Fate of Aneurysms of the Distal Arch and Proximal Descending Thoracic Aorta After Transaortic Endovascular Stent-Grafting

CARDIOVASCULAR Fate of Aneurysms of the Distal Arch and Proximal Descending Thoracic Aorta After Transaortic Endovascular Stent-Grafting Taijiro Sueda, MD, Kazumasa Orihashi, MD, Kenji Okada, MD, Yuji Sugawara, MD, Katsuhiko Imai, MD, and Kazuhiro Kochi, MD Department of Cardiovascular Surgery, Graduate School of Biomedical Sciences, Hiroshima University, Hiroshima, Japan Background. The purpose of this study was to evaluate the midterm results of transaortic stent-grafting for distal aortic arch aneurysms or proximal descending aortic aneurysms and the feasibility of this method for thoracic aortic aneurysm repair. Methods. Twenty-three patients with true distal aortic arch aneurysms or proximal descending thoracic aortic aneurysms were repaired with the stent-graft introduced through the incision on the proximal arch aorta. Follow-up computed tomography was performed every 6 months in 21 surviving patients. The maximum dimension of the excluded aneurysmal space and the maximum aneurysmal diameter were measured and evaluated to determine whether the aneurysmal space decreased or disappeared after this alternative procedure. Results. There was 1 hospital death (4.3%) due to cerebral embolism. Another patient died of pneumonia 1 year after surgery. Twenty-one patients (91%) survived during the follow-up period, but 1 patient (4.3%) suffered from paraplegia. The follow-up period ranged from 12 to 62 months (average, 34.3 15.2). There were no instances of aneurysmal rupture during the follow-up period. Postoperative serial computed tomography scans showed disappearance or significant shrinkage of the excluded aneurysmal space in 20 of 21 patients (95%), except for the one patient with endoluminal leakage. Conclusions. Transaortic endovascular stent-grafting was an effective alternative approach to treating distal aortic arch aneurysms or proximal descending aortic aneurysms. The excluded aneurysm disappeared or shrunk after successful placement of the stent-graft. (Ann Thorac Surg 2003;76:84 9) 2003 by The Society of Thoracic Surgeons The endoluminal repair of thoracic aneurysms is an innovative technique for the treatment of aortic aneurysms. It was originally applied to the descending thoracic aortic aneurysm by the transcatheter placement of endoluminal grafts [1, 2]. This procedure is indicated for dissecting aneurysm in which the primary entry is located in the descending thoracic aorta and for true aneurysm of the descending thoracic aorta in several institutions [3]. However the percutaneous insertion of the stent-graft is often difficult to adapt to the branched and curved portion of the aortic arch because the proximal neck that is essential for transluminal endovascular stent-grafting cannot be secured sufficiently in this type of aneurysm or dissection. Because the distal aortic arch aneurysm is often situated in the root of the left subclavian artery, endoluminal coverage of the aneurysm may cause obstruction of the left subclavian artery or endoluminal leakage into the aneurysm because of inadequate placement of the stent-graft. Kato and colleagues [4] devised a new method of Accepted for publication Feb 4, 2003. Address reprint requests to Dr Sueda, Department of Cardiovascular Surgery, Graduate School of Biomedical Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima, 734-8551, Japan; e-mail: sueda@hiroshima-u.ac.jp. endoluminal stent-grafting through a circumferential incision on the aortic arch. We modified this method and reported a simple procedure [5, 6] in which a selfexpandable stent is anchored into the distal portion of the graft, and can be inserted into the descending aorta through a small aortic incision on the proximal arch aorta. In this study we evaluated the midterm results of this stent-graft by serial computed tomography (CT) examinations and investigated the fate of the excluded aneurysmal space. Material and Methods Patients Twenty-three patients with true distal aortic arch aneurysms or proximal descending thoracic aortic aneurysms were enrolled in this study. There were 18 men and 5 women and their mean age was 69.7 6.9 years (range, 52 to 83). All patients had thoracic aortic aneurysms that were located at the root of the left subclavian artery and extended into the descending thoracic aorta and were operated upon with the transaortic stent-graft procedure during the last 5 years. Five patients had proximal extension of their aneurysm above the left subclavian artery and 2 patients had subclavian arterial aneurysms. The maximum size of aneurysmal diameter ranged from 5.2 2003 by The Society of Thoracic Surgeons 0003-4975/03/$30.00 Published by Elsevier Inc PII S0003-4975(03)00266-2

