DOI: 10.1148/rg.251045046
RadioGraphics 2005;25:157-173
© RSNA, 2005
Stent-Graft Placement for the Treatment of Thoracic Aortic Diseases1
Eric Therasse, MD,
Gilles Soulez, MD,
Marie-France Giroux, MD,
Pierre Perreault, MD,
Louis Bouchard, MD,
Jean-François Blair, MD,
Nathalie Beaudoin, MD,
Andrew Benko, MD and
Vincent L. Oliva, MD
1 From the Departments of Radiology (E.T., G.S., M.F.G., P.P., L.B., V.L.O.) and Surgery (J.F.B., N.B.), Centre Hospitalier de l’Université de Montréal (CHUM)-Hôtel-Dieu, 3840 St-Urbain St, Montreal, Quebec, Canada H2W 1T8; and the Department of Radiology, Centre Hospitalier Universitaire de Sherbrooke (CHUS), Sherbrooke, Quebec, Canada (A.B.). Presented as an education exhibit at the 2003 RSNA Scientific Assembly. Received March 17, 2004; revision requested April 16 and received May 26; accepted June 1. All authors have no financial relationships to disclose. Address correspondence to E.T. (e-mail: eric.therasse.chum@ssss.gouv.qc.ca).
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Abstract
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The recent development of aortic stent-grafts has brought the management of thoracic aortic diseases into the realm of interventional radiology. Stent-graft placement is now an alternative to surgery for the treatment of descending thoracic aortic aneurysms, ulcers, and fistulas and is sometimes indicated in cases of mycotic aneurysm, posttraumatic aortic rupture, or thoracic descending aortic dissection. Pretreatment imaging is crucial for evaluating patient eligibility, selecting the appropriate stent-graft, and planning the intervention. Stent-graft treatment of long atherosclerotic aneurysms, lesions close to aortic branch vessels, and aortic dissections is subject to technical pitfalls, and adverse events such as endoleaks, stent migration or misplacement, aortic perforation, and vascular trauma will require specific interventions, although they occur in only a minority of patients. Thoracic stent-graft placement in good surgical candidates remains controversial because long-term results are unknown. However, short-term morbidity and mortality rates from endovascular treatment compare favorably with those from surgery, and stent-graft placement is proving to be a safe, minimally invasive, and effective treatment for thoracic aortic diseases and is already the best option in many affected patients who are poor surgical candidates.
© RSNA, 2005
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Introduction
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Most diseases of the thoracic aorta are serious or life-threatening conditions for which surgical treatment is associated with a relatively high mortality rate (7%–12% in elective cases and up to 40% in emergency situations) (1,2). The recent development of aortic stent-grafts, aimed at reducing the morbidity and mortality resulting from the treatment of various diseases affecting the descending thoracic aorta, has brought the management of these diseases into the realm of interventional radiology. Vascular imaging is crucial in evaluating patient eligibility for endovascular treatment, selecting the appropriate stent-graft, and planning the intervention. Crossing tortuous anatomy and positioning the stent-graft with precision are sometimes difficult or impossible without endovascular expertise and appropriate catheter technology. Follow-up imaging and treatment of adverse events also require knowledge of vascular and interventional radiology. Radiologists, who are already accustomed to using imaging and interventional materials and techniques, are in the ideal position to be involved with these interventions. In addition, radiologists should be aware of possible associated complications so that they can prevent or treat these complications.
In this article, we review the indications and the methods used for stent-graft placement for thoracic aortic diseases. We also discuss and illustrate specific entities that require careful attention in this setting (arteriosclerotic aneurysms, traumatic aortic ruptures, aortic aneurysms with tracheobronchial compression, aortobronchial and aortoesophageal fistulas, iatrogenic aneurysms, mycotic aneurysms, aortic dissections). In addition, we summarize the reported results of stent-graft placement for thoracic aortic diseases and the advantages and limitations of stent-graft treatment. Finally, we discuss the management of possible complications of thoracic stent-graft insertion (endoleaks, aortic perforation, iliac artery trauma, stent-graft misplacement).
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Indications
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With respect to diseases of the descending thoracic aorta, the indications for stent-graft placement are generally the same as those for surgical treatment (1,3). Although the contraindication for surgery is often the poor medical condition of the patient, the contraindication for endovascular treatment is most often related to anatomic considerations. Stent-graft placement requires (a) adequate vascular access (sufficient diameter of the iliac artery and abdominal aorta without severe tortuosity) and (b) an aortic lesion without excessive tortuosity and whose neck extends more than 15 mm above the celiac artery and is more than 5 mm distal to the left subclavian artery (LSA), without mural thrombus and dilatation. In good surgical candidates, there is controversy regarding which patients should undergo stent-graft placement and which should undergo surgery because the long-term results of endovascular treatment are still unknown. In poor surgical candidates, stent-graft placement is usually indicated as an elective or emergency procedure for a wide spectrum of pathologic and iatrogenic conditions (4–8).
