Visceral/Renal Artery Debranching for Complex Thoracoabdominal Hybrid Procedures via Retroperitoneal Abdominal Aortic Exposure: A Preliminary Report
Article Outline
Visceral/renal artery debranching can lengthen the distal landing zone in patients with complex thoracoabdominal aortic disease, thus enabling endograft repair. Initial reports of “hybrid” procedures are promising, but they usually describe transperitoneal visceral/renal artery exposure. This clinical series describes four complex thoracoabdominal aortic aneurysm/dissection cases in which the visceral and renal artery debranching procedure was accomplished via a retroperitoneal approach.
Accomplishing endovascular aneurysm exclusion with a secure proximal and distal sealing region can be a challenging task in the treatment of patients with complex thoracoabdominal aortic pathology. In many cases the arterial disease process involves the entire descending thoracic aorta and ends near or within the visceral aortic segment. To enable endograft repair, the distal landing zone can be lengthened by first debranching the visceral/renal arteries. Initial reports of these so-called hybrid procedures are promising, but they usually describe transperitoneal visceral/renal artery exposure.1, 2, 3, 4, 5, 6 This clinical experience describes four complex thoracoabdominal aortic aneurysm (TAA)/dissection cases in which the visceral and renal artery debranching procedures were accomplished via a retroperitoneal approach.
Case 1
An 81-year-old male patient with previous transperitoneal tube graft repair of a ruptured abdominal aortic aneurysm (AAA) in 1985 presented with a 9 cm type III TAA. Past medical history included recent left lower lobe lumpectomy for nonmetastatic adenocarcinoma, hypertension, non-insulin-dependent diabetes, hypercholesterolemia, hypertriglyceridemia, cigarette abuse, and chronic renal insufficiency with impending renal failure. In this case, the risk of open surgical repair of the TAA was considered to be too high due to the fact that the patient had had a left thoracotomy 4 months previously and had multiple significant comorbid medical conditions. To further complicate matters, the patient's creatinine was >3.0, kidney length was 8 cm bilaterally, and the old infrarenal tube graft had a 90-degree kink in its midbody (Fig. 1). The patient was advised that treatment of the TAA would very likely result in permanent renal failure. A two-stage open visceral and renal debranching/endovascular procedure was proposed for complete exclusion of the TAA.
Fig. 1
Magnetic resonance study demonstrating type III TAA with infrarenal graft kink.
In the first-stage procedure, the old Dacron graft was exposed via a left retroperitoneal approach. A 10 mm Dacron tube graft was secured end-to-side to the old graft superior to the 90-degree kink but also at least 2 cm inferior to the proximal suture line. This graft was then anastomosed end-to-end to the very distal external iliac artery just above the inguinal ligament to facilitate straight passage into the abdominal aorta for subsequent endovascular TAA exclusion. Retrograde bypass to the celiac axis, superior mesenteric artery (SMA), and left renal artery was performed using a 14 × 7 mm trifurcated Dacron graft (Vascutek, Inchinnin, UK) that had its origin inferior to the graft kink (Fig. 2).7 Right renal artery bypass was performed using a separate 6 mm Dacron graft that was also secured end-to-side to the old graft inferior to the graft kink (Fig. 2). The visceral/renal graft origins were positioned as described so that graft occlusion would not occur when the endograft introducer sheath was subsequently passed through the 10 mm graft conduit for the second-stage procedure.
Fig. 2
Intraoperative photo demonstrating aortoiliac graft conduit superiorly and retrograde bypass grafts to visceral/renal arteries inferiorly. Note that the single limb graft crosses over the distal aspect of the TAA to its destination at the right renal artery.
In the second-stage procedure performed 2 weeks later, a cerebrospinal fluid (CSF) drain was placed to minimize spinal cord ischemia in light of the fact that he had prior AAA repair. Endovascular repair of the TAA was performed from distal to proximal. Intravascular ultrasound (IVUS) was used to identify the distal 2.5 cm landing zone, which was within the old graft between the infrarenal anastomotic suture line and the proximal graft hood of the 10 mm Dacron conduit. A 26 mm × 10 cm TAG thoracic endoprosthesis was deployed at this distal level. Complete TAA exclusion was then performed using three more TAG endografts deployed proximally in successive fashion.
