MMCTS
(March 29, 2007). doi:10.1510/mmcts.2006.001966
Copyright © 2007 European Association for Cardio-thoracic Surgery
Procedure
Post-traumatic blunt rupture of the aorta: endo-aortic stenting therapy
Alessandro Santo Bortone*,
Emanuela de Cillis,
Donato d'Agostino,
Vito Paradiso and
Luigi de Luca Tupputi Schinosa
Department of Emergency and Transplantation, Division of Cardiovascular Surgery, University of Bari, Bari, Italy
* Corresponding author: * Istituto di Cardiochirurgia, Policlinico, Piazza Giulio Cesare 11, 70124 Bari, Italy. Tel.: +39-080-5592196; fax: +39-080-5592192. E-mail: abortone{at}cardiochir.uniba.it
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Summary
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With the increased use of the endovascular approach, the management and outcome of traumatic aortic injuries have changed dramatically over the past 10 years. Understanding pathogenic mechanism underlying aortic injury is critical in choosing the kind of stent-graft to be used. The possible mechanisms of non-penetrating blunt trauma of the aorta have been studied for a long time and are not completely clarified yet. The principal hypotheses concern the differential acceleration and deceleration movements exerting in horizontal and/or longitudinal planes, associated with the abrupt increase of endoluminal pressure and direct or indirect compression of the thoracic aorta from the ribcage structures. When blunt chest trauma causes direct compression of the sternum and spine with a sudden increase in endoluminal pressure, the rupture more frequently involves the ascending aorta or the descending thoracic aorta downstream the isthmus area. On the other hand, when the trauma generates differential acceleration and deceleration movements the rupture involves more frequently the isthmus because this region represents one of the points of fixity of the aorta through the junction of the ligamentum arteriosus and the first ribs. The following presentation is aimed at illustrating some of the possible pathophysiological mechanisms of post-traumatic blunt rupture of the aorta and the indications for its endovascular treatment.
Key Words: Post-traumatic aortic lesion • Isthmus region • Endovascular treatment
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Introduction
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Traditionally, from an etiological point of view, injuries of the thoracic aorta are divided into penetrating and blunt chest traumas or may be iatrogenic due to an intra-aortic procedure. Injury from sudden deceleration is the most common traumatic condition observed clinically on the thoracic aorta and our interest will be focused on it (Photo 1).
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Photo 1 The aortic arch represents a particularly moving structure which develops, during the cardiac cycle, an oscillatory pendular movement around the points of fixity and with the maximum degree of torsion and strain on the isthmus region. This is a reconstruction of a CT scan that shows the double ‘S’ configuration of the isthmus.
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According to the most recent data traumatic disruption of the aorta has a mortality rate of 80%. Approximately 80–90% of non-penetrating thoracic aortic injuries are caused by acute differential deceleration after motor vehicle, car accidents, fall from heights or compression by heavy objects [1]. Most of these patients die at the scene of the accident or on transfer to the hospital [2]. The survival of the remaining crash victims depends on the adventitial and peri-adventitial tissues which allow for the development of a contained rupture. Open surgical repair is still today associated with a high risk due to the concomitant life-threatening involvement of different organs and results in 30% peri-operative mortality and 8% of paraplegia [3]. Recently, endoluminal stent-graft treatment has emerged as an alternative to conventional surgery because of its less traumatic nature in patients affected by blunt chest trauma and aortic disruption, especially in the presence of multiple and extensive associated lesions [4]. During the first three years of our experience only two stent-graft devices were available at our department: TalentTM (Medtronic World Medical Manufacturing Corp, Sunrise, FL, USA), and Excluder® (Gore – MMCTSLink 139). Reports on the mid- and long-term results with the use of this first generation of stent-graft in this particular group of patients have been encouraging [5] (Photos 2 and 3).
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Photo 2 First generation of endoprostheses: Excluder® (Gore – MMCTSLink 139) stent-graft consisting of a nitinol skeleton arranged as a continuous wire covered by e-PTFE graft. Its spring system exerts a lighter pressure on the aortic wall thus reducing the risk of perforation.
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Photo 3 First generation of endoprostheses: TalentTM (Medtronic World Medical Manufacturing Corp, Sunrise, FL, USA). It was a modular self-expanding endoprosthesis consisting of circumferential nitinol stent springs arranged as a tube covered by low profile Dacron graft.
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Presently with the improvement of stent-graft technology, including higher flexibility of the delivery system and conformability of the fabric itself, a new generation of stent-graft is available including: E®-vita (Jotec – MMCTSLink 140), Gore-Tag® (Gore – MMCTSLink 141) and RelayTM (Bolton Medical, Sunrise, FL, USA) (Photo 4).
