Ann Thorac Surg 2006;82:567-572
© 2006 The Society of Thoracic Surgeons
Original article: Cardiovascular
Extended Applications of Thoracic Aortic Stent Grafts
François Dagenais, MDa,*,
Rahul Shetty, MDa,
Jean-Pierre Normand, MDb,
Roc Turcotte, MDb,
Patrick Mathieu, MDa,
Pierre Voisine, MDa
a Department of Cardiac Surgery, Laval Hospital, Québec City, Québec, Canada
b Department of Radiology, Laval Hospital, Québec City, Québec, Canada
Accepted for publication March 7, 2006.
* Address correspondence to Dr Dagenais, Department of Cardiac Surgery, Laval Hospital 2725 chemin Ste-Foy, Québec, Canada, G1V 4G5 (Email: francois.dagenais{at}chg.ulaval.ca).
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Abstract
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BACKGROUND: Thoracic stent-grafts (TSG) show excellent early and mid-term results for localized diseases of the descending aorta. Extending TSG applications for arch pathologies or to other yet unproven indications remains to be established. We herein report our experience in 18 patients with extended applications of TSG.
METHODS: Ten patients with inadequate proximal aortic neck length required coverage of at least one arch vessel with or without extra-anatomic bypass. One patient required an extra-anatomic visceral bypass to extend the distal aortic neck, 6 patients were treated with TSG for yet unproven indications, and 1 patient required an unusual vascular access.
RESULTS: A mean of 2.4 ± 1.0 stents per patient were inserted. Primary or secondary success rate was 100%. Hospital mortality occurred in one patient (5.5%). Mean follow-up was 24.1 ± 13.7 months. Four endoleaks were diagnosed: two of type 1, one of type 2, and one that remains undetermined. Two patients died during follow-up; both deaths were linked to the presence of a type 1 endoleak. Actuarial survival at 3 years was 79.0%. Freedom from endoleak and stent-graft-related death at 3 years were, respectively, 71.0% and 83.7%. No stent-graft migration was observed.
CONCLUSIONS: Early and mid-term results of extended applications of TSG are acceptable in well-selected high-risk patients. Endoleak at follow-up remains a concern and may impede long-term outcome of TSG in complex procedures.
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Introduction
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Dake and colleagues [1] proposed, in 1994, the endovascular approach for the treatment of thoracic aortic aneurysms. Indications rapidly expanded to include blunt traumatic aortic ruptures, complicated penetrating ulcers, and complicated type B dissections. Early and mid-term results are encouraging especially in patients with a high comorbid profile [2, 3]. However, anatomic prerequisites such as proximal and distal aortic neck lengths and aortic diameter significantly limit the applicability of thoracic stent grafts. Furthermore, significant aortoiliac atherosclerosis may render stent-graft insertion difficult or impossible. To obviate these problems, new procedures such as great vessel transposition with stent-grafting or novel vascular access approaches have been described to extend the applications of thoracic stent-grafts [4]. However, reports assessing the results of these procedures remain limited. In addition, indications of thoracic stent grafts have been extended to diseases such as mycotic aneurysms, postoperative complications, and patients with connective tissue disorders [5, 6]. The use of thoracic stent-grafts for such indications remains to be validated.
The objective of the present study is to report results of extended applications of thoracic stent-grafts either through proximal or distal aortic neck extension with or without hybrid procedures, the use of unusual vascular access approaches, or the use of stent-grafts for yet unproven indications.
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Material and Methods
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Definition of Extended Stent-Graft Application
At the Laval Hospital (Québec City, Canada), patients with pathologies of the thoracic aorta are referred to a dedicated aortic clinic and are evaluated by a single surgeon (FD). Our thoracic stent-graft program was initiated in May 2001 and obtained our Institutional Review Board approval. Patients with good open operative risks are considered for open surgery. In patients with significant comorbidities or coinjuries, stent-graft eligibility is considered in the presence of at least two of the following comorbidities: age greater than 75, presence of significant heart or pulmonary disease, renal failure (creatinine > 200 µmol/L), known coagulopathy, redo-thoracotomy, or high expected open operative mortality. An aortic diameter 40 mm or less and proximal and distal aortic necks 2 cm or more are required. Aortic diameters are measured using axial contrast-enhanced chest computed tomography (CT). Neck length measurements are performed using CT images and angiography. Neck length in the arch is measured on the lesser aortic curve. In circumstances of less than 2 cm of proximal or distal aortic neck, patients were considered for extended stent-graft applications. The neck length requirement of 2 cm or more was evaluated either through coverage of the left subclavian artery or through arch or visceral debranching. Unusual vascular access and unproven indications such as mycotic aneurysms and connective tissue disorders were also considered as extended applications for thoracic stent-grafts. Informed consent is obtained for all stent-graft patients. For patients with extended stent-graft applications, additional information was given regarding the limited early and mid-term results of these procedures.
