Endoluminal Stent Graft Research Articles

Experimental Force Measurements on a Bifurcated Endoluminal Stent Graft Model: Comparison with Theory

The goal of this study was to experimentally validate a steady-state mathematical model, which can be used to compute the forces acting on a bifurcated endoluminal stent graft. To accomplish this task, an acrylic model of a bifurcated graft was used for the force measurements. The graft model was connected to the inlet piping with a flexible rubber membrane that allowed the graft model to move. This allowed us to measure the force owing to the movement of the graft model with a calibrated load cell. Steady-state blood flow was assumed, and the working fluid was water. The experimental data were found to be consistent with the results from a previously published mathematical model: the graft force is strongly dependent on the proximal or inlet pressure and the inlet area. The force tends to be weakly dependent on flow rate. More research work will be required to determine whether the steady-state force model examined in this article provides a realistic determination of the forces on an endoluminal stent graft that is subject to pulsatile blood flow.

Emergent infrahepatic vena cava stenting for life-threatening perforation

During a lumbar vertebral fusion, a box cage perforated the inferior vena cava wall and migrated toward the right atrium. This case report describes the use of a Talent endoluminal stent-graft to control the subsequent life-threatening bleeding and to prevent further migration of the box cage into the right atrium, with the risk of pulmonary embolization. It shows that the use of minimal invasive endovascular stent-grafts to control for massive vena cava bleeding might be a less invasive procedure and, in similar cases, could be a life-saving alternative to open surgery.

Experimental Force Measurements on a Bifurcated Endoluminal Stent Graft Model: Comparison with Theory

Experimental Force Measurements on a Bifurcated Endoluminal Stent Graft Model: Comparison with Theory

Endoluminal stenting of a common carotid artery pseudoaneurysm due to blunt trauma

Injury to the carotid artery as a consequence of blunt trauma is a rare occurrence. When it does occur such damage is associated with profound morbidity and a significant mortality rate. Standard treatment modalities range from a conservative approach with anticoagulation and observation to aggressive surgical management. This case report details an alternative approach using an endoluminal stent graft to successfully exclude a damaged right common carotid artery and associated large pseudoaneurysm. Endoluminal stents appear to be effective and safe in the treatment of blunt carotid artery injuries with good short-term prognosis.

Endovascular repair of thoracic aortic disease: What we have learned

The use of endoluminal stent-grafts to treat different thoracic aortic pathologies is emerging as a less invasive alternative to conventional surgery in patients with serious coexisting illnesses. Many advances have been made since Parodi and coworkers 1 described their first experience using a stent-graft to treat an abdominal aneurysm and it has since become possible to treat thoracic as well as abdominal aortic diseases. 2,3 The endovascular technique is minimally invasive and is associated with acceptable morbidity and mortality rates. This article describes our experience with endovascular management of different thoracic aortic pathologies. In addition, treatment strategies and indications are discussed and current limitations of endovascular techniques are shown.

Frequency and influence of perfused lumbar arteries (PLA) and inferior mesenteric arteries (PIMA) on development

To evaluate frequency and influence of perfused lumbar arteries (pLA) and inferior mesenteric arteries (pIMA) on develop-ment and incidence of type-2 endoleaks (EL-II) and volume changes of AAA after EVR. 114 patients underwent transfemoral insertion of endoluminal stent-grafts for treatment of AAA. Pre- and post-operative CT scans before discharge, at 1, 3, 6 months and biannually thereafter were performed ; pLA and pIMA were evaluated in each follow-up scan. Volumes of the aneurysmal sacs were measured. Median follow-up was 24 months. Six months after stent-graft implantation pIMA and/or at least 2 pLA were seen in 45 patients (50,5%) ; 11 patients (12,4% of the study cohort) had an EL-II. A tendency to minor mean volume loss in patients with pLA/ ptIMA and significant trend to volume increase in patients with EL-II in later follow-ups was seen. We found a high incidence of pLA/ptIMA in patients after EVR. Persistent lumbar and inferior mesenteric artery perfusion is associated with significantly higher EL-II rates after EVR of AAA. Significant différences in volume changes in later follow-ups were seen between patients with or without EL-II.

