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Eur J Cardiothorac Surg 2008;34:810-819. doi:10.1016/j.ejcts.2008.07.046
Copyright © 2008, European Association for Cardio-thoracic Surgery. Published by Elsevier. All rights reserved.
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Endovascular treatment for thoracoabdominal aneurysms: outcomes and results

Michael P. Siegenthalera,*, Ernst Weigangc, Kerstin Brehmb, Wulf Euringerb, Tobias Baumannb, Markus Uhlb, Sujatha Raghua, Friedhelm Beyersdorfb

a Division of Cardiac Surgery, the Heart Lung and Esophageal Surgery Institute, UPMC Presbyterian, Suite C-700, 200 Lothrop St., Pittsburgh, PA 15213, United States
b Center for Cardiovascular Disease, University of Freiburg, Freiburg, Germany
c Clinic for Cardiothoracic and Vascular Surgery, University Hospital Mainz, Mainz, Germany

Received 18 September 2007; received in revised form 16 June 2008; accepted 1 July 2008.

* Corresponding author. Address: The Heart Lung and Esophageal Surgery Institute, UPMC Presbyterian, Suite C-700, 200 Lothrop Street, Pittsburgh, PA 15213, United States. Tel.: +1 412 648 6648; fax: +1 412 802 8020. (Email: siegenthlaermp{at}upmc.edu).


   Abstract
Top
 Abstract
1. Introduction
 2. Materials and methods
 3. Results
 4. Discussion
 5. Summary
 6. Conclusion
 Appendix A
 References
 
Objective: Endovascular treatment of thoracoabdominal aortic aneurysms (TAAA) in combination with selective open surgical revascularization may be an alternative to conventional surgical repair. We analyzed our patient outcomes after elective and emergent endovascular TAAA repair. Methods: Mortality and outcome data from 21 consecutive patients treated with endovascular TAAA repair between 2000 and 2006 were reviewed. An integrated neuroprotective approach was used on all patients. Mortality risk estimates for open surgery (OS) were calculated using the published risk assessment models and compared to our outcomes. Results: Of the 21 patients, 9 had acute presentation: acute pain (9), rupture (6), and malperfusion (1). The celiac axis was overstented in 15. Nine hybrid open surgical procedures were performed: visceral/renal arteries (5), infrarenal aorta (3) and complete arch revascularization (1). Eleven patients had previous aortic surgery. Thirty-day mortality rate was 4.8% (1/21, predicted OS value 8.3%), 1-, 2- and 3-year survival was 80%. One hospital death occurred due to ischemic colitis after inferior mesenteric artery overstenting. No patient with acute presentation died during the initial hospital admission. There was no paraplegia (predicted OS rate 11.46%) and one event of delayed temporary paraparesis 3 weeks after hospital discharge corrected with raising the blood pressure. Other neurologic complications included one minor left pontine stroke with complete resolution, postoperative confusion (1) and saphenous nerve injury (1). No new late endoleaks occurred after initial complete aneurysm exclusion. Five patients underwent early (<30 days) and four patients underwent late endovascular reinterventions for persistent endoleak. An additional reintervention included percutaneous stenting of a superior mesenteric artery stenosis. Actual freedom from late reintervention was 81%, and 76% at 1-, 2 and 3-year follow-up. Late major adverse events included one stent infection leading to multi-organ failure and death. Conclusions: Endovascular treatment of thoracoabdominal aneurysms with selective visceral and renal revascularization is associated with low mortality and can only be effectively performed by a surgeon. High-risk patients and those with acute presentation appear to benefit most from this therapy. Early results up to three years of this therapy are encouraging, but further follow up to validate long-term results is required.

Key Words: Thoracoabdominal aneurysm • Endovascular repair • Visceral revascularization


   1. Introduction
Top
 Abstract
 1. Introduction
2. Materials and methods
 3. Results
 4. Discussion
 5. Summary
 6. Conclusion
 Appendix A
 References
 
Many patients with aneurysms of the distal arch and descending thoracic aorta are amenable to the emerging endovascular treatment techniques, but the role of endovascular treatment for thoracoabdominal aneurysms is uncertain.

Open surgical management of thoracoabdominal aneurysms (TAAA) involves complex operative procedures and carries an operative mortality of 10–20% in real life series involving registry data [1–3]. A few centers of excellence were able to report better data [4,5].