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Photo 4 Last generation of endoprostheses: RelayTM (Bolton Medical, Sunrise, FL, USA). This stent-graft consists of a highly compliant Dacron-woven crimped graft material that is a 3D shaped isthmus oriented. The double ‘S’ configuration of the torsional bar naturally follows the anatomy. The proximal part reinforces the sealing point and reduces the traumatism of the anchorage point, the free-flex® has a very rounded shape with an increased number of petals.
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From an anatomical point of view the site of rupture was identified in the isthmus region in more than 80% of cases, while in 20% the lesion was located in the proximal third of straight descending thoracic aorta in the posterior mediastinum (Schematic 1, Photo 5, Video 1).
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Schematic 1 The isthmus area is characterized by three-dimensional angles and until now stent-grafts were not designed to accommodate this anatomy.
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Photo 5 This is a vinyl model of a real three-dimensional isthmus reconstruction that shows the double ‘S’ configuration of the isthmus: the aortic arch with the innominate artery, left common carotid artery and subclavian one and then the descending thoracic aorta.
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Video 1 Architecture of the isthmus unfolded in three different planes from the anterior middle and posterior mediastinum.
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We have observed different level types of aortic wall involvement injury: from partial intimal laceration with various degrees of involvement of the tunica media and subsequent pseudoaneurysm formation to complete transection of the vessel with adventitial and peri-adventitial layers which, together with the surrounding mediastinal structures, allow for a contained rupture.
Case 1 (acute)
Statistically, the occurrence of post-traumatic pseudoaneurysm formation is the most frequent. In this patient the trauma typically determined a complete intimal and medial laceration without longitudinal dissection (Photo 6).
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Photo 6 Preoperative angio CT-scan: acute post-traumatic pseudoaneurysm located on the infero-posterior side of the aorta at the level of isthmus concavity.
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The capacity of the adventitial layer to support mechanical stress is basic for the development of post-traumatic pseudoaneurysm. The pleural layer and organizing periaortic hematoma act as a support for the weakened aortic wall by reducing the hemorrhage and subsequently favoring the healing process. When the deceleration is horizontal and the laceration of aortic wall is incomplete, this pattern generally concerns the infero-posterior side of the aorta at the level of the isthmic concavity. Indeed, the aortic arch represents a particularly moving structure which develops, during the cardiac cycle, an oscillatory pendular movement around the points of fixity with the maximum degree of torsion and strain of the isthmus [6].
Patients are often young and have a healthy aorta. Associated lesions are present at various grade in most patients including contusions and soft tissue hematomas, osteo-articular lesions of the ribcage, pelvis and limbs, internal organ injuries, i.e. liver laceration with intraparenchimal hematoma or peritoneal hemorrhage, brain and spine injuries, pleural effusion, hemothorax, etc. The latter often appears as the consequence of the periaortic hematoma that rarely is the cause of active life-threatening hemorrhage.
The first control is performed within 72 h from the procedure, in order to assess the position of the graft, the optimal sealing and complete exclusion of the pseudoaneurysm (Photo 7). New scans are obtained at 6 and 12 months after the procedure and scheduled once a year thereafter.
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Photo 7 Postoperative evaluation by angio CT-scan: total exclusion of the pseudoaneurysm from bloodstream is evident with optimal stent-graft sealing in the absence of any endoleak.
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During follow-up, spiral CT revealed a complete healing of the aortic wall, at first confirmed by the reduction in size and then by the total regression of the pseudoaneurysm itself, at six months in all patients that presented with an acute post-traumatic pseudoaneurysm (Photo 8).
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Photo 8 Six-month spiral angio CT reconstructions revealed a complete healing of the aortic wall, at first confirmed by reduction in size and then by complete regression of the pseudoaneurysm.
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Case 2 (chronic)
In patients affected by acute pseudoaneurysm the treatment within two weeks helps prevent calcification of the aortic wall and eliminates the risk of chronic evolution of the lesion. Indeed, this process is characterized by the long-term anatomical and clinical consequences of the development of a calcified mass at the isthmic level (Photo 9).
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Photo 9 Preoperative aortic angiogram: large chronic post-traumatic pseudoaneurysm localized at the isthmic level of the descending thoracic aorta.
