Volume 36, Issue 2 , Pages 152-157, August 2008
Improved Outcomes with Endovascular Stent Grafts for Thoracic Aorta Transections
Article Outline
Abstract
Objective
To retrospectively assess the outcome of endovascular stent-graft implantation for thoracic aortic transections (ETAT).
Design
Retrospective review.
Methods
16 patients median age 30 years, treated between May 2000 and April 2007. Median injury severity score was 33 (range 29 to 66) in 14 acute patients; 2 patients had thoracic pseudoaneurysms. The Cook-Zenith endograft was used in eight patients, Medtronic-Talent (6) and Gore-Excluder (2). Average procedure time was 90 minutes, blood loss 100 (range 40 to 3000) mls, screening time 10.8 (range 5.9 to 22.6) minutes, and contrast dose was 195 (range 60 to 400) mls.
Results
Graft deployment was successful in all cases. There was one death within 30 days. The left subclavian artery was completely covered in one case, and partially in three. Two patients had Type I endoleak, and one delayed Type II endoleak. One patient had iatrogenic right coronary artery dissection. Two patients developed difficult to treat hypertension, and one acute renal failure.
Conclusion
Endovascular intervention is a safe and effective treatment for aortic transection in multiple trauma patients. ETAT reduces the major morbidity and mortality associated with open repair in multiple trauma patients. The majority of these patients are young and long-term follow up is necessary to assess graft durability.
Keywords: Thoracic aortic transection, Multiple trauma, Stent-grafts
Introduction
Thoracic aortic rupture or transection (TAT) is an acute and commonly fatal, deceleration or blunt injury, associated with multiple trauma. Rupture of the thoracic aorta is the second most common cause of death from motor vehicle accidents (after head injury) with an overall mortality of over 90%.1, 2 TAT is immediately fatal in 85% of cases, and of those arriving in hospital alive, 60 to 70% will survive if given appropriate and timely treatment.3
TAT typically involve the intima and media; is nearly always transverse to the axis of the vessel, and may be complete or incomplete as characterized by Parmley et al.1 Over ninety percent of TAT occur in the ‘peri-isthmic’ region of the thoracic aorta, adjacent to the ligamentum arteriosum and just distal to the left subclavian artery.4, 5 The mechanism of injury of TAT is thought to involve sudden deceleration in high-speed impacts, especially frontal, or right and left side impacts, and perhaps associated with vehicle roll.2, 3 This frequently involves shearing or bending stresses, from movement of the relatively mobile aortic arch with respect to the descending aorta.6, 7, 8 Patients with TAT usually have multiple injuries, and patients in the Prospective Study of Blunt Aortic Injury had a mean Injury Severity Score of 42.3
The first successful surgical repair of TAT was reported in 1960,9 and standard recommended management included angiography and urgent surgery.1 Surgery is usually performed via a posterolateral thoracotomy, using a clamp and sew technique, or cardiopulmonary bypass; and carries a substantial risk of death and paraplegia.10 Some authorities have encouraged delayed operative management, in patients with multiple severe associated injuries, until a physiologically more appropriate time.11, 12, 13 Aggressive medical management is used to ‘stabilize’ patients until operative repair, but the risk of fatal aortic rupture remains.3 Some patients however do survive without treatment and may develop chronic pseudoaneurysms, or even complete resolution.14
The advent of endovascular stent-graft therapy has revolutionized the repertoire of treatment options for vascular diseases.15, 16, 17 The first case of endovascular management of TAT was reported in 1988.15 Further reports established that treatment with endovascular stents is technically feasible, less invasive, and associated with less physiological insult to critically injured patients.18, 19 We report our seven-year experience of endovascular therapy for patients with thoracic aortic injury (ETAT).
Methods
We retrospectively reviewed all patients with TAT presenting to two Level I trauma centres in Sydney, New South Wales, Australia between May 2000 and April 2007. All patients with multiple injuries, were scored for injury severity on admission using an anatomical scoring system, and further assessed, investigated and managed with the multiple trauma protocol (Advanced Trauma Life Support guidelines).20, 21
All trauma victims had a chest radiograph. The radiographic findings that most accurately indicate the possibility of mediastinal blood include disturbance of the normal shadows of the mediastinal contour, (obscured aortic arch or descending aorta; abnormal contour of the arch; loss of the aorto-pulmonary window; widening of the left paraspinal stripe or extension to the left extra-pleural apex and right paratracheal soft tissue density). A widened mediastinum (greater than 8
cm at the level of the arch), or a mediastinal/chest width ratio of >0.25% has been popular but unreliable, indicators of potential aortic injury. All patients with suspected TAT had contrast-enhanced computerized tomography (CTA), providing angiographic-like images of the aorta and great vessel.22, 23 Multi-detector CT confirmed the diagnosis of TAT in all cases, and the reconstructed images were used in planning for endovascular and open surgery24 (Fig. 1).