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Methods
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Devices
Many stent-grafts are commercially available worldwide; as of this writing, however, none has been approved by the U.S. Food and Drug Administration for use in the thoracic aorta. All thoracic stent-grafts have a metallic skeleton with a covering membrane (either polytetrafluoroethylene or polyester). Most have either proximal or distal uncovered stents for better stent-graft anchoring to the aortic wall, and some also have metallic barbs for the same purpose (Fig 1). Thoracic stent-grafts are all self-expanding and constrained by a sleeve or sheath. The deployment of stent-grafts varies depending on the device used; in general, however, they are delivered either by holding the stent-graft stationary with a pusher rod while withdrawing the delivery sheath or by pulling a string that releases the stent-graft–covering sleeve (Fig 2). Most commercially available thoracic stent-grafts demonstrate no significant shortening during or after deployment.
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Figure 1a. Thoracic aortic stent-grafts. (a) Photograph shows the Talent stent-graft (Medtronic Vascular, Santa Rosa, Calif), which has an internal nitinol skeleton, a polyester membrane, and a proximal uncovered stent without barbs (arrowheads). (b, c) Photographs show the Zenith stent-graft (Cook, Bloomington, Ind), which has a steel skeleton, a membrane that is outside the metallic cage at the extremities of the stent-graft for better sealing, and no proximal uncovered stent (to prevent vascular erosion at proximal aortic curvatures). The stent-graft also has anchoring barbs at its extremities (arrowheads in c).
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Figure 1b. Thoracic aortic stent-grafts. (a) Photograph shows the Talent stent-graft (Medtronic Vascular, Santa Rosa, Calif), which has an internal nitinol skeleton, a polyester membrane, and a proximal uncovered stent without barbs (arrowheads). (b, c) Photographs show the Zenith stent-graft (Cook, Bloomington, Ind), which has a steel skeleton, a membrane that is outside the metallic cage at the extremities of the stent-graft for better sealing, and no proximal uncovered stent (to prevent vascular erosion at proximal aortic curvatures). The stent-graft also has anchoring barbs at its extremities (arrowheads in c).
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Figure 1c. Thoracic aortic stent-grafts. (a) Photograph shows the Talent stent-graft (Medtronic Vascular, Santa Rosa, Calif), which has an internal nitinol skeleton, a polyester membrane, and a proximal uncovered stent without barbs (arrowheads). (b, c) Photographs show the Zenith stent-graft (Cook, Bloomington, Ind), which has a steel skeleton, a membrane that is outside the metallic cage at the extremities of the stent-graft for better sealing, and no proximal uncovered stent (to prevent vascular erosion at proximal aortic curvatures). The stent-graft also has anchoring barbs at its extremities (arrowheads in c).
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Figure 2a. Stent-graft deployment. Photographs show the Zenith delivery system, whose sheath may be straight or curved (a), depending on the anatomy at the lesion site. Most stent-grafts are deployed by holding the inner catheter (arrow in b) stationary while the outer sheath (arrowhead in b) is withdrawn.
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Figure 2b. Stent-graft deployment. Photographs show the Zenith delivery system, whose sheath may be straight or curved (a), depending on the anatomy at the lesion site. Most stent-grafts are deployed by holding the inner catheter (arrow in b) stationary while the outer sheath (arrowhead in b) is withdrawn.
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Imaging and Measurements
Multi–detector row computed tomography (CT) allows reliable assessment of anatomic relationships between the lesion and the aortic branches as well as evaluation of the iliac and femoral arteries (diameter, tortuosity) for vascular access. Multi–detector row CT now permits multiplanar high-resolution vascular imaging from the brachiocephalic vessels to the common femoral arteries during a single breath hold of less than 20 seconds (Fig 3) and is the best imaging modality for planning an emergency procedure in hemodynamically unstable patients. With a 16-detector-row CT scanner, a complete evaluation of the aorta and iliac arteries is usually performed with a collimation of 1.5 mm or less and a tube current of 120 kVp. Iodinated contrast material with a concentration of 300 mg of iodine per milliliter is administered at a flow rate of 4–5 mL/sec (total volume, <120 mL). Magnetic resonance (MR) imaging is advantageous when slow flow conditions are suspected (dissection, endoleaks) and in patients with renal failure. MR imaging does not allow easy access to patients and is often not compatible with the life support and monitoring equipment that these patients may require. MR imaging protocol usually includes electrocardiography-gated spin-echo T1-weighted sequences performed in the axial and sagittal oblique planes. Angiograms are obtained with a gadolinium-enhanced three-dimensional gradient-echo sequence. Digital subtraction angiography with a calibrated catheter may be necessary to measure the "landing zones" (the aortic segments proximal and distal to the lesion where the stent extremities will be positioned) and lesion length in the absence of three-dimensional imaging facilities.
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Figure 3a. Multi-detector row CT evaluation of a type B dissection. (a) Curved multiplanar reformatted image allows accurate measurement of aortic and iliac artery diameters. (b) Volume-rendered image clearly displays aortic tortuosity, the extent of dissection, and the relationship of the dissection to the LSA (arrowhead). (c, d) Left (c) and right (d) anterior volume-rendered images demonstrate tortuosity of the iliac arteries.