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This area represents an area of reduced resistance due to the constant transmural pressure exerted by the blood flow and the progressive dilatation of the impaired aortic segment leads to the development of a hard calcified shell exerting compression on the surrounding structures. In this situation the complete healing of the aortic wall is not achieved even after a proper endovascular treatment (Photos 10, 11, 12 and Video 2).
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Photo 10 Three-month spiral angio CT reconstruction showing the optimal sealing without endoleak of an implanted stent-graft of highly compliant Dacron-woven crimped graft material. The ‘spiral strut®’ that follows the proximal sealing point is ‘double S’ shaped in three-dimensions and follows perfectly the vessel anatomy and, therefore, transmits and absorbs the torsional forces.
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Photo 11 Three-month spiral angio CT reconstruction: proximal and distal sealing was obtained with complete exclusion of the pseudoaneurysm.
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Photo 12 Three-month spiral angio CT 3D rendering: although the stent-graft had sealed off the false pseudoaneurysm from the blood stream, its wall was heavily calcified and the treatment saved the patient from rupture but, neither eliminated the compression on the adjacent organs nor reduced the risk related to a persistent area of poor resistance.
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Video 2 Final angiographic control after deployment: stent-graft in place with total exclusion of the pseudoaneurysm from bloodstream. The proximal uncovered stent is positioned across the origin of the left subclavian artery.
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Case 3 (emergency)
In this case, contrast-enhanced spiral CT revealed a circumferential disruption of the descending thoracic aorta immediately downstream of the isthmus (Photo 13).
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Photo 13 Acute traumatic descending thoracic aortic transection following a motor vehicle accident. Contrast-enhanced spiral CT revealed circular disruption of the descending thoracic aorta immediately beyond the isthmic region.
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TEE confirmed the complete transection of proximal thoracic aortic segment in sub-isthmic position with almost complete intimal detachment in the horizontal plane and extending into the longitudinal one for approximately 2 cm (Video 3).
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Video 3 Multiplan transesophageal echocardiography (TEE) confirmed the complete transection of proximal thoracic aortic segment in sub-isthmic position with almost complete intimal detachment in the horizontal plane and extending in a longitudinal one for approximately 2 cm. Secondary to complete transection an intussusception of leaflets with pseudocoarctation was detected and Doppler analysis showed a 70 mmHg transaortic peak gradient.
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Secondary to complete transection an intussusception of the rupture rims with pseudocoarctation was detected. Doppler analysis showed a 70 mmHg transaortic peak gradient. Angiographic study confirmed that, because of the peculiar mechanism of trauma with extensive disruption of the intimal tunica and the inner invagination, the blood flow did not reach the sub-adventitial layer and a post-traumatic pseudoaneurysm did not develop [7] (Videos 4 and 5).
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Video 4 Angiographic study confirmed that, due to the peculiar mechanism of the trauma with extensive disruption of the intimal tunica and inner leaflets invagination, blood flow did not reach the sub-adventitial layer and post-traumatic pseudoaneurysm did not develop.
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Video 5 Angiographic study of the lesion. A percutaneous right brachial artery approach was selected allowing a 6F pigtail catheter to be inserted over a hydrophilic guide wire in order to identify the right subclavian artery and to perform safely the angiographic controls.
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Endovascular procedure
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The procedures were carried out in the angiography suite under general anesthesia and controlled hypotension (mean systolic blood pressure of 70 mmHg) obtained by ß-blockers and vasodilators. For preoperative assessment, all patients underwent chest X-ray, 5 mm contrast enhanced spiral CT-scan of the chest, abdomen and pelvis and arteriography in order to evaluate the site, morphology and extension of the aortic lesion, the distance from left subclavian artery, the characteristics of the proximal and distal neck (Videos 4 and 5). The common femoral artery was surgically exposed. In all patients this vascular access was considered appropriate due to the relatively young age of the patients. One hundred IU/kg of heparin were administered intravenously in order to get ACT values of 250–350 s. According to each case, a percutaneous left and/or right brachial artery approach was selected allowing a 6F pigtail catheter to be inserted for angiographic controls (Videos 4 and 5).
The left subclavian artery was always identified by advancing throughout a hydrophilic guide wire which was easily withdrawn at the end of the procedure (Video 6).
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Video 6 Then the pigtail was advanced into the descending aorta at the level of the transection in order to maintain the invaginated rims of the rupture opened and by using a telepheric technique, a second 6F pigtail catheter was advanced directly through the right femoral artery previously exposed until the level of transection. With the two opposite angiographic catheters we were sure to be exactly in the middle of the pseudo-valve.
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Final angiography showed optimal sealing at the proximal and distal landing sites and complete exclusion of the pseudoaneurysm from blood flow in the absence of primary endoleak (Videos 7, 8, 9 and 10).
