Eur J Vasc Endovasc Surg (2011) 42, 442e447
Endovascular Approaches to Acute Aortic Type A Dissection: A CT-Based Feasibility Study J. Sobocinski a, N. O’Brien a, B. Maurel b, M. Bartoli c, Y. Goueffic d, T. Sassard e, M. Midulla f, M. Koussa a, A. Vincentelli a, S. Haulon a,* a
Vascular and Cardiac Surgery, Hoˆpital Cardiologique, CHU LILLE, INSERM U1008, Universite´ Lille Nord, France Vascular and Cardiac Surgery, CHU TOURS, France c Vascular and Cardiac Surgery, CHU MARSEILLE, France d Vascular and Cardiac Surgery, CHU NANTES, France e Cardiac Surgery, Hoˆpital Louis Pradel, CHU LYON, France f Cardio-vascular Imaging, Hoˆpital Cardiologique, CHU LILLE, France b
Submitted 5 January 2011; accepted 7 April 2011 Available online 20 July 2011
KEYWORDS Type A dissection; Endograft; Workstation
Abstract Background: Open graft replacement of the ascending aorta is the current treatment of choice for Stanford acute type A dissections. However, approximately 20% of patients are deemed unfit for open surgery. To determine if an endovascular option exists for this latter group of patients, we performed a computed tomography (CT)-based feasibility study. Methods: A cohort of consecutive patients presenting to the cardiovascular care unit (CVCU) for an acute Stanford type A aortic dissection between 2006 and 2009 was retrospectively analysed. Inclusion criterion was a high-quality preoperative angio-CT scan that could be analysed on a three-dimensional (3D) workstation. Numerous anatomical parameters of the dissection were studied, including the location and the length of the primary proximal entry tear. Finally, we determined which of the patients would have been potential candidates for an endovascular repair (stentgraft implantation). Results: A total of 102 patients were included in our study. The median distance of the primary entry tear to the closest coronary artery was 23 mm (range 0e128). The median true lumen and true þ false lumen (total) diameters at the level of the entry tear was 38 mm (range 22 e78) and 46 mm (range 28e93), respectively. The median length of the ascending aorta was 84 mm (range 40e130). An endovascular repair with a tubular stentgraft was deemed feasible in 37 patients. An additional eight patients were also candidates for a tubular endovascular repair but would have required a carotidecarotid cross over bypass. Finally, an arch-branched stentgraft could have been used in 13 patients to exclude an entry tear located in the arch.
* Corresponding author. Tel.: þ33 320 445 005; fax: þ33 320 445811. E-mail address:
[email protected] (S. Haulon). 1078-5884/$36 ª 2011 European Society for Vascular Surgery. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.ejvs.2011.04.037
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Conclusion: Open repair of acute type A dissection is and remains the ‘gold standard’ of care. Our study demonstrates that approximately half the patients undergoing an open repair could potentially benefit from an endovascular repair. This new treatment option has not been evaluated to date. ª 2011 European Society for Vascular Surgery. Published by Elsevier Ltd. All rights reserved.
Acute aortic dissection is the most common catastrophe affecting the aorta, with an overall mortality of 27% reported in the International Registry of Aortic Dissection (IRAD).1 A thorough understanding of the clinical presentation, classification and pathophysiology of aortic dissection is a necessary prerequisite for either open surgical, endovascular or medical treatment. Open graft replacement of the ascending aorta with or without aortic valve replacement is the current treatment of choice for Stanford type A dissections, and improvements in cardiac surgery techniques over the last two decades have been associated with improved outcomes.24 Regarding Stanford type B dissections, various clinical presentations may be encountered but generally only complicated forms (visceral malperfusion or impending rupture) undergo repair. Advances in imaging techniques and in endovascular techniques have changed patient management during recent years, allowing more rapid diagnosis and decision making in terms of therapeutic options.5e7 The goals of endovascular therapy in aortic dissection are to remodel the dissected aorta by sealing the proximal entry tear, thus redirecting flow into the true lumen and promoting depressurisation and thrombosis of the false lumen. Accurate location of the entry tear and proper assessment of the proximal landing zone are fundamental to successful endovascular stentgraft repair. Dake et al. reported that with type B dissection, nearly 80% of compromised branch vessels were reperfused after proximal entry tear stentgrafting.8 Moreover, aneurysmal enlargement in the chronic phase of dissection, another concern that necessitates the use of extended graft replacements for thoracic and thoracoabdominal lesions with a major risk for paraplegia, may be restricted by adequate management of the proximal aortic tear. Recent publications have demonstrated the feasibility of an endovascular approach in the ascending aorta even in patients with acute aortic syndrome.9,10 From the databases of several University Hospitals across France, we undertook an original study to determine the feasibility of endovascular treatment in patients presenting with an acute type A aortic dissection.
