Abdominal aortic aneurysm ( abdominal aortic aneurysm, AAA) is a common arterial dilatation disease that often occurs in the elderly, and rupture is its most common and most dangerous complication, ranking 10th among the causes of death in men over 65 years of age. Its traditional surgical approach is AAA resection + artificial vessel replacement, but the procedure is highly invasive and not suitable for patients with serious comorbidities such as heart, lung and kidney. Although endovascular aortic repair (EVAR) is a revolutionary technique with outstanding advantages, it also has its own specific complications, and the presence of intraoperative and postoperative complications and their reasonable management have a greater impact on the outcome. We performed 47 cases of EVAR from January 2002 to June 2012, and retrospectively analyzed the patients’ data to discuss the diagnosis and treatment of common stent-related complications. 1. Clinical data From January 2002 to June 2012, a total of 47 cases of EVAR were performed in our department, with a minimum age of 33 years and a maximum age of 88 years, and a mean age of 75±5.9 years. Most of them were in the age group of 70-79 years old, with 97.6% of patients over 50 years old, 92.7% of patients over 60 years old, and 63.4% of patients over 70 years old. There were 38 male cases and 9 female cases, and the ratio of male to female was about 4:1. (1) Stent type vessels and delivery system The patients in this group used Talent stents ( Medtronic, USA), one of which was aortic-unilateral iliac artery type, and the rest were bifurcation type stents, and different structures and forms were selected according to different morphological structures of AAA. The size of the main stent type vascular delivery device was between 18-24F. (2) Methods Preoperative CTA or MRA examinations were performed to clarify the diagnosis, and AAA-related data were measured to select the grafts, and the surgical methods were performed with reference to the literature; postoperative CTA or MRA examinations were performed before discharge, 6 and 12 months after surgery, and every year after surgery to clarify the presence of endoleaks and staging, the morphological structure of the stented vessels, patency, and the presence of displacement. 2. Results All cases completed the surgery, and the average follow-up time after surgery was 35.71±23.16 months. Among them, one case covered one side of the renal artery, one case covered one side of the collateral renal artery, and one case of the stenosed iliac artery ruptured during the expansion process. There were 11 cases of postoperative intra-stent thrombosis, including one case of iliac artery stent obstruction and one case of femoral artery obstruction each within one week after surgery; nine cases of stent vessel obstruction were found during follow-up, including six cases of iliac artery vascular occlusion, three cases of stent obstruction below the level of renal artery, one case of complete obstruction, and two cases of incomplete obstruction. The distal stent retreated into the lumen of the tumor in 2 cases. There were 8 cases of endoleaks, including 6 cases of type II endoleaks and 2 cases of type III endoleaks. In this group of cases of renal artery obstruction, the main body of the stent was retracted downward with an overexpanded balloon in the main body of the stent, and the stent was retracted downward with guide wires through the left and right bifurcations of the stent, respectively, without success, and finally a stent was implanted in the renal artery. The cases in which the collateral renal artery was covered were not specially treated and were followed up. Renal function was good in both cases during the follow-up. In the case of right iliac artery stenosis with rupture bleeding during dilatation of the right iliac artery, the ruptured iliac artery was immediately surgically exposed and ligated, and femoral-femoral artery bypass was performed, and the blood flow in the lower extremity was good after surgery. In the case of femoral artery and bifurcation vessel thrombosis with in-stent thrombosis, which occurred on the same day and 3 days after surgery, respectively, we performed femoral artery dissection and embolization in the interventional room, in which an autologous saphenous vein graft was performed for femoral artery obstruction and a bare stent was implanted for in-stent thrombosis. One case of thrombosis in the left iliofemoral artery with lower extremity claudication was treated with catheter thrombolysis followed by implantation of a bare stent in the stented segment, while the rest of the occluded cases had no lower extremity ischemic symptoms and were not treated. None of the patients had any lower extremity ischemia after treatment and follow-up to date. In one case, the Cuff retracted into the lumen of the abdominal aortic aneurysm, and a straight artificial vascular stent was repositioned in the Cuff with the proximal and distal ends of the stent anchored to the normal vessel. In the other case, the bifurcation vessel retracted from the right iliac artery into the abdominal aortic aneurysm and caused bleeding from the aneurysm rupture, which was confirmed by both CT and intervention, we first filled the balloon to stop the bleeding in the right branch stent, and then surgically incised abdominal aortic aneurysm, ligated the right branch