Multislice CT Angiography of Fenestrated Endovascular Stent Grafting for Treating Abdominal Aortic Aneurysms: a Pictorial Review of the 2D/3D Visualizations

Fenestrated endovascular repair of an abdominal aortic aneurysm has been developed to treat patients with a short or complicated aneurysm neck. Fenestration involves creating an opening in the graft fabric to accommodate the orifice of the vessel that is targeted for preservation. Fixation of the fenestration to the renal arteries and the other visceral arteries can be done by implanting bare or covered stents across the graft-artery ostia interfaces so that a portion of the stent protrudes into the aortic lumen. Accurate alignment of the targeted vessels in a longitudinal aspect is hard to achieve during stent deployment because rotation of the stent graft may take place during delivery from the sheath. Understanding the 3D relationship of the aortic branches and the fenestrated vessel stents following fenestration will aid endovascular specialists to evaluate how the stent graft is situated within the aorta after placement of fenestrations. The aim of this article is to provide the 2D and 3D imaging appearances of the fenestrated endovascular grafts that were implanted in a group of patients with abdominal aortic aneurysms, based on the multislice CT angiography. The potential applications of each visualization technique were explored and compared with the 2D axial images.     

Fenestrated Stent Graft Repair of Abdominal Aortic Aneurysm: Hemodynamic Analysis of the Effect of Fenestrated Stents on the Renal Arteries

Objective

We wanted to investigate the hemodynamic effect of fenestrated stents on the renal arteries with using a fluid structure interaction method.

Materials and Methods

Two representative patients who each had abdominal aortic aneurysm that was treated with fenestrated stent grafts were selected for the study. 3D realistic aorta models for the main artery branches and aneurysm were generated based on the multislice CT scans from two patients with different aortic geometries. The simulated fenestrated stents were designed and modelled based on the 3D intraluminal appearance, and these were placed inside the renal artery with an intra-aortic protrusion of 5.0-7.0 mm to reflect the actual patients'' treatment. The stent wire thickness was simulated with a diameter of 0.4 mm and hemodynamic analysis was performed at different cardiac cycles.

Results

Our results showed that the effect of the fenestrated stent wires on the renal blood flow was minimal because the flow velocity was not significantly affected when compared to that calculated at pre-stent graft implantation, and this was despite the presence of recirculation patterns at the proximal part of the renal arteries. The wall pressure was found to be significantly decreased after fenestration, yet no significant change of the wall shear stress was noticed at post-fenestration, although the wall shear stress was shown to decrease slightly at the proximal aneurysm necks.

Conclusion

Our analysis demonstrates that the hemodynamic effect of fenestrated renal stents on the renal arteries is insignificant. Further studies are needed to investigate the effect of different lengths of stent protrusion with variable stent thicknesses on the renal blood flow, and this is valuable for understanding the long-term outcomes of fenestrated repair.     

3D Stereoscopic Visualization of Fenestrated Stent Grafts

The purpose of this study was to present a technique of stereoscopic visualization in the evaluation of patients with abdominal aortic aneurysm treated with fenestrated stent grafts compared with conventional 2D visualizations. Two patients with abdominal aortic aneurysm undergoing fenestrated stent grafting were selected for inclusion in the study. Conventional 2D views including axial, multiplanar reformation, maximum-intensity projection, and volume rendering and 3D stereoscopic visualizations were assessed by two experienced reviewers independently with regard to the treatment outcomes of fenestrated repair. Interobserver agreement was assessed with Kendall’s W statistic. Multiplanar reformation and maximum-intensity projection visualizations were scored the highest in the evaluation of parameters related to the fenestrated stent grafting, while 3D stereoscopic visualization was scored as valuable in the evaluation of appearance (any distortions) of the fenestrated stent. Volume rendering was found to play a limited role in the follow-up of fenestrated stent grafting. 3D stereoscopic visualization adds additional information that assists endovascular specialists to identify any distortions of the fenestrated stents when compared with 2D visualizations.     

A Technique of “Chimney Nellix” for the Management of Type 1a Endoleak After EVAR

This report presents 3 procedures with visceral “chimney stenting” in conjunction with an endovascular aneurysm sealing (EVAS) device, known as chEVAS, for treatment of type 1a endoleak. It includes the first published chEVAS in a patient with previous fenestrated endovascular aneurysm repair (FEVAR). Cases include an 80-year-old man 8 years after FEVAR for a juxtarenal abdominal aortic aneurysm (AAA); an 85-year-old woman 9 months after endovascular aneurysm repair (EVAR) for a ruptured infrarenal AAA; and an 84-year-old woman 3 months after EVAR for a symptomatic infrarenal AAA. Technical success was achieved in all cases, with 1 postoperative death. The remaining 2 patients had no residual type 1a endoleak at 10 and 14 months respectively.     