Dissections aiguës de l'aorte : traitement

Whatever their type, acute dissections of the aorta must always be considered major cardiovascular emergencies. Above all, patients must be referred to a surgical ICU and medically conditioned. Arterial hypertension must be reduced to physiological values without compromising the neurological status or the urinary output and pain must be eliminated since it increases arterial hypertension. For all dissections involving the ascending aorta (De Bakey type I and II or Stanford type A), surgery must be undertaken as soon as possible. “Distal” dissections (De Bakey Type III or Stanford type B) are classically treated medically, except in case of life-threatening complications. Because of the very nature of the disease, one of the main problems in treating acute dissections is to perform solid and tight anastomoses. The use of Teflon ® felt remains the most usual and widespread method. First imagined in 1976 and published in 1979 by Guilmet et al., the use of GRF glue has constituted a major progress in terms of procedure simplification and improvement of the immediate results. In type A dissections, the main goal of the emergency operation is to prevent a death due to tamponnade, acute aortic valve regurgitation or severe malperfusion. Surgical treatment has also another goal, which is to achieve the most complete and safe repair in order to avoid further complications and, consequently, late re-operations or death. In order to avoid rupture or malperfusion during surgery, false channel must not be pressurized during cardio pulmonary bypass. This is best achieved by canulating the right axillary artery. Concerning the aortic root, in patients without annulo-aortic ectasia or Marfan’s syndrome: if the valve is normal and the aortic root either not dilated or torn, both must be preserved; if the valve is diseased and the aortic root safe, the valve must be replaced and the root preserved; if the aortic root is destroyed and the valve safe, a valve-sparing procedure (Yacoub’s or David’s technique) may be considered. In patients with annulo-aortic ectasia or Marfan’s syndrome, it is absolutely mandatory that the whole aortic root be replaced. In most cases this is performed using a modified Bentall’s procedure with a valved conduit. In some cases a valve-sparing procedure may be also considered. Concerning the distal repair, if the intimal tear is entirely located on the ascending aorta, this segment only must be replaced. This is the best performed through an “open distal anastomosis” under circulatory arrest. If the intimal tear is located on or extends to the transverse arch, this segment should be replaced. In most cases, only a “Hemi-arch” replacement is necessary. Although recently advocated in all patients, the complete replacement of the transverse arch is time-consuming and probably risky. We think that it should be indicated only in case of retrograde dissection or rupture of the transverse arch. This surgical eclectic policy seems to best fit the pathophysiological reality of acute type A dissection and to be a safe warrant of gratifying immediate and long term results. Concerning acute type B dissections, therapeutic indications are more controversial. Classically non complicated type B dissections remain non surgical. Patients must be treated medically an regularly surveyed through non invasive imaging methods. Recently the use of endoluminal stent-grafting has been proposed in complicated and non complicated acute type B dissections. The experiences are rather limited so far but the technique seems quite promising and might totally change the therapeutic indications in a near future.

Stenting of the thoracic aorta – the radiologist's view

BACKGROUND: Endoluminal stent graft repair is emerging as a less invasive alternative to conventional open surgery in the management of diseases of the descending thoracic aorta. In this overview we will discuss the current concept of stent graft therapy of various diseases of the thoracic aorta from an interventional radiologist's point of view. METHODS: Since 1996, 84 patients with atherosclerotic aneurysms of the descending thoracic aorta, aortic dissections, acute traumatic ruptures, chronic traumatic aneurysms and penetrating atherosclerotic ulcers underwent endoluminal stent graft repair at our institution. 18 patients presented with life-threatening symptoms and were treated on an emergency basis. All procedures were performed in an angiographic suite with state-of-the-art digital subtraction angiographic equipment. Follow-up was at 1, 3, 6, and 12 months after treatment and yearly thereafter. RESULTS: The primary technical success rate ranged from 78% to 95%, the 30-day mortality rate was 7% if including elective as well as emergency interventions. Endoleaks were the most common procedure-related complications. They occurred at a rate of 11% and had to be treated by extension cuffs or additional endograft segments. Data of our institution are presented in comparison to the current literature. CONCLUSIONS: Stent graft repair of thoracic aortic aneurysms, aortic dissections and related pathologies is a fascinating new technique offering a less invasive treatment option to patients who are unsuitable for surgical repair. For patients at high surgical risk, endovascular stent graft placement can be advocated as standard therapy.