Materials and Methods The medical records and imaging studies of all patients treated for an acute Stanford type A aortic dissection at five French university hospitals (Lille, Lyon, Marseille, Nantes and Tours) between 2006 and 2009 were reviewed. Aortic dissection diagnosed within 2 weeks of the onset of symptoms was considered acute. Inclusion criterion was presentation to the cardiovascular care unit (CVCU) with an acute type A aortic dissection identified on arterial-phase contrast-enhanced computed tomography (CT) scan. The only exclusion criterion was the absence of a workable (high-quality arterial phase and maximum slice-thickness of 3 mm) preoperative angiocomputed tomography (CT) scan with DICOM data.
We classified the dissections according to the two usual classification schemes: the DeBakey classification11 and the Stanford classification.12 Demographic data including patient number, age and sex, history of systolic hypertension, concurrent medication and previous major conditions were collected. Surgical data including the type of surgical repair, the mean length of hospital stay and mortality were also collected. The continence of the aortic valve was noted according to the echocardiography report. Preoperative CT scans were analysed for the purpose of this study using the Terarecon Workstation (AquariusWS; Terarecon, San Francisco, CA, USA). We accurately determined the location and the length of the primary proximal entry tear relative to the origin of the side branches (coronary arteries and supra-aortic trunks) of the aorta. As per definition, the proximal entry tear was the entry tear closest to the coronary arteries. We did not try to locate the sino-tubular junction as it is often dilated in acute type A dissections. Aortic measurements were performed by two vascular surgeons with vast experience in endograft planning with this dedicated workstation. Measurements included distances and diameters evaluated on true lumen centreline reconstructions, using 3D and multiplanar (MPR) reconstructions at multiple levels in the aorta and its side branches as described by O’Neill et al.13 A centreline of flow (CLF) was generated by using the semi-automated centreline algorithms on the workstation. The calculated centreline was confirmed manually by scrolling through the MPR images to ensure that it accurately reflected the centre point of the arterial lumen. Reconstructions perpendicular to the CLF were then displayed in a two-dimensional format from which diameter and length measurements were calculated (Figs. 1 and 2). The total diameter of the aorta (external wall to the opposite external wall) as well as corresponding diameters of the true and false lumen were measured at several levels, including diameters 15 mm above the lower coronary artery, at the entry-tear level, proximally to the inominate trunk origin, proximally to the left common carotid origin and proximally and distally to the left subclavian artery. Maximum thoracic diameters, maximum abdominal diameters and maximum left and right common iliac diameters were also measured. The morphology of the aortic arch was determined as described by Casserly et al.14 This classification describes the degree of angulation of the aortic arch and thus reflects potential difficulties in endograft navigation in the aortic arch. The number of entry or re-entry tears along the intimal flap according to angio-CT scan findings was evaluated. The patency of the false lumen was evaluated at multiple levels in the aorta: ascending aorta, aortic arch, descending aorta and abdominal aorta, and common iliac arteries. Aortic branch vessel malperfusion (including neurological events) was noted. Diameters, calcifications, tortuosity and patency of the iliofemoral vessels were assessed.
