- Email: [email protected]
Distal Stent Graft-Induced New Entry: An Emerging Complication of Endovascular Treatment in Aortic Dissection
Distal Stent Graft-Induced New Entry: An Emerging Complication of Endovascular Treatment in Aortic Dissection Antonio Pantaleo, MD, Giuliano Jafrancesco, MD, Francesco Buia, MD, Alessandro Leone, MD, Luigi Lovato, MD, Vincenzo Russo, MD, Luca Di Marco, MD, Roberto Di Bartolomeo, MD, and Davide Pacini, MD Departments of Cardiac Surgery and Radiology, S. Orsola-Malpighi Hospital, University of Bologna, Bologna, Italy
Background. Aortic dissection is a major cardiovascular disease associated with a high mortality rate. In complicated type B dissection, with favorable anatomy, endovascular surgical repair (thoracic endovascular aortic repair [TEVAR]) is considered the treatment of choice. Intimomedial injury induced by stent graft, or stent graftinduced new entry (SINE), has a clinically significant incidence. SINE can occur at the proximal or distal level of the stent graft. The aim of this retrospective study was to investigate the incidence, mechanism, and predictive factors of late distal SINE. Methods. We reviewed 139 discharged patients after TEVAR for type B or residual aortic dissection after type A surgery, from January 2007 to March 2013. Three intervals of computed tomography imaging were collected, including before and after primary TEVAR and with the first detection of distal SINE. Four accessible measurement methods for precise size selection of the stent graft before and after the procedure were analyzed at the distal end level of the primary stent graft. Results. Among the 139 patients, only 108 had complete preoperative and follow-up imaging and were enrolled in the study. The mean age of the patients was 59.7 ± 11.7 years, and 92 patients (85.2%) were men. Seventy had type B aortic dissection, and 38 had residual
aortic dissection after type A surgery. The mean followup period was 36.1 ± 25.7 months. During follow-up, distal SINE occurred in 30 patients (27.8%), and 18 of them (60%) underwent secondary TEVAR whereas the remaining 12 patients were medically treated. No statistically significant differences in demographic and clinical conditions were seen between patients with or patients without SINE. The incidence of SINE was lower for acute than for chronic dissection (16% versus 50%). At the multivariate analysis, the independent factors associated with SINE development were the oversizing ratio of the area (odds ratio 1.858; 95% confidence interval: 1.109 to 3.064; p [ 0.018) and of the mean diameter (odds ratio 1.858; 95% confidence interval: 1.109 to 3.064; p [ 0.018). Conclusions. Type B aortic dissection can be treated effectively with TEVAR. The incidence of distal SINE is not negligible but is not associated with poor outcomes. The main determinant of SINE seems to be an excessive oversizing, which is particularly evident in the distal end. More accurate sizing can be obtained by evaluating the area of the true lumen.
A
incidence and needs to be differentiated from the natural disease progression or iatrogenic injury from endovascular manipulation [7]. SINE can occur at the proximal or at the distal end of the stent graft, or even at both ends, and appears to be noticeably life threatening [7, 14]. The aim of this study was to investigate the incidence, mechanism, and predictive factors of late distal SINE.
ortic dissection is one of the most devastating cardiovascular diseases, and its management remains a challenge. Medical treatment represents the gold standard for uncomplicated acute, subacute, and chronic type B aortic dissection [1, 2]. Open or endovascular surgical repair is recommended for complicated cases [3], but thoracic endovascular aortic repair (TEVAR) is preferred because it is associated with reduced early mortality and morbidity [4, 5]. However, several controversies remain with the long-term durability of the procedures [6–13]. Intimomedial injury induced by stent graft, defined as stent graft-induced new entry (SINE), has a not negligible Accepted for publication Feb 1, 2016. Address correspondence to Dr Pacini, Unit a Operativa di Cardiochirurgia, Universit a degli Studi di Bologna, Policlinico S. Orsola-Malpighi, Via Massarenti 9, Bologna 40138, Italy; email: [email protected].
Ó 2016 by The Society of Thoracic Surgeons Published by Elsevier
(Ann Thorac Surg 2016;-:-–-) Ó 2016 by The Society of Thoracic Surgeons
Material and Methods Patients From January 2007 to March 2013, 139 patients undergoing TEVAR for type B or residual aortic dissection after type A surgery were discharged from our institution. Only patients with complete follow-up imaging (preoperative and postoperative) were considered eligible for the study. 0003-4975/$36.00 http://dx.doi.org/10.1016/j.athoracsur.2016.02.001
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Stent Grafts System
Recognition of SINE and Secondary Interventions
Five different types of stent grafts were used: Talent, Valiant, and Valiant Captivia (Medtronic Vascular, Santa Rosa, CA); E-Vita Open (Jotec GmbH, Hechingen, Germany); and Relay Plus (Bolton Medical, Sunrise, FL).
Once SINE was detected, medical therapy was initially preferred to optimize blood pressure. Patients with stable SINE underwent medical treatment and were followed by CT angiography at 3 to 6 months from the diagnosis, depending on the SINE location and aortic dimensions, and yearly afterward. Surgical or endovascular repair were performed in case of enlargement of the false lumen (more than 5 mm per year), overall aortic diameter greater than 55 mm, contained rupture, pseudoaneurism formation, malperfusion caused by true lumen compression due to expanded false lumen, and occurrence of symptoms. The secondary TEVAR procedure was conducted in the same fashion as the primary TEVAR. One or two pieces of thoracic stent graft were implanted. The proximal end of the stent graft was inserted into the previous endoprosthesis to cover the new entry of intimal erosion. We chose the proper size of the stent graft to carefully fit the distal landing zone below the SINE.