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Figure 3b. Multi-detector row CT evaluation of a type B dissection. (a) Curved multiplanar reformatted image allows accurate measurement of aortic and iliac artery diameters. (b) Volume-rendered image clearly displays aortic tortuosity, the extent of dissection, and the relationship of the dissection to the LSA (arrowhead). (c, d) Left (c) and right (d) anterior volume-rendered images demonstrate tortuosity of the iliac arteries.
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Figure 3c. Multi-detector row CT evaluation of a type B dissection. (a) Curved multiplanar reformatted image allows accurate measurement of aortic and iliac artery diameters. (b) Volume-rendered image clearly displays aortic tortuosity, the extent of dissection, and the relationship of the dissection to the LSA (arrowhead). (c, d) Left (c) and right (d) anterior volume-rendered images demonstrate tortuosity of the iliac arteries.
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Figure 3d. Multi-detector row CT evaluation of a type B dissection. (a) Curved multiplanar reformatted image allows accurate measurement of aortic and iliac artery diameters. (b) Volume-rendered image clearly displays aortic tortuosity, the extent of dissection, and the relationship of the dissection to the LSA (arrowhead). (c, d) Left (c) and right (d) anterior volume-rendered images demonstrate tortuosity of the iliac arteries.
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Stent-graft diameter is determined on the basis of multi–detector row CT or MR imaging findings. Generally, 10%–15% oversizing of stent-grafts is required to prevent migration and provide good apposition to the aortic wall. Ideally, stent-grafts (excluding the length of the uncovered, bare extremities) should cover the lesion and at least 1.5 cm of the normal aorta at each extremity. Whenever possible, greater proximal and distal coverage should be used to prevent late stent-graft migration and endoleak due to aortic disease progression. A stent used for the treatment of aortic dissection may be relatively short, since the goal is simply to close the entry tear (9).
Stent-Graft Placement
Stent-grafts are usually placed with the patient under general anesthesia, in either the angiography suite or the operating room. The least tortuous iliac artery or that with the widest lumen is chosen for vascular access. The stent-graft delivery system is inserted through a surgical femoral cutdown over a stiff 260-cm guide wire. Heparin (5,000 U) is administered intravenously before arteriotomy. When the iliac arteries are too tortuous or too small, vascular access may be achieved through the common iliac artery with use of a temporary iliac artery conduit or through the infrarenal aorta (10). Aortic tortuosity may impede stent-graft insertion, even when the stent-graft is positioned over a very stiff guide wire. In such cases, guide wire placement through right arm and femoral accesses may help the delivery sheath to track the wire on which tension is applied at both extremities. During stent-graft deployment, the location of the lesion is determined in relation to anatomic landmarks or to an angiographic catheter in the left arm (when the lesion is close to the LSA). To prevent stent-graft migration during deployment, systolic blood pressure should be lowered to less than 90 mm Hg with use of sodium nitroprusside. Adenosine-induced cardiac standstill has been proposed to ensure precise stent-graft positioning but is not often used (11). After stent-graft deployment, a latex balloon is inflated within the stent-graft to achieve complete stent expansion. Proximal or distal stent-graft extensions should be available in case the stent-graft does not deploy optimally or is not properly positioned.
When there is less than 15 mm of normal aorta between the lesion and the LSA, the covered part of the stent-graft may have to cross the origin of the LSA to ensure adequate length of the proximal landing zone. A left carotid-subclavian artery bypass (Fig 4) may be created beforehand, although many authors have reported coverage of the LSA ostium without symptoms (5). In elective cases, however, carotid and contralateral vertebral artery perfusion should be assessed before stent-graft insertion if it is decided not to perform a carotid-subclavian artery bypass procedure.
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Figure 4a. Carotid-subclavian artery bypass created prior to stent-graft placement. (a) Digital subtraction angiogram shows a descending thoracic artery aneurysm less than 15 mm from the LSA. (b) Drawing illustrates a bypass (arrow) that was created between the left common carotid artery and the LSA. (c) Digital subtraction angiogram shows a stent-graft that has been positioned over the origin of the LSA. (d) Digital subtraction angiogram obtained after stent-graft deployment demonstrates complete exclusion of the aneurysm.
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Figure 4b. Carotid-subclavian artery bypass created prior to stent-graft placement. (a) Digital subtraction angiogram shows a descending thoracic artery aneurysm less than 15 mm from the LSA. (b) Drawing illustrates a bypass (arrow) that was created between the left common carotid artery and the LSA. (c) Digital subtraction angiogram shows a stent-graft that has been positioned over the origin of the LSA. (d) Digital subtraction angiogram obtained after stent-graft deployment demonstrates complete exclusion of the aneurysm.