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Figure 1 a: the aortic diameters (true lumen and total aortic diameter) were evaluated at several levels perpendicular to the centerline flow lumen (a: diameter 15 mm above the lower coronary artery, b: diameter at the proximal entry tear level, c: diameter proximally to the inominate trunk origin, d: diameter proximally to the left common carotid origin, e & f: diameters proximally and distally to left subclavian artery origin, g: maximum diameter in the descending thoracic aorta) b: 3D-reconstruction of an angio-CT scan with centerline flow lumen.
Figure 2 a: the lengths were also calculated from a centerline flow lumen reconstruction (CFL) (a: distance from the closest coronary artery to the proximal entry tear (ET), b: length of the ET, c: length from the ET to the inominate trunk, d: length from the ET to the left common carotid, e: length from the ET to the left subclavian artery). b: Multiplanar reconstruction of an angio-CT scan performed to measure the distance from the coronary artery to the proximal entry tear.
A patient was considered to be a candidate for an endovascular approach (stentgraft implantation) if he/she fulfilled the following anatomical criteria:
- Iliofemoral vessels had to be suitable for a 24Fr endovascular delivery system (diameter >7 mm and angulation 20 mm before the origin of the inominate trunk were suitable for a branch device repair if the dissection did not extend into the inominate trunk or the LCC.
Results We included 102 patients in our study. All patients underwent surgical repair of their dissection. We excluded 110 patients with acute type A dissections during the study period because of the absence of a workable preoperative angio-CT scan. Demographic characteristics of the patients are described in Table 1. All patients presented with an acute type A aortic dissection (Stanford classification). Of these, 77% had a type I DeBakey aortic dissection, 18% a type II and 5% a retrograde type III. Echocardiography demonstrated that 44% of patients had no aortic insufficiency, while the remaining patients with aortic regurgitation were distributed as 23% with grade I regurgitation, 20% with grade II, 8% with grade III and 5% with grade IV. An ascending aorta replacement, a Bentall procedure and a TironeeDavid procedure were performed in 70%, 29% and 1% of patients, respectively. An aortic valve repair (including replacement or valvuloplasty) was performed in 35% of patients. The 30-day mortality rate was 24%. Based on our selection criteria for an endovascular repair, 32 patients could have been treated with a tubular stentgraft implanted between the coronary arteries and the inominate trunk. The five patients presenting with a type III De Bakey aortic dissection with retrograde involvement of the ascending aorta were also candidates for an endovascular approach (coverage of the proximal entry tear in the descending aorta) with a tubular stentgraft. An additional eight patients with a distally located entry tear, near the origin of the inominate trunk (length < 20 mm) Table 2
445 were candidates for a tubular stentgraft implantation in combination with an extra-anatomic carotidecarotid bypass. Finally, a supplementary 13 patients could have been treated with an arch-branched stentgraft to exclude an entry tear located near the inominate trunk and LCC origins. All morphological and anatomical criteria results are summarised in Tables 2 and 3.
Discussion The aim of this multi-centric study was to determine theoretically what proportion of patients presenting with an acute type A dissection could be eligible for an endovascular repair. Our goal is not to advocate an endovascular approach in all type A dissections, but to evaluate if an alternative treatment could be proposed to patients currently contra-indicated for open surgery, the current gold standard. The IRAD registry1 reported that more than 20% of patients with acute type A aortic dissection are refused surgery, because they are considered at ‘high-risk’ for an open approach. Stentgraft implantation has the potential to minimise the surgical insult in these high-risk patients and accordingly offer a treatment option.15 The demographic characteristics and surgical outcomes for our cohort are similar to those encountered in literature.1,16,17 In type A aortic dissections with an entry tear located in the ascending aorta, pioneers have reported successful endovascular repairs.10,20,22,23 In 2008, Wang successfully treated 11 patients with an acute type A aortic dissection using a hybrid approach. The supra-aortic vessels were transposed by an open approach and the proximal entry tear was sealed by stentgraft implantation.23 Retrograde type A aortic dissections are type A dissections with an entry tear not located in the ascending aorta (De Bakey type III) and represent 7e38% of all type A dissections.18e20 In this subset of patients, endovascular repair is currently performed by sealing the proximal entry tear with an endograft implanted in the descending thoracic aorta. Preliminary clinical results are encouraging.21 The advances in diagnostic imaging modalities and the development of dedicated workstation software are mandatory pathways to a better understanding of complex aortic diseases such as dissections and to the design of a new generation of endografts. Multi-detector computed
Lengths (mm) evaluated.