Patient Characteristics
Since May 2001, eighteen patients were treated for extended applications of thoracic stent-grafts. Patient characteristics are depicted in Table 1.
Table 2
describes the clinical features leading to the extended application of thoracic aortic stent-grafts. Aortic diseases treated were a penetrating ulcer in 6 patients (including one case of aortoesophageal fistula), a blunt traumatic aortic rupture in 4 patients, an aneurysm in 5 patients including 2 patients with connective tissue disorders, a complicated type B aortic dissection in 2 patients, and a postoperative pseudoaneurysm in 1 patient. Operative indication was based on the presence of symptoms in 12 patients and on size of the aorta in 6 patients. All patients fulfilled the comorbid profile requirement of our institution for thoracic stent-graft implantation except one who refused open surgery. This patient, with a 5 cm chronic traumatic isthmic aneurysm, decided to select an endovascular approach although an open approach was recommended. All patients were followed prospectively in a dedicated aortic clinic. Patients were evaluated clinically and by chest CT at 3, 6, 12, and 18 months postoperatively and yearly thereafter.
Operative Techniques
All procedures were conducted in an operating room setting with the use of a high resolution C-arm fluoroscopy. Vascular access was obtained through the common femoral artery in 14 patients. In 3 patients, the stent-graft was introduced through a branch of a previous aortobifemoral graft. In one patient with a penetrating ulcer of the proximal descending aorta and severe aortoiliac disease, a left video-assisted 5 cm minithoracotomy (seventh intercostal space) was used to suture a 10 mm Dacron graft on the minimally diseased distal descending thoracic aorta. A Talent graft (Medtronic, Santa Rosa, CA) was directly inserted in the 10 mm graft exteriorized through a counter-incision (Fig 1). Adequate proximal length for stent-graft fixation required coverage of the left subclavian in 9 patients. In 2 patients with distal arch aneurysms, an additional carotid-carotid bypass using an 8 mm reinforced GoreTex graft (W.L. Gore & Associates, Flagstaff, AZ) was required. A preoperative left carotid to left subclavian interposition graft was performed in 2 patients. One patient with a complicated penetrating ulcer had a severe stenosis of the left vertebral artery and a nondominant right vertebral artery, while another patient with a fusiform aneurysm just distal to the left subclavian artery had a patent left internal mammary artery to the left anterior descending artery. A 79 year old dialyzed patient with significant coronary artery and pulmonary diseases presented with a ruptured thoracoabdominal aneurysm. A retroperitoneal revascularization of the celiac and mesenteric arteries was required to increase the distal aortic neck length. The bypass was performed using a 14/7 mm Dacron graft with the inflow on a previous aortobifemoral graft. Two patients with connective tissue disorders (Ehlers-Danlos and Marfan diseases) with previous open resection of the descending aorta were treated by stent-grafts; one for a pseudoaneurysm at the proximal anastomosis and the other for distal progression of the aneurysm. In seventeen patients, the Talent graft (Medtronic) was utilized while one patient had placement of a Zenith Cook graft (Cook, Bloomington, IN). Graft size was selected by adding 10% to 25% to the diameter of the proximal aortic landing site measured by chest CT. Oversizing was limited to 10% in dissection cases and increased up to 25% in cases of arch stenting. Completion angiogram and predischarge chest CT were obtained in all patients.
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Fig 1. Postoperative chest computed tomographic scan depicting (A) excluded proximal descending aortic penetrating ulcer, and (B) a 10 mm graft stump on the distal descending aorta that allowed insertion of the stent-graft.
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Results
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In-Hospital Results
A mean of 2.4 ± 1.0 stents per patient were inserted. Completion angiography and predischarge chest CT showed good stent-graft placement without endoleak (primary or secondary success rate of 100%). One in-hospital death occurred (5.5%) in a patient with debranching and revascularization of the celiac and mesenteric arteries followed by stent-grafting. This patient developed ischemic colitis on postoperative day 4. The patient was reexplored and the left colon was found to be necrotic with a normal Doppler signal in the extra-anatomic bypass. The patient succumbed to infectious complications. No paraplegia was encountered in the 18 patients. The mean hospital stay was 5.3 ± 2.1 days.