Ann Thorac Surg SUEDA ET AL 2003;76:84 9 FATE OF ANEURYSMS AFTER STENT-GRAFTING 85 Fig 1. Conventional transaortic stent-grafting procedure. (A) A hemicircular aortotomy was performed on the anterior wall of the proximal arch aorta. The sheath catheter was inserted into the descending thoracic aorta through a small aortotomy and advanced beyond the distal end of the aneurysm. (B) After the stent-graft was adequately positioned, the distal end of the stent-graft was dilated with a balloon catheter. The proximal end of the stent-graft was sutured onto the posterior aortic wall intraluminally and the anterior aortic wall transmurally at aortotomy. (C) The aortotomy was closed with the anterior wall of the proximal end of the stent-graft. (D) In patients with proximal extension of the aneurysm, the left subclavian artery was ligated and reconstructed by the small prosthesis used for arterial perfusion. CARDIOVASCULAR to 8.4 cm (mean diameter, 6.6 cm 1.5 cm). Ten of 23 patients had other cardiac disorders, including 7 with severe coronary artery disease, 2 with aortic valve regurgitation, and 1 with tricuspid valve regurgitation. Three patients had stenosis of the iliac arteries, femoral arteries, or both, caused by atherosclerotic obliteration. Concommitant surgeries were performed in 16 of 23 patients (70%) including 7 coronary arterial bypasses, 2 aortic valve replacements, 1 tricuspid annuloplasty, 5 subclavian-subclavian arterial bypasses, and 2 total arch replacements. A subclavian-subclavian arterial bypass was selected in patients with left subclavian arterial aneurysm or aneurysmal extension proximal to the left subclavian artery. We principally used cannulation through the right subclavian artery with a small prosthesis (8 mm in diameter, ringed polytetrafluoroethylene [PTFE]; Gore- Tex, Minneapolis, MN) or through the ascending aorta, except in 1 patient with calcified ascending aorta. We used this small prosthesis as a conduit for subclaviansubclavian arterial bypass after termination of extracorporeal circulation. Procedure The procedure for insertion of the stent-graft was described in a previous report [5]. A Gianturco Z-stent (Cook, Bloomington, IN) with a diameter of 30 mm or 40 mm was inserted into the distal end of the Dacron graft (Intervascular, Clearwater, FL) with porosity of 250 ml/m 2 and diameter of 22 mm to 34 mm, and sutured to the exterior of the graft. Stent-grafts of all sizes were prepared and sterilized preoperatively. The stent-graft was introduced into a 30F sheath catheter. The size of stent-graft was decided by measuring the diameter of the intact descending thoracic aorta with preoperatice CT or intraoperative transesophageal echocardiography (TEE). The distal end of the stent-graft was adequately positioned under observation of TEE guidance [6] and dilated with a large balloon catheter to attach the stent-graft to the wall of the descending aorta. The proximal end of the stent-graft was sutured circumferentially onto the intact wall of the aortic arch. The incision of the aortic arch was closed with the anterior wall of the stent-graft (Fig 1A C). Subclavian-subclavian arterial bypass was performed in patients with aneurysmal extension proximal to the left subclavian artery (Fig 1D). Most of the patients (21 of 23) were treated by the above mentioned procedure (conventional transaortic stent-grafting). In 2 patients with huge aneurysms extending into the proximal and distal aorta, the aortic arch was transected proximal to the left subclavian artery and a stent-graft was inserted into the descending aorta. The proximal end of the stent-graft was sutured circumferentially to the transected aortic arch. Thereafter the ascending and the proximal aortas were replaced with a branched graft, which was anastomosed to the proximal end of the stent-graft (hybrid transaortic stent-grafting; Fig 2). Transaortic insertion of the stent-graft was performed under selective cerebral perfusion and moderate hypothermia (rectal temperature 25 C, selective cerebral perfusion flow 600 to approximately 800 ml/min). The stent-graft procedure was principally indicated for patients with distal aortic arch aneurysms or proximal descending thoracic aortic aneurysms with other cardiac disorders in whom both the ascending aorta and the proximal aortic arch had not been diagnosed with aneurysms by preoperative CT, except for 2 patients with aortic arch aneurysms in whom a conventional total arch replacement was difficult because of the distal extention of the aneurysm.