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Figure 4c. Carotid-subclavian artery bypass created prior to stent-graft placement. (a) Digital subtraction angiogram shows a descending thoracic artery aneurysm less than 15 mm from the LSA. (b) Drawing illustrates a bypass (arrow) that was created between the left common carotid artery and the LSA. (c) Digital subtraction angiogram shows a stent-graft that has been positioned over the origin of the LSA. (d) Digital subtraction angiogram obtained after stent-graft deployment demonstrates complete exclusion of the aneurysm.
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Figure 4d. Carotid-subclavian artery bypass created prior to stent-graft placement. (a) Digital subtraction angiogram shows a descending thoracic artery aneurysm less than 15 mm from the LSA. (b) Drawing illustrates a bypass (arrow) that was created between the left common carotid artery and the LSA. (c) Digital subtraction angiogram shows a stent-graft that has been positioned over the origin of the LSA. (d) Digital subtraction angiogram obtained after stent-graft deployment demonstrates complete exclusion of the aneurysm.
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Follow-up
After stent-graft insertion, patients may experience postimplantation syndrome, consisting of low-grade fever, back pain, mild leukocytosis, and elevation of the C-reactive protein level (3,9). This syndrome is self-limiting and resolves within 1 week without specific treatment. Contrast material–enhanced thoracic CT is performed at the time of discharge; at 3, 6, and 12 months after stent-graft insertion; and annually thereafter. Chest radiographs are obtained at the same time intervals to assess for metallic failure of the stent-graft.
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Situations That Are Subject to Technical Pitfalls
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Arteriosclerotic Aneurysms
Arteriosclerotic aneurysms of the descending thoracic aorta typically occur in elderly patients with comorbid conditions, especially hypertension and chronic obstructive pulmonary disease. These aneurysms often manifest in a diffusely diseased and tortuous aorta, relatively normal-looking segments of which may dilate over time. The aneurysms tend to elongate, producing vector forces that may eventually cause the stent-graft to migrate (Fig 5). Therefore, it is advisable that the landing zones of the stent-graft be at least 2 cm long and that multiple stent-grafts (when deployed) generously overlap to prevent late disconnection (4). Stent-graft fixation barbs may also help prevent migration. Penetrating ulcers are generally easier to treat with stent-grafts than are true atherosclerotic aneurysms because these false aneurysms are shorter and have a relatively normal proximal and distal neck.
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Figure 5a. Elongation of an arteriosclerotic aneurysm. Drawing in a depicts a long aneurysm of the descending thoracic aorta distal to the LSA. The aneurysm is treated with two stent-grafts with minimal overlapping (arrowheads in b), but, over time, vector forces (arrows in b) induce migration and disconnection of the stent-grafts (c).
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Figure 5b. Elongation of an arteriosclerotic aneurysm. Drawing in a depicts a long aneurysm of the descending thoracic aorta distal to the LSA. The aneurysm is treated with two stent-grafts with minimal overlapping (arrowheads in b), but, over time, vector forces (arrows in b) induce migration and disconnection of the stent-grafts (c).
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Figure 5c. Elongation of an arteriosclerotic aneurysm. Drawing in a depicts a long aneurysm of the descending thoracic aorta distal to the LSA. The aneurysm is treated with two stent-grafts with minimal overlapping (arrowheads in b), but, over time, vector forces (arrows in b) induce migration and disconnection of the stent-grafts (c).
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Traumatic Aortic Ruptures
Traumatic aortic ruptures are most frequently due to deceleration injuries (eg, those sustained in motor vehicle accidents). Surgical graft interposition is the standard treatment, but its optimal timing when other life-threatening lesions must also be treated has yet to be defined. In poor surgical candidates with impending rupture, who often have other life-threatening lesions, emergency stent-graft placement has a lower mortality rate than does standard surgery (4,5). Chronic posttraumatic aneurysms are frequently discovered incidentally several years after the trauma. Treatment of chronic posttraumatic aneurysms with stent-grafts remains controversial, especially (given the absence of long-term data) in young patients. In older patients, who are not always willing to undergo major surgery for an asymptomatic condition, stent-graft placement may be an alternative treatment to consider. Whether stent-graft placement will become the primary treatment for aortic rupture is still unknown. Traumatic ruptures usually involve the aortic isthmus in proximity to the LSA, and endovascular treatment may require either covering the LSA origin or using a notched or fenestrated stent-graft (Fig 6). Because traumatic ruptures often occur in young patients with a narrow aortic arch, a more flexible stent-graft would be appropriate. In most patients treated with stent-grafts, aneurysm shrinkage is complete 1 year after the intervention.
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Figure 6a. Traumatic rupture of the descending thoracic aorta. (a) Digital subtraction angiogram shows a posttraumatic false aneurysm (arrow) very close to the LSA. (b) Photograph shows a Talent stent-graft that was notched (arrowheads) to prevent covering the LSA. (c) Follow-up image shows complete exclusion of the false aneurysm and a patent LSA.