Primary Endovascular Procedure The anatomy of the aortic dissection was defined by preoperative thoracoabdominal computed tomography (CT). A proximal landing zone of 2 cm in length was identified, and aortic dimensions at this level were calculated on multiplanar reconstruction images. Endoprosthesis selection was performed according to the proximal landing zone diameter. We adopted an oversizing no greater than 10% to 15% of the proximal landing zone diameter in acute as well as in chronic dissection. Femoral or iliac artery was surgically isolated. Guidewire and pigtail catheter were introduced into the true lumen in a retrograde manner up to the ascending aorta under fluoroscopic guidance. A second guidewire pigtail was also introduced in the true lumen through the brachial artery to ascending aorta to perform additional angiography. Intraoperative transesophageal echocardiography and angiography were used to check the correct disposition of the guidewire in the true lumen of the aorta. The stent graft was introduced through the femoral arteriotomy and advanced on a stiff guidewire up to the proximal landing zone to cover the entry tear. In case of short proximal landing zone (less than 20 mm), the left subclavian artery was covered and, in elective cases, was previously revascularized by a carotid-to-subclavian bypass. The distal landing zone was then identified to cover the reentry tears in the descending aorta above celiac artery level and preserving as many intercostal arteries as possible to reduce the risk of paraplegia. If necessary, adjunctive stent grafts were deployed to extend distally the endovascular coverage. Advancement and deployment were done under fluoroscopic and transesophageal echocardiography control. The patient’s systolic blood pressure was lowered to less than 90 to 100 mm Hg to prevent the windsock effect and distal migration during stent graft deployment. Finally, angiography and transesophageal echocardiography control confirmed the correct position of the stent graft, the coverage of the primary entry and the absence of endovascular leaks, and the patency of the supraaortic trunks and the visceral arteries as well as the carotidsubclavian bypass graft if present.
Data Collection and Analysis Three intervals of CT imaging were collected, including before and after primary TEVAR and with the first detection of distal SINE. Four accessible measurement methods for precise size selection of stent graft before and after procedure were analyzed at the distal end level of the primary stent graft. These included measurement of the maximal transverse diameter (max Ø), mean of the maximal and minimal transverse diameters (mean Ø), circumference (Circ), and area (Area) of the true lumen (Xa; Fig 1). The diameters, circumference, and area of the distal end of the fully expanded stent graft were defined as predicted distal stent size (Xpred). The aortic diameters of the proximal landing zone before the primary endovascular procedure, as well as the diameter of the graft in cases of frozen elephant trunk or traditional elephant trunk was also measured. All CT measurements were performed by the interventional radiologists, always using the same postprocessing software.
Definitions and Mathematical Measurements of Mismatch Rate The oversizing ratio at the presumed distal stent end before implantation was defined as [(X pred Xa) / Xa 100%] considering the max Ø, the mean Ø, the Circ, and the Area of the true lumen [15]. The oversizing rate at the presumed distal stent end before implantation was defined as [A/B 100]; where A was the distal diameter of the selected stent graft and B was the maximal diameter of the true lumen at presumed level of distal end of stent graft [2].
Follow-Up Imaging Protocols In all patients, the thoracoabdominal aorta was analyzed with multislice CT angiography after TEVAR at discharge (1 week), then at 3, 6, and 12 months, and yearly thereafter. We evaluated the aortic sizes and flow in the true and false lumen, presence of endoleaks, and the integrity and position of the stent grafts in each patient. The SINE over the distal end of stent graft was documented.
Statistical Analysis Data were analyzed using SPSS 18.0 software (SPSS Inc, Chicago, IL). Continuous variables were expressed as mean SD and were compared using the Wilcoxon rank sum test. Values of p less than 0.05 were considered to be statistically significant. All the preoperative or intraoperative variables that achieved a p value of less than 0.2
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PANTALEO ET AL DISTAL STENT GRAFT-INDUCED NEW ENTRY
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Fig 1. (A) Sagittal computed tomography images from a patient affected by type B aortic dissection with primary tear distal to left subclavian artery. The preoperative image demonstrates a small diameter true lumen in the planned distal landing zone (indicated by X) of the descending thoracic aorta. Axial computed tomography scans at the “X level” show (B) minimum diameter (Min Diam) and maximum diameter (Max Diam), and (C) circumference (Circ) to area measurements of the true lumen.
in the univariate analysis were examined with multivariate analysis using stepwise logistic regression to evaluate the independent risk factors for SINE development.
Results During the study, 139 patients having undergone TEVAR for aortic dissection were discharged from the hospital, and SINE was detected in 42 (30.2%). In 37 patients (26.6%), SINE was distal, whereas in 5 (3,6%), it was proximal. The proximal SINEs were subsequently treated with conventional surgery by partial or total aortic arch replacement. Of the 139 patients, 25 were excluded because of incomplete preoperative imaging, and 6 died during follow-up. Only 108 have been enrolled in this study. There were 92 men (85.2%) and 16 women (14.8%); the mean age of the patients was 59.7 11.7 years. Detailed demographic data and risk factors are shown in Table 1. Seventy patients had type B aortic dissection, and 38 had residual aortic dissection after type A surgery. Among the 70 patients with type B aortic dissection, 26 had acute and 44 had chronic dissection (Table 1). The primary surgical repair of the 38 type A residual patients during the acute phase consisted of ascending
aorta and aortic arch replacement; ascending aorta, aortic arch replacement, and elephant trunk; and ascending aorta, aortic arch replacement, and frozen elephant trunk in 18, 7, and 13 patients, respectively. During primary TEVAR, a mean of 1.55 stent grafts per patient were implanted. Aortic stent grafts included Talent or Valiant (Medtronic Vascular) in 93 patients, Relay Plus (Bolton) in 14 patients, and E-Vita open (Jotec) in only 1 patient. Fifty-seven patients (52.7%) received 1 stent graft, 43 (39.8%) received 2 stent grafts and 8 (7.5%) received 3 stent grafts. In 37 patients (34.2%), the proximal landing zone was in zone 2, and in 27 of them, a carotid to left subclavian artery bypass was made before stent graft implantation. In the remaining 9 cases, 5 of which were an emergency, the bypass graft was not performed. The mean follow-up period was 36.1 25.7 months (range, 0.2 to 95). During follow-up, distal SINE occurred in 30 patients (27.8%). The mean period for detection of distal SINE after primary TEVAR was 24.8 20.67 months (range, 0.2 to 74.23). Eighteen (60%) of the 30 patients successfully underwent secondary TEVAR because they matched the criteria for reoperation. Only 1 of them required immediate endovascular treatment because of an overall aortic diameter greater than 55 mm associated with compressed true lumen causing visceral