Endovascular stent grafting for thoracoabdominal disease has been used mainly in populations with significant comorbidities [6]. The aortic segment that has to be replaced in open surgery does not strictly correspond with the segment that has to be covered with an endovascular stent graft. A stent graft can be landed distally at the visceral vessels or even covering the celiac axis in a large aorta using a 46 mm stent graft without endovascular or surgical revascularization of the visceral or renal arteries. In conventional open cases, an aorta of that size needs replacement. If complete covering of the visceral and renal aortic segment is necessary, branched or fenestrated endografts or a hybrid open surgical revascularization is required. These approaches are both feasible but technically challenging. The branched and fenestrated endograft treatment is getting a lot of attention and early results are encouraging [6]. This treatment is currently only available in elective cases, as the current grafts have to be custom made. In theory, even if a hybrid revascularization is required in addition to endovascular therapy, the significant morbidity of a large conventional open thoracoabdominal procedure, which includes aortic cross-clamping and mechanical pump support, can be reduced to the morbidity of a large abdominal operation without aortic clamping and the endovascular manipulation of a stent graft with visceral organ ischemia times of 10–15 min [7].

We report our series of 21 patients who underwent endovascular TAAA repair by isolated stent grafting or a single stage hybrid open endovascular procedure. We compare the observed mortality with the predicted mortality risk scores derived from published risk assessment models for surgical replacement of the thoracoabdominal aorta [4,8–10].


   2. Materials and methods
Top
 Abstract
 1. Introduction
 2. Materials and methods
3. Results
 4. Discussion
 5. Summary
 6. Conclusion
 Appendix A
 References
 
2.1 Study design
We performed a retrospective review of the mortality and adverse events from a series of 21 patients who underwent endovascular repair of TAAA between 2000 and 2006. In this period, 92 patients with thoracic aortic pathology were treated with stent graft interventions by our group of cardiovascular surgeons. The ethics committee of the University of Freiburg approved this retrospective data collection. All patients undergoing endovascular aortic stent grafting were identified. Outcome data were retrospectively collected from hospital records. Follow-up data were obtained from outpatient clinic notes and from phone calls to either the patient's primary care physician or to the patient himself. Twenty of the 21 patients of this series had their TAAA repair performed by or under the supervision of the first author.

Of the 21 TAAA patients, mortality and paraplegia risk was assessed using the published risk scores illustrated in Table 1 [4,8–10]. These scores were derived from a very large open surgical experience and allow the calculation of a predicted mortality of an entire cohort as well as individual patient's risk assessment for either all adverse events, for paraplegia or for the likelihood of death. As the urgency of patients’ presentation could be argued in all cases but in frank ruptures, we calculated the risk scores that include all urgent and elective cases as well as the scores exclusively for elective patients and applied them to our entire cohort. All clinical outcomes were recorded and compared to these predictive models.


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  		Table 1 Risk score models
 
2.2 Definition of thoracoabdominal aneurysms
The definition of TAAA was based on the definition used by a large series of a center of excellence [9], using the Crawford extent of the aneurysms. The definition for the Crawford extent by this group involved the recording of the segments of the thoracoabdominal aorta that was surgically replaced. We used the same definition and classified the Crawford extent of the TAAA based on the aortic segment that would need replacement in an open surgical procedure.

We identified 21 patients with TAAA who were treated with thoracic stent grafts, in which, for an open surgical procedure, visceral aortic replacement would have been required.

2.3 Patient selection
During the study period, all patients with TAAAs who needed treatment were considered candidates for an endovascular and possibly hybrid approach. Only young patients with connective tissue disease or those with anatomy unsuitable for endovascular repair were treated with open surgery during the study by the same surgeons who perform the endovascular procedures. Unsuitable anatomy for stent grafting included the absence of suitable landing zones for stent graft therapy due to length of the landing zone or their size. Proximal landing zones had to be ≥15 mm in length and distal landing zones ≥10 mm. Vascular access did not influence our decision to use stent grafts or open surgery, as in cases with poor vascular access either the iliac artery or the aorta was used for stent graft implantation. During the study period, 24 patients underwent elective open surgical TAAA repair. The result of 20 patients in this cohort has been previously published by our group [11].

2.4 Perioperative management and spinal cord-protecting strategies
Preoperative evaluation for patients was similar to patients undergoing open surgical repair. Cardiac catheterization was used liberally in most elective cases. The procedures were performed using general anesthesia. Since a complete neuromuscular blockade significantly interferes with the ability to carry out trans cranial motor evoked potential (tcMEP) monitoring, vecuronium was administered as a short-term muscle relaxant only once, at the induction of general anesthesia. A total intravenous anesthetic regimen using benzodiazepine (0.01–0.03 mg/kg body weight) and fentanyl (0.004–0.007 mg/kg body weight) was administered. Patients were not given any further relaxants or inhalative anesthetics during the operation to prevent interference with the neurophysiological monitoring.