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Figure 6b. Traumatic rupture of the descending thoracic aorta. (a) Digital subtraction angiogram shows a posttraumatic false aneurysm (arrow) very close to the LSA. (b) Photograph shows a Talent stent-graft that was notched (arrowheads) to prevent covering the LSA. (c) Follow-up image shows complete exclusion of the false aneurysm and a patent LSA.
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Figure 6c. Traumatic rupture of the descending thoracic aorta. (a) Digital subtraction angiogram shows a posttraumatic false aneurysm (arrow) very close to the LSA. (b) Photograph shows a Talent stent-graft that was notched (arrowheads) to prevent covering the LSA. (c) Follow-up image shows complete exclusion of the false aneurysm and a patent LSA.
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Aortic Aneurysms with Tracheobronchial Compression
Descending thoracic aortic aneurysms with tracheobronchial compression are usually large and may also compress the esophagus and the left pulmonary artery. Affected patients may present with cough or pneumonia due to compression of the left mainstem bronchus. When present, shortness of breath is often positional, indicating varying compression of the major airways by the aneurysm. So far, there is very little experience with aortic stent-graft treatment of these lesions. Aneurysm shrinkage may be minimal and may not be complete until several months after stent-graft placement. Therefore, in poor surgical candidates, thoracic aortic stent-graft placement without prior bronchial stent placement is a viable option when the patient has no respiratory symptoms, bronchial compression is not complete, and there is no evidence of atelectasis or pneumonia (Fig 7).
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Figure 7a. Aortic aneurysm with bronchial compression treated with stent-graft placement. (a) CT scan shows left bronchial compression (arrowhead) by a chronic posttraumatic aortic false aneurysm (arrows). (b) CT scan obtained 4 years after stent-graft placement shows a markedly shrunken aneurysm (arrow) and no bronchial compression.
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Figure 7b. Aortic aneurysm with bronchial compression treated with stent-graft placement. (a) CT scan shows left bronchial compression (arrowhead) by a chronic posttraumatic aortic false aneurysm (arrows). (b) CT scan obtained 4 years after stent-graft placement shows a markedly shrunken aneurysm (arrow) and no bronchial compression.
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Aortobronchial and Aortoesophageal Fistulas
Aortobronchial and aortoesophageal fistulas are rare but frequently fatal disorders that are most often due to aortic aneurysms or dissections, esophageal or lung malignancies, or posttraumatic or surgical lacerations. Although there is very little experience with stent-graft treatment of aortoesophageal or aortobronchial fistulas, this treatment is a possible option in emergency or palliative cases if the patient has unresectable cancer or is unfit for surgery (Fig 8). Although mediastinitis following stent-graft treatment of aortoesophageal fistula has been reported, the risk of graft infection may be less with stent-grafts than with surgical graft interposition because stent-grafts are separated from potentially infected mediastinal tissues by the aortic wall (12).
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Figure 8a. Aortoesophageal fistula treated with stent-graft placement in a patient with hematemesis. (a) Sagittal reconstructed image from multi-detector row CT data shows an atherosclerotic aneurysm (arrows) of the descending thoracic aorta. (b) Multi-detector row CT scan shows compression of the esophagus (arrowheads) by the aneurysm (arrow). (c) Digital subtraction angiogram obtained after stent-graft placement demonstrates complete exclusion of the aneurysm. The patient no longer experienced hematemesis.
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Figure 8b. Aortoesophageal fistula treated with stent-graft placement in a patient with hematemesis. (a) Sagittal reconstructed image from multi-detector row CT data shows an atherosclerotic aneurysm (arrows) of the descending thoracic aorta. (b) Multi-detector row CT scan shows compression of the esophagus (arrowheads) by the aneurysm (arrow). (c) Digital subtraction angiogram obtained after stent-graft placement demonstrates complete exclusion of the aneurysm. The patient no longer experienced hematemesis.
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Figure 8c. Aortoesophageal fistula treated with stent-graft placement in a patient with hematemesis. (a) Sagittal reconstructed image from multi-detector row CT data shows an atherosclerotic aneurysm (arrows) of the descending thoracic aorta. (b) Multi-detector row CT scan shows compression of the esophagus (arrowheads) by the aneurysm (arrow). (c) Digital subtraction angiogram obtained after stent-graft placement demonstrates complete exclusion of the aneurysm. The patient no longer experienced hematemesis.
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Iatrogenic Aneurysms
Iatrogenic aneurysms of the thoracic aorta are most often the result of surgical interventions and are frequently a late complication of surgical repair of aortic coarctation. These false aneurysms may appear at the insertion site of an extracorporeal circulation cannula (Fig 9) or at the site of patch angioplasty sutures (Fig 10). Stent-graft repair of such aneurysms is very appealing because (a) surgical reintervention is generally more difficult and hazardous than the primary surgical procedure, and (b) the aneurysm aperture is generally narrow and short, whereas proximal and distal landing zones are usually not diseased.