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Video 7 Once the desired location was reached, the stent-graft was deployed by pulling a string attached to the graft and control angiography was performed.
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Video 8 After deployment of the endoprosthesis, an arteriogram was made to assess the optimal sealing at the proximal and distal sites with complete readjustment of intimal layers to the aortic wall and disappearance of the transaortic gradient related to the post-traumatic pseudocoarctation.
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Video 9 Touch-up and molding at the proximal site of implantation to reach optimal sealing of the graft.
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Video 10 After deployment of the endoprosthesis, an arteriogram was made to check the optimal sealing at the proximal and distal sites. A slight but non-significant filling defect was seen at the final angiographic control due to incomplete self-expansion of the nitinol support structure.
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Transesophageal echocardiography (TEE) monitoring was used to assess the complete exclusion of the lesion from the blood flow and the absence of primary endoleaks (Video 11).
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Video 11 The disappearance of transaortic gradient was confirmed by Doppler TEE upstream and downstream to the endoprosthesis.
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A complete readjustment of intimal leaflets to the aortic wall was obtained and disappearance of transaortic gradient related to the post-traumatic pseudocoarctation was found. The disappearance of transaortic gradient was confirmed by Doppler TEE upstream and downstream to the endoprosthesis itself (Photo 14).
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Photo 14 The contrast-enhanced CT scan associated with the vessel analysis, performed before discharge, revealed a patent aorta without any pressure gradient but persistence of slight endoprosthesis step at the site of the pseudocoarctation due to the fact that the low radial force of the endoprosthesis was not enough to avoid this effect as well as the so-called ‘tapered effect’.
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The contrast-enhanced CT scan performed before discharge revealed the normally patent aorta with fibrosis of readjusted circumferential intimal flap and disappearance of the pressure gradient at the site of pseudocoarctation, due to the fact that the outer nitinol support had reached its thermal memory expansion (Video 12).
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Video 12 3D rendering of angio CT scan performed immediately before discharge.
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Because of the closeness of the proximal neck to the left subclavian artery, partial or total covering of the artery was necessary in some patients in order to achieve an optimal sealing. A carotid-left subclavian artery bypass was performed in two cases during the first year of our experience. Presently we have abandoned this associated procedure because it proved not necessary (Photo 15).
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Photo 15 Vessel analysis of left subclavian artery: in some patients partial or total covering of the subclavian artery was necessary in order to achieve optimal sealing. None of the patients with partial or total covering of the left subclavian artery developed a steal syndrome, left arm ischemia and/or vertebro-basilar insufficiency during follow-up.
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Case 4 (emergency)
The fourth case concerns a 32-year-old male admitted with complete laceration of the straight portion of the thoracic aorta secondary to a frontal collision from which the patient survived because of the formation of a hematoma contained in periaortic and mediastinal surrounding tissues (Videos 13 and 14).
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Video 13 Preoperative emergency angiography in a 32-year-old male admitted with complete laceration of the thoracic aorta secondary to frontal collision: uncontained rupture of the middle descending thoracic aorta. Due to the emergency condition, only percutaneous left common femoral approach was chosen, allowing a 6F pigtail catheter to be inserted over a hydrophilic guide wire in order to perform all angiographic controls.
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Video 14 After identification of the celiac trunk and renal arteries, insertion and positioning of a Relay stent-graft is performed. The deployment of this stent-graft is obtained through a dedicated three-stage delivery system, with a rigid external sheath, and a very flexible internal sheath which follows the guide wire before final settlement of the device. Final angiographic control shows optimal sealing proximally and distally of the stent-graft with complete exclusion of the lesion from bloodstream without endoleak and optimal and safe retrieval of the delivery system.
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Conclusions
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According to our experience, endovascular repair can represent first choice treatment in patients with traumatic transection following severe deceleration accidents associated with multiple injuries. Endovascular repair of acute complete aortic transection may result in being safe and effective provided that an accurate selection of device is achieved. Our experience also demonstrates the feasibility and safety of endovascular treatment, also in patients with extensive associated injuries. Indeed the severity of coexisting non-aortic lesions adversely affect the conventional surgical treatment. Stent-graft repair can represent in these patients the treatment of choice, also because it allows the patient to timely undergo medical or surgical management of all associated lesions and a prompt rehabilitation with shorter hospital stay. These patients are often young and the endovascular approach represents a viable alternative for its less traumatic approach with a slight impact on trauma destabilization.
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References
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Summary
Introduction