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Table 1. Patient Demographic Data and Risk Factors Demographics and Risk Factors Male Female Age Body surface area Systemic hypertension Smoking Dysplidemia Diabetes mellitus Chronic kidney disease COPD Marfan syndrome Associated CVD Redo Urgent/emergency Subclavian artery coverage Intraoperative complications Aortic kinking Pathology Acute type B dissection Not acute type B dissection Type B residual Type B chronic
Overall (n ¼ 108)
SINE (n ¼ 30)
No SINE (n ¼ 78)
p Value
92 (85.2) 16 (14.8) 59.68 11.65 1.97 0.2 81 (74.9) 39 (36.1) 14 (12.9) 5 (4.6) 8 (7.4) 2 (1.8) 7 (6.4) 8 (7.4) 61 (56.5) 26 (24) 37 (34.2) 5 (4.5) 21 (19.4)
23 (76.7) 7 (23.3) 60.19 10.64 1.95 0.2 21 (70) 12 (40) 6 (20) 1 (3.3) 0 (0) 0 (0) 2 (6.7) 3 (10) 16 (53.3) 5 (16.7) 9 (30) 2 (6.6) 8 (26.7)
69 (88.5) 9 (11.5) 59.48 12.1 1.97 0.2 60 (76.9) 27 (34.6) 8 (10.3) 4 (5.1) 8 (10.2) 2 (2.6) 5 (6.4) 5 (6.4) 45 (57.7) 21 (26.9) 28 (35.9) 3 (3.8) 13 (16.7)
0.14 0.14 0.8 0.54 0.45 0.6 0.21 1 0.1 1 1 0.7 0.51 0.26 0.56 0.6 0.24
26 82 38 44
(24) (76) (35.2) (40.6)
5 25 10 15
(16.6) (83.3) (33.3) (50)
21 57 28 29
(26.9) (73.1) (35.9) (37.2)
0.26 0.26 0.8 0.22
Values are n (%) or mean SD. COPD ¼ chronic obstructive pulmonary disease;
CVD ¼ cardiovascular disease;
malperfusion. The mean period from detection of distal SINE to reoperation was 6.4 6.2 months (range, 0.1 to 25.1). The remaining 12 patients (40%) were medically treated without changes of size and morphology of the false lumen. No statistically significant differences in demographic and clinical conditions were seen between patients with or without SINE (Table 1). Among 30 SINE observed in our population, 7 patients were women and 23 were men, with SINE incidence among women higher than among men (43.8% versus 25%, respectively). Conversely, the incidence of SINE in acute and chronic dissection was 19.2% and 30.5%, respectively. The distal end of the stent lying in an angled portion of the descending aorta (aortic kinking) was found in 8 patients (26.7%) with SINE and in 13 patients (16.7%) without SINE, but the difference between the two groups was not significant (p ¼ 0.24). The oversizing ratio of the Area was significantly higher in patients with SINE (3.36 2.82 versus 2.67 1.8, p ¼ 0.02). Moreover, the oversizing ratio of the max Ø (0.55 0.61 versus 0.38 0.40, p ¼ 0.06) as well as the oversizing rate, A/B (155.52 60.91 versus 138.6 40.51, p ¼ 0.06), were also higher in the SINE group even if they did not reach a complete statistical significance (Table 2). At the multivariate analysis, the independent factors associated with SINE development were the oversizing ratio of the Area (odds ratio 1.858, 95% confidence interval: 1.109 to 3.064; p ¼ 0.018) and the oversizing ratio of the mean Ø
SINE ¼ stent-induced new entry.
(odds ratio 1.858, 95% confidence interval: 1.109 to 3.064; p ¼ 0.018; Table 3).
Comment In the 1990s, a new era in the treatment of aortic diseases for abdominal as well as for thoracic aorta began [4, 16]. Endovascular repair is the preferred technique for the treatment of a large number of the descending thoracic aorta pathologies, and the efficacy, as well as the feasibility of these procedures, has been widely demonstrated [5]. Aortic dissection has one of the highest mortality rates of any cardiovascular disease. Medical treatment and clinical follow-up remain the gold standard for the treatment of uncomplicated acute or chronic type B dissection. Conversely, for complicated cases of type B aortic dissection the endovascular treatment, whenever possible, is preferable to open surgery for a reduced early mortality and morbidity [17–19]. In our institution, from November 1999 to December 2013, we treated 220 patients with TEVAR for type B dissection with good early and late results; the overall early mortality rate was 5%. However, some aspects of endovascular treatment have to be clearly defined, and sizing in dissections is one of the most important. Indeed, choosing an adequate-size stent graft in such aortic diseases seems to be a subject of controversy. It has been reported that the correct size of the stent graft
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Table 2. Oversizing Ratio Diameter, Area, Circumference, and Rate Overall (n ¼ 108)
Variables Oversizing Oversizing Oversizing Oversizing Oversizing
ratio maximum diameter ratio mean diameter ratio area ratio circumference rate A/B
0.43 0.72 2.86 0.61 143.3
0.47 0.37 2.14 0.32 47.37
SINE (n ¼ 30) 0.55 0.76 3.36 0.63 155.52
0.61 0.43 2.82 0.37 60.91
No SINE (n ¼ 78)
p Value
0.06 0.15 0.02 0.32 0.06
0.38 0.71 2.67 0.61 138.6
0.40 0.34 1.8 0.30 40.51
Values are mean SD. SINE ¼ stent-induced new entry.
should be 10% larger than the diameters of the thoracic true lumen in acute dissection or 20% larger in chronic dissection; however, the nondissected mid aortic arch is the most useful target segment for proximal size measurements [20]. The difference in diameter between the aortic arch and the distal true lumen of the descending aorta has been demonstrated in dissection [21]. Owing to these differences, the proximal sizing of the prosthesis is more correct than the distal one that instead must be adapted. That can be the reason why a greater number of degenerations develop distally than proximally, and in this regard we observed 37 of the 139 patients (26.6%) who had available postoperative CT scan control with distal SINE and only 5 (3.6%) with proximal SINE. This incidence is perfectly comparable with that reported in the literature [7, 15]. Proximal SINE has to be considered a threatening lesion that can result in retrograde dissection [14] and must be immediately treated. For this reason, after the development of proximal SINE, our 5 patients were urgently treated by partial or total aortic arch replacement. Distal SINE is more benign, and treatment, if necessary, can be postponed and well programmed. We successfully treated with a secondary TEVAR only 18 of Table 3. Multivariate Analysis for Risk Factors of Stent-Induced New Entry Development Characteristics Female Age Body surface area Systemic hypertension Dyslipidemia Diabetes mellitus Chronic kidney injury Marfan syndrome Aortic kinking Acute type B dissection Residual type B dissection Oversizing ratio maximum diameter Oversizing rate A/B Oversizing ratio area Oversizing ratio mean diameter CI ¼ confidence interval;
OR
95% CI
p Value
3.140 . . . . . . . . . . 2.641
0.893–9.524 . . . . . . . . . . 0.993–7.026
0.076 0.841 0.928 0.783 0.108 0.860 0.999 0.969 0.236 0.445 0.325 0.052
. 1.843 0.034
. 1.109–3.064 0.001–0.802
0.631 0.018 0.036
OR ¼ odds ratio.