Distance from the distal coronary artery to the IT Distance from the distal coronary artery to the LCC Distance from the distal coronary artery to the ET Proximal entry tear length Distance from the ET to the IT Distance from the ET to the LCC Distance from the ET to the LSCA Innominate trunk length Dissection extension length Number of entry tears
Median
Mean
Range
84 99 23 23 58 71 87 35 496 2
85 99 28 39 59 74 87 35 373 2
40e130 0e148 0e128 1e221 0e118 0e134 19e148 14e64 20e699 1e6
IT: innominate trunk, LCC: Left Common Carotid, ET: proximal entry tear, LSCA: Left Subclavian Artery.
446 Table 3
J. Sobocinski et al. Diameters (mm) evaluated. Median Mean Range
Aorta at the proximal entry tear level: True lumen 38 38 Total aortic diameter 46 48 Aorta 15 mm above the closest coronary artery: True lumen 36 37 Total aortic diameter 46 48 Aorta proximal to the IT origin: True lumen 35 35 Total aortic diameter 42 42 IT origin diameter 15 15 Aorta proximal to the LCC origin: True lumen 33 33 Total aortic diameter 38 39 LCC origin diameter 9 9 Aorta proximal to the LSCA origin: True lumen 31 31 Total aortic diameter 34 35 Aorta distal to the LSCA origin: True lumen 27 27 Total aortic diameter 32 32 Descending thoracic aorta maximal diameter: True lumen 26 26 Total aortic diameter 33 34 Abdominal aorta maximal diameter: True lumen 17 18 Total aortic diameter 22 22 Left common iliac maximal diameter: True lumen 9 9 Total diameter 13 14 Right common iliac maximal diameter: True lumen 8 9 Total diameter 14 14 Left external iliac maximal diameter: 8 8 Right external iliac maximal diameter: 8 8
2278 28e93 19e67 28e93 23e49 27e61 9e24 19e51 25e57 6e13 17e40 23e52 20e35 21e52 12e39 23e58 12e25 16e36 5e15 10e21 5e14 10e19 7e12 7e11
ET: proximal entry tear, IT: inominate trunk, LCC: left common carotid.
tomography (MDCT) has rapidly evolved from four-detector row systems in 1998 to 256-slice and 320-detector row CT systems nowadays. Current spatial and temporal resolution of the 64-detector MDCT scanners performed in coronary artery or aortic valve CT studies, with small detector element size and fast gantry rotation speed, provide very reliable anatomical imaging studies to accurately analyse aortic dissections.24,25 The endovascular treatment of aortic acute dissections and chronic aneurysms has different goals. In the setting of an aneurysm, proximal and distal sealing and fixation systems are mandatory to avoid the secondary migration of the endograft into the aneurysm sac. This would result in an endoleak reperfusing the sac, with a risk of fatal rupture. The goal of the endovascular approach in acute aortic dissections is to cover the entry tear in the proximal aorta, redirecting the entire flow into the true lumen and thereby blocking inflow into the false lumen. This theoretically changes the flow dynamics such that the true lumen can reexpand and the false lumen collapse or even thrombose. Even if, in most cases, there are several entry and re-entry
tears, simply covering the most proximal one is often sufficient to initiate remodelling of the proximal aorta and reverse malperfusion conditions. The endograft is not implanted in the aorta to bridge two healthy aortic segments between a sac, but rather in a non-dilated true lumen to seal a hole. The forces exerted on the endograft are thus significantly different, and once remodelling of the aorta has occurred, the endograft serves no further function. Because 46 mm is currently the maximum diameter that endograft manufacturers can provide, we therefore selected 38 mm as the maximum true lumen diameter deemed to be eligible for an endovascular approach. We consider that a minimum of 20% oversizing is required in the ascending aorta because