Double-Barrel Technique for Preservation of Aortic Arch Branches During Thoracic Endovascular Aortic Repair

Article Outline

• Abstract
• Introduction
• Methods
• Results
• Discussion
• References
• Copyright

Thoracic endovascular aortic repair (TEVAR) may involve either planned or inadvertent coverage of aortic branch vessels when stent grafts are implanted into the aortic arch. Vital branch vessels may be preserved by surgical debranching techniques or by placement of additional stents to maintain vessel patency. We report our experience with a double-barrel stent technique used to maintain aortic arch branch vessel patency during TEVAR. Seven patients underwent TEVAR using the double-barrel technique, with placement of branch stents into the innominate (n = 3), left common carotid (n = 3), and left subclavian (n = 1) arteries alongside an aortic stent graft. Gore TAG endografts were used in all cases, and either self-expanding stents (n = 6) or balloon-expandable (n = 1) stents were utilized to maintain patency of the arch branch vessels. In three cases the double-barrel stent technique was used to restore patency of an inadvertently covered left common carotid artery. Four planned cases involved endograft deployment proximally into the ascending aorta with placement of an innominate artery stent (n = 3) and coverage of the left subclavian artery with placement of a subclavian artery stent (n = 1). TEVAR using a double-barrel stent was technically successful with maintenance of branch vessel patency and absence of type I endoleak in all seven cases. One case of zone 0 endograft placement with an innominate stent was complicated by a left hemispheric stroke that was attributed to a technical problem with the carotid-carotid bypass. On follow-up of 2-18 months, all double-barrel branch stents and aortic endografts remained patent without endoleak, migration, or loss of device integrity. The double-barrel stent technique maintains aortic branch patency and provides additional stent-graft fixation length during TEVAR to treat aneurysms involving the aortic arch. Moreover, the technique uses commercially available devices and permits complete aortic arch coverage (zone 0) without a sternotomy. Although initial outcomes are encouraging, long-term durability remains unknown.

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Introduction 

Successful endovascular stent-graft repair of thoracic aortic aneurysms involving the aortic arch requires sufficient proximal neck length for stent-graft fixation and seal, while preserving perfusion to critical aortic arch branches. Aortic arch “debranching” performed through a median sternotomy or utilizing extra-anatomic cervical bypass or vessel transposition is commonly used to create additional proximal neck length for stent-graft fixation and seal during thoracic endovascular aortic repair (TEVAR). However, open arch debranching can increase procedural complexity and morbidity, offsetting some of the benefit of endovascular repair. Custom-made branched stent grafts have been employed for arch aneurysm repair, but experience with these devices remains limited and investigational.

We first reported placement of an additional branch stent alongside the aortic stent graft (the “double-barrel” technique) as a “bail-out” procedure after inadvertent coverage of the left carotid artery during a TEVAR case.¹ Since that time, we have employed this technique for preservation or restoration of aortic arch branch vessel patency during TEVAR in six additional patients. We have found the double-barrel technique to be a useful strategy for preservation of branch vessel patency during repair of aneurysms involving the aortic arch and report our experience herein.

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Methods 

All patients who underwent TEVAR with double-barrel stent placement for preservation of aortic arch branch vessel patency at the University of California San Francisco Medical Center between 2005 and 2007 were included in this study. The study was approved by the institutional review board in accordance with governing and institutional policies. Patients underwent the double-barrel stent procedure during TEVAR either to treat inadvertent coverage of the left carotid artery (n = 3) or as a planned procedure intended to maintain patency of an aortic arch branch when patients were considered to be poor candidates for surgical “debranching” procedures (n = 4). Patient demographics and procedural details are summarized in Table I.

Table I. Patient demographics and operative details

CT, computed tomography; MRA, magnetic resonance angiography; CAD, coronary artery disease; CRF, chronic renal failure; COPD, chronic obstructive pulmonary disease.

All procedures were performed in a dedicated operating room using either a fixed or portable c-arm fluoroscopy unit. If cervical bypass and/or transposition were a planned part of the procedure, this was performed prior to TEVAR. All procedures were performed under general anesthesia with systemic heparinization. Carotid to carotid bypass was performed with a polytetrafluoroethylene (PTFE) graft tunneled in the retropharyngeal position. Either left carotid to left subclavian bypass (using PTFE graft) or transposition was performed to accomplish left subclavian revascularization. When indicated, the proximal left subclavian artery was occluded proximal to the left vertebral artery origin by direct ligation or as a staged procedure by subsequent coil embolization via left brachial artery access.