stent, and then performed femoral-femoral artery bypass grafting. (1) Occlusion of renal artery or collateral renal artery For infrarenal AAA, the condition for EVAR is that the neck of the aneurysm is greater than 1.5 cm. However, with the improvement of stenting, the indications for EVAR have been gradually expanded, such as the use of proximal grafts with bare stents for proximal abdominal aortic aneurysms with a neck shorter than 1.5 cm, which are fixed beyond the renal artery to achieve proper fixation of the grafts without occluding the renal artery. However, for severe tortuosity, the overlying part of the graft was inadvertently released beyond the renal artery due to inaccurate positioning of the renal artery during the graft release process or operational errors. In the case of infra-renal AAA with an aneurysm diameter of more than 1.5 cm, the neck of the aneurysm is severely calcified and the lumen is irregular, so in order to prevent endoleaks, the proximal graft with bare stent is used to fix the renal artery or the balloon expansion causes the plaque to shift and block the renal artery. In the present case, after balloon expansion of the proximal end of the stent, the stent compressed the calcified plaque in the wall of the proximal renal abdominal aorta and the plaque compressed the renal artery. Therefore, in order to prevent such complications, the length and nature of the neck of the aneurysm should be carefully evaluated before surgery, and the position of the bilateral renal arteries should be carefully positioned before each stent release. Of course, prevention is more important. Of course, prevention is more important. If the neck of the aneurysm is less than 1.5 cm as measured by preoperative CTA or MRA, or if the tortuosity or calcification is severe, a guidewire or catheter can be reserved in the renal artery to prevent chimney technique in case of renal artery blockage. Blockage of the collateral renal artery generally does not require treatment, and Marin found in his study that renal infarction with an infarct area of less than 20% did not result in decreased renal function, and this view was confirmed in this group of cases. (2) Injury to the introducer artery The common injury to the introducer artery is a tear or even rupture of the intima of the iliac or femoral artery, resulting in a local hematoma and hemorrhage. The main reasons for the formation of this injury include obvious stenosis of the introducing artery, difficulty or inability to pass through the thick stent delivery device, severe atherosclerosis of the introducing artery, mismatch between the internal diameter of the introducing artery and the diameter of the stent, if the operation is forced, rough or repeatedly introduced, or excessive balloon expansion, or too long introduction time, etc. In order to avoid injury to the inlet artery, the inlet artery should be carefully evaluated before surgery, and the appropriate stent and suitable inlet artery should be selected; the stent should be introduced under fluoroscopic surveillance at any time during surgery to avoid blind insertion, and the inlet artery with stenosis can be pre-dilated with a balloon and closely observed under fluoroscopy. Injuries to the inlet artery, whether it is an intimal tear or arterial dissection, must be properly reconstructed to avoid affecting the blood supply to the lower extremity. For arterial injuries, endothelial tears or ruptures close to the introducer femoral artery incision, endarterectomy, patching, arterial repair and reconstruction, or even artificial revascularization is possible if the extent is short, especially for arterial dissection injuries. If the arterial intimal tear and other injuries are located proximal to the arterial incision, especially if the location is high and difficult to handle, bare stents can be used to fix the intima and change the incision according to the situation, and if necessary, timely intermediate open surgery such as femoral-femoral artery bypass. In our case, it was a rupture bleeding due to right iliac artery stenosis during pre-expansion. Due to the high location of the rupture, we adopted rupture artery ligation + femoro-femoral artery bypass, and the lower limb showed no ischemia after surgery. (3) Endoleak The most unique and common complication of EVAR is endoleak, which refers to detectable persistent blood flow outside the graft lumen and within the tumor cavity after EVAR, and is an important factor affecting the efficacy of EVAR, with an incidence of 15% to 50%. The name endoleak was introduced by White et al. at the ISES European Summer Symposium in Marseille, France, on June 28, 1996, as a specific new term to describe this phenomenon. The causes of endoleaks are mainly related to anatomic conditions, graft type, and level of manipulation, but the etiology of endoleaks is still unclear. . It may also be related to the design of the graft, including the structure of the stent and the compliance of the overmold. The relationship between endoleaks and aneurysm progression and rupture, as well as the natural evolution of various endoleaks, is not fully understood, so there is still controversy regarding the management of endoleaks. Type III endoleaks should be treated as soon as they are diagnosed because of the direct communication between the tumor cavity and the systemic blood, and can be treated by extension or