of the flow dynamics. In addition, we did not want the total aortic diameter including the false lumen to be greater than the largest endograft (46 mm). We considered 20 mm as the minimum proximal and distal length required to seal the entry tear, although this was probably an overestimation of what is truly required when one considers the aforementioned role of an endograft in an acute aortic dissection. There are many challenges when one considers the implantation of an endograft in the ascending aorta: the arch curvature, the need to cross the aortic valve to position a stiff wire in the left ventricle, the flow forces exerted by the aortic current and the need to preserve flow to the coronary arteries and the supra aortic trunks. The arch curvature is not a major obstacle anymore to the advancement of endograft delivery systems. These are now manufactured with nitinol inner cannulas that resist kinking, with a short atraumatic tip that can be safely positioned in the left ventricle, and with a hydrophilic coating that tracks easily even through tortuous anatomy. In addition, manufacturers are launching a new generation of endografts with a lower profile. In the future, insertion of these endografts through an axillary approach will be possible. Positioning a stiff wire into the left ventricle is now routine practice in the many centres performing percutaneous aortic valve replacement and should therefore not be considered a major issue. It is nevertheless a dangerous manoeuvre that can lead to left ventricle perforation if the tip of the wire is not always located. The flow forces exerted by the aortic current preclude accurate positioning of the endograft in the ideal position, abutting the ostium of the most distal coronary artery. Rapid pacing with wires positioned in the right ventricle from a femoral vein approach is now the recommended mechanism to allow the endovascular therapist to precisely deliver the endograft. We do not yet have the ability to preserve flow to the coronary arteries through a fenestrated or a branched endograft and, thus, a 20-mm neck is mandatory to achieve a secure seal proximal to the entry tear. If, however, the entry tear abuts the inominate trunk, this latter vessel can be covered after an extra-anatomic bypass is performed between the left and the right common carotid arteries. If the entry tear abuts the LCC artery origin, then we would recommend the use of a branched endograft. A current design is undergoing evaluation and should be commercially available soon. It is a tubular endograft incorporating inner branches that are cannulated from a right and left axillary approach (the left approach necessitates a prior left carotid to left subclavian artery bypass or transposition). Covered bridging stents are then
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implanted between the supra aortic trunks and the inner branches to achieve exclusion of the arch lesion and antegrade perfusion to the supra aortic trunks. The major limitation of our study is the high number of patients (>50%) that were excluded because of inadequate preoperative imaging. However, we believe that our study cohort is large enough to provide relevant data, and no similar work has been yet published. A more accurate study could be performed on gated CT scans, but the multi-row angio-CTs that we collected had adequately thin acquisitions that allowed a precise analysis on the workstation. Finally, it is important to point out that this study just demonstrates the feasibility of an endovascular approach to acute type A aortic dissection in selected patients but, as yet, we have no idea of the efficacy of such an endovascular treatment of acute type A dissections.