The detailed neuroprotective management was used whenever logistically feasible and has been reported previously [11–13]. If a change in tcMEP or somato-sensory evoked potential (SSEP) was noted, intra cranial pressure (ICP) was lowered to below 12 mmHg and the mean arterial blood pressure was pharmacologically raised with noradrenaline until the evoked potential changes were completely reversed. The CVP was reduced to below 12 mmHg via restrictive volume management and nitroglycerin application. We also performed cerebrospinal fluid drainage if the ICP exceeded 15 mmHg, regardless of the spinal cord function as measured by evoked potentials. Cerebrospinal fluid (CSF) was monitored and controlled by means of an external lumbar drainage routinely inserted by a neurosurgeon at least 12 h before surgery, minimizing the risk of intrathecal or epidural bleeding with intra- and postoperative anticoagulation.

2.5 Preoperative imaging
CT angiogram (Siemens, Munich, Germany) was the primary preoperative imaging modality to determine individual aortic anatomy and obtain measurements for stent graft sizing. Conventional catheter-based diagnostic arteriograms were only selectively obtained. For difficult anatomy we used an Aquarius workstation, (TeraRecon, San Mateo, California, USA), for instance to assess if a short distal landing zone in a Crawford extent I or V aneurysm might be adequate or to determine a precise diameter in tortuous segments with a centerline determination.

2.6 Operative technique: open surgical revascularization
For hybrid open surgical revascularization, the necessary bypass targets such as the common hepatic artery, the renal arteries and the superior mesenteric artery were dissected free after a median laparotomy. The safest possible inflow area of the common iliac artery was identified for the proximal bypass anastomoses. Preferably, we used greater saphenous vein for the intraabdominal bypasses, or if they were insufficient or unavailable, a ring enhanced PTFE or a Vascutek Gelweave bifurcated prosthesis was used for the renal and for the visceral arteries. An end-to-end technique for the superior mesenteric artery after its passage underneath the pancreas was preferred over an infracolic end-to-side approach. The celiac artery was not dissected free at its origin. After completion of the common hepatic bypass and only after aortic endovascular stenting was it suture ligated at its origin at the aorta using a large prolene suture ligature. The trifurcation to the splenic and left gastric artery was left patent using this method.

2.7 Operative technique; endovascular treatment
If at all possible we used a minimalist approach using only an endovascular intervention without surgical revascularization, even if covering of the celiac artery was required. This approach was used even in distal landing zones shorter than 2 cm, as is often the case in Crawford extent 1 aneurysms. The decision to add an open hybrid surgical revascularization was only made if absolutely unavoidable and depended mainly on the visceral blood supply, the quality and size of the landing zone and the anatomy and extent of the aneurysm. For short distal landing zones, the Valiant stent graft was manually reversed and reinserted into the deployment system prior to implantation to provide better anchorage with distal bare springs. If a distal landing zone at the visceral vessels was very short, the risks of distal type 1 endoleak and the possibility of a required early reintervention was explained to the patient and was deliberately taken, if a more invasive approach could be avoided in this manner. Prior to covering the celiac artery with a stent graft, the anatomy and collaterals of the mesenteric vascular bed were carefully evaluated on CT angiography.

A similar approach was taken with covering the subclavian artery, if required to provide an adequate landing zone. After studying the cerebral blood supply and in the absence of contraindications including anatomical variations or stenoses, we used our previously described approach and overstented the subclavian artery without simultaneous surgical revascularization [14]. Delayed revascularization was then selectively used if necessary.

