Journal of Vascular Surgery
Volume 43, Issue 2, Supplement , Pages A81-A84, February 2006

Visceral vessel relocation techniques

  • Mark A. Farber, MD

      Affiliations

    • Corresponding Author InformationReprint requests: Mark A. Farber, MD, Division of Vascular Surgery, University of North Carolina, CB #7212, 2145 Bioinformatics Bldg, Chapel Hill, NC 27599-7212.

University of North Carolina Hospitals, Chapel Hill, NC.

Received 25 October 2005; accepted 26 October 2005.

Article Outline

 

It has been more than a decade since the first implantation of a thoracic stent graft was reported, and only recently has the first device been approved by the Food and Drug Administration.1, 2 Even though the technology has been approved by the Food and Drug Administration for 5 years for infrarenal aneurysmal repair, devices for use in the thoracic aorta are considered first generation and are limited by constraints similar to those that infrarenal devices are subject to. Additionally, complicated devices that allow for fenestration or branched designs are lacking or are only in the initial phases of development.3

Providing adequate distal fixation and accomplishing aneurysm exclusion with an appropriate sealing region is the most challenging task in many patients.4 Almost all infrarenal devices require 1.5 cm of aortic neck length to provide adequate fixation and seal for aneurysmal exclusion. Additional length is needed in the thoracic aorta, however, given its larger size; 2.0 to 3.0 cm is generally thought to be sufficient. Some experts rely on a ratio calculation and target a fixation length of 0.75 times the aortic diameter as a minimal acceptable length. It is also crucial that the aortic walls be fairly parallel and free of significant calcification and thrombus. Although isolated thoracic aortic lesions can still meet these requirements, many thoracic aortic processes involve the entire descending thoracic aorta and end at, or near, the crus of the diaphragm or in the visceral section. In these cases, obtaining adequate fixation can be problematic. The angle of the descending thoracic aorta also plays a major role in the migration of thoracic stent grafts, possibly causing a cephalad migration of the caudal aspect of the device. It can also make precise deployment rather difficult; many times it is necessary to deploy an additional distal extension.5 Implanting the device in a region where significant angulation exists can jeopardize the durability of the endovascular repair. Finally, most stent graft deployment mechanisms are designed for precise proximal placement with minimal or no control over the distal attachment site or landing zone. Therefore, accurate deployment near the celiac artery becomes more challenging. Given the aforementioned issues, it is advisable to lengthen the distal neck by performing aortic debranching techniques in a small but not insignificant number of patients.

Although additional fixation can be obtained on the proximal aspect of the aneurysm by either carotid subclavian bypass or coverage of the left subclavian artery, the visceral section of the aorta is less forgiving. Although there are reports of celiac artery coverage without incident, severe complications may arise from either hepatic or splenic ischemia, resulting in the potential demise of the patient.6, 7 It has been our approach to routinely revascularize all celiac arteries if coverage is planned unless certain contraindications exist. These include prohibitive abdominal surgical risks, a diminutive hepatic or inflow vessel that may potentially jeopardize collateral flow, or documented celiac artery occlusion. In patients who have a replaced right hepatic artery originating from the superior mesenteric artery (SMA), adequate collateral flow may exist to the liver. Documentation of adequate gastric and splenic flow is, however, still recommended.

Initial reports of hybrid procedures have described promising results.8, 9, 10, 11, 12, 13, 14 Before performing visceral procedures, it is important to evaluate the hemodynamic and anatomic status of the visceral section, including both renal arteries. Because most patients undergo detailed imaging with either magnetic resonance imaging or computed tomography for diagnosis, many of the anatomic aspects usually are already identified. If, however, any questions about the anatomy arise, visceral angiography can be performed. For hemodynamic evaluation we have relied on duplex ultrasonography, which has a high degree of accuracy when performed in experienced peripheral vascular laboratories. Once these studies have been completed, appropriate inflow vessels can be identified, and the baseline status of the patient can be documented.