Follow-Up
Follow-up was complete in all patients. Mean follow up was 24.1 ± 13.7 months; 3.7 ± 2.5 chest CT per patient. Four endoleaks were diagnosed: two of type 1, one of type 2, and one that remains uncertain.
Type 1 endoleaks
A patient with multiple comorbidities (end-stage renal failure, coronary artery disease, and chronic obstructive pulmonary disease) underwent stent-grafting for multiple mycotic ulcers of the descending aorta including one with a contained rupture. A type 1 endoleak was diagnosed one month postoperatively on a chest CT. The patient expired owing to a probable aortic rupture before reintervention could be done. An 84 year old patient with a symptomatic 9 cm distal arch aneurysm underwent stent-grafting with a carotid-carotid bypass. Twelve months postoperatively a type 1 endoleak was diagnosed. Owing to end-stage renal failure and advanced age, no further treatment was undertaken and the patient died suddenly 20 months postoperatively.
Type 2 endoleak
A 72-year-old man with an aneurysm involving the ascending aorta, arch, and proximal descending aorta underwent an ascending and arch aortic replacement with an elephant trunk procedure and revascularization of an aberrant right subclavian artery. The second stage procedure was completed by a stent-graft positioned within the elephant trunk. Six months postoperatively, contrast within the stump of the right aberrant subclavian artery was observed on chest CT. A type 2 endoleak through a right subclavian steal phenomenon was diagnosed by angiography. Direct puncture on the right subclavian stump with coil embolization was performed (Fig 2). Lastly, a 76 year old patient with severe chronic obstructive pulmonary disease underwent stent-grafting for an aortoesophageal fistula owing to a giant penetrating ulcer (Fig 3). The patient presented recurrent episodes of hematemesis but no site of aortic fistula could be found on multiple angiographic and CT examinations and in spite of restenting. The patient is still alive 54 months after stent-grafting.
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Fig 2. Angiogram showing (A) type 2 endoleak owing to a subclavian steal through the aberrant right subclavian artery, and (B) coil embolization of the aberrant right subclavian artery.
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Fig 3. Angiogram showing (A) a giant penetrating ulcer of the mid-descending aorta responsible for the aortoesophageal fistula, and (B) exclusion of the giant penetrating ulcer after stent-graft implantation. (oad = RAO [right anterior oblique] view.)
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The 2 patients with connective tissue disorders are free from complication at 22 and 37 months. The Marfan patient stented for a pseudoaneurysm at the proximal anastomosis showed complete regression of the aneurysm sac at follow-up (Fig 4). The 2 patients who expired after the diagnosis of a type 1 endoleak were the only two deaths encountered at follow-up. Actuarial freedom from all cause of death at 3 years was 79.0%. Freedom from endoleak and stent-graft related death at 3 years were, respectively, 71.0% and 83.7%. No stent-graft migration was observed.
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Fig 4. (A) Angiogram depicting a large pseudoaneurysm located at the proximal anastomosis in a Marfan patient with a previous thoracoabdominal repair; (B) exclusion of the pseudoaneurysm after stent-graft implantation; and (C) complete regression of the pseudoaneurysm sac at follow-up.
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Comment
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Thoracic stent-grafts show good results for limited diseases of the descending aorta [7]. The present study demonstrates acceptable results of extended applications of thoracic stent-grafting in circumstances in which the proximal or distal aortic fixation sites are inadequate or in unusual or yet unproven indications for stent-grafting. Although these procedures were defined as extended applications for thoracic stent-grafting, requirements in terms of neck length and aortic diameter were identical to conventional stent-graft procedures. Primary or secondary success rate was 100%. Failure to respect adequate aortic neck length or diameter may jeopardize procedural success rate.