Duplex scanning after endovascular aneurysm repair: an alternative to computed tomography

Late complications following endovascular aneurysm repair indicate the need for long-term surveillance. Clinical trials involving endoluminal stent grafts have typically used computed tomography angiography as the main imaging modality for surveillance. However, computed tomography angiography exposes the patient to higher levels of ionizing radiation, nephrotoxic agents, and increased cost compared to duplex ultrasound. Duplex ultrasound scanning has been widely used for surveillance of abdominal aortic aneurysms for many years. It is well established and the procedure of choice for noninvasive imaging of the aorta. It offers the advantages of easy access, decreased cost, no radiation exposure, and no nephrotoxicity. There is little controversy about duplex scanning for preoperative patient evaluation or surveillance of patients with small aneurysms. However, the use and reliability of duplex scanning in the evaluation and surveillance of patients following endovascular repair is controversial. This article will discuss the benefits, techniques, and limitation of duplex ultrasound in the long-term surveillance of endografts following endovascular abdominal aortic aneurysm repair.

Surgical pitfalls during explantation of a thoracic aortic endoprosthesis

The loss of cyclooxygenase in platelets, which lack the capacity for new protein synthesis, constitutes a loss of function for the remainder of their lifetime. The average life span of platelets is 7 days; therefore the conventional practice is to stop aspirin therapy 1 week before the planned procedure. However, the results of this study show that inhibition of platelet aggregation with aspirin vanishes earlier than expected. The life span of the platelet and platelet aggregation as a whole need to be understood separately. Although it may take 10 days for the total platelet population to be renewed and thus restore normal cyclooxygenase activity, it has been shown in vitro that if as few as 20% of total platelets have normal cyclooxygenase activity, aggregation would remain normal. Our study has confirmed this finding in the clinical situation. This study has several limitations. One of these is the small study population. We therefore should extend this study and investigate the outcomes. Another limitation concerns aspirin dosages, which were low (81 mg/d) in this study. If the aspirin dosage had been higher, the speed of recovery of aggregation might have been different. In conclusion, this study indicates that inhibition of platelet

Aortic aneurysm repair with endovascular grafts: Developing a graft surveillance program

The objective of this study was to describe the development of a comprehensive surveillance program for monitoring the long-term follow-up of endoluminal stent graft (ELG) patients. Despite high procedural success rates, ELG patients remain at ongoing risk for aneurysm sac expansion, rupture, and other adverse events that make long-term surveillance imperative. As they perform more ELG, practitioners face increased logistical difficulty performing appropriate patient follow-up. A computer-based data ELG registry was created using Epi Info, a program developed by the Centers for Disease Control and Prevention that enables users to design a data entry form, enter data, and perform statistical analyses. The database has been used to track 259 patients (214 men and 45 women) who underwent ELG between November 1999 and October 2003. One-year follow-up was available for 182 patients, 2-year follow-up for 104 patients, and 3-year surveillance data for 40 patients, which represent follow-up rates of 89.6%, 78.8%, and 61.5%, respectively. There were 25 late deaths. The Kaplan-Meier estimate for 1-year survival was 92.5%. Twenty-one patients underwent 24 secondary angiographic procedures at a mean 8.6 +/- 10.3 months (range, 1-37.6) after stent-graft repair. No mortality was observed in association with a secondary intervention. There were no late conversions to open aneurysm repair. The Kaplan-Meier estimate for freedom from secondary intervention for all patients at 1 year was 91.0%. A computer-based registry facilitates appropriate and timely patient follow-up and may improve the long-term outcome from ELG.