Short-term and Midterm Results of Fenestrated Anaconda Endograft in Patients with Previous Endovascular Aneurysm Repair

Purpose

To review short-term and midterm results of the fenestrated Anaconda stent graft in management of patients with pre-existing endovascular aortic stent graft and persistent type 1a endoleak.

Initial experience of branched endovascular graft for abdominal aortic aneurysm with complex anatomy of proximal neck: planning and technical considerations

The purpose of this report was to demonstrate initial Japanese cases of abdominal aortic aneurysm (AAA) with complex anatomy of proximal neck treated using a Zenith fenestrated endograft with branched endovascular technique and to describe the device’s design and technical considerations. Planning and sizing of endografts were performed using high-resolution computed tomography on a three-dimensional workstation. Branched endograft technique combined with reinforced fenestrated device and balloon-expandable stent graft was used in two patients because of challenging morphology for the fenestrated device with a bare stent. Successful exclusion of the aneurysm sac was achieved in both patients with antegrade perfusion in incorporated visceral vessels. Endovascular repair using a fenestrated device with graft material incorporating the visceral arteries is feasible. The combination of the reinforced fenestration and the balloon-expandable stent graft can provide an adequate sealing effect for the compromised anatomy. Initial and midterm results are reported with further follow-up and patient accrual.     

Delayed complications following EVAR

More than a decade after the first clinical attempts, two large randomized studies have proven that endovascular aortic aneurysm repair (EVAR) provides immediate advantages over open repair. In the long run, however, a relatively high number of reinterventions is necessary to improve the long-term efficacy of EVAR, which may outweigh the early benefits. Since EVAR is gaining popularity in the medical community and in patients with abdominal aortic aneurysm (AAA), it is expected that a growing number of patients will present with delayed complications requiring some kind of reinterventions. For the patient's safety, vascular surgeons and interventional radiologists involved in EVAR must be well aware of these complications and the ways to overcome them. We began our endovascular program for AAA in 1994 and currently follow 485 patients with a variety of manufactured grafts. In this article we describe the delayed complications observed with EVAR, their mechanisms, favoring factors, and ways to treat them.     

Helical CT Angiography of Abdominal Aortic Aneurysms Treated with Suprarenal Stent Grafting: A Pictorial Essay

The endovascular repair of abdominal aortic aneurysm (AAA) with stent grafts is rapidly becoming an important alternative to open repair. Suprarenal stent grafting, recently modified from conventional infrarenal stent grafting, is a technique for the purpose of treating patients with inappropriate aneurysm necks. Unlike open repair, the success of endoluminal repair cannot be ascertained by means of direct examination and thus relies on imaging results. The use of conventional angiography for arterial imaging has become less dominant, while helical computed tomography angiography (CTA) has become the imaging modality of choice for both preoperative assessment and postoperative followup after treatment with stent graft implants. There is an increasing likelihood that radiologists will become more and more involved in the procedure of aortic stent grafting and in giving the radiological report on these patients treated with stent grafts. It is necessary for radiologists to be familiar with the imaging findings, including common and uncommon appearances following aortic stent grafting. The purpose of this pictorial essay is to describe and present normal and abnormal imaging appearances following aortic stent grafting based on helical CTA.     

Three-year follow-up of fenestrated thoracoabdominal stent graft bridging an endovascular thoracic stent graft and a surgical abdominal aortic graft

This case report describes repair of a type I endoleak at the distal landing zone of a thoracic aortic stent graft by endovascular placement of a thoracoabdominal fenestrated stent graft (Cook, Brisbane, Australia). The fenestrated stent graft was interposed between a previous abdominal aortic aneurysm (AAA) Gelsoft tube graft (Sulzer Vascutek Ltd, Inchinnan, United Kingdom) and two overlapping Zenith thoracic endografts (Cook Inc, Bloomington, Indiana). Placement was made more complex because the distal thoracic endograft had rotated into a horizontal position. At 3-year clinical and computed tomography (CT) follow-up, continued clinical and radiologic success was shown with no further intervention required.     