Back to Article Outline

Celiac artery debranching 

In patients who require only a short amount of lengthening of the distal landing zone, one of three techniques can be used: celiac coil embolization, renohepatic bypass, or celiac revascularization from the aortoiliac region. Although renosplenic bypass could be performed, it has never been reported in the literature. In patients being evaluated for celiac coil embolization, consideration must be given to the preservation of splenic function. Prior reports of splenic artery embolization have documented preservation of immunoprotective function in patients through collaterals and the short gastrics.15, 16 However, these have been performed in patients without thoracic aortic disease processes. The likelihood of preserved protection may be reduced in patients with aneurysmal disease, given the reduced number of intercostals and the disease process. Appropriate vaccines should therefore be given before the procedure if there is any potential for the loss of splenic function. Additionally, it is important to document the collateral circulation from the SMA to the liver before coil embolization.

As mentioned previously, severe complications have been reported when the celiac artery has been acutely occluded.6, 7 To help preserve collateral flow after embolization, all efforts should be made to place the coils only in the main celiac trunk. In isolated cases where the aneurysm ends above the celiac artery and the stent graft will abut the orifice of the celiac artery, coil embolization may not be necessary, because the device will perform the same function as coils placed in the artery. However, caution is advised in this situation: if a type II endoleak from the celiac artery occurs after the deployment of the stent graft, access is extremely limited, if not impossible, via endovascular means.

Celiac artery revascularization can be achieved from several approaches, of which the renohepatic bypass is probably the most simple and well tolerated. Designed primarily to treat renal occlusive disease before endovascular techniques, the bypass procedure can used in reverse fashion (Fig 1). Most procedures are performed through a subcostal incision, although a midline celiotomy can be used if necessary. The hepatic artery is identified through the lesser omentum. Control and anastomosis proximal to the gastroduodenal artery (GDA) is ideal, although not always possible. After a Kocher maneuver is performed, the inferior vena cava, right renal vein, and right renal artery are identified and dissected. Additionally, the celiac artery should be dissected before heparinization so that it may be ligated at the completion of the procedure. An appropriate conduit, either autologous or synthetic, should be chosen to match the target vessel diameters. Many surgeons prefer the autologous saphenous vein when treating patients with occlusive renal disease, because it may impart a greater long-term patency. This concern has not been documented in the treatment of patients without occlusive disease. After systemic heparinization, the side-to-end renal anastomosis is usually performed first, followed by the hepatic artery reconstruction in an end-to-side fashion. Generally the bypass follows a gentle curved “C” configuration. If needed, an end-to-end anastomosis can be performed to the GDA. Caution should be taken when the GDA is used, because it provides important mesenteric collateral flow should complications arise with the bypass. Once the bypass is completed and satisfactory flow is established, the celiac artery should be ligated at its origin to avoid the potential for subsequent type II endoleak.

When renal artery disease precludes usage of the renal artery as an inflow source, retrograde bypass can be performed from the aortoiliac segment. Antegrade bypasses (supraceliac or descending thoracic aorta) are generally not possible, given the proximity of the aneurysm to the visceral section. However, it should be noted that in type IV thoracoabdominal aortic aneurysms, antegrade bypass techniques can serve as a means for visceral debranching to provide an avenue for endovascular repair in selected patients.

In patients for whom the infrarenal aorta will be used as the inflow source, several considerations exist. Patients with thoracic aneurysms may develop extension of their disease to the infrarenal aorta, thereby involving the inflow site, or the infrarenal aorta may contain significant atherosclerotic disease, thus affecting the durability of the bypass. Some surgeons therefore use the iliac arteries as inflow sources. In this scenario, passage of the thoracic endograft past the inflow bypass graft should be avoided, and the contralateral iliac should be used for endovascular graft deployment. If this is not possible, then consideration should be given to a simultaneous iliac conduit. In either situation, the bypass is tunneled in a retropancreatic fashion and anastomosed to the celiac artery. Prosthetic conduits are generally used in this situation, given their longer length.

Back to Article Outline

SMA reconstructions 

In a large number of patients, the celiac and SMA are located in proximity to one another, and both vessels must be relocated to ensure adequate neck length. A transabdominal approach is required for adequate exposure. The choice of inflow source is usually determined by either previous aortic surgery or the extent of aneurysmal or occlusive disease. When infrarenal aneurysmal disease is concomitant, the location of the iliac donor site is critical: if future endovascular repair of abdominal aortic aneurysm is planned, then the bypass may need to originate from either the very distal common iliac or external iliac artery, depending on their individual lengths and the extent of disease involvement. Either bifurcated or individual grafts can be constructed, depending on the anatomy. The celiac artery limb is tunneled much as described previously, and the SMA limb placed in a lazy “C” configuration.