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Figure 9a. Iatrogenic aneurysm at the insertion site of an extracorporeal circulation cannula. (a) Coronal oblique reconstructed image from multi-detector row CT data obtained 1 year after thoracoabdominal aortic aneurysm repair shows a large false aneurysm (arrowheads) with a fistula (arrow) at the insertion site of an extracorporeal circulation cannula. (b) Multi-detector row CT scan obtained 9 months after stent-graft placement helps confirm resolution of the fistula.
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Figure 9b. Iatrogenic aneurysm at the insertion site of an extracorporeal circulation cannula. (a) Coronal oblique reconstructed image from multi-detector row CT data obtained 1 year after thoracoabdominal aortic aneurysm repair shows a large false aneurysm (arrowheads) with a fistula (arrow) at the insertion site of an extracorporeal circulation cannula. (b) Multi-detector row CT scan obtained 9 months after stent-graft placement helps confirm resolution of the fistula.
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Figure 10a. Late false aneurysm at the site of patch angioplasty sutures in a patient with hemoptysis. (a) Digital subtraction angiogram obtained 3 decades after surgical repair of a thoracic coarctation reveals a false aneurysm (arrow). (b) Coronal oblique reconstructed image from multi-detector row CT data obtained 6 years after stent-graft insertion shows complete resolution of the aneurysm.
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Figure 10b. Late false aneurysm at the site of patch angioplasty sutures in a patient with hemoptysis. (a) Digital subtraction angiogram obtained 3 decades after surgical repair of a thoracic coarctation reveals a false aneurysm (arrow). (b) Coronal oblique reconstructed image from multi-detector row CT data obtained 6 years after stent-graft insertion shows complete resolution of the aneurysm.
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Mycotic Aneurysms
Mycotic aneurysms of the thoracic aorta generally progress to rupture without surgery. Conventional surgical treatment of mycotic aneurysms consists of either in situ placement of an aortic graft or surgical resection of the aneurysm with aortic ligation and creation of an extraanatomic bypass. The first strategy implies a single surgical intervention but carries a high risk of graft infection. Patients who undergo the second procedure are at less risk for graft infection, but the strategy involves two major surgeries and also carries a risk of infectious aortic stump rupture. Although stent-graft treatment of mycotic aneurysms carries a risk of graft infection, there are several reports of a favorable outcome after stent-graft repair of mycotic aneurysms in patients who were denied surgery because of their poor general status (8,13). Stent-graft insertion may be used to gain time to improve the patient’s condition before surgery and, in some patients, may even be the definitive treatment (Fig 11).
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Figure 11a. Mycotic aneurysm treated with stent-graft placement in a patient with Salmonella septicemia. (a) Digital subtraction angiogram shows a thoracoabdominal false aneurysm (arrowheads). (b) Digital subtraction angiogram obtained after stent-graft placement demonstrates exclusion of the aneurysm. (c) Coronal reconstructed image from multi-detector row CT data obtained 1 year later shows complete resolution of the aneurysm with no sign of infection.
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Figure 11b. Mycotic aneurysm treated with stent-graft placement in a patient with Salmonella septicemia. (a) Digital subtraction angiogram shows a thoracoabdominal false aneurysm (arrowheads). (b) Digital subtraction angiogram obtained after stent-graft placement demonstrates exclusion of the aneurysm. (c) Coronal reconstructed image from multi-detector row CT data obtained 1 year later shows complete resolution of the aneurysm with no sign of infection.
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Figure 11c. Mycotic aneurysm treated with stent-graft placement in a patient with Salmonella septicemia. (a) Digital subtraction angiogram shows a thoracoabdominal false aneurysm (arrowheads). (b) Digital subtraction angiogram obtained after stent-graft placement demonstrates exclusion of the aneurysm. (c) Coronal reconstructed image from multi-detector row CT data obtained 1 year later shows complete resolution of the aneurysm with no sign of infection.
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Aortic Dissections
Stanford type B dissection is treated medically unless complications (eg, rupture, aneurysm formation, persistent pain, refractory hypertension, organ ischemia) supervene. The mortality rate for surgical treatment of chronic type B dissection is 15% and reaches almost 40% for acute dissections (14). Stent-graft insertion has been used successfully in treating organ ischemia due to dynamic compromise of the aortic branches but is unlikely to be effective in treating static vascular obstructions (Fig 12) (9,15–18). Stent-graft placement may also be indicated for the treatment of false lumen aneurysms of the descending aorta (Fig 13), which will develop within 4–5 years in 14%–20% of patients with acute type B dissection who receive medical treatment alone (16). Whether stent-graft placement for uncomplicated acute type B dissections can prevent aneurysm formation is not known.
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Figure 12. Drawing of the abdominal aorta (lateral view [A = anterior, P = posterior]) illustrates the two main types of vascular compromise associated with aortic dissection. Static vascular obstruction is not related to flow distribution between the true and false lumina and may result when the dissection flap extends directly into an aortic branch (arrow). Dynamic vascular obstruction is related to flow dynamics between the true and false lumina and may result when the flap prolapses over the origin of the branch vessel (arrowheads) or collapses the true aortic lumen from above.