Standard technique was used for stent graft placement. In open surgical cases, the planned landing zone was often marked with the radioopaque marker of a sponge or with surgical clips allowing deployment of the stent graft without using contrast. In cases of dissection, transesophageal echocardiography was used as an adjunct to confirm the position of the wire in the true lumen. The common femoral artery was preferred for stent graft insertion; if this was not feasible, the common iliac artery or the aorta were used. All stent graft procedures were performed in the operating room. The patients were placed in a supine position and a roll was placed underneath the left torso if a steep left anterior oblique view had to be accomplished. After exposure of a suitable access artery and correct positioning of the stent graft over a super stiff wire (Lunderquist, Cook Medical Inc., Bloomington, Indiana, USA), the self-expanding endoprosthesis (Talent and Valiant, Medtronic Inc., Minneapolis, Minnesota, USA and TAG Excluder, W. L. Gore and Associates Inc., Flagstaff, Arizona, USA) was deployed in the target region of the aorta under fluoroscopic guidance. Hypotension was not routinely used. After stent graft deployment, molding to the landing zones and to the stent connection sites was routinely performed using an endovascular balloon catheter (Reliant balloon, Medtronic Inc. or Trilobe balloon, W.L. Gore, Inc.), except in cases of acute dissection. Angiographic control for endoleaks was performed. Prior to discharge, a control CT scan or MRI in patients with compromised renal function was performed. Small distal type I endoleaks were usually treated with an early reintervention, small type II and III endoleaks were treated expectantly. If necessary, 3D reconstructions were performed with an Aquarius workstation to characterize and understand endoleaks. Fig. 1 shows an example of a type 3 endoleak that was better understood after a 3D reconstruction. A follow-up imaging study was routinely obtained 3 months after hospital discharge.


Figure 1
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  		Fig. 1. The complex aneurysm involving the entire aortic arch and the entire descending and upper thoracoabdominal aorta (Crawford extent I) is shown (A). After aortic arch debranching and endovascular therapy, this patient developed a type III endoleak (B), which could be better understood after 3D reconstruction (C). The stents had been distracted by the aorta settling back into its original position after being straightened out during the stent graft placement. Treatment involved an additional stent graft (D), leading to resolution of the endoleak (E) by restoring the stent chain (F).

 
2.8 Data collection and analysis
Postoperative data collection included patient outcomes and all significant postoperative events. Previously published risk assessment scores [4,8–10] (Table 1) were calculated for our cohort. For continuous data with normal distribution, the mean ± the standard deviation are reported. Continuous data with non-normal distribution, such as the time in the ICU are reported as median and interquartile range (IQR). Categorical data are summarized as absolute numbers and percentage. Survival data were analyzed using Kaplan–Meier survival analysis using Prism software for Mac (GraphPad Software, Inc., San Diego, California. USA). Freedom from reintervention rates were calculated using the actual method for event free survival [15].


   3. Results
Top
 Abstract
 1. Introduction
 2. Materials and methods
 3. Results
4. Discussion
 5. Summary
 6. Conclusion
 Appendix A
 References
 
3.1 Patient population
Table 2 lists the pertinent patient characteristics including demographic data, preoperative risk factors for TAAA repair, the Crawford extent of the aneurysm and the underlying aortic disease. Nine patients had an acute presentation including 6 patients with a rupture and 11 patients had undergone previous aortic surgery. The overall predicted mortality for our cohort was 8.3% and the predicted paraplegia rate was 11.5% using the newest risk score model derived from acute and elective cases [4]. The mathematical models designed for elective cases yielded lower predicted mortality and paraplegia rates (Table 2). Follow-up was complete in all patients but 2 who were lost to follow-up. The average follow-up was 17 ± 10 months (range 3–32 months).


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  		Table 2 Patient characteristics
 
3.2 Intraoperative data and surgical results
Median operative time was 3.2 h (IQR, 3.4). Detailed intraoperative and postoperative data are shown in Table 3 . The combined open procedures took longer than the purely endovascular cases (6.1 h vs 2.1 h). Nonparametric analyses comparing combined open procedures with endovascular cases revealed a significant difference in OR time, ICU time and total hospital stay but no significant difference in ventilation time. Vascular access was predominantly femoral (15, 71%), in some cases access to the aorta (4, 19%) or the common iliac arteries iliac (2, 10%) was required. There were no iliac ruptures or vascular reconstructions other than localized endarterectomies without patch material for loosened fragments of intima during the stenting process. There was no intraoperative mortality (Table 4 ).


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  		Table 3 Intraoperative and postoperative patient data
 

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  		Table 4 Treatment based on extent of aneurysm and pathology
 
Transfusion requirements were, in general, low (Table 3). Of note, even a Jehovah's Witness with a ruptured thoracoabdominal aneurysm survived the surgery without blood transfusions. All patients were discharged home except 2 who needed to be discharged to a long-term care facility.

3.3 Visceral artery management
In all 21 patients, a large stent graft could be deployed with the distal landing zone just at or over the celiac axis. Preservation of a patent celiac artery was initially felt to be important, and this led to the occurrence of distal type 1 endoleaks due to an insufficient distal landing zone early in our experience (Fig. 2 ). We even performed a laparotomy with a bypass just for the celiac artery in an early patient. As experience grew, no laparotomy was performed for an exclusive celiac artery overstenting if there was a normal take off of the superior mesenteric artery and normal collateral pancreaticoduodenal arcades. In 15 patients, the celiac artery was ultimately covered with a stent graft; only 5 of them had a surgical bypass to this vessel. There were no problems noted using this approach.