Multislice CT angiography in aortic stent grafting: relationship between image noise and body mass index

PURPOSE: To investigate the correlation between image noise and body mass index (BMI) in multislice CT angiography (MSCT) for patients with abdominal aortic aneurysm (AAA) treated with endovascular stent grafts. MATERIALS AND METHODS: Seventeen patients who underwent MSCT following endovascular repair of AAA were included in the study. Image noise (standard deviation of the CT attenuation: S.D.) and signal to noise ratio (SNR) were plotted against BMI to demonstrate the correlation using a linear regression method. Image quality of 3D reconstructions was correlated to the SNR and BMI. RESULTS: The r-value of linear regression between S.D. and BMI was 0.578 (p<0.05), 0.835 and 0.802 (p<0.001), respectively, at the level of renal artery, aortic aneurysm and common iliac artery. The r-value of linear regression between SNR and BMI was 0.332, 0.516 and 0.552 (p<0.05), respectively, at above three levels. Image quality of 3D reconstructions was compromised in five patients and diagnosis was affected in two patients with BMI more than 30. CONCLUSION: A significant correlation was observed between image noise and BMI in MSCT angiography of endovascular repair of AAA. Our findings are valuable for optimisation of MSCT angiography scanning protocols and reduction of radiation dose in MSCT examinations.     

Large Diameter Limbs for Dilated Common Iliac Arteries in Endovascular Aneurysm Repair. Is It Safe?

In this prospective study we examined whether dilated common iliac arteries (CIAs) can provide a safe distal seal in endovascular aneurysm repair (EVAR) with the use of bifurcated stent grafts with large diameter limbs. Sixteen patients with 26 dilated CIAs with a diameter of 6 mm who were offered EVAR using stent grafts with large diameter limbs were included in the study (Group A). Forty-two patients who also underwent EVAR without iliac dilatation, matched for age, sex and surgical risk were used for comparison (controls-Group B). In group A mean CIA diameter was 18.2 mm (16–28) and mean abdominal aortic aneurysm (AAA) diameter was 6.87 ± 1.05 cm; mean age was 77.2 ± 4.8 yrs (67–81). Mean follow-up was 33.6 months (2.8 yrs). CIA diameter changes and development of endoleaks were assessed by CT angiography (CTA). Overall iliac dilatation was present in 16/58 of our patients (27.6%). In 10 patients dilatation was bilateral (17.3%). Partial or complete flow to the internal iliac artery (IIA) territories was preserved in all patients post-EVAR. On follow-up, stable caliber of the dilated CIAs was observed in 21 patients (84%), enlargement of 1mm in 3 (16%), and failure of the distal attachment in 1 (6.2%). Compared to the control group there was no statistical significance in the incidence of complications. Dilated common iliac arteries provide a safe distal seal in patients who have undergone EVAR, thus obviating the need for additional endovascular procedures and sparing flow in the IIA vascular bed.     

局部麻醉穿刺下完全无对比剂腔内修复腹主动脉瘤1例

目的 探讨对比剂过敏高危腹主动脉瘤患者接受局部麻醉穿刺下完全无对比剂主动脉腔内修复术(EVAR)的可行性.方法 对1例对比剂过敏腹主动脉瘤患者,在不使用对比剂、局部麻醉穿刺条件下实施EVAR术.结果 手术获成功.术后MRI随访结果显示,患者腹主动脉瘤完全隔绝,无内漏,覆膜支架内血流通畅,双侧肾动脉显影良好.结论 局部麻醉穿刺下完全无对比剂EVAR术治疗对比剂过敏伴全身麻醉禁忌高危腹主动脉瘤患者安全有效,但严格掌握适应证、术前充分评估是手术成功的关键.     

Endovascular Aneurysm Repair and Sealing (EVARS): A Useful Adjunct in Treating Challenging Morphology

An 81-year-old male with previous open abdominal aortic aneurysm repair presented with asymptomatic large pseudoaneurysms at both ends of an open surgical tube graft. Endovascular aneurysm sealing (EVAS) in combination with the iliac limbs of a standard endovascular aneurysm repair (EVAR) successfully excluded both pseudoaneurysms from circulation. We describe the combination of elements of EVAS and EVAR and have termed this endovascular aneurysm repair and sealing (EVARS). EVARS has the advantage of harnessing the benefits of endobag sealing in aortic necks unsuitable for standard EVAR whilst providing the security of accurate stent placement within short common iliac arteries. In conclusion, EVAS may be combined with standard endovascular iliac limbs and is a possible treatment option for pseudoaneurysm following open aneurysm repair.     

