Complications of endovascular repair for thoracic and abdominal aortic aneurysm: an imaging spectrum

Multislice CT angiography: a practical guide to CT angiography in vascular imaging and intervention

The development of multidetector CT (MDCT) has revolutionized CT angiography (CTA). Not only are new techniques now in the remit of CTA, but all the studies previously performed on single slice or helical CT can now be done with better resolution. The advantage of MDCT relevant to CTA is the ability to acquire high resolution, near isotropic data sets in a shorter acquisition time. Also important is the ability to achieve a longer scanning range in the arterial phase, which has seen the introduction of CTA of the peripheral arterial system. Image processing techniques have also progressed rapidly, with simplification of a previously cumbersome process. The high spatial resolution and relatively non-invasive nature make MDCT angiography a strong and serious competitor to established vascular imaging techniques. The implication is that traditional diagnostic pathways for evaluation of the vascular system have changed.

Suitability of 7 Aortic Stent-Graft Models for MRI-Based Surveillance

PURPOSE

To evaluate the magnetic resonance imaging (MRI) characteristics of commercially available stent-grafts used for abdominal aortic aneurysm repair.

METHODS

Seven endovascular grafts (AneuRx, Lifepath, Talent, Excluder, Zenith, Quantum LP, and Ancure) were suspended in a water bath containing gadolinium and scanned using a 1.5-T clinical MRI scanner. Two different scan techniques (T(1)-weighted spoiled gradient echo and spin echo) based upon a clinical MRI endograft surveillance protocol were used for each stent-graft. The scans were evaluated for susceptibility artifacts and radiofrequency (RF) shielding and caging artifacts.

RESULTS

For most endografts, the lumen and structures surrounding the endograft were well visualized. However, the ferromagnetic properties of the Zenith and Lifepath devices resulted in large susceptibly artifacts that obliterated the endograft lumen as well as adjacent structures. All fully supported grafts showed some amount of signal loss from the graft lumen caused by RF caging. For the Ancure graft, evaluation around the attachment sites might be problematic.

CONCLUSIONS

An MRI-based surveillance protocol appears to be a viable option for the AneuRx, Talent, Excluder, and Quantum LP stent-grafts.

Multidetector row computed tomography of the aorta and peripheral arteries

MDCT represents a significant advance on SDCT and the advantages it brings are particularly clear in CTA applications. It allows cost effective assessment of longer segments of vascular territories to be imaged with higher spatial, contrast, and temporal resolution. It has replaced SDCT as the new CT standard and its technical abilities are rapidly approaching the temporal resolution of EBCT. With 3-D post processing tools its main benefit is in imaging studies customized to the patient's pathology, with greater measurement accuracy and reliable longitudinal assessment. MDCTA is increasingly applied not to individual vascular territories but to a complete assessment dictated by the pathology, such as the entire aorta and branch vessels in aneurysm evaluation and the aorta and the coronary arteries in dissection cases or the vascular and non-vascular chest in acute chest pain. Greater accuracy of vessel assessment will lead to a refinement of interventional and surgical techniques for an individual patient and facilitates conservative management of conditions that can be reliably monitored non-invasively and the development of intervention criteria. MDCTA will continue to increase its major role in peripheral vascular evaluation in the future though its reliability in assessing small vessels below the knee and in the foot remains to be conclusively proven to obviate the need for diagnostic catheter angiography.

CT of acute abdominal aortic disorders

Aortic aneurysm rupture, aortic dissection, PAU, acute aortic occlusion, traumatic aortic injury, and aortic fistula represent acute abdominal aortic conditions. Because of its speed and proximity to the emergency department, helical CT is the imaging test of choice for these conditions. MR imaging also plays an important role in the imaging of aortic dissection and PAU, particularly when the patient is unable to receive intravenous contrast material. In this era of MDCT, conventional angiography is used as a secondary diagnostic tool to clarify equivocal findings on cross-sectional imaging. Ultrasound is helpful when CT is not readily available and the patient is unable or too unstable to undergo MR imaging.