The use of extra-anatomic revascularization procedures increases aortic neck length for stent-graft fixation. Limited reports have shown that arch stent-grafting with extra-anatomic bypass is feasible [4, 8, 9]. However, despite acceptable operative mortality, the durability of the repair remains to be defined, especially with regard to the development of late endoleaks. The three-dimensional orientation of the arch, its increased diameter, its angulation, and the presence of arch vessel ostia render the arch more challenging for stent-graft fixation. The current technology requires significant developments to optimize stent-graft deployment and fixation in the arch. On the other hand, during the past decade, morbidity and mortality linked to open arch surgery have decreased mainly owing to the improvement in cerebral protection techniques and the establishment of specialized teams dedicated to these pathologies [10]. Under such circumstances, the use of stent-grafting with extra-anatomic bypass should not be generalized to good open risk patients until better assessment of the limitations and pitfalls of this technique are defined. Until then, patients with arch pathologies should be thoroughly evaluated for the risks of open surgery ideally by an experienced team with combined expertise in open arch surgery and thoracic stent-grafting.
Conversely, owing to the high morbidity and mortality linked to thoracoabdominal surgery, the use of extra-anatomic bypasses with stent-grafting seems appealing for extensive thoracoabdominal disease with insufficient distal aortic neck length for traditional stent-grafting. However, extra-anatomic visceral bypass with inflow from the infrarenal aorta are challenging procedures, especially in light of the high prevalence of atherosclerosis in this population. Furthermore, retrograde extra-anatomic graft patency in such circumstances remains a concern and has to be investigated further.
The use of branch stent-grafts may obviate the necessity for extra-anatomic bypass procedures. Application of branch stent-grafts in the arch, albeit reported [11], remains limited because of technical difficulties related mainly to the anatomy of the arch and the presence of significant atherosclerosis in this population. Although more studies assessing the feasibility of branch stent-grafts for the visceral arteries are reported, it remains a procedure with significant pitfalls [12, 13]. The development of new technology and stent-graft designs may eventually facilitate these procedures [14].
Experience of thoracic stent-grafts for mycotic aneurysms is limited. Semba and colleagues [6] have reported the use of thoracic stent-grafts for the treatment of 3 patients with mycotic aneurysms. They achieved complete thrombosis of the mycotic aneurysm in all patients with no aortic-related death at mid-term. Of three patients with mycotic aneurysms treated with stent-graft in our series, one patient with multiple mycotic aneurysms succumbed to an aortic rupture owing to an early endoleak. Until more experience is gained with stent-grafting in mycotic aneurysms, an open approach should be favored in patients with acceptable risks for open surgery. In the presence of prohibitive open operative risks, stent-grafting may be performed in the absence of active sepsis.
Two patients in our cohort were known to have connective tissue disorders. Both patients had previous thoracotomies with resection of the descending thoracic aorta. Considering the fixation site within the Dacron graft at one end and the risk of reoperation, decision was taken to treat these 2 patients by an endovascular approach. Mid-term outcomes are excellent in both patients. Reports assessing the use of stent-grafts in patients with connective tissue disorders are very limited. Ince and colleagues [15] reported their experience in 6 patients. Two patients required reoperation at mid-term and one patient died suddenly after 12 months. Owing to the wall abnormalities found in patients with connective tissue disorders, stent-grafts should be used cautiously and follow-up should be very tight to identify any stent-graft related complications.
Although extended stent-graft procedures seem attractive for patients with extensive aortic disease and severe comorbidities, one should consider the patients overall life expectancy excluding the aortic pathology. Although this judgment is often difficult, the three deaths encountered in this study were patients with severe comorbidities and limited survival even when excluding their aortic disease. Eggebrecht and colleagues [16] have also identified the preoperative clinical health status as an important determinant of postinterventional outcome. Analysis of large cohorts of thoracic stent-graft patients will enable to establish prognostic factors linked to survival, which will validate the benefits in undertaking complex stent-graft procedures. Furthermore, one cannot overemphasize the necessity of a well-structured follow-up for these complex procedures. Identification of an endoleak on chest CT should be evaluated promptly by angiography. As supported by the present study, the presence of a type 1 endoleak portends a poor outcome and should be treated aggressively.
In summary, the present study demonstrates acceptable results for extended applications of thoracic stent-grafts. Results are dependent on patient selection and team expertise. Endoleak remains a concern at follow-up and long-term outcome of extended thoracic stent-graft procedures need to be better determined before generalizing its use. Stent-graft technology will evolve and continue to adapt to specifications related to these more complex procedures. Until then, open surgery should be favored in patients with acceptable open operative risks. Establishment of specialized multidisciplinary teams with combined expertise in open and stent-graft approaches should be encouraged to optimize the decision-making process in this difficult cohort of patients.
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Abstract
Introduction