CARDIOVASCULAR 86 SUEDA ET AL Ann Thorac Surg FATE OF ANEURYSMS AFTER STENT-GRAFTING 2003;76:84 9 Table 1. Results of the Transaortic Stent-Grafting Operative death 1/23 (4.3%) due to cerebral embolism Late death 1/23 (4.3%) due to pneumonia Major complication Paraplegia 1/23 (4.3%) Endolumimal leakage Transient 1/23 (4.3%) Permanent 1/23 (4.3%) Late aneurysmal rupture 0/21 (0%) Shrinkage of aneurysm 20/21 (95%) paired observations. A p value of less than 0.05 was considered to be statistically significant. The stent-grafting procedure was approved by the Institutional Review Board for human studies of the Hiroshima University Hospital and was performed after informed consent had been obtained from all patients. Fig 2. Hybrid transaortic stent-grafting procedure. (A) The aortic arch was transected proximal to the left subclavian artery and a stent-graft was inserted into the descending aorta. (B) The proximal end of the stent-graft was sutured circumferentially to the transected aortic arch. (C) The ascending and the proximal aortas were replaced with a branched graft, which was anastomosed to the proximal end of the stent-graft. Postoperative CT scans were taken every 6 months in every survivor. The excluded aneurysmal space was evaluated by measuring the size of the outer and inner diameter of the excluded aneurysm in CT slices and compared at the same level of the CT slices in different periods (Fig 3). The maximum aneurysmal diameter was also measured at the same level of the CT slices. Shrinkage of the excluded aneurysmal space of each CT slices was also calculated serially by comparing them with that of the control CT slice taken at 1 month after surgery (Fig 3). The results were recorded as means SD and statistical significance was calculated using Student s t test for Fig 3. Percent shrinkage of aneurysmal diameter measured by transectional computed tomography slices Excluded aneurysmal space was evaulated by measuring the diameter of aneurysm, not including the diameter of the stent-graft at 1 month (control) after surgery and each follow-up period. Percent shrinkage of the excluded aneurysm was calculated by comparing the diameter of the excluded aneurysmal space with that of the control. Results Twenty-one patients received a stent-graft insertion through a small incision on the proximal aortic arch (conventional transaortic stent-graft) and 2 patients received their stent-graft insertion through a circumferential amputation of the distal aortic arch with concomitant total arch replacement (hybrid transaortic stent-graft). The size of the stent-graft ranged from 24 to 34 mm in diameter. There was 1 hospital death due to a cerebral embolism during retrograde perfusion through the femoral artery (1 of 23; mortality 4.3%). Twenty-two patients (95.7%) were discharged but 1 patient died of pneumonia 1 year later and 1 of the hybrid stent-graft patients suffered from paraplegia due to a left vertebral arterial embolism (morbidity 4.3%). The other 20 patients survived without any serious complications during the follow-up period. Intraoperative transesosphageal echocardiography revealed endoluminal leakage in 2 of the 23 patients (8.6%). One of these patients had minimal leakage from the distal portion of the stent-graft, which disappeared during the follow-up period, but the other patient showed persistent leakage from the stent-graft into the excluded aneurysmal space during the follow-up period (Table 1). In this case an additional transcatherter stent-grafting was applied but failed owing to inappropriate deployment. As the aneurysmal diameter was growing very slowly (2 mm yearly) and the risk of aneurysmal rupture was thought to be low, this patient was observed without reoperation during the follow-up period. The coronary bypass grafts were all patent in those patients undergoing concomitant coronary artery bypass grafting. Postoperative serial CT examinations were available in 21 patients and continued during the follow-up period. they revealed extreme shrinkage of the excluded aneurysmal space size in 20 of 21 patients, except for the patient with endoluminal leakage. Changes in the maximum aneurysmal diameter decresased significantly from 6.6 cm (at discharge) to 5.4 cm (at 12 months) and 4.6 cm (at 24 months; Fig 4). The shrinkage of the excluded

Ann Thorac Surg SUEDA ET AL 2003;76:84 9 FATE OF ANEURYSMS AFTER STENT-GRAFTING 87 Fig 4. Changes in the excluded aneurysmal space. Excluded aneurysmal spaces decreased or disappeared after successful stent-graft placement. Cases 1, 2, and 3 are patients with complete disappearance of the excluded aneurysmal space. Dashed line is the baseline for comparison. CARDIOVASCULAR aneurysmal space size decreased significantly from 100% (at discharge) to 61% (at 12 months) and 32% (at 24 months) postoperatively. Among 20 patients with successful thromboexclusion, 7 patients showed extreme shrinkage of the excluded aneurysmal space and excluded aneurysmal spaces disappeared during the follow-up period (Fig 5). The size of aneurysms is regressing in all of the thromboexcluded patients but the patient with endoluminal leakage showed gradual dilation of the aneurysm during the follow-up period (Fig 6). There were no aneurysmal ruptures in the 21 patients who survived during the entire follow-up period, which ranged from 12 months to 62 months (average, 34.3 15.2). No late neurologic disorders such as cerebral embolism or peripheral embolism were observed. Comment The transluminal placement of endovascular stent-grafts was used to treat abdominal aortic aneurysms initially [7]. When a transcatheter endovascular stent-graft is considered for a patient with a thoracic aortic aneurysm, Fig 5. Complete disappearance of the excluded aneurysmal space. Three patients showed extreme shrinkage of the excluded aneurysmal space (upper panel), which disappeared or vanished completely during the follow-up period (lower panel).