The Use of Stent Grafts for the Treatment of Aneurysms and Dissections of the Thoracic Aorta: A Single Centre Experience

OBJECTIVE

To review the results of stent graft treatment for diseases of the thoracic aorta.

DESIGN

A retrospective study of the results of thoracic stent graft procedures in a single centre.

METHODS

The results of 30 procedures performed in 24 patients were analysed. Eleven patients had aneurysmal dilatation of the descending thoracic aorta (>5.5 cm), nine patients had complicated type B dissection, three had penetrating ulcers and one had a traumatic pseudoaneurysm. Imaging follow-up consisted of CT scans performed at one, three, six and 12 months following the procedure and annually thereafter.

RESULTS

One technical failure occurred due to a ruptured external iliac artery. There were no other immediate failures. The primary technical success rate was 83%. The 30-day procedural and patient mortality rates were 7 and 8%, respectively. No neurological complications occurred. Seven patients had the subclavian artery covered without complications. Secondary intervention was required in 21%. During the follow-up period (mean 11 months, range 1-48 months.) there were five deaths, two of which were related to stent graft infection.

CONCLUSION

Thoracic stent grafts offer a realistic alternative to surgery.

Thoracic aortic stent graft: comparison of contrast-enhanced MR angiography and CT angiography in the follow-up: initial results

The objective of this study was to compare contrast-enhanced magnetic resonance angiography (CE MRA) and multislice computed tomographic angiography (MS CTA) in the follow-up of thoracic stent-graft placement. The CE MRA and MS CTA were performed following nitinol stent-graft treatment due to thoracic aneurysm ( n=4), intramural bleeding ( n=2) and type-B aortic dissection ( n=5). Corresponding evaluation of arterial-phase imaging characteristics focused on the stent-graft morphology and leakage assessment. Stent-graft and aneurysm extensions were comparable between both techniques. Complete exclusion (aneurysm, n=4; dissection, n=2) was assessed with high confidence with CE MRA and MS CTA. Incomplete exclusion (intramural bleeding, n=2; dissection, n=3) was assigned to lower confidence scores on CE MRA compared with MS CTA. On CE MRA the stent-graft lumen demonstrated an inhomogeneous signal, the stent struts could not be assessed. The CE MRA can be used as alternative non-invasive imaging for follow-up of nitinol stent grafts. Arterial-phase leak assessment can be less evident in CE MRA compared with MS CTA studies; therefore, the use of late-phase imaging seems to be necessary. The diagnostic gap of stent-graft fracture evaluation using MRA may be filled with plain radiographs.

Endovascular exclusion of thoracic aortic aneurysms: mid-term results of elective treatment and in contained rupture

PURPOSE

The purpose is to present results of endovascular exclusion (stent-graft treatment) of aneurysms of the descending thoracic aorta both in elective cases and in emergencies.

METHODS

Indications for stent-graft treatment were dependent on multislice angio-CT evaluation revealing a proximal neck of at least 10 mm between the left common carotid artery and the onset of aneurysm. All stent grafts were inserted in the operating room; 43 transfemoral, 2 transiliac. The stent grafts used were Corvita, Stenford, Vanguard, AneuRx, Talent, and Excluder. Deployment was achieved under fluoroscopic control, endoleaks were checked for with D S A on the operating table and postoperatively by angio-CT. Long-term follow-up consisted of evaluation with angio-CT after 6 and 12 months, and from there on once a year and with plain chest X-rays. Follow-up was achieved in all patients.

RESULTS

Mean follow-up is 21 months (1-66); 30-day mortality is 3/45, no permanent neurologic deficit. Thirty patients were treated electively, 15 with contained rupture. Left subclavian artery overstenting proved to be necessary in 12 patients for proper proximal sealing of the aneurysm, type I endoleaks were observed in 10 patients, one early conversion, 7 proximal extension cuffs, one sealed spontaneously, one still at risk. Among patients where LSA had been overstented only one wanted a transposition, all others did well without left-hand ischemia or subclavian steal syndrome.

CONCLUSION

Endovascular treatment is less invasive and has reasonable mortality and morbidity but is limited to well-defined morphologies. Mid-term results are promising but it has to be observed whether these will translate into long-term durability.