Figure 1
CTA of a patient with TAT used in planning endovascular (or open surgical) management.
In the early stages of this report open procedures were the most common treatment option offered, but endovascular procedures are now routinely offered as the first option in suitable patients. Altogether, 42 patients with a diagnosis of TAT were assessed (see Table 1). Thirty-nine patients with TAT were acute admissions from road traffic accidents; and one patient had a fall from five meters. Two patients aged 26 and 43 years, were referred for treatment, with a pseudoaneurysm from serious road accidents, 2 years and 9 months respectively, from various Pacific Islands; both were treated with endovascular procedures. Of the 40 acutely presenting patients, 14 had endovascular repair of their injuries, 12 had open surgery, and 14 patients died in the Emergency Department (ED) and prior to any intervention. Retrospective review suggested that seven of the 12 patients who had open surgery were unsuitable for the endovascular technique (e.g. short neck, arch involvement, luminal obstruction), reflecting case selection. The endovascular procedure was performed after other life threatening injuries were addressed.
Table 1. Details of patients diagnosed with TAT presenting to two Level I trauma centres in Sydney, New South Wales, Australia
| All patients (n=42) | Endovascular patients (n=16) | |
|---|---|---|
| Age | 28 (range 17 to 80) years | 30 (range 17 to 75) years |
| Sex | 35 males, 7 females | 13 males, 3 females |
| Injury Severity Score | 50 (range 24 to 75) | 33 (range 24 to 66) |
| Mechanism of injury | No of patients | No of patients |
| Fall from 5m | 1 | – |
| Pedestrian | 6 | 1 |
| Motorcycle rider | 6 | 1 |
| Motor vehicle driver | 18 | 12 |
| Motor vehicle passenger | 11 | 2 |
| Associated Injuries | Percentage | Percentage |
| Head | 64 | 62 |
| Abdominal | 47 | 52 |
| Limbs | 52 | 56 |
| Chest | 70 | 75 |
| Procedures | Number | Number |
| Endovascular | 16 | 16 |
| Open | 12 | – |
| None | 14 | – |
All procedures were performed in the operating theatre using a mobile C-arm; and with the cardiothoracic surgeons on standby. A single bolus of heparin was given to patients without concomitant cerebral, or solid abdominal organ injuries on a case-by-case basis. A femoral artery cutdown was performed, and percutaneous 5F pigtail calibrated catheter access was obtained from the other femoral artery for further diagnostic imaging (see Fig. 2). A 5F left brachial artery diagnostic catheter was additionally placed (in some cases) for accurate assessment and identification of the left subclavian artery origin.
Figure 2
Angiogram demonstrating TAT in a 17-year old male involved in a head-on motor vehicle accident.
A super-stiff wire was placed in the ascending aorta under fluoroscopic guidance, over which the endograft was positioned and deployed. All endografts were oversized by 10 to 20%,25 and deployed using a 22–24F delivery system. After deployment, the endograft was moulded as necessary using a Cook balloon (Cook Medical, Bloomingdale, Indiana, USA). In this study, we used transoesophageal echo to ensure accurate endograft placement, and completion angiography was performed to check graft position and to identify endoleaks, (see Fig. 3). Clinical examination, chest radiographs and CT follow-up was performed at one month, three months, six months, 12 months and annually thereafter, (see Fig. 4).
Figure 3
The intra-operative use of transoesophageal echo, and subclavian catheter for the accurate positioning and deployment of the endograft.
Figure 4
(CT) reconstruction of the thoracic aorta and great vessels in a patient with TAT after deployment of the endograft.