CARDIOVASCULAR 88 SUEDA ET AL Ann Thorac Surg FATE OF ANEURYSMS AFTER STENT-GRAFTING 2003;76:84 9 Fig 6. Endoluminal leakage into the aneurysm through the stentgraft. (A) Postoperative computed tomography showed endoluminal leakage from the stent-graft. (B) Endoluminal leakage caused gradual dilation of the aneurysm 12 months after this procedure. many anatomical and technical problems must be addressed. In particular anatomical suitability is important and usually makes the endoluminal deployment of such a device difficult in aortic arch aneurysms because of the severely curved configuration of the aortic arch and the risk of obstruction of the cervical arterial branches [2, 3]. We had performed transcatheter stent-grafting in 7 cases of thoracic aortic aneurysms during the same period. Our small experience of transcatheter stent-grafting showed the difficulty of complete exclusion of the distal aoric arch aneurysm when the aneurysm extended to the aortic arch, which caused endoluminal leakage easily in the proximal site of the stent-graft. There was 1 case of major endoluminal leakage (14%), which required operative correction, and 1 case of cerebral embolism (14%) due to obstruction of the left subclavian artery in 7 cases with transcatheter stent-grafts. Moreover we encountered many patients with distal aortic arch aneurysms that also required coronary artery bypass grafting or other cardiac surgery. Therefore we performed transaortic endovascular stent-grafting procedures for distal aortic arch aneurysms or proximal descending thoracic aortic aneurysms [6]. The transaortic endovascular stent-grafting was originally reported by Kato and associates [4]. They perfomed a transection of the aortic arch for insertion of the stent-graft. However most distal aortic arch aneurysms or proximal descending aortic aneurysms are located just distal to the left subclavian artery. Therefore we modified that procedure and enhanced the technique by decreasing the incision on the aortic arch. We can introduce the stent-graft through a small incision in the aortic arch between the left common carotid artery and the left subclavian artery. This method has several advantages such as a decrease in bleeding from the small aortotomy, a shorter operative time, and no damage to the left recurrent nerve. Moreover the risk of distal displacement of the stent-graft is nil by suturing the proximal end of the stent-graft. From our experience of transcatheter stent-grafting for abdominal aortic aneurysms, some stents dislocated after transcatheter placement of stentgraft. We perform this procedure through a median strenotomy and it does not require any special instruments except for a large sheath catheter and a Gianturco Z-stent. We had previously performed a prosthetic replacement of the distal aortic aneurysm through a left thoracotomy. In our experience the procedure through the left thoracotomy was difficult to perform concomitant with a coronary arterial bypass or valve surgery. There was 1 case of serious cerebral embolism. We principally used antegrade aortic cannulation through the ascending aorta or the right subclavian artery. But we used transfemoral arterial perfusion in this patient because of the calcified ascending aorta and caused shower embolism by retrograde perfusion. The other case failed in paraplegia because the aneurysm was severely atheroscleroric and the left subclavian artery was stenotic with a thick atheroma, which caused thromboembolism into the left vertebral artery. The operative mortality and morbidity were as same as those of conventional prosthetic replacement. It means this procedure is under progression and requires further refinements to perform more safely but perioperative factors such as selective cerebral perfusion time, the perfusion time, and blood loss were less than those of conventional prosthetic replacement. The successful 20 cases demonstrated significant shrinkage of the excluded aneurysmal space upon CT examinations during the follow-up period. Several patients showed complete disappearance of the aneurysm during the follow-up period. These CT findings confirm the complete exclusion of the aneurysm by this procedure and no risk of aneurysmal rupture after a successful placement of the transaortic stent-graft [8, 9]. We compared the diameter of aneurysms during the follow-up period with that measured 1 month after surgery because we intended to evaluate shrinkage of the excluded aneurysmal space. In general the diameter of the excluded aneurysm tends to reduce not immediately but dilates once occasionally and begins to shrink later, from 1 to 6 months after transcatheter stent-grafting [1 3]. But our