7 Kato M, Ohnishi K, Kaneko M, Ueda T, Kishi D, Mizushima T, et al. New graft-implanting method for thoracic aortic aneurysm or dissection with a stented graft. Circulation 1996;94(9 Suppl):II188e193. 8 Schoder M, Czerny M, Cejna M, Rand T, Stadler A, Sodeck GH, et al. Endovascular repair of acute type B aortic dissection: longterm follow-up of true and false lumen diameter changes. Ann Thorac Surg 2007;83(3):1059e66. 9 Inoue K, Hosokawa H, Iwase T, Sato M, Yoshida Y, Ueno K, et al. Aortic arch reconstruction by transluminally placed endovascular branched stent graft. Circulation 1999;100(19 Suppl): II316e321. 10 Ihnken K, Sze D, Dake MD, Fleischmann D, Van der Starre P, Robbins R. Successful treatment of a Stanford type A dissection by percutaneous placement of a covered stent graft in the ascending aorta. J Thorac Cardiovasc Surg 2004;127(6):1808e10. 11 Me De Bakey, Da Cooley, Creech O. Surgical considerations of dissecting aneurysm of the aorta. Ann Surg 1955;142(4):586e610. 12 Daily PO, Trueblood HW, Stinson EB, Wuerflein RD, Shumway NE. Management of acute aortic dissections. Ann Thorac Surg 1970;10(3):237e47. 13 O’Neill S, Greenberg RK, Resch T, Bathurst S, Fleming D, Kashyap V, et al. An evaluation of centerline of flow measurement techniques to assess migration after thoracic endovascular aneurysm repair. J Vasc Surg 2006;43(6):1103e10. 14 Casserly IP, Kapadia SR. Advances in percutaneous valvular intervention. Expert Rev Cardiovasc Ther 2005;3(1):143e58. 15 Nashef SA, Roques F, Michel P, Gauducheau E, Lemeshow S, Salamon R. European system for cardiac operative risk evaluation (EuroSCORE). Eur J Cardiothorac Surg 1999;16(1):9e13. 16 Bavaria JE, Brinster DR, Gorman RC, Woo YJ, Gleason T, Pochettino A. Advances in the treatment of acute type A dissection: an integrated approach. Ann Thorac Surg 2002; 74(5):S1848e52. 17 Rampoldi V, Trimarchi S, Eagle KA, Nienaber CA, Oh JK, Bossone E, et al. Simple risk models to predict surgical mortality in acute type A aortic dissection: the International Registry of Acute Aortic Dissection score. Ann Thorac Surg 2007;83(1):55e61. 18 Miller DC, Mitchell RS, Oyer PE, Stinson EB, Jamieson SW, Shumway NE. Independent determinants of operative mortality for patients with aortic dissections. Circulation 1984;70(3 Pt 2): I153e64. 19 Lansman SL, Galla JD, Schor JS, Ergin MA, Griepp RB. Subtypes of acute aortic dissection. J Card Surg 1994;9(6):729e33. 20 Kato N, Shimono T, Hirano T, Ishida M, Yada I, Takeda K. Transluminal placement of endovascular stent-grafts for the treatment of type A aortic dissection with an entry tear in the descending thoracic aorta. J Vasc Surg 2001;34(6):1023e8. 21 Nienaber CA, Kirche S. Open and endovascular treatment of type A dissection. In: European vascular Course, ed Minerva medical; 2010. 22 Zimpfer D, Czerny M, Kettenbach J, Schoder M, Wolner E, Lammer J. Treatment of acute type a dissection by percutaneous endovascular stent-graft placement. Ann Thorac Surg 2006;82(2):747e9. 23 Wang S, Chang G, Li X, Hu Z, Li S, Yang J, et al. Endovascular treatment of arch and proximal thoracic aortic lesions. J Vasc Surg 2008;48(1):64e8. 24 Lee MS, Chun EJ, Kim KJ, Kim JA, Vembar M, Choi SI. Reproducibility in the assessment of noncalcified coronary plaque with 256-slicemulti-detectorCT and automated plaque analysis software. Int J Cardiovasc Imaging 2010;26(Suppl 2):237e44. 25 Klass O, Walker MJ, Olszewski ME, Ahner J, Feuerlein S, Hoffman MH, et al. Quantification of aortic valve area at 256slice computed tomography: Comparison with transesophageal echocardiography and cardiac catheterization in subjects with high-grade aortic valve stenosis prior to percutaneous valve replacement. Eur J Radiol; in Press.
Conclusion Approximately half of the patients currently undergoing open repair of an acute type A dissection could potentially be candidates for an endovascular repair. It is reasonable to extrapolate that the same proportion of patients who currently refused surgery on the basis of being unfit for open repair would have anatomy suitable for an endovascular repair. Clinical studies should be conducted in this subgroup of patients to determine a potential future role of endovascular repair in acute type A dissections.
Conflict of Interest Ste ´phan Haulon is a consultant for Cook Medical.
Funding None.
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