the 37 cases, whereas the remaining 19 were medically treated and followed with serial CT scans. Various risk factors for distal SINE have been evaluated in previous studies [7, 13, 20, 22]. In our cohort of 108 patients, neither baseline characteristics nor the type of aortic dissection was statistically significant for distal SINE development. However, we found a lower incidence of distal SINE in acute than in chronic dissection (17% and 50%, respectively), even if it did not reach statistical significance. This finding can be related to the different aortic wall characteristics in the acute and chronic phase of dissection. In acute dissection, the aortic wall is more elastic, and it can adapt better to a stent graft than a fibrotic, calcified, and inelastic aortic membrane typical of the chronic dissection. The morphology of the thoracic aorta, angled or kinked, at the level of the distal portion of the stent graft can promote SINE development because of increasing shear forces at that level. Although we found a higher rate of angled aorta at the distal landing zone in patients with distal SINE (26.7%) versus those without SINE (16.7%), the difference between the two groups was not statistically significant (p ¼ 0.24). Stent oversizing represents the strongest risk factor for SINE development. We found as independent risk factors for distal SINE, the oversizing ratio mean diameter and oversizing ratio area. Area and mean diameter are more accurate than other estimates (minimum or maximum diameter and circumference) for correct measurement of the aorta. Moreover, we were looking for a threshold value, beyond which there was a greater risk of SINE developing. Based on multivariate analysis, we found that the risk increased when the value of prestenting graft oversizing area was 3.5 or more; with these oversizing values, the stronger mechanical radial force of the stent can easily induce intimomedial membrane disruption and lead to SINE occurrence. Another important aspect to be considered in the assessment of the risk for SINE is the pathologic fragility of aortic wall, which is evident in patients with connective tissue disease. This finding explains the negative results of TEVAR for Marfan patients [23], and the higher incidence of SINE among these patients [7]. We treated 7 Marfan patients, with an incidence of distal SINE of 28.6%, which was comparable to that of the non-Marfan patients (27.7%). As opposed to the experience of Dong and colleagues [14], which reported exclusively proximal
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SINE in patients with Marfan syndrome, we described only distal SINE because in these patients the proximal landing zone was always a surgical prosthesis. Occurrence of SINE could even be influenced by different radial forces in the stent supplied by the manufacturer. Unfortunately, we could not investigate this aspect because, in most of our patients, we implanted stent grafts from the same company. Regarding the choice of the stent type, a tapered stent graft should be preferred for the majority of patients with dissection. However, the more common available tapered grafts have a maximal tapering end of only 4 mm, and often the discrepancy between the proximal and the distal landing zone is larger [15]. Therefore, it could be reasonable to avoid excessive oversizing, to implant a smaller tapered graft for the distal part first and then a larger stent graft for the proximal part. Moreover, the ideal grafts should also have lower radial force and higher flexibility to better adapt to the dissected aorta, and it would be desirable to be able to select, according to the anatomy or the specific etiology, the most suitable device for a patient’s characteristics.
Study Limitations The present study has several limitations. It is a retrospective study that did not permit an accurate estimation of the incidence of distal SINE at follow-up. The population examined is heterogeneous, and includes patients with residual type A dissection and chronic and acute type B dissections. Moreover, the examined period was a mean of only 36.1 months, and longer follow-up should be required.
Conclusion Complicated type B dissections can be successfully treated by TEVAR. The incidence of distal SINE is not negligible, but its occurrence is not associated with poor outcomes. Stent-induced new entry seems to be less frequent in cases of acute dissection. Complicated distal SINE can be usually treated with secondary TEVAR. The main determinant of SINE seems to be excessive oversizing that, owing to the tapered aspect of dissection, is particularly evident in the distal end. More accurate sizing can be obtained by evaluating the area of the true lumen instead of the traditional diameter measurement.
References 1. Fattori R, Cao P, De Rango P, et al. Interdisciplinary expert consensus document on management of type B aortic dissection. J Am Coll Cardiol 2013;61:1661–78. 2. Feng J, Lu Q, Zhao Z, et al. Restrictive bare stent for prevention of stent graft-induced distal redissection after thoracic endovascular aortic repair for type B aortic dissection. J Vasc Surg 2013;57(Suppl):44–52.