Gore TAG (W.L. Gore, Flagstaff, AZ) stent grafts were delivered through open femoral artery access over a Lunderquist wire (Cook, Bloomington, IN) in all cases. An angiographic pigtail catheter was placed into the ascending aorta from a percutaneous contralateral femoral approach. Retrograde catheterization of surgically exposed right common carotid or left common carotid arteries was used for introduction of either innominate or left common carotid artery stents, respectively. The left brachial artery was accessed for placement of the left subclavian artery branch stent. Wire and sheath access was gained from the branch vessel into the ascending aorta alongside the undeployed stent graft. The branch stent was advanced and positioned with its proximal edge adjacent to the proximal edge of the Gore TAG graft within the aortic arch (Fig. 1a). Angiography was again performed to confirm positioning, followed by rapid sequential deployment of the TAG graft and then the branch stent (Fig. 1b). Deployment of the two stents occurred in rapid succession and was performed by separate operators overseeing the branch artery and aortic devices. Stents involving the innominate branch artery were deployed with the back end of the stent positioned proximal to the right carotid artery origin. Simultaneous “kissing balloon” dilatation of the aortic stent graft with a Gore Tri-Lobe balloon and the branch artery stent with an appropriately sized angioplasty balloon was performed to optimize graft-stent and graft-wall apposition (Fig. 1c). Prior to both stent-graft deployment and ballooning, the systolic blood pressure was reduced to 80 mm Hg with vasodilators. Ballooning of the stents was similarly performed with rapid insufflation and deflation within seconds to avoid prolonged outflow obstruction or cerebral ischemia. Lastly, completion angiography was performed to assess the repair and aneurysm exclusion.

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• Fig. 1 

  A Aortic stent graft and branch stent positioning. B Postdeployment. C Balloon angioplasty postdeployment.

Double-barrel stents placed for rescue purposes after inadvertent arch branch coverage were, of course, performed in slightly different sequence. Upon recognition of inadvertent graft coverage of the left carotid orifice, the left common carotid artery was exposed through a cutdown incision in the lower neck and retrograde catherization was performed. Wire access into the ascending aorta was obtained followed by branch stent deployment alongside the aortic stent graft as described above.

All patients were maintained on clopidogrel (75 mg daily) and aspirin (81 mg daily) postoperatively. All patients underwent computed tomographic (CT) angiography prior to discharge unless contraindicated due to renal dysfunction. One patient who did not undergo proximal left subclavian artery ligation or embolization at the time of the primary procedure underwent left brachial catheterization and embolization prior to discharge for treatment of a type II endoleak. Follow-up included CT angiography at regular intervals; however, two patients were lost to follow-up.

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Results 

Seven patients underwent TEVAR using the double-barrel stent technique for treatment of thoracic aortic aneurysms involving the aortic arch (Table I). In three cases the technique was used to manage unintended left carotid coverage during TEVAR and involved retrograde branch stent placement to restore left common carotid artery perfusion. The four planned double-barrel stent procedures included three patients who underwent total arch stent graft coverage with placement of an innominate artery branch stent and cervical bypasses to provide brachiocephalic perfusion. The remaining planned procedure involved placement of a branch stent to maintain patency of a covered left subclavian artery.

Placement of the double-barrel branch stent was technically successful in all cases. Operative time ranged from 3.5 and 7.0 hr. Blood loss averaged 350 mL, with a maximum blood loss of 700 mL. Completion angiography showed exclusion of the aortic pathology with no perigraft contrast in five out of seven cases. In one patient there was a small proximal type I endoleak that had resolved by CT angiography on postoperative day 3. In another patient, a type II endoleak from the left subclavian artery was treated by percutaneous coil embolization on postoperative day 6.

A unifying feature of the four planned procedures was the presence of a short proximal aortic neck length between the innominate or subclavian arteries and the aneurysm. These four cases involved necks (center-line distance between distal edge of branch artery to proximal aneurysm margin) that were 12, 12, 10 (innominate arteries), and 11 (subclavian artery) mm in length. Additional length for proximal fixation gained via double-barrel stenting in these cases was 12, 22, 12, and 24 mm, respectively. In every case the double-barrel technique provided a total proximal neck fixation length >20 mm (Fig. 2).

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• Fig. 2 

  A Preoperative three-dimensional reconstruction and postoperative B three-dimensional and C multiplanar reconstructions of double-barrel endovascular repair with cervical debranching.