Imaging of aortic stent-grafts and endoleaks

Although the technical success of stent-graft implantation is established and relatively safe, data on the long-term safety and efficacy of endovascular repair are just emerging. Because several late complications of aortic stent-graft placement have been observed, life-long follow-up remains essential. Imaging methods form an integral part of every stage of endovascular aortic aneurysm repair. The current imaging strategy should include initial plain films, CT angiography, and color-coded Duplex sonography. Plain films are an excellent means to detect migration, angulation, kinking, and structural changes of the stent mesh, including material fatigue, at follow-up. Helical CT angiography is considered a potentially revolutionary method for the noninvasive complete postprocedural assessment of aortic sten-grafting. Current data justify the use of biphasic C angiography as the postprocedural imaging technique of choice in most patients [118]. Ultrasound offers the advantages of low cost and lack of radiation exposure. High-quality ultrasound reliably excludes endoleaks in patients after stent-grafting of AAAs. There is a substantial variability, however, in measuring the diameter of aneurysm sacs; thus, confirmation using an alternative study is prudent in cases that demonstrate a significant change in size during follow-up. MR angiography serves as an attractive alternative to CT angiography in patients with impaired renal function or known allergic reaction to iodinated contrast media. With current techniques, the visualization of aortic stent-grafts (with the exception of stainless-steel-based devices) is sufficient with MR angiography. There is evidence that MR imaging is superior to CT angiography in detecting small type 2 endoleaks or for excluding retrograde perfusion in patients with suspected endotension. The role of diagnostic catheter angiography is limited to assessment of vascular pathways in equivocal cases or for suspected endotension. Currently, a consensus view about postprocedural management after aortic stent-graft implantation is lacking. The authors propose performing a baseline CT angiography at discharge and a biphasic CT angiography and Duplex ultrasound scan at three months. In patients with no evidence of an endoleak, CT angiography, plain film and Duplex sonography (abdomen) should be repeated every year after endovascular repair. If an endoleak is present at follow-up, immediate appropriate treatment should be initiated.

Percutaneous treatment of iatrogenic iliocaval fistula related to endograft placement for abdominal aortic aneurysm

The authors report a case of iatrogenic dissection occurring during endovascular treatment of an abdominal aortic aneurysm. The dissection was related to catheterization maneuvers that led to the development of a symptomatic arteriovenous fistula, which was successfully closed by coil embolization.

Complications in endoluminal repair of abdominal aortic aneurysms

In this review the technical and systemic complications occurring during endoluminal repair of abdominal aortic aneurysms are summarized. According to the data in the literature the technical success-rate of the endoluminal procedure should be >90% and the overall complication-rate <10%. It should be differentiated between complications which have an adverse effect on the outcome of the procedure, and technical problems, which complicate the procedure but do not affect the outcome. The majority of the technical problems can be solved endoluminally. The 30-day mortality rate should be in the same range as elective open surgical repair. One major factor influencing the immediate results is the experience of the interventional team.

Acute aortic abnormalities

Aneurysm and type B dissections account for most acute abdominal aortic abnormalities. The postsurgical aorta deserves special attention owing to the risk of complications. Most aortic abnormalities presenting acutely are emergencies that carry a high risk of mortality, and imaging plays a critical role in patient evaluation. Modern helical CT scanners provide excellent spatial resolution, are readily available, and allow for rapid imaging. For these reasons, helical CT angiography is the imaging modality of choice for initial evaluation of the acute aorta.

Abdominal aortic aneurysms before and after endograft implantation: evaluation by computed tomography

The evaluation of patients with abdominal aortic aneurysms for endograft candidacy and their follow-up after treatment are heavily dependent on radiologic imaging. Factors never considered during conventional open repair have become crucial to patient selection and procedural success, and the new and developing nature of the field of endovascular repair necessitates close surveillance of these devices after deployment. Computed tomography (CT) has emerged as the single most effective imaging tool for the preprocedural assessment and subsequent follow-up of these patients. This article outlines the technical parameters for obtaining pre- and postoperative CT examinations in endograft patients and discusses the important imaging findings.