Figure 2
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  		Fig. 2. A Crawford extent I aneurysm with a typical short distal landing zone (A), arrow, is depicted. After stent graft placement with the bare springs covering the celiac artery, there was a distal type I endoleak (B,C). This was corrected with distal stent extension (D, E).

 
In one patient, the proximity of the stent graft and the bare springs to the superior mesenteric artery led to an increased flow velocity of the superior mesenteric artery by ultrasound. This was treated percutaneously with an uncovered stent graft.

The one hospital death (4.8%) occurred in a high-risk elective case of a 79-year-old female with an extent IV aneurysm due to ischemic colon necrosis after inferior mesenteric artery overstenting. Her individual predicted risk score for open surgery was 40%. In this patient, all the other visceral and renal vessels were bypassed, but the revascularization of a large inferior mesenteric artery was omitted (Fig. 3 ). After initial extubation, she developed subsequent multiorgan failure and expired on postoperative day 3.


Figure 3
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  		Fig. 3. The preoperative anatomy of a Crawford extent IV aneurysm with extensive calcifications in the patient who died in the early postoperative phase is shown (A, B). A large inferior mesenteric artery (C, arrow) was not surgically revascularized. The postoperative reconstruction with occlusion of the inferior mesenteric artery and the patent visceral bypass grafts are shown (D).

 
3.4 Mortality
Hospital mortality was 4.8%, and 4 patients in this cohort have died to date. Fig. 4A depicts the Kaplan–Meier survival curves of this population. The survival rate at 1–3-years was 80%. There were three deaths directly attributable to the aneurysm or the surgical procedure: the above mentioned patient with ischemic colitis, one patient who developed a stent graft infection 3 months after treatment for a ruptured TAAA and one patient who died after 3 months in a chronic care facility after having survived an initially difficult postoperative course with multiorgan failure after treatment of a ruptured TAAA.


Figure 4
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  		Fig. 4. The figure illustrates the Kaplan–Meier survival curve of our cohort (A) and the actual freedom from aneurysm related reinterventions after hospital discharge (B) for the entire cohort, for aneurysm and dissection.

 
There was one additional late death after 6 months, this patient had an autopsy and no rupture of his stented Crawford extent II aneurysm was found.

3.5 Paraplegia
No patient suffered perioperative paraplegia. We observed one case of late transient paraparesis 3 weeks after hospital discharge. This event was associated with too many antihypertensive medications lowering the patient's blood pressure at levels below normal and reversed with discontinuing her antihypertensive medications. This patient is now fully ambulatory with a minimal unilateral residual motor/sensory deficit.

3.6 Early reinterventions
No open surgical reinterventions were required for endoleaks or to treat the aneurysm. There were six early endovascular reinterventions in five patients. Five early reinterventions were due to a distal type I endoleak. Treatment included distal stent extension (3) or percutaneous balloon dilatation (2). In all cases of early reintervention, the distal type I endoleak was due to an attempt to preserve the celiac artery (Fig. 2).

One early reintervention was due to in stent stenosis in a patient with a chronic type B aortic dissection and aneurysmal dilatation to 8 cm of the false lumen with compression of the true lumen. At his initial operation, no forceful balloon dilatation of the distal stent landing zone was performed, which led to an instent stenosis, which was later successfully treated with a balloon dilatation.

3.7 Late reinterventions
No new late endoleaks occurred after initial complete aneurysm exclusion. Five patients needed a late endovascular reintervention. The majority (4) was due to persistent distal type 1 endoleak (3), shown in Fig. 1, one was due to a worsening type III endoleak, depicted in Fig. 2. Initial treatment of these endoleaks had been expectantly. Redo endovascular stent grafting was successful in three patients except in one patient with septic multiorgan failure due to an endovascular stent graft infection. One reintervention was treatment of a superior mesenteric artery with an uncovered stent graft for a stenosis with flow resistance due to the proximity of the bare springs of the stent graft at the origin of the SMA. Interestingly, four out of five late reinterventions were in patients who had a previous dissection. Actual freedom from aneurysm related reintervention rates at 1, 2 and 3 years was 95% and 86%, and 81% at 1 and 2–3 years for chronic dissection. Fig. 4B illustrates the actual freedom from reintervention for all patients, for patients with dissections and with true aneurysms after discharge from the hospital. There was no mortality associated with the reinterventions. The morbidity associated with the reinterventions included one patient who required an urgent groin cut down due to bleeding after removal of a 12 F sheath. There was no other morbidity associated with the reinterventions.