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3. Ehrlich MP, Dumfarth J, Schoder M, et al. Midterm results after endovascular treatment of acute, complicated type B aortic dissection. Ann Thorac Surg 2010;90:1444–8. 4. Dake MD, Miller DC, Semba CP, et al. Transluminal placement of endovascular stent-grafts for the treatment of descending thoracic aortic aneurysms. N Engl J Med 1994;331:1729–34. 5. Nienaber C, Kische S, Ince H, et al. Thoracic aortic stent-graft devices: problems, failure modes, and applicability. Semin Vasc Surg 2007;20:81–9. 6. Neuhauser B, Czermak BV, Fish J, et al. Type A dissection following endovascular thoracic aortic stent-graft repair. J Endovasc Ther 2005;12:74–81. 7. Dong ZH, Fu WG, Wang YQ, G, et al. Retrograde type A aortic dissection after endovascular stent graft placement for treatment of type B dissection. Circulation 2009;119:735–41. 8. Zipfel B, Hammerschmidt R, Krabatsch T, et al. Stent-grafting of the thoracic aorta by the cardiothoracic surgeon. Ann Thorac Surg 2007;83:441–8. 9. Fattori R, Nienaber CA, Rousseau H, et al. Results of endovascular repair of the thoracic aorta with the Talent thoracic stent graft: the Talent thoracic retrospective registry. J Thorac Cardiovasc Surg 2006;132:332–9. 10. Flores J, Shiiya N, Kunihara T, et al. Reoperations after failure of stent grafting for type B aortic dissection: report of two cases. Surg Today 2005;35:581–5. 11. Muhs BE, Balm R, White GH, et al. Anatomic factors associated with acute endograft collapse after Gore TAG treatment of thoracic aortic dissection or traumatic rupture. J Vasc Surg 2007;45:655–61. 12. Hinchliffe RJ, Krasznai A, Schultzekool L, et al. Observations on the failure of stent-grafts in the aortic arch. Eur J Vasc Endovasc Surg 2007;34:451–6. 13. Kato N, Hirano T, Kawaguchi T, et al. Aneurysmal degeneration of the aorta after stent-graft repair of acute aortic dissection. J Vasc Surg 2001;34:513–8. 14. Dong Z, Fu W, Wang Y, et al. Stent graft induced new entry after endovascular repair for Stanford type B aortic dissection. J Vasc Surg 2010;52:1450–7. 15. Weng SH, Weng CF, Chen WY, et al. Reintervention for distal stent graft induced new entry after endovascular repair with a stainless steel-based device in aortic dissection. J Vasc Surg 2013;57:64–71. 16. Parodi JC, Palmaz JC, Barone HD. Transfemoral intraluminal graft implantation for abdominal aortic aneurysms. Ann Vasc Surg 1991;5:491–9. 17. Szeto WY, McGarvey M, Pochettino A, et al. Results of a new surgical paradigm: endovascular repair for acute complicated type B aortic dissection. Ann Thorac Surg 2008;86:87–93. 18. Swee W, Dake MD. Endovascular management of thoracic dissections. Circulation 2008;117:1460–73. 19. Leurs LJ, Bell R, Degrieck Y, et al. Endovascular treatment of thoracic aortic diseases: combined experience from the EUROSTAR and United Kingdom thoracic endograft registries. J Vasc Surg 2004;40:670–9. 20. Shimono T, Kato N, Yasuda F, et al. Transluminal stent-graft placements for the treatments of acute onset and chronic aortic dissections. Circulation 2002;106:I241–7. 21. Xu SD, Huang FJ, Du JH, et al. A study of aortic dimension in type B aortic dissection. Interact Cardiovasc Thorac Surg 2008;7:244–8. 22. Riambau V, Guerrero F, Murillo I, Rivadeneira M, Monta~ na X, Matute P. Stent grafting-related acute type B redissection. Vascular 2008;16:101–5. 23. Pacini D, Parolari A, Berretta P, et al. Endovascular treatment for type B dissection in Marfan syndrome: is it worthwhile? Ann Thorac Surg 2013;95:737–49.
Background. Aortic dissection is a major cardiovascular disease associated with a high mortality rate. In complicated type B dissection, with favorable anatomy, endovascular surgical repair (thoracic endovascular aortic repair [TEVAR]) is considered the treatment of choice. Intimomedial injury induced by stent graft, or stent graftinduced new entry (SINE), has a clinically significant incidence. SINE can occur at the proximal or distal level of the stent graft. The aim of this retrospective study was to investigate the incidence, mechanism, and predictive factors of late distal SINE. Methods. We reviewed 139 discharged patients after TEVAR for type B or residual aortic dissection after type A surgery, from January 2007 to March 2013. Three intervals of computed tomography imaging were collected, including before and after primary TEVAR and with the first detection of distal SINE. Four accessible measurement methods for precise size selection of the stent graft before and after the procedure were analyzed at the distal end level of the primary stent graft. Results. Among the 139 patients, only 108 had complete preoperative and follow-up imaging and were enrolled in the study. The mean age of the patients was 59.7 ± 11.7 years, and 92 patients (85.2%) were men. Seventy had type B aortic dissection, and 38 had residual
aortic dissection after type A surgery. The mean followup period was 36.1 ± 25.7 months. During follow-up, distal SINE occurred in 30 patients (27.8%), and 18 of them (60%) underwent secondary TEVAR whereas the remaining 12 patients were medically treated. No statistically significant differences in demographic and clinical conditions were seen between patients with or patients without SINE. The incidence of SINE was lower for acute than for chronic dissection (16% versus 50%). At the multivariate analysis, the independent factors associated with SINE development were the oversizing ratio of the area (odds ratio 1.858; 95% confidence interval: 1.109 to 3.064; p [ 0.018) and of the mean diameter (odds ratio 1.858; 95% confidence interval: 1.109 to 3.064; p [ 0.018). Conclusions. Type B aortic dissection can be treated effectively with TEVAR. The incidence of distal SINE is not negligible but is not associated with poor outcomes. The main determinant of SINE seems to be an excessive oversizing, which is particularly evident in the distal end. More accurate sizing can be obtained by evaluating the area of the true lumen.
A
incidence and needs to be differentiated from the natural disease progression or iatrogenic injury from endovascular manipulation [7]. SINE can occur at the proximal or at the distal end of the stent graft, or even at both ends, and appears to be noticeably life threatening [7, 14]. The aim of this study was to investigate the incidence, mechanism, and predictive factors of late distal SINE.
ortic dissection is one of the most devastating cardiovascular diseases, and its management remains a challenge. Medical treatment represents the gold standard for uncomplicated acute, subacute, and chronic type B aortic dissection [1, 2]. Open or endovascular surgical repair is recommended for complicated cases [3], but thoracic endovascular aortic repair (TEVAR) is preferred because it is associated with reduced early mortality and morbidity [4, 5]. However, several controversies remain with the long-term durability of the procedures [6–13]. Intimomedial injury induced by stent graft, defined as stent graft-induced new entry (SINE), has a not negligible Accepted for publication Feb 1, 2016. Address correspondence to Dr Pacini, Unit a Operativa di Cardiochirurgia, Universit a degli Studi di Bologna, Policlinico S. Orsola-Malpighi, Via Massarenti 9, Bologna 40138, Italy; email: [email protected].
Ó 2016 by The Society of Thoracic Surgeons Published by Elsevier
(Ann Thorac Surg 2016;-:-–-) Ó 2016 by The Society of Thoracic Surgeons
Material and Methods Patients From January 2007 to March 2013, 139 patients undergoing TEVAR for type B or residual aortic dissection after type A surgery were discharged from our institution. Only patients with complete follow-up imaging (preoperative and postoperative) were considered eligible for the study. 0003-4975/$36.00 http://dx.doi.org/10.1016/j.athoracsur.2016.02.001
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Stent Grafts System
Recognition of SINE and Secondary Interventions
Five different types of stent grafts were used: Talent, Valiant, and Valiant Captivia (Medtronic Vascular, Santa Rosa, CA); E-Vita Open (Jotec GmbH, Hechingen, Germany); and Relay Plus (Bolton Medical, Sunrise, FL).