Midterm Results of Endoluminal Stent Grafting of the Thoracic Aorta

The purpose of this study was to evaluate the overall outcome of repair of thoracic aortic lesions with endoluminal grafts. Patients were studied prospectively following the implantation of a thoracic endovascular device. Preoperative imaging was performed by helical computed tomography (CT), angiography, transesophageal ultrasonography, or magnetic resonance imaging. Procedures were performed in an endovascular surgical suite under general anesthesia. All patients were evaluated with CT and chest radiography at discharge and at 1, 6, and 12 months. From December 1999 to November 2001, thirty-two patients were enrolled in the study (mean age 62 years; 20 male and 12 female patients). Seventeen patients had dissections, five patients had ruptured aortic ulcer, five patients had traumatic ruptures, three patients had atherosclerotic aneurysms, and two patients had pseudoaneurysms. An American Society of Anesthesiology score of III or IV was evaluated in 22 (69%) patients. The procedure was performed under emergency conditions in 11 cases. All prostheses were implanted successfully. There were no conversions. Three patients (9%) presented with a neurologic event following the implantation procedure, which was lethal in one case (hemorrhagic stroke). Two other patients died during early follow-up of myocardial infarction and multiorgan failure. The early death rate was 9%. The mean follow-up was 13.5 months. During follow-up, the maximal diameter of the aorta shrunk (> or = 5 mm) in 9 (28%) patients, remained stable in 17 (53%) patients, and increased (> or = 5 mm) in 6 (19%) patients. All patients presenting with an increased diameter were initially treated for dissections. A type 1 endoleak was diagnosed on the discharge CT scan in one patient. It sealed spontaneously thereafter. A type 3 endoleak was diagnosed 3 months after the procedure in one patient. A complementary stent graft was implanted in two patients presenting with a dissection with persistent patent false lumen and aortic enlargement. Three patients died during follow-up (two aneurysm-related and one aneurysm-unrelated death). The morbidity and mortality rates reported in our series related to the preoperative morbid conditions of the patients treated. Thoracic aorta endografting is an alternative to open surgery in this subset of patients.

Endoluminal stent-graft placement for acute rupture of the descending thoracic aorta.

To investigate the results of endovascular stent-graft placement for the treatment of acute perforating lesions of the descending thoracic aorta. A total of 31 consecutive patients underwent interventional treatment for perforating lesions of the descending aorta. In 21 cases (group A), the aortic perforation was due to rupture of a descending thoracic aneurysm or dissection, whereas 10 patients (group B) were treated for traumatic transection of the descending aorta. A total of 42 endoprostheses were implanted. The implantation procedure was successful in all cases without peri-interventional complications. In one case, implantation of a second endoprosthesis became necessary due to type I endoleak. Overall, the 30-day mortality was 9.7%. As all three deaths occurred in group A, the mortality rate in this group was 14.3% versus 0% in group B. Similarly, postinterventional complications were more prevalent, with 28.6% in group A (renal failure n = 4; stroke n = 2) versus 10.0% in group B (renal failure n = 1). No paraplegia and no further deaths or ruptures occurred during follow-up (mean 17 months). Interventional stent-graft placement is an effective treatment option for the emergency repair of descending aortic perforations.

Endoluminal stent-graft repair of aortobronchial fistulas: bridging or definitive long-term solution?

