Endovascular repair of blunt thoracic aortic injury: Techniques and tips

Since the initial report1Semba C.P. Kato N. Kee S.T. Lee G.K. Mitchell R.S. Miller D.C. et al.Acute rupture of the descending thoracic aorta: repair with use of endovascular stent grafts.J Vasc Intervent Radiol. 1997; 8: 337-342Abstract Full Text PDF PubMed Scopus (217) Google Scholar of treating blunt aortic injuries (BAI) with endovascular methods, its application in the traumatically injured patient has continued to gain acceptance and use. This may be attributed to an increase in the number of available thoracic stent grafts as well as the accumulation of experience by endovascular specialists. Additionally, experience has revealed several important procedural details that help ensure a successful result. This article describes the techniques and tips that may be useful to optimize outcomes for this high-risk group of patients. Over the past decade, diagnostic evaluation associated with trauma patients has rapidly progressed to multidetector spiral computed tomography (CT) imaging for the vast majority of injuries. While a recent report claims that CT scanning has supplanted aortography as the gold standard for diagnosing BAI2Demetriades D. Velmahos G.C. Scalea T.M. Jurkovich G.J. Karmy-Jones R. Teixeira P.G. et al.Operative repair or endovascular stent graft in blunt traumatic thoracic aortic injuries: results of an American Association for the Surgery of Trauma Multicenter Study.J Trauma. 2008; 64 (discussion 570-1.): 561-570Crossref PubMed Scopus (318) Google Scholar, there are shortcomings of axial imaging that warrant mention. CT imaging should be performed with 1-2 mm intervals to optimize the detection and evaluation of intimal defects of the aorta. However, due to emergent conditions and the need to obtain images of multiple body regions (head, neck, chest, abdomen/pelvis) this sometimes cannot be accomplished, and 3-5 mm intervals are used. As such, axial images can be misleading or suboptimal when evaluating the aorta in the typical location for BAI, the isthmus. Therefore, it is critical that three-dimensional and centerline reconstructions be performed to identify not only the location of the injury but also accurately measure the aortic diameter and the distance from branched vessels. In cases where thoracic imaging is suboptimal or pelvic imaging (to appropriately evaluate the iliac arteries) is missing, it has been our practice to perform a second, more detailed CT. In instances where femoral access is felt to be too small for delivery of the stent graft, iliac or aortic conduits can be utilized. Conduits should be avoided, however, in patients with pelvic fractures or hematomas. If the lesion location requires coverage of the left subclavian artery (SCA), then additional imaging will be required to determine if the patient possesses dominant left vertebral artery (VA) architecture. This will either involve additional CT imaging of the head and neck or intraoperative bilateral vertebral angiography. Whether left SCA coverage is required will depend upon the location of the lesion and the degree of aortic curvature. The absolute and relative indications for left SCA revascularization at our institution are listed in the Table. It has been our practice to maintain left SCA antegrade perfusion in cases where the patient has left VA dominance. Our approach is to use a parallel stent technique (Fig 1) instead of performing a carotid to SCA bypass or transposition. This technique has been successful as most lesions from BAI are along the inferior curve of the aorta and placing a bare stent from the subclavian along the superior aspect of the aorta has not increased the incidence of type Ia endoleaks in our experience.TableIndications for left subclavian revascularizationAbsolute indicationsLeft inferior mammary artery bypassStenotic or occluded right vertebral arteryLeft vertebral terminating in the posterior inferior cerebellar arteryLeft vertebral arising from the archRelative indicationsLeft-hand dominant individualsLarge left vertebral in comparison to the rightExtensive thoracic coverage Open table in a new tab Access for intraprocedural angiographic visualization also warrants some discussion. In most cases, access through the left brachial artery provides excellent interrogation of the great vessel origins and the vertebral arteries. If parallel stenting is necessary, sheath access is already established prior to stent graft deployment. In cases where the left SCA perfusion is not a concern, access can be accomplished by either the ipsilateral or contralateral femoral artery depending upon the vessel diameter and delivery catheter size. Until recently (June 2008), only the Gore TAG device (W. L. Gore and Associates, Flagstaff, Ariz) was approved for implantation in to the thoracic aorta for aneurysmal disease. While its use for BAI is considered off-label, it has been used successfully with few exceptions or complications. There are now three devices commercially approved for thoracic aortic aneurysmal disease, enabling the treatment of aortic sizes between 18 mm and 42 mm in