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a Department of Vascular Surgery, University Hospital Innsbruck, Austria
b Department of Radiology, University Hospital Innsbruck, Austria
Received 10 August 2007; received in revised form 27 September 2007; accepted 15 October 2007.
* Corresponding author. Address: Department of Vascular Surgery, University Hospital Innsbruck, Anichstrasse 35, A-6020 Innsbruck, Austria. Tel.: +43 512 504 80800; fax: +43 512 504 22559. (Email: Beate.Neuhauser{at}i-med.ac.at).
| Abstract |
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Key Words: Endovascular thoracic aortic repair Severe complication Type B dissection
| 1. Introduction |
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The aim of this report was to describe our experience with endovascular stent-graft repairs in type B aortic dissection focusing on serious secondary complications resulting in immediate or late conversion to open repair.
| 2. Materials and methods |
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2.2 Pre-procedural imaging studies
In all patients, CT angiography of the entire aorta with three-dimensional vascular reconstruction was performed preoperatively to determine the anatomical feasibility for the stent-graft procedure, the level of entry and re-entry sites, location, extension, and relationship between the dissection membrane and significant aortic branches such as the left subclavian artery and visceral vessels. Dimensions of stent grafts used were determined on the basis of contrast-enhanced spiral CT images (HiSpeed Advantage and Light Speed QX/I; General Electric Medical Systems, Milwaukee, WI) and angiographic images.
2.3 Stent-graft device
Two types of stent grafts were used in this series: the GORE Thoracic Excluder Endoprothesis (W.L. Gore and Associates, Inc., Flagstaff, AZ), a modular system manufactured with an expanded polytetrafluoroethylene prosthesis supported by a self-expanding nitinol stent exoskeleton; and the Talent endoluminal stent graft system (Medtronic AVE, Sunrise, FL), a self-expanding endograft consisting of a polyester (Dacron) graft fabric and self-expanding nitinol exoskeleton with bare springs at the proximal site of the covered portion. The stent-graft procedure was described in detail previously [19].
In patients with a short proximal landing zone, the origin of the left subclavian artery was crossed with the uncovered or covered portion of the stent graft to extend the landing zone. A four-vessel cerebral angiography was obtained prior to overstenting to document the collateral blood supply to the left subclavian artery in these patients. A carotid-to-carotid and subclavian-to-carotid bypass procedure was performed in one patient prior to the stent-graft procedure to extend the proximal landing zone to the left carotid artery. A completion angiography was performed to ensure complete sealing and adequate device placement and to assess the adequacy of the repair. A completion CT scan was performed within 2 days post-procedure in all patients to confirm complete sealing of the entry tear and the lack of endoleaks.
2.4 Follow-up investigation
Median follow-up time was 48.3 months (range 2–97 months). Clinical examinations and contrast-enhanced spiral CT post stent grafting was performed after 3, 6, and 12 months and annually thereafter. Follow-up CTs were repeated more frequently for the investigation of suspected complications such as changes in the morphologic characteristics or progress of the dissection, or new-onset endoleaks. Intra-arterial digital subtraction angiography (DSA) was done in cases of suspected complications. The presence and source of endoleaks are classified at all time intervals according to the standard classification [20].
2.5 Data collection
A patient database was used to record clinical variables, including information on patient history, clinical presentation, medical and surgical/endovascular treatment, and outcomes including mortality and morbidity prospectively. Yearly follow-up data were obtained including clinical and imaging data, as well as information about mortality and morbidity.
2.6 Statistical evaluation
Statistical analysis was performed by using the Statistical Package for Social Sciences (SPSS) for Windows 10.1.3. Patient survival rates were calculated according to the Kaplan–Meier life table method (Fig. 1
).
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| 3. Results |
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A 63-year-old male developed a type III endoleak 619 days post stent grafting due to migration between the originally perfectly placed two stent grafts. A further stent graft was successfully deployed; however, 39 months later the patient developed a retrograde type A dissection. Significant descending aortic enlargement at the distal end of the stent graft following the second endovascular stent-graft procedure was observed from 60 mm up to 84 mm within 24 months. The patient and his relatives declined thoraco-abdominal aortic replacement. Thirty-nine months after the second stent-graft procedure a retrograde type A dissection occurred unrelated to the additional endovascular procedure, resulting in emergency graft replacement of the ascending aorta.
In a 43-year-old male completion angiography and follow-up CT scan 2 days post-procedure was unremarkable. However, 26 days after the initial procedure, the patient developed a retrograde type A dissection resulting in emergency graft replacement of the ascending aorta. The stent grafts themselves were intact and well positioned within the descending aorta. The new entry tear was located in the ascending aorta, clearly unrelated to the stent-graft procedure. The patient had an uneventful postoperative course. Follow-up investigations were done at an outside hospital. Proximal descending aortic enlargement from 50 mm to 70 mm was detected after 50 months. Graft replacement of the aortic arch and the descending aorta was performed. The patient had serious respiratory complications and finally deceased due to sepsis 51 months after the initial symptoms and endovascular stent-graft therapy for type B dissection. Autopsy was declined.
