automatic abdominal aortic aneurysm segmentation and 2D-mesh generation / 医用生物力学

Objective To develop an automatic segmentation and mesh generation technique for abdominal aortic aneurysm (AAA) and to build a 2D numerical analysis model that can be used for finite element analysis (FEA). Methods A method that totally based on morphology processing was developed to segment all the components of the AAA. For each closed curve that obtained, its signed distance function was then calculated. According to the set relationships between each curve, the final signed distance function was calculated. Under the control of this function and an equilibrium relationship, iterated Delaunay algorithms were used until the equilibrium relationship was satisfied or the set conditions were reached. Then the program ended and the finite element model was generated. Results Automatic segmentation of the lumen as well as semiautomatic segmentation of the wall and calcification were achieved. Different parts of the AAA were meshed, and the type and density of the mesh could be controlled. Two finite element models were established for stress analysis: one was the coupling mesh of the thrombus and the wall, and the other was the coupling mesh of the thrombus, the wall and the calcifications. Conclusions An automatic segmentation and mesh generation algorithm with high accuracy has been developed, without any complicated computation or initial curve. The mesh generation algorithm tends to produce high quality meshes and the generation is easy to be controlled by only two parameters. The generated mesh has been verified to be useful in FEA simulation.

Successful Treatment of Aneurysm-Associated Disseminated Intravascular Coagulation with Endovascular Aneurysm Repair (EVAR) / 日本心臓血管外科学会雑誌

A 80-year-old woman was referred to our hospital for coagulation abnormality and huge abdominal aortic aneurysm (AAA). She had persistent hemorrhage from the surgical wound after the operation for her cubital tunnel syndrome 5 days before. Enhanced computed tomography image revealed AAA with a maximum diameter of 91 mm. Laboratory data were compatible with disseminated intravascular coagulation (DIC). Due to the marked hemorrhagic status, we thought the open repair of AAA was an extremely risky procedure. We initiated the medical treatment with gabexate mesilate. However, the hemorrhage continued after 2 weeks of medical therapy. We performed endovascular aneurysm repair (EVAR). DIC improved after the procedure. Postoperative enhanced computed tomography image showed regression of the aneurysm with no endoleak. EVAR might be an acceptable procedure for AAA with DIC.

Endovascular Repair of a Secondary Aortoenteric Fistula / 日本心臓血管外科学会雑誌

A 71-year-old man who had undergone repair of a ruptured abdominal aortic aneurysm with a tube graft 3 months ago was transferred from another hospital with an Aortoenteric Fistula (AEF) for surgical treatment. Computed tomographic (CT) angiography revealed pseudoaneurysm formation at the proximal anastomotic site. Waiting for the elective operation, he developed massive hematemesis with shock. Endovascular stent-graft repair was emergently performed because of high risk for conventional open surgery. Gastrointestinal bleeding was successfully controlled. The psuedoaneurysm disappeared, which was confirmed by postoperative CT angiography. At 1-year follow-up, he has shown no clinical and radiographic evidence of recurrent infection or bleeding. For the case with shock, Endovascular repair could be a bridge to open surgery because it is fast and minimally invasive. Endovascular repair of AEF is technically feasible and may be the definitive treatment in selected patients without signs of infection and gastrointestinal bleeding.