Back to Article Outline

Complete visceral revascularization 

On occasion, the entire visceral section must be revascularized. Inflow source, celiac artery, and SMA considerations are identical to those already mentioned. In addition, prefabricated Dacron (DuPont, Wilmington, Del) branched grafts can be used. Each renal artery should be considered separately. For the left renal artery, three options exist: splenorenal bypass, iliorenal bypass, or attachment to one limb of the celiac or SMA reconstruction. The right renal artery similarly can be managed with a heporenal bypass, iliorenal bypass, or attachment to the visceral reconstruction limb. The method for iliorenal bypass has been described previously and involves an end-to-side anastomosis to the inferior aspect of the renal artery.8 Either prosthetic or autologous bypass can be performed and generally tunneled underneath the ureter.

Back to Article Outline

Special considerations 

Type IV thoracoabdominal aortic aneurysms merit special mention. Because visceral involvement is associated with proximal attachment site issues, additional options should be considered. Descending thoracic aorta reconstruction can be performed that allows for complete visceral debranching, because only partial occlusion clamps are used and the procedure is well tolerated.8 This process is achieved through two stages. The first stage consists of a thoracoceliac, thoracomesenteric, and left renal bypass. The patient is positioned in the right lateral decubitus orientation after intubation with a double-lumen endotracheal tube. A bean bag and axillary roll are routinely required to aid in positioning. A ninth-interspace thoracoretroperitoneal incision is used to expose the thoracic and upper abdominal aorta (Fig 2). Mobilization of the peritoneum and its contents from the undersurface of the diaphragm is performed bluntly. The diaphragm is incised in a curvilinear fashion 2 cm from its costal edge to preserve innervation and with marking stitches to facilitate reapproximation. The inferior pulmonary ligament is divided, as well as the crus of the diaphragm. The celiac and superior mesenteric vessels are exposed until a suitable bypass graft site is obtained. The left kidney is undisturbed in its native position to facilitate distal exposure of the SMA. A partial occlusion clamp technique is used to maintain distal aortic flow to the kidneys and spinal cord. The proximal anastomoses are performed with a single clamp application to minimize repeated trauma to the thoracic aorta. Prosthetic bypass graft conduits are used and routed through the diaphragmatic hiatus to their respective vessels in an end-to-side fashion to establish antegrade flow. We typically use two separate grafts for mesenteric bypass. In our opinion, this allows greater freedom in graft orientation, although a bifurcated graft is an acceptable alternative. Revascularization of the left kidney is accomplished with a bypass graft from the thoracomesenteric graft to the left renal artery. The second stage of the repair consists of a bypass graft from the right external iliac artery to the right renal artery through a retroperitoneal exposure and endovascular abdominal aortic aneurysm repair to provide complete exclusion of the aneurysm (Fig 3). In all reconstructions, the proximal portion of the reconstructed vessels is ligated to prevent type II endoleak after endovascular repair.

The descending thoracic aorta is relatively free of atherosclerotic disease. Thoracoretroperitoneal revascularization provides several technical advantages. It allows for easy exposure of the thoracic and abdominal aorta, and, when necessary, concomitant procedures can be performed for renal and lower extremity revascularization. It is, however, more difficult in patients who have undergone prior left chest surgery. Because the descending thoracic aorta is rarely diseased, only partial occlusion is required, thereby reducing the potential for renal and spinal cord ischemia associated with supraceliac clamping. Even in debilitated patients, the incision is well tolerated.

Back to Article Outline

Conclusion 

Until branched and fenestrated endograft techniques become widely distributed, hybrid surgery will be necessary to reduce the major morbidity and mortality associated with thoracoabdominal aneurysm repair. Because of the complexity of the disease and comorbid conditions encountered in this patient population, the approach to each patient should be individualized, taking into account the risks and benefits of all options, including open surgical repair, observation, and hybrid procedures. Furthermore, the potential need for future procedures and plans should be considered thoroughly.