Ann Thorac Surg SUEDA ET AL 2003;76:84 9 FATE OF ANEURYSMS AFTER STENT-GRAFTING successful cases showed immediate shrinkage of the excluded aneurysm after surgery. This rapid shrinkage is a specific character of transaortic stent-grafting because this procedure can accomplish endovascular coverage completely by suturing the proximal end of the stent-graft. Ishihara and colleagues [10] reported the midterm result of the transaortic stent-grafting for acute type A dissection. They used this stent-graft for acute type A dissection combined with total prosthetic replacement of ascending and arch aorta. After placement of the stentgraft into the descending aorta, the residual false lumen disappeared completely during the follow-up period. In this series we found extreme shrinkage or disappearance of the excluded aneurysmal space after this stent-grafting procedure even in patients with true thoracic aortic aneurysm. Although our experience of transaortic stent-graftng is limited and there are several caveats for indication and prevention of neurologic complications, transaortic stentgrafting is feasible for treatment of true thoracic aortic aneurysms. References 1. Mitchell RS, Dake MD, Semba CP, et al. Endovascular stent-grafting repair of thoracic aortic aneurysms. J Thorac Cardiovasc Surg 1996;111:1054 62. 2. Slonim MD, Nyman U, Semba CP, Miller CD, Mitchell RS, Dake MD. Aortic dissection: percutaneous management of ischemic complications with endovascular stents and balloon fenestration. J Vasc Surg 1996;23:241 53. 3. Dake MD, Miller DC, Semb CP, Mitchell RS, Walker PJ, Liddell RP. Transluminal placement of endovascular stentgrafts for the treatment of descending thoracic aortic aneurysms. N Engl J Med 1994;23:1729 34. 4. Kato M, Ohnishi K, Kaneko M, et al. A new graft-implanting method of descending thoracic aortic aneurysm or dissection with a stent-graft. Circulation 1996;94(Suppl 2):188 93. 5. Sueda T, Watari M, Okada K, Orihahshi K, Matsuura Y. Endovascular stent-grafting through the aortic arch: an alternative approach for distal arch aortic aneurysm. Ann Thorac Surg 2000;70:1251 4. 6. Orihahshi K, Matsuura Y, Sueda T, et al. Echocardiographyassisted surgery in transaortic endovascular stent grafting. Role of transesophageal echocardiography. J Thorac Cardiovasc Surg 2000;120:672 8. 7. Parodi JC, Palmaz JC, Barone HD. Transfemoral intraluminal graft implantation for abdominal aortic aneurysms. Ann Vasc Surg 1991;5:491 9. 8. Uchida N, Ishihara H, Sakashita M, et al. Repair of the thoracic aorta by transaortic stent grafting (open stenting). Ann Thorac Surg 2002;73:444 9. 9. Watari M, Sueda T, Ishii O, et al. Shrinkage of excluded aneurysmal spaces: the excellent results of endovascular stent grafting through the aortic arch for distal arch aneurysm. J Thorac Cardiovasc Surg 2001;122:829 32. 10. Ishihara H, Uchida N, Yamasaki C, Sakashita M, Kanou M. Extensive primary repair of the thoracic aorta in Stanford type A acute aortic dissection by means of a synthetic vascular graft with a self-expandable stent. J Thorac Cardiovasc Surg 2002;123:1035 40. 89 CARDIOVASCULAR INVITED COMMENTARY This paper offers a very interesting approach to the complex problem of managing distal aortic arch aneurysms or dissections. However, this idea is not new. Borst published the elephant trunk principle for true aortic aneurysms in 1983, and our group applied the principal to type B aortic dissections. Results were encouraging for both diseases. This approach is especially useful for complex dissections with retrograde extensions that start after the origin of the left subclavian artery. In these patients, it is possible to treat the ascending aorta and arch during circulatory arrest and to occlude the distal intimal tear with a stent graft. Sueda s study shows shrinkage of the excluded aneurysms over time during medium-term follow-up (34 months) and confirms our experience both with thoracic and abdominal aneurysms. The comparison group of 20 patients treated by conventional operations is not appropriate because these patients are completely different from the study patients. We would also point out that an autoexpandable stent can be introduced through a purse string suture in the aortic arch to exclude distal arch aneurysms or dissections using transesophageal echocardiographic monitoring. This allows simultaneous treatment of the aortic problems and aortocoronary bypass grafts without using cardiopulmonary bypass. Enio Buffolo, MD R. Borges Lagoa, 1080-cj. 701 São Paulo SP Cep 04038-002 Brazil e-mail: buffolo@terra.com.br 2003 by The Society of Thoracic Surgeons 0003-4975/03/$30.00 Published by Elsevier Inc PII S0003-4975(03)00702-1