Results
Graft deployment was successful in all 16 cases; all grafts were introduced via the common femoral artery. The fourteen acute patients in our series had stent-graft placement at a median of 24 (range 6 to 96) hours after presentation to the ED, including after treatment of other concomitant life-threatening injuries and delayed diagnosis; there were no deaths in patients awaiting planned intervention for TAT. Three graft types were used for the 16 patients treated with endograft; the Cook-Zenith thoracic graft, the Talent thoracic endograft and the Gore thoracic endograft. The operative details are summarized in Table 2.
Table 2. Operative Details for patients who had endograft repair for traumatic aortic transection of the thoracic aorta
| Graft types | Cook-Zenith (8) |
| Medtronic-Talent (6) | |
| Gore-Excluder (2) | |
| Follow-up | 19 (range 10 to 63) months |
| Aortic diameter | 26 (range 22 to 30) mm |
| Graft diameter | 28 (range 24 to 34) mm |
| Length of aorta covered | 10 (range 10 to18) cm |
| Procedure time | 90 (range 35 to 402) minutes |
| Screening time | 10.8 (range 5.9 to 22.6) minutes |
| Contrast dose | 195 (range 60 to 400) mls |
| Blood loss | 100 (range 40 to 3000) mls |
| Left subclavian artery coverage | Complete: (1) |
| Partial: (3) | |
| Endoleak | Type I (2) |
| Type II (1) | |
| Number of stents | Single: 13 patients |
| Two: 3 patients |
There was one death, in a 17 year-old male with TAT, (who also sustained a severe head injury with a subdural haematoma, haemo-pneumothorax, with cervical spine, pelvic, rib and limb fractures), at Day 11 from complications related to his head injury. Major complications included a 23 year-old woman with an asystolic arrest as a result of iatrogenic dissection of the right coronary artery by the guide wire, after graft deployment. It was felt that the tip of the super-stiff guidewire managed to cause the dissection of this vessel. She proceeded to have successful coronary artery bypass by the cardiothoracic team; blood loss in this patient was approximately three litres.
Two patients developed difficult to treat hypertension in the early post-operative period, following thoracic endografting.26 Two further patients had injury to the access vessel, one needing a femoral artery patch, and one a brachial pseudoaneurysm repair. One patient without pre-existing renal dysfunction developed procedure-related acute renal failure, which recovered completely. No episodes of paraplegia were observed in this series.
Two small proximal Type I endoleaks were identified on completion angiography; the proximal attachment site of the graft was further ballooned and the endoleak became much less evident; and completely resolved by the first post-operative scans. A Type II endoleak was noted at two months in patients who needed two (2) overlapping stent-grafts for TAT repair. Overall there was one death in the 14 patients that were treated with stent-grafts acutely (7% mortality). This compares to the open surgical group with two deaths in the 12 patients (17% mortality). All complications in both the open and stented groups are shown in Table 3; and all surviving patients remain well on follow up.
Table 3. Complications in patients treated acutely with open surgical and endoluminal procedures
| Complication | Stented group (n=14) | Open Surgical group (n=12) |
|---|---|---|
| Death | 1 (7%) | 2 (17%) |
| Paraplegia | 0 | 1 (8%) |
| Endoleak | 3 (21%) | – |
| Renal Failure | 1 (7%) | 1 (8%) |
| Acute Limb Ischaemia | 0 | 1 (8%) |
| Vascular Access Injury | 2 (14%) | 2 (14%) |
| Wound Complications | 0 | 4 (28%) |
| DVT/PE | 0 | 1 (8%) |
Discussion
The majority of TAT (>90%) occurs in the peri-isthmic region of the thoracic aorta.1 The strength of the peri-isthmic aorta is 63%, and the descending aorta 80%, that of the ascending aorta respectively.7 Studies on the possible mechanisms of TAT, using human cadavers concluded that tethering of the descending aorta, by the parietal pleura is the principal aspect of this injury.27 In motor vehicle accidents, associated injuries including sternal fractures,28 are poor predictors of TAT, and crash and vehicle characteristics, including the use of seat belts and airbags are better indicators.29
Katyal et al., using a trauma registry and autopsy results, found 94% of TAT occurred in the peri-isthmic region, and were complete aortic transections; the average distance from the left subclavian artery along the inferior arch was 15 millimetres and 29 millimetres along the superior arch was.5 Borsa et al., investigating aortograms of patients with TAT, found the distance of the pseudoaneurysm from the left subclavian was 5.8 (range −8.9 to 34.5) mm along the lesser aortic curve, and 14.9 (range −16.1 to 56.0) mm along the greater curve.30 Our data, and other reports suggest that subclavian coverage is performed in over 25% of cases.19 Subclavian coverage is generally well tolerated in the absence of a contraindication, such as dominant left vertebral artery or coronary artery bypass, although complications have been described.31
Paraplegia is a catastrophic event, which occurs overall in 9.9% of patients following open repair of TAT. Von Oppell in a meta-analysis of open repair, also found that the cumulative risk of paraplegia increased with increasing aortic cross-clamp time.32 Paraplegia is a much less frequent occurrence with endovascular thoracic grafting.33 In a large series of patients undergoing open thoracoabdominal aneurysm repair, Griepp et al. found that the incidence of paraplegia increased when more than ten (10) intersegmental vessels were ligated.34 All but three grafts used in this report were single stents, with coverage of the minimal number of intercostal arteries.