Comparison between computational models of abdominal aortic aneurysm / 医用生物力学

Objective To compare the differences in the hemodynamic parameters of abdominal aortic aneurysm (AAA) between fluid-structure interaction model (FSIM) and fluid-only model (FM), so as to discuss their application in the research of AAA. MethodsAn idealized AAA model was created based on patient-specific AAA data. In FM, the flow, pressure and wall shear stress (WSS) were computed using finite volume method. In FSIM, an Arbitrary Lagrangian-Eulerian algorithm was used to solve the flow in a continuously deforming geometry. The hemodynamic parameters of both models were obtained for discussion. Results Under the same inlet velocity, there were only two symmetrical vortexes in the AAA dilation area for FSIM. In contrast, four recirculation areas existed in FM; two were main vortexes and the other two were secondary flow, which were located between the main recirculation area and the arterial wall. Six local pressure concentrations occurred in the distal end of AAA and the recirculation area for FM. However, there were only two local pressure concentrations in FSIM. The vortex center of the recirculation area in FSIM was much more close to the distal end of AAA and the area was much larger because of AAA expansion. Four extreme values of WSS existed at the proximal of AAA, the point of boundary layer separation, the point of flow reattachment and the distal end of AAA, respectively, in both FM and FSIM. The maximum wall stress and the largest wall deformation were both located at the proximal and distal end of AAA. Conclusions The number and center of the recirculation area for both models are different, while the change of vortex is closely associated with the AAA growth. The largest WSS of FSIM is 36% smaller than that of FM. Both the maximum wall stress and largest wall displacement shall increase with the outlet pressure increasing. FSIM needs to be considered for studying the relationship between AAA growth and shear stress.

Dissected Abdominal Aortic Aneurysm in a 24-Year-Old Female-Minimally Invasive Right Retroperitoneal Approach- / 日本心臓血管外科学会雑誌

A 24-year-old woman with an abdominal aortic aneurysm (AAA) caused by mucoid medial degeneration of the aortic wall in the absence of Marfan syndrome is reported. She required a Y-shaped graft replacement of the abdominal aorta through a minimal incision and recovered successfully.

Pathogenesis of Abdominal Aortic Aneurysm

Abdominal aortic aneurysm (AAA) ranks as the 13th leading cause of death in the USA, being responsible for 0.8 per cent of all deaths. The pathogenesis of an AAA is complex and multifactorial. The common feature of both AAA and atherosclerosis is inflammation. However, atherosclerosis is primarily found within the intima and media, whereas AAA typically affects the media and adventitia. Four mechanisms relevant to AAA formation have been identified; 1) Proteolytic degradation of aortic wall connective tissue. Matrix metalloproteinases (MMPs) and other proteases, derived from macrophages and aortic smooth muscle cells, are secreted into the extracellular matrix, causing destruction of the aortic media and supporting lamina through the degradation of elastin and collagen. 2) Inflammation and immune responses. Autoimmunization and infection can cause infiltration of macrophages and lymphocytes. The reactive oxygen species can cause matrix degradation and apoptosis. 3) Biochemical wall stress. A decreased elastin-collagen ratio and an increased wall tension at infrarenal sites cause preferential sites for AAA. 4) Molecular genetics. Certain phenotypes have been associated with AAA, but no single genetic defect or polymorphism has been identified as a common denominator for AAA.

Clinical Characteristics of the Abdominal Aortic Aneurysm

PURPOSE: In old age, abdominal aortic aneurysm (AAA) is not a rare disease and potentially fatal. Also, there has been a lack of concern for this disease in the emergency department. Our study investigated the clinical characteristics of AAAs seen in the emergency center to assess the needs of the diagnostic approach to this disease in the emergency center. METHODS: Eighty patients with an AAA between Jan. 1995 and Jul. 2002 were enrolled. Data were obtained from a retrospective review of medical records. We analyzed the clinical characteristics of the AAA on the basis of the patient 's age and sex, risk factors, presenting symptoms and signs, physical findings, diagnostic tools, and findings. RESULTS: AAAs were predominant in males (82.5%). A smoking history (57.5%), old age over 65 (71.3%) and hypertension (50.0%) were the most common risk factors. In this study, the initial diagnosis of a AAA was mostly determined by the existence of a pulsating abdominal mass, and the overall sensitivity of a pulsating abdominal mass was 57.5%. Although the most common presenting symptom was abdominal pain(51.3%), about one third of the patients had no subjective symptoms. Twenty-one of the patients had a ruptured AAA at the time of diagnosis. There was no remarkable difference in the incidence of large AAA (> 5 cm) or ruptured AAA between elderly (> 65years) and the young (< 65 years). CONCLUSION: Because of the absence or vagueness of symptoms and signs, an AAA might be initially excluded without a careful examination. For the early detection and prevention of a ruptured AAA, emergency medical doctors should carefully evaluate and assess patients with risk factors even though they have non-specific symptoms of the gastrointestinal or urinary system.