Review of perioperative complications revealed no episodes of myocardial infarction, pneumonia, or wound complications. There were no instances of perioperative renal insufficiency. Hospital stay ranged 3-12 days with the exception of the patient suffering polytrauma who required an extended inpatient course for care of intra-abdominal and spinal injuries unrelated to TEVAR. One case of zone 0 endograft placement with an innominate stent was complicated by a left hemispheric stroke that was attributed to a technical problem with the carotid-carotid bypass, requiring revision of the bypass graft on postoperative day 1. This patient eventually recovered full neurological function and lives independently. This same patient also required treatment for atrial fibrillation during the postoperative course.

Clinical follow-up ranged from 2 months to 2 years. Two patients died during follow-up, at 9 and 30 months, respectively, of non-device- or aneurysm-related causes. There were no reports of delayed stroke, aortic rupture, or other morbidity/mortality related to aortic arch repair. No secondary procedures were required after hospital discharge. One patient experienced neurological decline during follow-up that was considered by his neurologist to be consistent with progression of preexisting Parkinson disease. On radiographic follow-up of 2-18 months, all double-barrel stents and endografts remained patent without endoleak, aneurysmal expansion, migration, or loss of device integrity. There has been no evidence of branch vessel dissection, stenosis, or occlusion to date.

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Discussion 

Endovascular stent graft approaches offer attractive, minimally invasive alternatives to open surgical repair of the thoracic aorta.², ³ However, treatment of aneurysms involving the aortic arch remains challenging due to the critical requirement to maintain perfusion of the arch branches. Stent-graft deployment within the arch with coverage of the subclavian, carotid, or innominate arteries requires additional adjunctive strategies to maintain blood flow to the brachiocephalic vasculature.⁴ Currently, endovascular treatment of aneurysms involving the aortic arch most often utilizes a hybrid approach with surgical “debranching” through cervical or sternotomy exposures to maintain brachiocephalic perfusion.⁵, ⁶, ⁷, ⁸, ⁹, ¹⁰ When compared to traditional open surgical repair, hybrid approaches may lessen morbidity and mortality by avoiding hypothermic circulatory arrest and aortic cross-clamping.¹¹, ¹², ¹³ However, hybrid techniques often still subject the patient to risks associated with sternotomy. Risk is especially heightened in patients who require redo sternotomy after prior cardiac surgery due to extensive adhesions and limited access to the ascending aorta for purposes of bypass. Cervical debranching via extra-anatomic bypass or transposition is also used as an adjunct during hybrid arch repair but has its own inherent morbidity in patients who either are poor operative candidates or require urgent cephalic revascularization. Endovascular repair of aortic arch aneurysms using fenestrated and branched aortic arch stent grafts with single or multiple limbs to maintain brachiocephalic perfusion have been reported;¹⁴, ¹⁵ but these devices remain investigational, and availability is very limited. Finally, complete stent-graft coverage of the aortic arch after extra-anatomic retrograde femoral-axillary bypass and carotid-carotid bypass to maintain brachiocephalic perfusion has been described.

Utilizing a double-barrel stent strategy, we have been able to maintain patency of aortic arch branches while minimizing or eliminating adjunctive surgical debranching procedures. This technique may further minimize perioperative morbidity associated with TEVAR procedures for treatment of aneurysms with arch involvement and short proximal necks. Furthermore, this strategy utilizes commercially available devices and, when applied to the left carotid and left subclavian arteries, may allow for elimination of cervical debranching. The double-barrel stent technique was first described by our group as a “bail-out” solution to treat inadvertent coverage of the left carotid orifice during TEVAR.¹ Since that time, Criado¹⁶ has described a series of eight patients who underwent placement of a bare metal stent interposed between the thoracic endograft and aortic wall. This technique was utilized for maintenance of patency in inadvertently covered left subclavian (n = 2) and left carotid (n = 6) arteries during TEVAR. The technique was technically successful in all patients, with maintained stent patency during limited follow-up and no instances of stroke, paralysis, or death.

We have also used the double-barrel technique to maintain patency of aortic arch branches that were intentionally covered during TEVAR.¹⁷ Most notably, we have used the technique in three patients with endograft coverage of all aortic arch branches (zone 0) and placement of a double-barrel stent to maintain patency of the innominate artery. In these three cases brachiocephalic perfusion was maintained via the innominate double-barrel stent and cervical bypass grafts and/or vessel transposition, allowing for exclusion of the entire aortic arch without median sternotomy for arch debranching. Successful aneurysm exclusion was achieved in all patients, though one patient suffered a stroke attributed to a technical problem with the carotid-carotid bypass.