Endovascular Abdominal Aortic Aneurysm Repair Using Transvenous Intravascular US Catheter Guidance in Patients with Chronic Renal Failure

PurposeTo describe the transvenous application of intracardiac echocardiography (ICE) for guidance during endovascular aortic repair (EVAR).Materials and MethodsEight patients with an infrarenal abdominal aortic aneurysm (AAA) and chronic renal failure were determined suitable for EVAR. The procedure was performed by deploying the transcaval and transiliac vein guidance of an ICE catheter to reduce the dosage of iodinated contrast medium. Multiple guidance parameters were assessed. The present study describes the EVAR procedure and postprocedure transabdominal ultrasound (US) follow-up results at 3–4 months.ResultsThe eight procedures were completed by using transvenous ICE guidance. No contrast medium was used in five patients, and 3–20 mL of isoosmolar contrast medium was administered in the other three. No endoleaks were detected by ICE immediately after stent deployment. One patient who had a single functioning kidney developed renal failure that was attributed to manipulation-related cholesterol embolization. That patient became dependent on dialysis and died 3.5 months after the procedure. No endoleaks were detected at 3–4-month US follow-up in the other seven patients.ConclusionsTransvenous ICE guidance is a promising method to reduce the dosage of iodinated contrast medium in patients with renal dysfunction undergoing EVAR. A prospective trial comparing this modality versus digital subtraction angiography guidance with iodinated contrast medium in terms of safety, accuracy, and long-term efficacy is recommended.     

Juxtarenal aortic aneurysm: endoluminal transfemoral repair?

Endoluminal transfermoral repair of an abdominal aortic aneurysm by a stent graft placement requires a segment of the nondilated infrarenal aorta of at least 15 mm long for safe stent graft attachment. The possibility of endoluminal treatment of a juxtarenal abdominal aortic aneurysm with partially covered spiral Z stent was assessed in experiment and in three clinical cases. In the experiment, the noncovered spiral Z stent was placed into the abdominal aorta, across the origins of renal arteries and mesenteric arteries, in six dogs. In the clinical cases, a partially covered stent graft was attached in 3 patients with the juxtarenal abdominal aortic aneurysm (of the group of 12 patients with abdominal aortic aneurysm). The stent grafts were attached with proximal uncovered parts across the origins of the renal arteries. In experiment, the renal artery occlusions or stenoses were not observed 36 months after stent placement, and in clinic 3 patients with the juxtarenal aortic aneurysm were successfully treated by stent graft placement. There were no signs of flow impairment into the renal arteries 14 months after stent graft implantation. This approach can possibly expand the indications for endoluminal grafting in the treatment of juxtarenal aortic aneurysms in patients who are at high risk for surgery.     

Endovascular abdominal aortic aneurysm repair: how many patients are eligible for endovascular repair?

PURPOSE: The purpose of this study was to determine how many patients with abdominal aortic aneurysm (AAA) are eligible for endovascular abdominal aortic aneurysm repair (EVAR). MATERIALS AND METHODS: We retrospectively reviewed computed tomography (CT) angiograms obtained between January 2002 and June 2003 in 182 patients with suspected AAA. Indication for surgical or endovascular treatment was based on clinical and radiological criteria. The percentage of patients eligible for EVAR was evaluated. RESULTS: Out of a total of 182 patients with suspected AAA studied by CT angiography, after combined radiological-surgical assessment, 130 were considered eligible for surgical or endovascular treatment (71.4%). EVAR was indicated in 51 patients (39.3%, group A) and surgical repair was indicated in 79 patients (60.7%, group B). The reasons for ineligibility for EVAR were the following: unfavourable anatomy of the proximal neck in 41 patients (51.9%), diameter of the aneurysm sac >7 cm in 13 patients (16.4%), markedly tortuous/dilated iliac axis in six patients (7.6%), age <65 years in 17 patients (21.5%) and patient refusal in two cases (2.5%). There were no statistically significant differences in aneurysm diameter (52.7+/-0.8 versus 49.8+/-1.2 mm, p=ns), patients' age (73.2+/-1.2 versus 70.6+/-2.02 years, p=ns) or proximal neck length (2.95+/-1 versus 3.03+/-1.2 cm, p=ns) between groups A and B. CONCLUSIONS: Endovascular repair of abdominal aortic aneurysms through the placement of aortic stent-grafts has now become a viable alternative to open surgery. In recent years, the number of patients treated with EVAR has steadily risen as a result of increased physician experience, availability of new and more versatile devices and improvements in noninvasive imaging techniques. Unfavourable neck anatomy is the primary factor for exclusion from endovascular repair.     