Once SINE was detected, medical therapy was initially preferred to optimize blood pressure. Patients with stable SINE underwent medical treatment and were followed by CT angiography at 3 to 6 months from the diagnosis, depending on the SINE location and aortic dimensions, and yearly afterward. Surgical or endovascular repair were performed in case of enlargement of the false lumen (more than 5 mm per year), overall aortic diameter greater than 55 mm, contained rupture, pseudoaneurism formation, malperfusion caused by true lumen compression due to expanded false lumen, and occurrence of symptoms. The secondary TEVAR procedure was conducted in the same fashion as the primary TEVAR. One or two pieces of thoracic stent graft were implanted. The proximal end of the stent graft was inserted into the previous endoprosthesis to cover the new entry of intimal erosion. We chose the proper size of the stent graft to carefully fit the distal landing zone below the SINE.
Primary Endovascular Procedure The anatomy of the aortic dissection was defined by preoperative thoracoabdominal computed tomography (CT). A proximal landing zone of 2 cm in length was identified, and aortic dimensions at this level were calculated on multiplanar reconstruction images. Endoprosthesis selection was performed according to the proximal landing zone diameter. We adopted an oversizing no greater than 10% to 15% of the proximal landing zone diameter in acute as well as in chronic dissection. Femoral or iliac artery was surgically isolated. Guidewire and pigtail catheter were introduced into the true lumen in a retrograde manner up to the ascending aorta under fluoroscopic guidance. A second guidewire pigtail was also introduced in the true lumen through the brachial artery to ascending aorta to perform additional angiography. Intraoperative transesophageal echocardiography and angiography were used to check the correct disposition of the guidewire in the true lumen of the aorta. The stent graft was introduced through the femoral arteriotomy and advanced on a stiff guidewire up to the proximal landing zone to cover the entry tear. In case of short proximal landing zone (less than 20 mm), the left subclavian artery was covered and, in elective cases, was previously revascularized by a carotid-to-subclavian bypass. The distal landing zone was then identified to cover the reentry tears in the descending aorta above celiac artery level and preserving as many intercostal arteries as possible to reduce the risk of paraplegia. If necessary, adjunctive stent grafts were deployed to extend distally the endovascular coverage. Advancement and deployment were done under fluoroscopic and transesophageal echocardiography control. The patient’s systolic blood pressure was lowered to less than 90 to 100 mm Hg to prevent the windsock effect and distal migration during stent graft deployment. Finally, angiography and transesophageal echocardiography control confirmed the correct position of the stent graft, the coverage of the primary entry and the absence of endovascular leaks, and the patency of the supraaortic trunks and the visceral arteries as well as the carotidsubclavian bypass graft if present.
Data Collection and Analysis Three intervals of CT imaging were collected, including before and after primary TEVAR and with the first detection of distal SINE. Four accessible measurement methods for precise size selection of stent graft before and after procedure were analyzed at the distal end level of the primary stent graft. These included measurement of the maximal transverse diameter (max Ø), mean of the maximal and minimal transverse diameters (mean Ø), circumference (Circ), and area (Area) of the true lumen (Xa; Fig 1). The diameters, circumference, and area of the distal end of the fully expanded stent graft were defined as predicted distal stent size (Xpred). The aortic diameters of the proximal landing zone before the primary endovascular procedure, as well as the diameter of the graft in cases of frozen elephant trunk or traditional elephant trunk was also measured. All CT measurements were performed by the interventional radiologists, always using the same postprocessing software.
Definitions and Mathematical Measurements of Mismatch Rate The oversizing ratio at the presumed distal stent end before implantation was defined as [(X pred Xa) / Xa 100%] considering the max Ø, the mean Ø, the Circ, and the Area of the true lumen [15]. The oversizing rate at the presumed distal stent end before implantation was defined as [A/B 100]; where A was the distal diameter of the selected stent graft and B was the maximal diameter of the true lumen at presumed level of distal end of stent graft [2].
Follow-Up Imaging Protocols In all patients, the thoracoabdominal aorta was analyzed with multislice CT angiography after TEVAR at discharge (1 week), then at 3, 6, and 12 months, and yearly thereafter. We evaluated the aortic sizes and flow in the true and false lumen, presence of endoleaks, and the integrity and position of the stent grafts in each patient. The SINE over the distal end of stent graft was documented.
Statistical Analysis Data were analyzed using SPSS 18.0 software (SPSS Inc, Chicago, IL). Continuous variables were expressed as mean SD and were compared using the Wilcoxon rank sum test. Values of p less than 0.05 were considered to be statistically significant. All the preoperative or intraoperative variables that achieved a p value of less than 0.2
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PANTALEO ET AL DISTAL STENT GRAFT-INDUCED NEW ENTRY
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Fig 1. (A) Sagittal computed tomography images from a patient affected by type B aortic dissection with primary tear distal to left subclavian artery. The preoperative image demonstrates a small diameter true lumen in the planned distal landing zone (indicated by X) of the descending thoracic aorta. Axial computed tomography scans at the “X level” show (B) minimum diameter (Min Diam) and maximum diameter (Max Diam), and (C) circumference (Circ) to area measurements of the true lumen.
in the univariate analysis were examined with multivariate analysis using stepwise logistic regression to evaluate the independent risk factors for SINE development.