The main benefit of the double-barrel technique is that it provides a greater length of aorta for proximal stent-graft fixation in aneurysms with relatively short necks. Theoretically, lengthening the zone of fixation can improve stent-graft orientation within the thoracic aorta and prevent lifting or “beaking” of the stent graft away from the inner curvature of the arch, which has been associated with stent-graft collapse. Importantly, it must be understood that while the double-barrel technique provides additional proximal fixation length, it does not provide additional proximal seal (Fig. 3). The branch stent pushes the aortic stent graft away from the aortic wall and thereby does interfere with complete circumferential apposition of the aortic stent graft to the aortic wall within the double-barrel stent segment. Proximal seal is only obtained distal to the double-barrel segment. Hence, a fundamental concept in this technique is that some amount of aortic neck distal to the double-barrel area is necessary to obtain an adequate zone of seal and prevent proximal type I endoleak. We have found the properties of the Gore TAG device to be well suited to this technique. The short nitinol stent rings permit deformation of the stent graft within the double-barrel zone without significantly altering wall apposition and seal distal to the double-barrel branch stent. Other stent-graft devices may also be suitable, but our experience with this technique is limited to the TAG device. Moreover, we have found that the double-barrel technique enables endovascular repair of thoracic aortic aneurysms with short necks that would otherwise be considered unsuitable for TEVAR. Of note, in our four cases where this technique was planned preoperatively, the proximal necks were all <12 mm in length. Arch aneurysms without any proximal neck distal to the innominate artery origin should not be treated with this technique.

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• Fig. 3 

  Double-barrel stent model demonstrating fixation and seal zones.

While the double-barrel technique may extend and simplify the application of endovascular techniques for treatment of aneurysms involving the aortic arch, obvious concerns about potential complications and durability still need to be understood before broader application can be advocated. Significant hemodynamic forces within the aortic arch and direct mechanical interaction between the branch stent and the aortic stent could lead to stent fracture or vessel injury. Loss of device integrity and catastrophic stent failure could lead to branch occlusion and major stroke. Fortunately, the smaller-diameter branch stent provides greater radial force than the larger-diameter thoracic endografts, maintaining patency of the aortic arch branch. As a failsafe against kinking or compression of the branch stent, a second stent was generally deployed within the branch stent to provide additional reinforcement.

We elected to size the branch stent to the maximum diameter of the branch artery, and the need for oversizing is unknown. It is unclear whether the choice of branch stent (covered vs. bare, self-expanding vs. balloon-expandable) impacts procedural success and long-term durability. Self-expanding stents were used in all but one of our cases because of concerns about compression or deformation of balloon-expandable stents. Care was taken to position the proximal edge of the branch stent adjacent to the proximal edge of the Gore TAG graft, thereby constraining the branch stent in position throughout its length. The space between the branch stent and the aortic stent graft creates a cul-de-sac that could serve as a site for thrombus formation and a source for cerebral emboli. For this reason, we have placed all patients on clopidogrel and use of a covered stent within the aortic branch may be more desirable.

Given the importance of accurate evaluation of fixation zones, seal zones, and vessel diameter, all patients who are being considered for aortic arch repair via double-barrel stents should undergo high-quality fine-cut CT angiography with three-dimensional and multiplanar reconstruction analysis. Presence of significant aortic arch thrombus, complex atheroma, or severe branch vessel stenoses found on preoperative imaging is considered a relative contraindication to the double-barrel procedure due to increased risk of neurological complications from embolization. Bovine trunk anatomy can complicate procedural planning for the double-barrel reconstruction. There were no cases of bovine anatomy in our series. However, we could envision two strategies to maintain patency of the left common carotid artery in this circumstance: carotid-carotid bypass with placment of a branch stent into the innominate artery or placement of kissing stents in the left common carotid artery and innominate artery. Innominate artery diameter may dictate which strategy is better suited in individual cases. We have no personal experience with placement of more than one branch stent into different arch branches to create “multiple barrels,” but this may be possible.¹⁸

In summary, the double-barrel technique may extend the limits of TEVAR through preservation of aortic arch branches while avoiding the need for sternotomy. Using this technique, proximal fixation can be obtained well into the ascending aorta (zone 0) for endovascular exclusion of arch pathology. Furthermore, the technique utilizes devices that are readily available. Follow-up of patients is limited at this time, and hence, the durability of this procedure remains unproven. Candidates for open reconstruction or contemporary hybrid endovascular procedures should not be offered this strategy as a primary option until further data can establish durability and freedom from late complications. Nonetheless, the double-barrel stent graft may be a viable alternative for arch aneurysm repair in those patients unfit for sternotomy and aortic clamping.

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