3.8 Other postoperative interventions
There were two subsequent peripheral vascular procedures unrelated to endoleaks. One patient required delayed subclavian artery revascularization after 8 months after a small pontine stroke and the continued presence of a steal syndrome. One patient with severe peripheral vascular disease, which had precluded the use of his iliac axis for stent graft deployment and required access to the infrarenal aorta, developed a left common iliac artery occlusion 10 months after his procedure and underwent successful femoro-femoral crossover bypass grafting.

There were three minor interventions due to local wound problems. One patient had in the past suffered a type B dissection with visceral malperfusion syndrome and had undergone a small and large bowel resection and superior mesenteric and celiac artery stents a few years prior to presenting to our center. After his original treatment, he had suffered multiorgan failure and repeated eviscerations, which were finally treated with a skin graft on his viscera. He presented to us a few years later with a large (69 mm) extent 2 TAAA. His preoperative risk score for open surgery was 73%. After completing his technically difficult combined open surgical procedure with complete visceral revascularization, we attempted a primary closure of his abdominal wall hernia after extensive skin mobilization. In the postoperative phase, a local hematoma under his skin flaps needed evacuation with a separate surgical procedure. One other patient had a resuturing of a chronic lymph fistula of his groin and one required late surgical treatment of a lymphatic groin cyst. There were no wound infections.


   4. Discussion
Top
 Abstract
 1. Introduction
 2. Materials and methods
 3. Results
 4. Discussion
5. Summary
 6. Conclusion
 Appendix A
 References
 
4.1 Mortality
Large registries show a mortality of 10–20% for open surgical repair of TAAA [1–3]. Only a few centers of excellence have published mortality rates below 10% [4,5]. Such results are unattainable by most centers. Despite the inclusion of a learning curve in our results, a very ill patient population, a completely non-selective approach, which involved treatment of everyone in need, and the inclusion of six patients with a rupture, we had a mortality of 4.8%, similar to these best published series. The predictive model used to generate the risk score did not include ruptured TAAAs and inclusion of rupture in the score would probably yield an ever higher expected mortality.

4.2 Paraplegia
Paraplegia and renal failure have been the most common complications after TAA repair and have been shown to be the main determinants of postoperative mortality [16]. The cause of postoperative neurological deficits after otherwise successful descending open thoracic aorta replacement is multifactorial [10]. Irreversible paraplegia is one of the most devastating complications after TAAA repair. The incidence of paraplegia or paraparesis ranges between 4% and 32% based on the published literature [17]. Svensson et al. have documented a 16% incidence of paraplegia or paraparesis; and complete paralysis in more than half of patients with deficits [5]. There are also reports of patients who underwent elective repair and the combined incidence of paraplegia/paraparesis was 3.6% [9]. Recently published retrospective reviews by Etz et al. (n = 858) reported a 2.7% incidence of paraplegia [18]; Maniar et al. (n = 60) reported 10% incidence of paraplegia/paraparesis [19]. Duration and degree of ischemia, reperfusion injury, and loss of critical intercostals and lumbar arteries could all contribute to spinal cord injury. The risk of spinal cord injury averages, based on the Crawford classification, 13% for extent I, 28–31% for extent II, 7% for extent III, and 4% for extent IV [17]. Extent of repair and acute presentation were also shown to be predictors of paraplegia [20]. Safi et al. summarizes the role of different surgical techniques decline in the incidence of paraplegia in the TAAA surgical patient population [21].

We had no event of perioperative paraplegia in this high-risk population, but observed one case of late transient reversible paraparesis 3 weeks after hospital discharge. This event was associated with lowering the patient's blood pressure at levels below normal and was reversed with discontinuing her antihypertensive medications. After stent grafting these patients depend on collateral blood flow to the spinal cord with adequate perfusion pressure and we feel that strict avoidance of hypotension is important and we now allow these patients to be slightly hypertensive for the first few months after thoracic stent graft therapy. Eleven of the patients in this series had previous aortic surgery, which increases the risk of paraplegia, but is not included in the risk scores calculated in this manuscript (Table 1). It is important to reemphasize that the previously described multimodality active surveillance approach of spinal cord function during the procedure and in the early postoperative phase appeared to be beneficial to us, as there were patients who lost their evoked potentials which led to immediate active interventions to increase the spinal cord perfusion [11–13]. The observed low rate of paraplegia using an endovascular approach might turn out as the largest advantage of this method for the treatment of TAAA.