Results During the study, 139 patients having undergone TEVAR for aortic dissection were discharged from the hospital, and SINE was detected in 42 (30.2%). In 37 patients (26.6%), SINE was distal, whereas in 5 (3,6%), it was proximal. The proximal SINEs were subsequently treated with conventional surgery by partial or total aortic arch replacement. Of the 139 patients, 25 were excluded because of incomplete preoperative imaging, and 6 died during follow-up. Only 108 have been enrolled in this study. There were 92 men (85.2%) and 16 women (14.8%); the mean age of the patients was 59.7 11.7 years. Detailed demographic data and risk factors are shown in Table 1. Seventy patients had type B aortic dissection, and 38 had residual aortic dissection after type A surgery. Among the 70 patients with type B aortic dissection, 26 had acute and 44 had chronic dissection (Table 1). The primary surgical repair of the 38 type A residual patients during the acute phase consisted of ascending
aorta and aortic arch replacement; ascending aorta, aortic arch replacement, and elephant trunk; and ascending aorta, aortic arch replacement, and frozen elephant trunk in 18, 7, and 13 patients, respectively. During primary TEVAR, a mean of 1.55 stent grafts per patient were implanted. Aortic stent grafts included Talent or Valiant (Medtronic Vascular) in 93 patients, Relay Plus (Bolton) in 14 patients, and E-Vita open (Jotec) in only 1 patient. Fifty-seven patients (52.7%) received 1 stent graft, 43 (39.8%) received 2 stent grafts and 8 (7.5%) received 3 stent grafts. In 37 patients (34.2%), the proximal landing zone was in zone 2, and in 27 of them, a carotid to left subclavian artery bypass was made before stent graft implantation. In the remaining 9 cases, 5 of which were an emergency, the bypass graft was not performed. The mean follow-up period was 36.1 25.7 months (range, 0.2 to 95). During follow-up, distal SINE occurred in 30 patients (27.8%). The mean period for detection of distal SINE after primary TEVAR was 24.8 20.67 months (range, 0.2 to 74.23). Eighteen (60%) of the 30 patients successfully underwent secondary TEVAR because they matched the criteria for reoperation. Only 1 of them required immediate endovascular treatment because of an overall aortic diameter greater than 55 mm associated with compressed true lumen causing visceral
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Table 1. Patient Demographic Data and Risk Factors Demographics and Risk Factors Male Female Age Body surface area Systemic hypertension Smoking Dysplidemia Diabetes mellitus Chronic kidney disease COPD Marfan syndrome Associated CVD Redo Urgent/emergency Subclavian artery coverage Intraoperative complications Aortic kinking Pathology Acute type B dissection Not acute type B dissection Type B residual Type B chronic
Overall (n ¼ 108)
SINE (n ¼ 30)
No SINE (n ¼ 78)
p Value
92 (85.2) 16 (14.8) 59.68 11.65 1.97 0.2 81 (74.9) 39 (36.1) 14 (12.9) 5 (4.6) 8 (7.4) 2 (1.8) 7 (6.4) 8 (7.4) 61 (56.5) 26 (24) 37 (34.2) 5 (4.5) 21 (19.4)
23 (76.7) 7 (23.3) 60.19 10.64 1.95 0.2 21 (70) 12 (40) 6 (20) 1 (3.3) 0 (0) 0 (0) 2 (6.7) 3 (10) 16 (53.3) 5 (16.7) 9 (30) 2 (6.6) 8 (26.7)
69 (88.5) 9 (11.5) 59.48 12.1 1.97 0.2 60 (76.9) 27 (34.6) 8 (10.3) 4 (5.1) 8 (10.2) 2 (2.6) 5 (6.4) 5 (6.4) 45 (57.7) 21 (26.9) 28 (35.9) 3 (3.8) 13 (16.7)
0.14 0.14 0.8 0.54 0.45 0.6 0.21 1 0.1 1 1 0.7 0.51 0.26 0.56 0.6 0.24
26 82 38 44
(24) (76) (35.2) (40.6)
5 25 10 15
(16.6) (83.3) (33.3) (50)
21 57 28 29
(26.9) (73.1) (35.9) (37.2)
0.26 0.26 0.8 0.22
Values are n (%) or mean SD. COPD ¼ chronic obstructive pulmonary disease;
CVD ¼ cardiovascular disease;
malperfusion. The mean period from detection of distal SINE to reoperation was 6.4 6.2 months (range, 0.1 to 25.1). The remaining 12 patients (40%) were medically treated without changes of size and morphology of the false lumen. No statistically significant differences in demographic and clinical conditions were seen between patients with or without SINE (Table 1). Among 30 SINE observed in our population, 7 patients were women and 23 were men, with SINE incidence among women higher than among men (43.8% versus 25%, respectively). Conversely, the incidence of SINE in acute and chronic dissection was 19.2% and 30.5%, respectively. The distal end of the stent lying in an angled portion of the descending aorta (aortic kinking) was found in 8 patients (26.7%) with SINE and in 13 patients (16.7%) without SINE, but the difference between the two groups was not significant (p ¼ 0.24). The oversizing ratio of the Area was significantly higher in patients with SINE (3.36 2.82 versus 2.67 1.8, p ¼ 0.02). Moreover, the oversizing ratio of the max Ø (0.55 0.61 versus 0.38 0.40, p ¼ 0.06) as well as the oversizing rate, A/B (155.52 60.91 versus 138.6 40.51, p ¼ 0.06), were also higher in the SINE group even if they did not reach a complete statistical significance (Table 2). At the multivariate analysis, the independent factors associated with SINE development were the oversizing ratio of the Area (odds ratio 1.858, 95% confidence interval: 1.109 to 3.064; p ¼ 0.018) and the oversizing ratio of the mean Ø
SINE ¼ stent-induced new entry.
(odds ratio 1.858, 95% confidence interval: 1.109 to 3.064; p ¼ 0.018; Table 3).
Comment In the 1990s, a new era in the treatment of aortic diseases for abdominal as well as for thoracic aorta began [4, 16]. Endovascular repair is the preferred technique for the treatment of a large number of the descending thoracic aorta pathologies, and the efficacy, as well as the feasibility of these procedures, has been widely demonstrated [5]. Aortic dissection has one of the highest mortality rates of any cardiovascular disease. Medical treatment and clinical follow-up remain the gold standard for the treatment of uncomplicated acute or chronic type B dissection. Conversely, for complicated cases of type B aortic dissection the endovascular treatment, whenever possible, is preferable to open surgery for a reduced early mortality and morbidity [17–19]. In our institution, from November 1999 to December 2013, we treated 220 patients with TEVAR for type B dissection with good early and late results; the overall early mortality rate was 5%. However, some aspects of endovascular treatment have to be clearly defined, and sizing in dissections is one of the most important. Indeed, choosing an adequate-size stent graft in such aortic diseases seems to be a subject of controversy. It has been reported that the correct size of the stent graft
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PANTALEO ET AL DISTAL STENT GRAFT-INDUCED NEW ENTRY
Table 2. Oversizing Ratio Diameter, Area, Circumference, and Rate Overall (n ¼ 108)
Variables Oversizing Oversizing Oversizing Oversizing Oversizing
ratio maximum diameter ratio mean diameter ratio area ratio circumference rate A/B
0.43 0.72 2.86 0.61 143.3
0.47 0.37 2.14 0.32 47.37
SINE (n ¼ 30) 0.55 0.76 3.36 0.63 155.52
0.61 0.43 2.82 0.37 60.91
No SINE (n ¼ 78)
p Value
0.06 0.15 0.02 0.32 0.06
0.38 0.71 2.67 0.61 138.6
0.40 0.34 1.8 0.30 40.51
Values are mean SD. SINE ¼ stent-induced new entry.