To describe our experience with endoluminal stent-graft repair of aortobronchial fistulas (ABF) and to analyze midterm results focusing on late chronic graft infections, secondary conversion, and survival. The records of 8 patients (6 men; mean age 69 years, range 28-88) treated between March 1997 and October 2003 for traumatic and postsurgical ABFs were reviewed. Seven presented with hemoptysis and 1 with hemorrhagic shock. According to the severity of emergency, patients underwent computed tomography, angiography, bronchoscopy, and transesophageal echocardiography. Preoperatively, no clinical signs of infection were evident. Two different stent-graft models (Talent and Excluder) were implanted using standard endovascular techniques. Procedural and clinical success was achieved in all patients. Paraplegia, secondary intervention, conversion, or procedure-related death was not observed. Mean follow-up was 30 months (range 0.6-77). One patient with a postsurgical ABF (Dacron tube graft) successfully treated with an Excluder stent-graft died 13 months later from hemorrhage secondary to aortoesophageal fistula repair procedures. A second patient died from pneumonia after 42 months. A third patient, in whom 2 Talent stent-grafts had been implanted to treat an ABF from the false lumen of a type B dissection, died 7 months later from massive hemorrhage. Endoluminal stent-grafting of ABF is feasible and the preferred method of treatment. Secondary conversion due to endograft infection is not absolutely mandatory, but close surveillance is necessary.

Endoluminal aortic stent grafts — morphology of complications

Infantile hemangiomas are endothelial tumors that grow rapidly in the first year of life and regress slowly during early childhood. Although hemangiomas are well-known vascular lesions, little is known about the mechanisms that cause the excessive endothelial cell proliferation in these most common tumors of infancy. To investigate the molecular basis of hemangioma, we isolated endothelial cells from several proliferative-phase lesions and showed that these cells are clonal and exhibit abnormal properties in vitro (E. Boye, Y. Yu, G. Paranya, J. B. Mulliken, B. R. Olsen, J. Bischoff: Clonality and altered behavior of endothelial cells from hemangiomas. J Clin Invest 2001, 107:745–752). Here, we analyzed mRNA expression patterns of genes required for angiogenesis, including members of the vascular endothelial growth factor (VEGF)/VEGF receptor family and the angiopoietin/Tie family, in hemangioma-derived and normal endothelial cells. KDR, Flt-1, Tie1, Tie2, and angiopoietin-2 (Ang2) were strongly expressed in cultured hemangioma-derived endothelial cells and in hemangioma tissue. In contrast, there was little expression of angiopoietin-1 (Ang1) or VEGF. We found Tie2 mRNA and protein up-regulated with a concomitant increase in cellular responsiveness to Ang1 in most hemangioma-derived endothelial cells. Ang2 mRNA was down-regulated in response to serum in hemangioma-derived endothelial cells, but not in normal endothelial cells, suggesting altered regulation. These findings implicate Tie2 and its ligands Ang1 and Ang2 in the pathogenesis of hemangioma.

Biliary-Venous Fistula Complicating Transjugular Intrahepatic Portosystemic Shunt Presenting With Recurrent Bacteremia, Jaundice, Anemia and Fever

A 50-year-old White man with noncirrhotic portal hypertension presented with bleeding from gastric varices. Bleeding was initially managed with band ligation and subsequent transjugular intrahepatic portosystemic shunt (TIPS). Over the next few months, the patient had recurrent episodes of anemia, jaundice, fever and polymicrobial bacteremia. Computed tomography (CT) of the abdomen and chest, upper and lower endoscopy, endoscopic retrograde cholangiopancreatography (ERCP), and echocardiography failed to explain the bacteremia and anemia. Follow-up CT scan and Doppler sonography 9 months after placement showed TIPS was occluded. Repeat ERCP showed a bile leak with free run-off of contrast from the left hepatic duct into a vascular structure. The patient's status was upgraded for liver transplantation with Regional Review Board agreement and subsequently received a liver transplant. Gross examination of the native liver demonstrated a fistula between the left bile duct and the middle hepatic vein. Pathologic evaluation confirmed focal necrosis of the left hepatic duct communicating with an occluded TIPS and nodular regenerative hyperplasia consistent with noncirrhotic portal hypertension. Infection is rarely reported in a totally occluded TIPS. Biliary fistulas in patent TIPS have been treated by endoluminal stent graft and endoscopic sphincterotomy with biliary stent placement. Liver transplantation may be the preferred treatment if TIPS becomes infected following its complete occlusion.