Renal insufficiency continued to worsen between cases despite the fact that the renal bypass grafts were noted to be patent by angiography during the second procedure, as were the visceral grafts. Ultimately, this case was complicated by permanent renal failure, which was an expected outcome in light of the patient's elevated preoperative creatinine level and small kidney size. This patient died of metabolic and renal complications 8 months following the hybrid procedure.
Case 2
A 47-year-old hypertensive female with chronic renal failure had emergent repair of an acute DeBakey type III aortic dissection tear using a single TAG thoracic endoprosthesis for mediastinal bleeding complications. The endograft was deployed just distal to the origin of the left subclavian artery. Postdeployment angiography demonstrated near-complete sealing of the dissection tear, and at this point it was felt prudent to follow the patient closely as opposed to risking aortic rupture by either aggressively ballooning the proximal seal area or deploying a second device. The widened mediastinum returned to normal, back pain abated, hypertension was controlled, and the patient was discharged to home 14 days later.
However, follow-up computed tomography (CT) scan performed at 1 month demonstrated a 6 cm dilation of the dissected descending thoracic aorta, and the patient reported persistent smoldering back pain. Thoracic aortography demonstrated a type I endoleak with filling of the aneurysmal false lumen, and there also appeared to be at least one reentry site at the level of the celiac axis. A single-stage open visceral debranching/endovascular procedure was proposed to lengthen the distal landing zone and to repair the distal reentry sites. Left carotid-to-subclavian artery bypass with proximal ligation of the subclavian artery was also proposed to lengthen the proximal landing zone, to prevent retrograde subclavian artery flow, and to ensure successful treatment of the type I endoleak and dilated false lumen.
In the second-stage procedure, a CSF drain was placed to minimize spinal cord ischemia due to the extent of aortic dissection and because of planned coverage of the left subclavian artery. Renal artery debranching was not performed because the patient was already dialysis-dependent, and the visceral aorta was exposed via a left retroperitoneal approach. Left nephrectomy was performed to facilitate this exposure. Retrograde infrarenal aortic-to-celiac axis–SMA bypass was performed using a bifurcated 12 × 6 mm Dacron graft, and a 10 mm Dacron graft conduit was sewn end-to-side to the graft body to facilitate TAG endograft deployment as the iliac artery diameter was too small (Fig. 3). The type I endoleak was successfully repaired by extending the proximal landing zone and deploying a second TAG endoprosthesis proximal to the previously deployed endograft. Retrograde left subclavian artery flow was eliminated by ligating the subclavian artery proximal to the vertebral artery, and left upper extremity perfusion was maintained by left common carotid-to-subclavian artery bypass. The distal reentry sites at the celiac axis level were successfully covered with a third TAG endoprosthesis, and the intervening nonaneurysmal descending thoracic aorta was left uncovered to maintain spinal cord perfusion.
Fig. 3
Intraoperative photo demonstrating Dacron graft conduit attached to the body of the bifurcated retrograde aorta–visceral bypass graft. This conduit was ligated proximally following endograft repair of the aortic dissection.
This case was complicated by spinal cord ischemia with resultant bilateral lower extremity paraparesis despite the purposely uncovered segment of distal descending thoracic aorta. She also had a severe hypertensive episode in the early postoperative period that caused acute cerebellar hemorrhage/stroke. This intracerebral bleed resulted in right upper extremity paraparesis. This patient was noted to be ambulatory with persistent lower extremity weakness at 12-month follow-up, but the upper extremity weakness had resolved.
Case 3
A 74-year-old female with significant smoking history with chronic obstructive pulmonary disease, hypertension, claudication, and valvular heart disease presented with a 7 cm type II TAA. Arch aortography demonstrated an insufficient seal zone distal to the subclavian artery and 60% stenosis of the proximal left common carotid artery. Abdominal aortography demonstrated bilateral renal artery fibromuscular disease with origin stenosis of right renal artery and severe aortoiliac occlusive disease with calcified tortuous iliac arteries. Pertinent surgical history included aortic valve replacement with ascending aortic aneurysm repair in 2003. Surgical risks were considered too high for total open TAA repair; therefore, a two-stage hybrid open/endovascular procedure was proposed for complete exclusion of the TAA.