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Figure 13a. False lumen aneurysm of the descending aorta treated with stent-graft placement. (a) Digital subtraction angiogram shows a Stanford B dissection with a false lumen aneurysm (arrow). (b) Digital subtraction angiogram obtained after stent-graft placement demonstrates complete exclusion of the false lumen. (c, d) CT scans obtained before (c) and 12 months after (d) stent-graft placement reveal shrinkage of the false lumen and expansion of the true lumen.
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Figure 13b. False lumen aneurysm of the descending aorta treated with stent-graft placement. (a) Digital subtraction angiogram shows a Stanford B dissection with a false lumen aneurysm (arrow). (b) Digital subtraction angiogram obtained after stent-graft placement demonstrates complete exclusion of the false lumen. (c, d) CT scans obtained before (c) and 12 months after (d) stent-graft placement reveal shrinkage of the false lumen and expansion of the true lumen.
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Figure 13c. False lumen aneurysm of the descending aorta treated with stent-graft placement. (a) Digital subtraction angiogram shows a Stanford B dissection with a false lumen aneurysm (arrow). (b) Digital subtraction angiogram obtained after stent-graft placement demonstrates complete exclusion of the false lumen. (c, d) CT scans obtained before (c) and 12 months after (d) stent-graft placement reveal shrinkage of the false lumen and expansion of the true lumen.
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Figure 13d. False lumen aneurysm of the descending aorta treated with stent-graft placement. (a) Digital subtraction angiogram shows a Stanford B dissection with a false lumen aneurysm (arrow). (b) Digital subtraction angiogram obtained after stent-graft placement demonstrates complete exclusion of the false lumen. (c, d) CT scans obtained before (c) and 12 months after (d) stent-graft placement reveal shrinkage of the false lumen and expansion of the true lumen.
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Closure of the entry tear often occurs spontaneously after stent-graft insertion, and excessive balloon dilation of the stent-graft to close the false lumen should be avoided because it may expand the aortic tear and weaken the aortic wall. Stent-graft insertion is a less complex procedure than balloon fenestration for the treatment of organ ischemia, although aortic fenestration and aortic branch stent placement may be required in addition to stent-graft placement (16,19). Careful follow-up is mandatory because dissections of the abdominal aorta may fail to close and may result in aneurysms. In addition, retrograde extension of the primary tear into the ascending aorta may occur after stent-graft treatment of a type B dissection (3).
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Results
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A summary of the reported results of stent-graft placement for diseases of the thoracic aorta is given in Table 1, and the advantages and limitations of stent-graft treatment compared with surgery are shown in Table 2 (3–7,9,10,15–18,20–22). Stent-graft insertion is technically successful in over 90% of patients, although it is suitable only in selected cases. There are very few reported long-term results of stent-graft placement. However, the reported morbidity and mortality from stent-graft treatment compare favorably with those from surgery, despite the fact that many patients were referred for endovascular treatment because they were considered to be at prohibitively high risk for surgery-related complications (3).
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Adverse Events
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Adverse events will occur after stent-graft placement in a minority of cases, and many of these complications can be diagnosed and managed with minimally invasive techniques. Aside from postimplantation syndrome, early adverse events include aortic or iliac artery trauma during the procedure, stent-graft misplacement, renal failure, myocardial infarction, pulmonary insufficiency, arterial embolism, paraplegia, and stroke (10,20). Although no randomized trials have been conducted comparing stent-graft placement with surgery for thoracic aortic disease, paraplegia seems less likely with stent-graft placement than with surgery (3,9). Late adverse events include endoleaks, stent-graft migration, infection, fracture or erosion, and aortic rupture.
Endoleaks
Type 1 endoleaks result from incomplete sealing of the stent-graft at the proximal or distal attachment site. Type 1 endoleaks are the most common endoleaks and put patients at high risk for aortic rupture (4). They occur more frequently when (a) the stent-graft landing zones are short, irregular, or ulcerated, (b) a suboptimal stent-graft diameter has been selected, or (c) the stent-graft is positioned across an angulated neck or in a narrow aortic arch and does not conform to the curved aortic contour (4). Type 2 endoleaks result from persistent circulation in the aneurysm from a tributary to the aortic lumen excluded by the stent-graft. These endoleaks are unusual and are less common in the region of the thoracic aorta than in the abdominal aortic region. Type 3 endoleaks arise from a defect of the stent-graft membrane itself or from the separation of components in modular stent-grafts. These endoleaks often result from stent-graft disconnection, which is more likely to occur when multiple stent-grafts with short overlapping areas are used. Many type 1 and type 3 endoleaks may be treated with insertion of a longer stent-graft (Fig 14).
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Figure 14a. Endoleak treated with placement of a longer stent-graft. (a) Digital subtraction angiogram shows a large penetrating ulcer of the descending thoracic aorta (arrow). (b) Digital subtraction angiogram obtained following placement of a short stent-graft demonstrates complete exclusion of the ulcer. (c) Digital subtraction angiogram obtained 4 years later reveals a type 1 endoleak, enlargement of the aneurysm, and stent-graft migration into the aneurysm (arrow). (d) Digital subtraction angiogram obtained after insertion of a longer stent-graft depicts complete exclusion of the aneurysm.