4.3 Reinterventions
There were no open surgical reinterventions for the thoracoabdominal aortic segment treated with a stent graft. No patient with a completely sealed aneurysm had a subsequent endoleak. The relative frequency of early reinterventions was part of our learning curve. Early in this experience we attempted to keep the celiac artery open and subsequently had to extend the distal stent graft landing zone with coverage of the celiac artery. We therefore focused our analysis mainly on the patients who underwent reinterventions to treat the TAAA after the initial treatment was completed and were discharged home. This allows us to estimate what reintervention rate to expect if a more aggressive strategy with liberal covering of the celiac artery is adapted and at the same time report all our reinterventions. It is also important to remember, that the associated morbidity and patient's acceptance for a repeat percutaneous or stent graft procedure is high, if this prevents a major open surgical TAAA repair. The goal of our treatment was not a low reintervention rate, but a minimal invasive approach for the management of TAAA with the least possible morbidity. There was only one late reintervention for a true aneurysm but 4 reinterventions for patients with dissection, which reemphasizes the challenge of these patients for endovascular treatment.

4.4 Endovascular management of TAAA
The hybrid procedure, which involves open revascularization of the mesenteric and renal arteries along with endovascular repair of the aorta, is emerging to be a potential alternative to a complete open surgical management. This procedure is preferred to open surgical repair in patients with severe comorbidities [6]. For most cases, we do not see any advantage in a staged approach and we performed the endovascular stent graft placement at the time of the open surgical procedure with no adverse sequelae. Advantages of the hybrid open surgical approach include its availability in emergency cases and known patency rates of visceral or renal arterial bypasses as opposed to the unknown long-term patency rates of branched or even fenestrated stent grafts.

Some might argue that those cases, in which complete overstenting of the visceral and renal segment was not necessary, were not real thoracoabdominal aneurysms. It is important to reemphasize that the cut-off for overstenting visceral arteries in a TAAA treated with a stent graft or for replacement during open surgery is not the same. Due to the currently available large stent grafts up to 46 mm, a distal seal can be accomplished in many patients with extent I aneurysms who, in an open surgical procedure, would invariably need replacement of this aortic segment. This strategy raises the question of the durability of such a tapered and often short landing zone. We share this concern and attempted to accomplish the best possible stability with the currently available stent grafts by using reversed Valiant stent grafts with distal bare springs. This might prevent distal stent migration, which could lead to serious complications and might mechanically stabilize these often tenuous landing zones. In this series with a follow-up of up to three years, we have not observed the new occurrence of a distal type endoleak after complete exclusion of the aneurysm.

4.5 Visceral artery management
We overstented 10 celiac arteries with no surgical revascularization without any associated adverse events. This strategy can only be successful if a detailed evaluation of the visceral arterial anatomy and possible anatomic variants is performed preoperatively. This observation, however needs confirmation in larger cohort. We do not advocate omitting a bypass to the common hepatic artery if an open surgical revascularization to other visceral or renal arteries is required. We always attempt to choose the safest strategy for a given patient, and if an open surgical procedure has to be performed anyways, a bypass to the celiac arterial system adds another layer of security should another visceral bypass not remain patent. In addition, we strongly advocate the revascularization of the inferior mesenteric artery (IMA) at the time of an open surgical procedure, as we lost our only patient in the hospital due to the lack of an IMA bypass. This patient initially did well and probably would have another fate if the inferior mesenteric artery had been revascularized at the time of the stent graft procedure.


   5. Summary
Top
 Abstract
 1. Introduction
 2. Materials and methods
 3. Results
 4. Discussion
 5. Summary
6. Conclusion
 Appendix A
 References
 
We presented a series of 21 patients treated with endovascular stent grafts and selective simultaneous open visceral artery revascularization, attempting to push the limits of currently available stent graft therapy. Endovascular management of TAAA is work intensive, can only be performed by a surgeon able to perform open TAAA surgery and is best accomplished by a dedicated team. The current early results, which include a learning curve, appear comparable to few centers of excellence performing large volume open TAAA surgery.


   6. Conclusion
Top
 Abstract
 1. Introduction
 2. Materials and methods
 3. Results
 4. Discussion
 5. Summary
 6. Conclusion
Appendix A
 References
 
Despite these encouraging early results, further follow up is needed and caution should be used before expanding a combined hybrid endovascular treatment approach to good surgical candidates for open TAAA repair. Endovascular stent grafting with selective visceral revascularization for the treatment of TAAA appears to be associated with low mortality and paraplegia rates, especially in cases with acute presentation including aortic rupture.