In the first-stage procedure, the patient underwent aorto–left common femoral–right common iliac artery bypass with a 24 × 12 mm bifurcated Dacron graft via a left retroperitoneal approach. She also had retrograde aortic-to-celiac–SMA–bilateral renal artery bypass using a trifurcated 12 × 6 mm Dacron graft with a fourth 6 mm Dacron limb sewn end-to-side to the graft body. This quad-limbed graft was positioned with graft origin on the right limb of the 24 × 12 mm bifurcated Dacron graft so that when the 24F TAG endoprosthesis delivery sheath was passed through the left limb of the aortofemoral bypass graft it would not cause visceral/renal ischemia during the second procedure.
In the second-stage procedure, performed 2 weeks later, a CSF drain was placed and the proximal landing zone was lengthened by performing left common carotid–subclavian artery bypass using a 6 mm Dacron tube graft. Retrograde open left proximal common carotid artery stent deployment for stenosis at this level preceded the carotid–subclavian bypass to ensure normal inflow. An Amplatzer (AGA Medical, Plymouth, MN) occluding device was then deployed in the proximal left subclavian artery through the distal hood of the bypass graft to eliminate a potential type II endoleak. Successful endovascular repair of the TAA was then performed from distal to proximal using four TAG endoprostheses. Figure 4 demonstrates angiographic evidence of patent visceral/renal artery graft limbs. The previously deployed left common carotid artery stent proved to be an excellent radiographic marker for accurate deployment of the most proximal TAG endoprosthesis.
Fig. 4
Intraoperative angiogram demonstrating patent multigraft limbs to visceral and renal arteries. (From left to right) Graft limbs are anastomosed to the right renal artery, left renal artery, SMA, and celiac axis.
This case was complicated by occipital hemorrhage/stroke, which resulted in temporary bilateral visual field defects. The patient also had temporary lower extremity paraparesis, and fortunately both complications were completely resolved by 3 months postoperation. Follow-up at 12 months demonstrated the patient was doing well.
Case 4
A 76-year-old male with a history of hypertension, atrial flutter, and severe emphysema presented with very tortuous type III TAA. Past surgical history was significant for aortobi-iliac repair of an infrarenal AAA in 2003 with a 24 × 12 mm bifurcated Dacron graft, and this procedure was performed via a left retroperitoneal approach. The patient was considered to be too high a risk for total open repair of the TAA due to emphysema, and a two-stage procedure was proposed including visceral/renal debranching followed by endograft exclusion of the TAA.
In the first-stage procedure, retroperitoneal exposure of the old infrarenal graft and abdominal aorta was once again performed using a left flank incision. Intense retronephric scarring precluded medial rotation of the left kidney, so it was left in situ; the abdominal aorta/old graft was exposed by medial reflection of the sigmoid colon and spleen. A quad-limbed graft was constructed as described in case 3 except that the trifurcated graft size was 14 × 7 mm. This multilimbed graft was attached end-to-side to the proximal aspect of the right limb of the old graft so that the 24F TAG endoprosthesis delivery sheath that would subsequently be passed through the left limb would not cause visceral/renal ischemia (Fig. 5).
Fig. 5
Intraoperative photo demonstrating redo retroperitoneal aortic exposure with left kidney left in situ (top). (From top to bottom) Graft limbs are anastomosed to the left renal artery, celiac axis, SMA, and right renal artery. The left renal vein crosses the aorta just superior to the right renal artery bypass graft.
In the second-stage procedure, performed 2 weeks later, a CSF drain was placed to minimize the risk of spinal cord ischemia in light of the fact that he had prior AAA repair. IVUS was used to identify the distal 2.5 cm landing zone, which was within the body of the old graft. The TAA was successfully repaired from distal to proximal using four TAG endoprostheses to ensure maximal graft overlap due to the tortuosity of the thoracic aorta. This case was not associated with a single complication at 10-month follow-up.
Discussion
Current thoracic endograft devices are well designed for arterial disease that is limited to the thoracic aorta. However, many cases are quite complex, as described above, and may involve the thoracoabdominal aorta proximal to the subclavian artery as well as distal to the diaphragmatic crura. To further complicate matters, large thoracic and thoracoabdominal aortic aneurysms usually become quite tortuous with time, often contain intraluminal thrombus, and can have calcified aortic walls. Providing secure endograft fixation with appropriate-length proximal and distal sealing regions can be a challenging task in these situations.1
As opposed to infrarenal devices that typically require 1.5 cm of aortic neck length to provide an adequate fixation zone and seal for aneurysm exclusion, additional sealing length is needed in the thoracic aorta.1, 8, 9 Additional fixation length proximal to arterial disease that encroaches upon the subclavian artery can be obtained in the aortic arch by either performing preliminary left carotid–subclavian artery bypass or covering the left subclavian artery during the procedure. Although most patients can tolerate acute coverage of the subclavian artery, our approach has been to first revascularize this vessel before endograft deployment to maintain prograde blood flow in the vertebral and subclavian arteries.8 Endovascular occlusion of the proximal subclavian artery using an Amplatzer device, for instance, can then be performed in retrograde fashion through the distal graft hood.