Coronary artery dissection, as a complication of diagnostic and therapeutic coronary artery studies, have been steadily decreasing.35 The advent of endovascular aortic procedures by vascular surgeons have introduced different techniques and tools including larger gauge and stiffer wires, placed in the ascending aorta. One patient in our experience had a dissection of the right coronary artery caused by the super-stiff guidewire. To avoid this complication, Wellons et al. recommends placement of the guidewire into the right axillary artery, to allow tracking of the device to the level of the left subclavian artery.36 Our group is now much more vigilant with the guidewire and have incorporated the Wellons' technique in our strategy.
Rigid thoracic endografts, may not conform to the aortic arch, and sit at an angle, predisposing to graft instability, with endoleak, migration, collapse and pseudo-coarctation of the descending thoracic aorta. Angulation of the aortic arch is a significant factor in these younger patients (with TAT and steep angulation); and stent graft manufacturers define an upper limit of angulation beyond which they do not recommend the use of their grafts. However, a precurved arch endo-prosthesis is currently being developed, to minimize difficulties in deployment and complications, especially endoleak. The two small Type I endoleaks observed in this series completely resolved. A Type II endoleak was incidentally noted in one of our multiple trauma patients at two months. Two endograft patients developed hypertension, (which we previously reported),26 that proved difficult to treat, perhaps due to interference of aortic compliance, or the radial force of the endograft interfering with normal baroreceptor function by the endograft, but we have also noted this after open surgery.26
Minimally invasive endovascular stent-graft implantation offers an alternative, to conventional thoracotomy and surgical repair; but the relatively young age of this patient group with TAT is of concern, as the risks of device failure, including stent-fractures, migration, endoleak and aortic erosion, are all unknown. Jacobs and colleagues investigated the durability of stents in the abdominal and thoracic aorta in 684 patients, and found 8.7% of patients with device failure, including metallic stent fractures, suture disruptions, and graft holes.37 Fattori et al., noted persistent endoleak in 14% of 457 patients with thoracic endograft; including seven patients with aortic rupture and death; stent graft migration, graft fabric alteration, and modular disconnection were also observed.38 However, there is evidence that some patients with TAT may have complete healing, and endografts in these patients may serve as a temporary bridge over a critical period.12
In addition to questions of graft durability, stent grafts are being placed in younger and younger patients (from early teenage life), uncertainty remain regarding changes to the thoracic aorta and stent grafts as patients' age (and grow), including long-term complications of vascular access and subclavian coverage. This is also the age group likely to be itinerant in this global village; and this patient group will need long-term follow-up. Despite a patient education programme regarding the endovascular devices, we have had significantly difficulty ensuring that patients attend for regular follow-up! Finally, life-long follow-up for stent-grafts include a large number of radiological procedures, including chest radiographs and at least annual CTA for long-term follow-up, translating to large cumulative radiation doses over the patients lifetime.39, 40 Surgeons and patients alike must be aware of the long-term risks of medical irradiation.
Conclusion
Endovascular intervention is a safe and effective treatment for TAT in multiple trauma patients. The morbidity and mortality associated with endovascular repair appears to be reduced, but procedure related complications including arterial injury, endoleak, and neurological deficit may occur. The majority of these patients are young and long-term follow up is necessary to assess graft durability.
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PII: S1078-5884(08)00208-6
doi:10.1016/j.ejvs.2008.03.012
© 2008 European Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.
Volume 36, Issue 2 , Pages 152-157, August 2008