diameter. While each of the three devices has different proximal and distal configurations, none of them has a disease specific indication for treating aortic transections. As such, they are prone to certain device specific complications. Prior to June 2008, when the endovascular specialist encountered a patient with an aortic intimal diameter less than 23 mm, infrarenal aortic cuffs were typically utilized to exclude the lesion.3Rosenthal D. Wellons E.D. Burkett A.B. Kochupura P.V. Hancock S.M. Endovascular repair of traumatic thoracic aortic disruptions with “stacked” abdominal endograft extension cuffs.J Vasc Surg. 2008; 48: 841-844Abstract Full Text Full Text PDF PubMed Scopus (20) Google Scholar, 4Riesenman P.J. Farber M.A. Rich P.B. Sheridan B.C. Mendes R.R. Marston W.A. et al.Outcomes of surgical and endovascular treatment of acute traumatic thoracic aortic injury.J Vasc Surg. 2007; 46: 934-940Abstract Full Text Full Text PDF PubMed Scopus (61) Google Scholar This allowed better device apposition against the inferior wall of the aortic arch and eliminated oversizing that in certain instances lead to device collapse.5Muhs B.E. Balm R. White G.H. Verhagen H.J.M. Anatomic factors associated with acute endograft collapse after Gore T.A.G.treatment of thoracic aortic dissection or traumatic rupture.J Vasc Surg. 2007; 45: 655-661Abstract Full Text Full Text PDF PubMed Scopus (139) Google Scholar While criteria for oversizing and neck lengths have not been established through clinical trials, endovascular experts consider the traditional oversizing seen with aneurysmal disease not as crucial since device migration is not a significant concern. Typically, devices are oversized approximately 10% for the treatment of BAI. Proximal neck length should be adequate to achieve exclusion of the lesion and may be impacted by the radius of curvature of the aorta. This can be achieved with less proximal neck length than the instructions for use recommends. Device positioning is governed by aortic curvature to ensure that the device aligns parallel to the aortic centerline rather than the specific position relative to the left SCA. While the addition of two new devices extends the treatment options for BAI, adequate devices with tapered configurations to treat small aortas are still not available. The patient is typically taken to the operating room in an expeditious fashion. While the procedure can be undertaken with local or regional anesthesia, most patients receive general anesthesia, unless contraindications exist, allowing for better control of breathing patterns during subtracted angiography of the chest. The procedure can be performed with or without heparin if necessary. In our institution, heparin is given at 80 units/kg unless contraindicated (associated closed head injury or other high risks for bleeding). Typically, stiff wires are used during the procedure (Lunderquist [Cook Inc, Bloomington, Ind] or Meier [Boston Scientific, Natick, Mass]) and retroflexed off the aortic valve. Once this has been established, the device can be brought up near the intended implantation site. Once appropriate angles and orientation is determined, then the device is deployed under fluoroscopic guidance. Correct image intensifier orientation and angle is critical for precise device placement. Angiographic delineation of the anatomy is achieved with a perpendicular view to the aortic arch (usually 35to 50 degrees left anterior oblique views). If necessary, vertebral angiography can also be conducted prior to device insertion if intracranial imaging was not obtained prior to surgery and left SCA coverage is planned. The final device orientation should approach a parallel configuration of the proximal stents with respect to the aortic centerline and achieve lesion exclusion (Fig 2). While some vascular specialists advocate reducing the mean blood pressure during deployment of thoracic devices, we have found it to be both device and disease specific and do not routinely employ its use. In cases where the patient is very hyperdynamic and the device cannot be positioned along the outer curve to enable precise deployment, reducing blood pressure with either inflow occlusion balloons or pharmacologic means may be helpful in achieving a more accurate deployment. While there is no published follow-up protocol currently, we routine follow our patients at 1, 6, and 12 months and then yearly for the first 5 years. After 5 years, we have been more liberal with our follow-up intervals and have extended it to every 2 to 3 years with noncontrasted imaging to reduce the life-long radiation exposure to the patient. Prior to the advent of endovascular therapy for BAI, there was a trend to delay the open repair of some injuries until the patient was relatively stable. However, this was not without some increased risk for rupture.6Hemmila M.R. Arbabi S. Rowe S.A. Brandt M. Wang S.C. Taheri P.A. et al.Delayed repair for blunt thoracic aortic injury: is it really equivalent to early repair?.J Trauma. 