Aortic-neck dilation after endovascular abdominal aortic aneurysm repair (EVAR): can it be predicted?

Purpose

This study was performed to evaluate whether dynamic computed tomography (CT) can provide functional vessel information predicting outcomes of aortic neck in patients undergoing endovascular aneurysm repair (EVAR) of an abdominal aortic aneurysm (AAA).

Materials and methods

Twenty patients with and 20 without AAA were enrolled. Electrocardiographically (ECG)-gated data sets were acquired with a 64-slice CT scanner. Axial pulsatility measurements were taken at three levels: 2 cm above the highest renal artery; immediately below the lowest renal artery; 1 cm below the lowest renal artery. Three independent readers performed the measurements. Systolic and diastolic blood pressures were measured in the brachial artery to calculate arterial-wall distensibility expressed as pressure strain elastic modulus (Ep). Cross-sectional area change, wall distensibility and Ep value were statistically compared.

Results

No significant differences were found in terms of Ep values in the suprarenal and juxtarenal level. In the AAA group, a significantly higher value was obtained at the infrarenal level. A subgroup of patients with AAA (45%) had a significantly higher Ep value at the infrarenal level.

Conclusions

Dynamic CT provided insight into the abdominal aorta pathophysiology. Identifying patients with higher infrarenal distensibility could change selection of graft size to improve proximal fixation.     

左锁骨下动脉烟囱技术在Stanford B型胸主动脉夹层腔内修复术中的应用

目的探讨左锁骨下动脉烟囱技术在Stanford B型主动脉夹层腔内修复术(EVAR)中的意义和技术要点。 方法回顾性分析35例临床和影像学确诊的Stanford B型主动脉夹层,且主动脉撕裂累及到左锁骨下动脉的患者,以CTA作为术前评估方法,术中覆膜支架覆盖左锁骨下动脉,以球囊扩张支架对左锁骨下动脉进行介入再通。 结果35例胸主动脉覆膜支架和左锁骨下动脉球囊扩张支架均放置成功,术后随访3～24个月,35例左锁骨下动脉烟囱支架通畅率100%。 结论Stanford B型胸主动脉夹层的EVAR治疗时,覆膜支架的近侧锚定区选择在正常的主动脉壁,可以降低继发医源性夹层的发生;覆盖左锁骨下动脉后采用烟囱技术可有效预防"盗血综合征"的发生,其技术简捷、安全。     

Financial Impact of PEVAR Compared With Standard Endovascular Repair in Canadian Hospitals

Objectives

The percutaneous endovascular abdominal aortic repair (PEVAR) approach is a minimally invasive technique that has demonstrated clinical benefit over traditional surgical cut down associated with standard endovascular abdominal aortic aneurysm (AAA) repair (EVAR). The objective of our study was to evaluate the budget impact to a Canadian hospital of changing the technique for AAA repair from the EVAR approach to the PEVAR approach.

Clinical experience with a customized fenestrated endograft for juxtarenal abdominal aortic aneurysm repair

Despite the numerous stent-graft devices available, unsuitable anatomy is still the greatest exclusion criterion for endovascular abdominal aortic aneurysm (AAA) repair (EVAR). The present report describes an on-site preprocedural customization of a conventional Zenith stent-graft device just before the endovascular procedure that includes the creation of fenestrations and scallops as necessary for the patient's anatomy. Three patients with difficult anatomy in whom conventional AAA repair posed a high degree of risk were treated with customization of the stent-graft device to fit disparate renal arteries. A single fenestration for the left renal artery was made in two cases, and a single scallop was made in the other case to accommodate the superior mesenteric artery. Gold beads were used to mark the location of the fenestration and scallop. The three cases were successfully performed without perceptible endoleaks in the follow-up period, which ranged from 4 to 14 months. No procedure-related complications were detected; however, pneumonia developed in one patient 3 weeks after EVAR. The initial results with this technique are encouraging, and the role of EVAR can be significantly increased with the use of this customization technique when the interventionalist does not have access to the commercially available devices or when the waiting time is too prolonged to accommodate the patient's clinical situation.