   Appendix A
Top
 Abstract
 1. Introduction
 2. Materials and methods
 3. Results
 4. Discussion
 5. Summary
 6. Conclusion
 Appendix A
References
 
Conference discussion

Dr R. Griepp (New York, NY): My question is, in how many of these patients were you able to preserve both hypogastric or internal iliac arteries, because of course we think those are very important to spinal cord perfusion?

Dr Siegenthaler: Yes, I agree with you. We preserved them in all patients in this series and did not occlude any internal iliac arteries. I actually had one case where we did an abdominal stent after a thoracic endograft. One of the iliac limbs was too long and covered a hypogastric artery, and the patient immediately lost his motor evoked potentials. So we used a very aggressive therapy algorithm that Dr Weigang had implemented at our clinic: We lowered the CSF pressure and raised the mean arterial blood pressure really high. Subsequently the MEPs recovered within a short time. But I think it is very crucial that the hypogastric arteries stay open.

Dr Griepp: I agree.

Dr H. Shennib (Phoenix, AZ): This is a really challenging group of patients, and the issues always with treating thoracoabdominal aneurysms is the length of the graft and the landing zones. You are always worried that if you extend and you keep on covering more of the aorta you risk spinal nerve injury, and the second issue is usually where do you land the graft and how do you preserve the important visceral branch vessels.

Now, you mentioned that you have actually covered the celiacs in some of those patients and got away with it, but you didn’t really tell us about the landing zone in those patients. Were you sparing the SMAs, recognizing that they are involved or not involved in the aneurysmal disease? How do you select your patients and how do you select your landing zone in patients with more than celiac artery occlusion? And how often do you resort to doing a debranching procedure with those patients?

The second question I have has to do with the type of graft that you put in. Now, I see that those are Medtronic, and I am not sure whether it is a Talent or a Valiant graft, and the other one is a Gore graft. And I am assuming that because you reversed the free landing zone that it is a reversed Valiant or Gore TAG graft?

Dr Siegenthaler: No, the Gore graft cannot be reversed but the Medtronic graft can be reversed on the OR table.

Dr Shennib: Well, that was my comment. Medtronic comes in and you don’t need to reverse it, particularly with the Valiant graft. I just wanted to get your opinion as to how do you choose your graft, and have you actually resorted at any time of putting the graft in from above, from the subclavian or axillary?

Dr Siegenthaler: To the Valiant graft, you can order the graft reversed and the company delivers it to you. But as I showed in the talk, a large proportion of these patients came with ruptures or urgent presentations. In such situations, it takes too long to order grafts. So what you can do with the Valiant stent graft, you can deploy it on the OR back table and reverse it yourself. This works very well and nicely. So if you have a stack of stents in different sizes for emergencies ready and you have one of those cases where you can’t wait, this can be a very nice option to choose the approach to reverse it. It cannot be done with the Gore because of the different deployment system.

In terms of the stent graft landing zone, I think we broke pretty much every rule in this series that you read about. In many cases of this series our landing zones were significantly shorter than 2 cm. Since the results of open conventional surgery in these often poly-morbid patients really aren’t that great, we will try to do the case with a short landing zone, and we will explain to all the patients that there is a significant risk that there might be an endoleak and that there will be a possibility that ultimately they will have to undergo a large operative procedure.

So this basically also answers to your next question: We did a debranching procedure only when it was absolutely necessary. If we felt that there was a possibility to get away leaving that usually slightly more narrow segment of a thoracoabdominal aneurysm at the visceral arteries intact and seal it on both sides or do an infrarenal replacement in addition to a very large stent graft just at the level of the celiac artery, we chose that approach in order to avoid a debranching procedure.

And then in terms of your last question about antegrade stent deployment, I only have used this for arch debranching cases. Otherwise with the Valiant system, which has a very nice deployment system and is pretty stiff, you can overcome even severe kinking at the thoracoabdominal junction and you can get up here and land the stent graft where you want to have it.


   Footnotes
 
{star} Presented at the 21st Annual Meeting of the European Association for Cardio-thoracic Surgery, Geneva, Switzerland, September 16–19, 2007.


   References
Top
 Abstract
 1. Introduction
 2. Materials and methods
 3. Results
 4. Discussion
 5. Summary
 6. Conclusion
 Appendix A
 References
 

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