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Figure 14b. Endoleak treated with placement of a longer stent-graft. (a) Digital subtraction angiogram shows a large penetrating ulcer of the descending thoracic aorta (arrow). (b) Digital subtraction angiogram obtained following placement of a short stent-graft demonstrates complete exclusion of the ulcer. (c) Digital subtraction angiogram obtained 4 years later reveals a type 1 endoleak, enlargement of the aneurysm, and stent-graft migration into the aneurysm (arrow). (d) Digital subtraction angiogram obtained after insertion of a longer stent-graft depicts complete exclusion of the aneurysm.
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Figure 14c. Endoleak treated with placement of a longer stent-graft. (a) Digital subtraction angiogram shows a large penetrating ulcer of the descending thoracic aorta (arrow). (b) Digital subtraction angiogram obtained following placement of a short stent-graft demonstrates complete exclusion of the ulcer. (c) Digital subtraction angiogram obtained 4 years later reveals a type 1 endoleak, enlargement of the aneurysm, and stent-graft migration into the aneurysm (arrow). (d) Digital subtraction angiogram obtained after insertion of a longer stent-graft depicts complete exclusion of the aneurysm.
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Figure 14d. Endoleak treated with placement of a longer stent-graft. (a) Digital subtraction angiogram shows a large penetrating ulcer of the descending thoracic aorta (arrow). (b) Digital subtraction angiogram obtained following placement of a short stent-graft demonstrates complete exclusion of the ulcer. (c) Digital subtraction angiogram obtained 4 years later reveals a type 1 endoleak, enlargement of the aneurysm, and stent-graft migration into the aneurysm (arrow). (d) Digital subtraction angiogram obtained after insertion of a longer stent-graft depicts complete exclusion of the aneurysm.
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Aortic Perforation
Aortic perforation may occur during stent-graft insertion and is easily recognized as a rapidly enlarging hematoma or hemothorax. Rapid covering of the perforation with a stent-graft is the first treatment option. Aortic perforation may also occur after stent-graft insertion due to erosion of the aortic wall by stent-graft struts. These perforations may be asymptomatic or may lead to aortic rupture or fistula formation. In curved landing zones, stent-grafts without proximal or distal uncovered stents may be more appropriate for preventing aortic erosion (Fig 15).
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Figure 15a. Aortic arch erosion caused by the uncovered stent of a stent-graft. (a) Digital subtraction angiogram obtained before stent-graft placement demonstrates a chronic posttraumatic false aneurysm of the descending aorta. (b) Digital subtraction angiogram obtained after placement of a stent-graft despite the absence of specific symptoms shows proximal bare stent struts (arrow) protruding through the aortic wall.
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Figure 15b. Aortic arch erosion caused by the uncovered stent of a stent-graft. (a) Digital subtraction angiogram obtained before stent-graft placement demonstrates a chronic posttraumatic false aneurysm of the descending aorta. (b) Digital subtraction angiogram obtained after placement of a stent-graft despite the absence of specific symptoms shows proximal bare stent struts (arrow) protruding through the aortic wall.
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Iliac Artery Trauma
Iliac artery trauma may occur when a stent-graft is forced through a small or tortuous iliac artery. Vascular trauma is especially likely in cases involving small, heavily or circumferentially calcified iliac arteries (Fig 16). Under such conditions, attempts at stent-graft insertion may cause iliac artery dissection or rupture and may even prove fatal (10). Iliac artery trauma is often associated with premature interruption of the stent-graft procedure. Most iliac artery traumas may be treated with stents or stent-grafts, although surgical endarterectomy or bypass may also be required (3).
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Figure 16a. Iliac artery trauma caused by attempts at stent-graft placement. (a) CT scan shows a large aneurysm of the descending thoracic aorta. (b) CT scan reveals circumferential calcifications of the left iliac artery (arrowheads). (c) Digital subtraction angiogram obtained during stent-graft placement shows a left iliac artery stenosis (arrow). (d) Digital subtraction angiogram obtained after a failed attempt at stent-graft placement demonstrates extensive dissection of the left iliac artery (arrowheads). (e) Digital subtraction angiogram obtained after stent-graft placement in the left iliac artery helps confirm resolution of the dissection.
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Figure 16b. Iliac artery trauma caused by attempts at stent-graft placement. (a) CT scan shows a large aneurysm of the descending thoracic aorta. (b) CT scan reveals circumferential calcifications of the left iliac artery (arrowheads). (c) Digital subtraction angiogram obtained during stent-graft placement shows a left iliac artery stenosis (arrow). (d) Digital subtraction angiogram obtained after a failed attempt at stent-graft placement demonstrates extensive dissection of the left iliac artery (arrowheads). | |
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Abstract
Introduction