A Case Report of Intentional Occlusion of an Aberrant Right Subclavian Artery during Endovascular Stent-graft Repair of a Descending Aortic Aneurysm

The use of endovascular stentgrafts in the descending thoracic aorta was first described by Parodi in 1994. We describe the first case of intentional occlusion of an aberrant right subclavian artery with an endoluminal stentgraft in the treatment of a descending thoracic aortic aneurysm (TAA) without the need for a subclavian revascularisation procedure. In view of the reported prevalence of 0.4–2% of arteria lusoria, and the increasing use of endovascular grafting, we feel that is a significant clinical entity.

Acute Thoracic Aortic Trauma: A Comparison of Endoluminal Stent Grafts with Open Repair and Nonoperative Management

The magnitude of injury necessary to cause a traumatic aortic tear often results in high mortality. Open surgery in these patients is often not well tolerated. The purpose of this study was to compare the outcomes of three different treatment options in patients with traumatic aortic injuries. This was a retrospective review of a prospectively maintained computer database. Over a period of 33 months, 27 patients were diagnosed with thoracic aortic tears on the basis of a computed tomogram or a diagnostic angiogram. All patients were initially seen by trauma surgery staff and managed nonoperatively ( n = 12) if the predicted mortality due to associated injuries approached 100%. Thoracic surgery staff were consulted on all other patients, and open surgical repair was performed in 10 patients. Thoracic stent grafts were used in five patients because of inability to ventilate following an attempted thoracotomy ( n = 2) or associated organ injury that prohibited anticoagulation (head +/- liver injury, n = 3). Overall, patients in the endovascular group had a higher injury severity score than that of the open surgical group (42 +/- 9 vs. 32 +/- 11). However, mortality was lowest in the endovascular group (20%), higher in the open surgical group (50%), and highest in the nonoperative group (92%). No paraplegia was noted, and all surviving patients have been free of complications during the follow-up period. Due to the small number of patients in each treatment, no strong recommendations can be made. However, the results of thoracic stent grafts for patients with traumatic thoracic pseudoaneurysms may prove to be a safer and less invasive treatment option.

Percutaneous Drainage and Explantation of an Infected Aortic Endoluminal Stent Graft

Endoluminal repair of abdominal aortic aneurysms (AAAs) has undergone explosive growth in the last decade. Although immediate benefits are attractive to both the patient and the treating physician, concerns regarding long-term success have dampened sustained enthusiasm for this technique. A rare but catastrophic complication is stent graft infection. This case report describes an early infection of an endoluminal aortic stent graft treated initially with percutaneous drainage and ultimately with staged extraanatomic bypass and graft explantation.

Endovascular Stent Grafting of Descending Thoracic Aortic Aneurysms

The treatment of descending thoracic aortic aneurysms using endovascular stents is one of the more recent advances in treatment and is receiving increasing attention as it is a less invasive alternative to open surgical repair. Although the technology is still primitive, significant improvements have lately been made in the design and deployment of the endovascular stent-grafts. Aortic stent-grafts were used initially to exclude abdominal, and later thoracic, aortic true and false aneurysms. These prostheses have been increasingly used to treat aneurysms, dissections, and traumatic ruptures of the descending thoracic aorta with good early and mid-term outcomes. Although the long-term outcome of patients with aneurysms of the descending thoracic aorta after stent graft implantation has not been investigated, continued refinement of the endovascular approaches has decreased the need for conventional open thoracic aortic aneurysm repair, especially in patients who are at a high risk for standard surgery because of advanced age or the presence of comorbid diseases. The placement of endoluminal stent-grafts to exclude the dissected or ruptured site of thoracic aortic aneurysms is a technically feasible and relatively safe procedure. With the rapid development of endovascular approaches, the treatment of the descending thoracic aortic aneurysms might alter even more, but an extended follow-up is necessary to determine the longer term outcome. Historical perspectives, advantages, device considerations, complications, and current perspectives of the endovascular stent grafting of the descending thoracic aortic aneurysms are elaborated on.