2004; 56: 13-23Crossref PubMed Scopus (63) Google Scholar Since the advent of thoracic endovascular aneurysm repair (TEVAR), we have rarely delayed the repair of a blunt aortic injury. On occasion when there is no periaortic hematoma and a small intimal defect is seen on CT imaging, we have observed and re-imaged the patient several days later to monitor the lesion. We have now performed over 25 endovascular aortic repairs for aortic transection with several different devices.4Riesenman P.J. Farber M.A. Rich P.B. Sheridan B.C. Mendes R.R. Marston W.A. et al.Outcomes of surgical and endovascular treatment of acute traumatic thoracic aortic injury.J Vasc Surg. 2007; 46: 934-940Abstract Full Text Full Text PDF PubMed Scopus (61) Google Scholar A recent meta-analysis of open vs endovascular repair reported several significant findings that are import to highlight.7Xenos E.S. Abedi N.N. Davenport D.L. Minion D.J. Hamdallah O. Sorial E.E. et al.Meta-analysis of endovascular vs open repair for traumatic descending thoracic aortic rupture.J Vasc Surg. 2008; 48: 1343-1351Abstract Full Text Full Text PDF PubMed Scopus (233) Google Scholar Seventeen retrospective studies were reviewed over a 4-year period between 2003 and 2007. While all the studies were nonrandomized, there were a total of 589 patients treated (369 open and 220 endovascular). The average time to repair was 1.5 vs 1 day, respectively, and was not statistically different between the two groups. Even though injury severity score was higher for the endovascular (EV) patients, the procedural mortality, 30-day mortality, and the paraplegia risk was lower for the EV group. These combined data are similar to our published series.4Riesenman P.J. Farber M.A. Rich P.B. Sheridan B.C. Mendes R.R. Marston W.A. et al.Outcomes of surgical and endovascular treatment of acute traumatic thoracic aortic injury.J Vasc Surg. 2007; 46: 934-940Abstract Full Text Full Text PDF PubMed Scopus (61) Google Scholar While there are no devices approved for treating thoracic transections, endovascular repair has rapidly become the preferred method of management for BAI at most major medical centers. Whether this is a result of the decreased incidence of spinal cord ischemia, morbidity or mortality is difficult to determine. Several technical tips should be discussed to avoid acute complications of device collapse and treatment failure. Device selection (diameter, conformability, and configuration) is critical in obtaining treatment success. Devices should be oversized approximately10%, however, current devices do not address aortic diameters that are less than 18 mm in diameter (frequently seen in the younger population). In addition, current devices lack distal aortic arch conformity. Both of these issues may contribute to device failure via device collapse and nonexclusion of the lesion.5Muhs B.E. Balm R. White G.H. Verhagen H.J.M. Anatomic factors associated with acute endograft collapse after Gore T.A.G.treatment of thoracic aortic dissection or traumatic rupture.J Vasc Surg. 2007; 45: 655-661Abstract Full Text Full Text PDF PubMed Scopus (139) Google Scholar It is for this reason that some vascular specialists prefer to use infrarenal aortic cuffs in an attempt to obtain better outcomes. Understand, however, that multiple components may also lead to treatment failure. Left SCA coverage is not always required, and device positioning should be based upon ideal device location to ensure exclusion of the injury. This may require coverage in a significant number, but not all patients. It is therefore critical to have adequate vertebral imaging to avoid posterior strokes. One must also keep in mind that more proximal device deployments have been associated with an increased incidence of stroke in patients being treated for aneurysmal disease.8Fairman R.M. Criado F. Farber M. Kwolek C. Mehta M. White R. et al.Pivotal results of the Medtronic Vascular Talent Thoracic Stent Graft System: the VALOR trial.J Vasc Surg. 2008; 48: 546-554Abstract Full Text Full Text PDF PubMed Scopus (231) Google Scholar While SCA revascularization may reduce paraplegia risks for patients with aneurysmal disease, the risk of paraplegia with EV repair of BAI is almost nonexistent with only one reported case.9Doss M. Wood J.P. Balzer J. Martens S. Deschka H. Moritz A. Emergency endovascular interventions for acute thoracic aortic rupture: four-year follow-up.J Thorac Cardiovasc Surg. 2005; 129: 645-651Abstract Full Text Full Text PDF PubMed Scopus (66) Google Scholar As a result of the limited invasiveness of the procedure, certain trauma patients can be treated in a more expeditious fashion. In patients with concomitant head injuries, there may be a benefit compared with delayed open repair, by allowing more aggressive management of blood pressure to maximizing cerebral perfusion. Whether this will result in improved outcomes remains to be seen. Repair of BAI has undergone significant change in the past 5 years. Imaging and device selection are critical to obtain successful outcomes. Disease specific devices that will accommodate the smaller aortic sizes and distal arch conformity that are encountered in this distinct patient population is crucial in allowing this therapy to move forward in the future.