superimposed grafts by considering intracavitary treatment first. Type IV endoleaks can be treated by re-luminal placement of stents. Type V (or endotension) is also followed up and should be treated intraluminally again if the tumor cavity increases significantly. It is also believed that regardless of the type of endoleak, if it does not heal spontaneously at 6 months after surgery, interventional or open surgery should be performed. Of course, the specific treatment method needs to be chosen according to different individuals. The endoleaks found in our group were not treated for the time being and were followed up closely, and no complications such as rupture have occurred so far. Of course, endoleaks should be prevented by keeping the graft in the riveted area in close fit with the neck of the tumor, assessing the morphology of the tumor neck accurately before surgery, and evaluating and selecting the appropriate size graft. (4) In-stent thrombosis The incidence of lower extremity ischemia after EVAR is 5.1% (0.6% to 9.9%). Although intraoperative atherosclerotic plaque dislodgement can also cause lower limb ischemia and “garbage foot”, in-stent occlusion is the most common cause of postoperative lower limb ischemia. Severe stenosis of the iliac artery, severe distortion of the iliofemoral artery, inappropriate graft selection, and excessive number of single limb placements are the main causes of thrombosis. When the iliac artery is angulated or severely twisted, the stent iliac branch is prone to fracture resulting in slow or interrupted blood flow and secondary thrombosis due to the lack of lateral anti-fracture support of the stent iliac branch in the structure. In cases of acute thrombosis, short duration of disease and less severe ischemia in the lower extremities, pharmacological treatment, placement of thrombolysis and stent implantation can be used. If the blood flow cannot be restored by the previous methods, especially if the lower extremity ischemia is severe, femoral artery dissection for thrombosis or artificial vessel femoral-femoral bypass is feasible. If the bifurcated artificial vessel is occluded by the iliac artery extension on one side of the stent, femoral-femoral artificial vessel bypass is feasible; if the main single iliac artery stent type artificial vessel is occluded, axillary one artery artificial vessel bypass is required. The preventive approach is to accurately evaluate and correctly select the appropriate caliber stent system before surgery, convert the superhard guidewire to a contrast catheter or exchange the guidewire at the end of the procedure to restore the original morphology of the iliac branch, clarify the morphology and flow rate of the bilateral iliac and femoral arteries by imaging, and perform lower limb iliac and femoral arteriography if necessary. If there is significant distortion within the iliac branch or in the junction segment between the distal end of the stent and the iliac artery and it affects the blood flow, or if there is more than moderate distortion of the iliac artery and it is located in the iliac branch according to the preoperative CTA findings, dilate it with a balloon, and if it is ineffective, place a metal bare stent in the iliac branch in phase I. (5) Stent displacement The incidence of stent displacement is reported to be about 0.5%-8%, which can lead to serious consequences such as type I endoleaks, continuous enlargement of the aneurysmal lumen or pseudolumen or even rupture. In one of our cases, the distal displacement of the stent resulted in rupture and bleeding of the tumor. The causes include inadequate proximal stent anchorage, progressive enlargement of the proximal tumor neck, angulation of the proximal tumor neck, vascular wall factors (such as thrombosis and calcification), as well as medical factors and stent design factors, such as removal of the guidewire, displacement of the stent by dragging out the stent when releasing the system, lack of suprarenal fixation, and lack of barbed device. If the stent is displaced and causes endoleaks, surgical treatment is indicated. Displacement of the distal end of the stent may also occur if the iliac artery fixation stent is too short and the anchorage area is located close to the aneurysm. In this case, a secondary distal type I endoleak develops and is usually treated with an extended stent. In our case, a stent was implanted to extend the length of the riveted zone for distal stent displacement, and no complications were observed at follow-up. In conclusion, EVAR treatment has been widely used and recognized through more than 20 years of development for its characteristics of less trauma, faster recovery, and lower postoperative complications and mortality, etc. The core of EVAR technology improvement is the development of stents, and the current common and unique complications, such as endoleak, stent displacement, and intra-stent thrombosis, are greatly related to the characteristics of the stent itself, which is that it cannot be used like vascular grafting. Therefore, the active development and improvement of stent characteristics will expand the indications and reduce the complications of endoluminal therapy. Of course, we have reasons to believe that with the continuous improvement of stent design, the complications of EVAR will gradually decrease and more and more cases will be suitable for EVAR treatment.