Back to Article Outline

References 

  1. Volodos NL , Karpovich IP , Shekhanin VE , Troian VI , Iakovenko LF . [A case of distant transfemoral endoprosthesis of the thoracic artery using a self-fixing synthetic prosthesis in traumatic aneurysm] . Grudn Khir . 1988;6:84–86
  2. Dake MD , Miller DC , Semba CP , Mitchell RS , Walker PJ , Liddell RP . Transluminal placement of endovascular stent-grafts for the treatment of descending thoracic aortic aneurysms . N Engl J Med . 1994;331:1729–1734
  3. Saito N , Kimura T , Odashiro K , Toma M , Nobuyoshi M , Ueno K , et al.   Feasibility of the Inoue single-branched stent-graft implantation for thoracic aortic aneurysm or dissection involving the left subclavian artery (short- to medium-term results in 17 patients) . J Vasc Surg . 2005;41:206–212 discussion 12
  4. Criado FJ , Clark NS , Barnatan MF . Stent graft repair in the aortic arch and descending thoracic aorta (a 4-year experience) . J Vasc Surg . 2002;36:1121–1128
  5. Ellozy SH , Carroccio A , Minor M , Jacobs T , Chae K , Cha A , et al.   Challenges of endovascular tube graft repair of thoracic aortic aneurysm (midterm follow-up and lessons learned) . J Vasc Surg . 2003;38:676–683
  6. Sunder-Plassmann L , Orend KH . Stentgrafting of the thoracic aorta-complications . J Cardiovasc Surg (Torino) . 2005;46:121–130
  7. Greenberg RK , O’Neill S , Walker E , Haddad F , Lyden SP , Svensson LG , et al.   Endovascular repair of thoracic aortic lesions with the Zenith TX1 and TX2 thoracic grafts (intermediate-term results) . J Vasc Surg . 2005;41:589–596
  8. Fulton JJ , Farber MA , Marston WA , Mendes R , Mauro MA , Keagy BA . Endovascular stent-graft repair of pararenal and type IV thoracoabdominal aortic aneurysms with adjunctive visceral reconstruction . J Vasc Surg . 2005;41:191–198
  9. Rimmer J , Wolfe JH . Type III thoracoabdominal aortic aneurysm repair (a combined surgical and endovascular approach) . Eur J Vasc Endovasc Surg . 2003;26:677–679
  10. Kotsis T , Scharrer-Pamler R , Kapfer X , Liewald F , Gorich J , Sunder-Plassmann L , et al.   Treatment of thoracoabdominal aortic aneurysms with a combined endovascular and surgical approach . Int Angiol . 2003;22:125–133
  11. Watanabe Y , Ishimaru S , Kawaguchi S , Shimazaki T , Yokoi Y , Ito M , et al.   Successful endografting with simultaneous visceral artery bypass grafting for severely calcified thoracoabdominal aortic aneurysm . J Vasc Surg . 2002;35:397–399
  12. Lundbom J , Hatlinghus S , Odegard A , Eide TO , Lange C , Aasland J , et al.   Combined open and endovascular treatment of complex aortic disease . Vascular . 2004;12:93–98
  13. Quinones-Baldrich WJ , Panetta TF , Vescera CL , Kashyap VS . Repair of type IV thoracoabdominal aneurysm with a combined endovascular and surgical approach . J Vasc Surg . 1999;30:555–560
  14. Chiesa R , Melissano G , Civilini E , Setacci F , Tshomba Y , Anzuini A . Two-stage combined endovascular and surgical approach for recurrent thoracoabdominal aortic aneurysm . J Endovasc Ther . 2004;11:330–333
  15. Reidy JF , Rowe PH , Ellis FG . Splenic artery aneurysm embolisation—the preferred technique to surgery . Clin Radiol . 1990;41:281–282
  16. Nincheri Kunz M , Pantalone D , Borri A , Paolucci R , Pernice LM , Taruffi F , et al.   Management of true splenic artery aneurysms. Two case reports and review of the literature . Minerva Chir . 2003;58:247–256

 Competition of interest: Dr Farber has been paid a consulting fee or been on the speaker’s bureau for Medtronic, Cook, and WL Gore.

PII: S0741-5214(05)01883-5

doi:10.1016/j.jvs.2005.10.055

Journal of Vascular Surgery
Volume 43, Issue 2, Supplement , Pages A81-A84, February 2006

Article Tools

* Image Usage & Resolution