In hospital mortality rate was 14% (4/28) including one stroke, two multi-organ failures, and one respiratory failure (4/27). Total mortality rate was 32% including one retrograde type A dissection, one myocardial infarction, one pulmonary failure, and one cerebral hemorrhage (8/28). The mortality was aortic disease-related in 14% (4/28). The procedure-related mortality rate following acute retrograde type A dissection was 20% (1/5). Mean follow-up was 43 months (range 2–97 months).
| 4. Discussion |
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The primary goal of endovascular stent-graft repair in type B aortic dissection is to provide false lumen thrombosis and aortic remodeling with false lumen reduction. Closure of the proximal entry tear is essential to achieve these primary goals [10,14]. After endovascular treatment, a strict imaging follow-up is essential to detect endoleaks, antegrade or retrograde dissection progression, development of proximal or distal aortic enlargement, all signs that might increase the risk of aortic rupture [11,15,22].
Extension of the dissection is a known event in type B dissection. It is important to note that patients with successful initial treatment of acute or chronic aortic dissection have a systemic illness that predisposes their entire aorta to dissection in an ante- or retrograde manner, the first possibility for retrograde type A dissection development following stent-graft repair. Medical therapy alone does not stop the blood flow to and within the false lumen. Expansion of the false lumen, aneurysm formation, or aortic rupture may occur. It has been estimated that nearly a third of patients surviving initial treatment for acute dissection will experience dissection extension or aortic rupture within 5 years of presentation [7,11].
The incidence of retrograde type A dissection with an entry in the descending aorta ranges from 4% to 20% among Stanford type A dissections [6,23]. Our results are similar to the Stanford group. Acute retrograde type A dissection after endovascular stent-graft repair is a rare complication that has been described in conjunction with the procedure [16,17]. However, as seen in five of our patients, one must be aware that this complication can occur not only during the procedure but even days, weeks, or months following stent-graft implantation, a fact that seems to be under-reported. Dissections that originate in the descending aorta and extend in a retrograde direction into the ascending aorta may lead to aortic valve regurgitation, cerebrovascular ischemia, pericardial tamponade, and obstruction of the coronary artery. Open surgery is the treatment of choice in an effort to avert these life-threatening complications.
The retrograde dissection was clearly related to the initial stent-graft procedure in three of our patients; the entry tear was not completely excluded by a Talent stent graft in the 87-year-old lady and showed a type I endoleak at the end of the procedure. By scrutinizing all images of that patient, who was initially treated for an acute type B dissection, the pre-interventional diagnosis of peri-aortic effusion was questioned. Retrospectively, the hypodense fringe encasing the ascending aorta was interpreted as an intramural hematoma. We suspect that the fragility of the aortic wall caused by this pathology finally resulted in a type A dissection, which was triggered by the stent-graft procedure. The 64-year-old male in whom a type III endoleak occurred due to disconnection between the second and third Talent stent graft while balloon dilatation was performed was in a high risk to develop a complication while waiting for an additional suitable stent graft. Not having the appropriate material available needs to be added on the list of risk factors for developing serious complications. The 65-year-old male, in whom two Gore Tag devices were used for type B dissection repair, showed the new entry tear next to the proximal part of the stent graft during emergency surgery. Balloon dilatation during the stent-graft procedure might have triggered the intimal damage resulting in retrograde type A dissection in that case. The poor quality of the aortic wall may be another cofactor leading to this severe complication. We suspect that repeated balloon dilatation provoked the retrograde type A dissection at least in one of our patients. Two out of five patients with type B dissection showed persistent blood flow into the false lumen at the end of the procedure. The small number of cases impaired the ability to draw final conclusions, however persistent blood flow might be a positive predictor for type A dissection due to the still existing pressure against the aortic wall within the false lumen.
Retrospectively, acute dissection may have been initiated during the endovascular procedure, and then extended in a retrograde manner during the following days or weeks. Wire and sheath handling or balloon dilatation during the endovascular procedure may have caused localized intimal minimal tears in the extremely fragile and easily injured intimal flap and aortic wall that progressed and resulted in a new-onset dissection. The device itself may have also contributed to the new-onset dissection. It is well known that the Gore Excluder prosthesis has a better longitudinal flexibility that adapts better to the aortic curve of the distal arch than the Talent device, which has a semi-rigid design. However, both types of stent grafts may require repeated balloon dilatation to accommodate the curved geometry of the aortic arch and to form a tight seal. Intimal injuries directed by local forces against the intima may have occurred. In addition, routinely performed stent-graft oversizing may have contributed to the intimal injuries despite exact measurements and the use of stent-graft oversizes recommended by the manufactures was used. Our inserted stent grafts are usually 10% larger than the diameter of the non-effected segment of the aorta proximal to the entry tear to achieve secure proximal sealing.
The new type A dissection had no relation to the stent graft in two patients. One patient initially admitted for acute type B dissection showed an entry tear located in the ascending aorta unrelated to the stent graft during emergent surgery 26 days later. The second patient developed a significant distal expansion of the descending thoracic aorta 39 months after an additional stent-graft procedure due to type III endoleak followed by retrograde type A dissection. No relation to the primary or secondary endovascular stent-graft procedure was found; the entry tear was located in the ascending aorta. The possible explanation for the new-onset type A dissection might be caused by disease progression.
| 5. Conclusion |
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Endovascular stent-graft repair of the thoracic aorta is an alternative to surgical repair, however not without significant morbidity and mortality. Potentially lethal complications, acute or delayed, may occur. Life-long surveillance is mandatory.
| References |
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