It is also crucial to obtain complete sealing distally; however, in many cases the aortic disease process involves the entire descending thoracic aorta and ends near or within the visceral segment. In these cases, obtaining a secure seal zone and adequate distal fixation can be problematic. This situation is compounded by the fact that thoracic endograft deployment mechanisms are currently designed for precise proximal positioning with minimal control over the distal landing zone or attachment site.1 Therefore, it is often necessary to lengthen the distal neck by performing visceral and renal artery debranching procedures prior to stent-graft repair of the thoracoabdominal aortic disease process.1, 2, 3, 4, 5, 6
The celiac axis and SMA are located in close proximity to each other in a large majority of patients. Thus, both vessels must be debranched to ensure adequate distal neck length when the disease process extends to this level.1 Total visceral and renal artery debranching is required to facilitate subsequent endograft repair when the thoracoabdominal aortic process extends through the visceral aorta into the infrarenal aorta. The choice of inflow source for retrograde bypass to these vessels must take into consideration any previous aortic surgery and the extent of aortoiliac occlusive or aneurysmal disease. When there is concomitant infrarenal aneurysmal or occlusive disease, the location of the iliac donor site should be well planned. For instance, the retrograde bypass graft or grafts may need to originate from either the very distal common iliac or external iliac artery so that the subsequent endograft used for infrarenal aortic aneurysm repair does not occlude the graft origins.1, 2, 3, 4, 5, 6 Also, it is wise to position any retrograde graft remote from the subsequent planned course of a large-caliber delivery sheath so that visceral/renal ischemia does not occur during endograft deployment. In some cases, infrarenal bypass grafting may be indicated, as discussed in case 3, to treat severe aortoiliac occlusive disease and to provide an adequate-caliber conduit for an endoprosthesis.
Using a multilimb bypass graft and a retroperitoneal approach, the celiac axis, SMA, and both renal arteries can all be debranched in a relatively straightforward fashion. In our practice the visceral and renal vessels are ligated proximally and then transected to facilitate eversion endarterectomy, if needed, and end-to-end grafting as opposed to end-to-side configurations. The right renal artery is best approached after the other vessels have been debranched and the iliolumbar vein(s) has been divided just inferior to the left renal artery as the viscera, left renal vein and left kidney can be further retracted medially. In addition, the Omni-Tract (Minnesota Scientific, St. Paul, MN) renal vein retractor can be positioned on the right renal artery side of the aneurysm from the patient's left flank and used to gently retract laterally. This maneuver widens the working area at the origin of the right renal artery. In our preliminary experience, patients seem to tolerate retroperitoneal visceral/renal artery debranching in a similar fashion as they do with any other aortic procedure performed using this operative approach.10
The graft limbs are constructed so that they course right along the native aorta in retrograde fashion, and this decreases the potential for graft limb kinking. In addition, since the grafts lay in an extraperitoneal plane, there is essentially no risk of graft–bowel contact with the potential for graft–enteric erosion. Redo retroperitoneal paravisceral/renal aortic exposure can be accomplished as discussed in case 4, but it is advisable to leave the left kidney in situ instead of redeveloping a retronephric plane of dissection.
Conclusions
Definitive hybrid TAA/dissection repair requires considerable forethought regarding paravisceral/renal aortic exposure, bypass graft origin, and subsequent endovascular maneuvers in relation to the visceral and renal bypass grafts. This preliminary experience demonstrates the feasibility of total retroperitoneal visceral and renal artery debranching combined with endovascular exclusion for repair of complex thoracoabdominal aortic pathology. However, despite this “minimalistic” approach, these cases demonstrate that major surgical complications persist, particularly during the second-stage endovascular exclusion procedure.
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PII: S0890-5096(07)00303-2
doi:10.1016/j.avsg.2007.07.021
© 2008 Annals of Vascular Surgery Inc. Published by Elsevier Inc All rights reserved.