should be 10% larger than the diameters of the thoracic true lumen in acute dissection or 20% larger in chronic dissection; however, the nondissected mid aortic arch is the most useful target segment for proximal size measurements [20]. The difference in diameter between the aortic arch and the distal true lumen of the descending aorta has been demonstrated in dissection [21]. Owing to these differences, the proximal sizing of the prosthesis is more correct than the distal one that instead must be adapted. That can be the reason why a greater number of degenerations develop distally than proximally, and in this regard we observed 37 of the 139 patients (26.6%) who had available postoperative CT scan control with distal SINE and only 5 (3.6%) with proximal SINE. This incidence is perfectly comparable with that reported in the literature [7, 15]. Proximal SINE has to be considered a threatening lesion that can result in retrograde dissection [14] and must be immediately treated. For this reason, after the development of proximal SINE, our 5 patients were urgently treated by partial or total aortic arch replacement. Distal SINE is more benign, and treatment, if necessary, can be postponed and well programmed. We successfully treated with a secondary TEVAR only 18 of Table 3. Multivariate Analysis for Risk Factors of Stent-Induced New Entry Development Characteristics Female Age Body surface area Systemic hypertension Dyslipidemia Diabetes mellitus Chronic kidney injury Marfan syndrome Aortic kinking Acute type B dissection Residual type B dissection Oversizing ratio maximum diameter Oversizing rate A/B Oversizing ratio area Oversizing ratio mean diameter CI ¼ confidence interval;
OR
95% CI
p Value
3.140 . . . . . . . . . . 2.641
0.893–9.524 . . . . . . . . . . 0.993–7.026
0.076 0.841 0.928 0.783 0.108 0.860 0.999 0.969 0.236 0.445 0.325 0.052
. 1.843 0.034
. 1.109–3.064 0.001–0.802
0.631 0.018 0.036
OR ¼ odds ratio.
the 37 cases, whereas the remaining 19 were medically treated and followed with serial CT scans. Various risk factors for distal SINE have been evaluated in previous studies [7, 13, 20, 22]. In our cohort of 108 patients, neither baseline characteristics nor the type of aortic dissection was statistically significant for distal SINE development. However, we found a lower incidence of distal SINE in acute than in chronic dissection (17% and 50%, respectively), even if it did not reach statistical significance. This finding can be related to the different aortic wall characteristics in the acute and chronic phase of dissection. In acute dissection, the aortic wall is more elastic, and it can adapt better to a stent graft than a fibrotic, calcified, and inelastic aortic membrane typical of the chronic dissection. The morphology of the thoracic aorta, angled or kinked, at the level of the distal portion of the stent graft can promote SINE development because of increasing shear forces at that level. Although we found a higher rate of angled aorta at the distal landing zone in patients with distal SINE (26.7%) versus those without SINE (16.7%), the difference between the two groups was not statistically significant (p ¼ 0.24). Stent oversizing represents the strongest risk factor for SINE development. We found as independent risk factors for distal SINE, the oversizing ratio mean diameter and oversizing ratio area. Area and mean diameter are more accurate than other estimates (minimum or maximum diameter and circumference) for correct measurement of the aorta. Moreover, we were looking for a threshold value, beyond which there was a greater risk of SINE developing. Based on multivariate analysis, we found that the risk increased when the value of prestenting graft oversizing area was 3.5 or more; with these oversizing values, the stronger mechanical radial force of the stent can easily induce intimomedial membrane disruption and lead to SINE occurrence. Another important aspect to be considered in the assessment of the risk for SINE is the pathologic fragility of aortic wall, which is evident in patients with connective tissue disease. This finding explains the negative results of TEVAR for Marfan patients [23], and the higher incidence of SINE among these patients [7]. We treated 7 Marfan patients, with an incidence of distal SINE of 28.6%, which was comparable to that of the non-Marfan patients (27.7%). As opposed to the experience of Dong and colleagues [14], which reported exclusively proximal
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SINE in patients with Marfan syndrome, we described only distal SINE because in these patients the proximal landing zone was always a surgical prosthesis. Occurrence of SINE could even be influenced by different radial forces in the stent supplied by the manufacturer. Unfortunately, we could not investigate this aspect because, in most of our patients, we implanted stent grafts from the same company. Regarding the choice of the stent type, a tapered stent graft should be preferred for the majority of patients with dissection. However, the more common available tapered grafts have a maximal tapering end of only 4 mm, and often the discrepancy between the proximal and the distal landing zone is larger [15]. Therefore, it could be reasonable to avoid excessive oversizing, to implant a smaller tapered graft for the distal part first and then a larger stent graft for the proximal part. Moreover, the ideal grafts should also have lower radial force and higher flexibility to better adapt to the dissected aorta, and it would be desirable to be able to select, according to the anatomy or the specific etiology, the most suitable device for a patient’s characteristics.
Study Limitations The present study has several limitations. It is a retrospective study that did not permit an accurate estimation of the incidence of distal SINE at follow-up. The population examined is heterogeneous, and includes patients with residual type A dissection and chronic and acute type B dissections. Moreover, the examined period was a mean of only 36.1 months, and longer follow-up should be required.
Conclusion Complicated type B dissections can be successfully treated by TEVAR. The incidence of distal SINE is not negligible, but its occurrence is not associated with poor outcomes. Stent-induced new entry seems to be less frequent in cases of acute dissection. Complicated distal SINE can be usually treated with secondary TEVAR. The main determinant of SINE seems to be excessive oversizing that, owing to the tapered aspect of dissection, is particularly evident in the distal end. More accurate sizing can be obtained by evaluating the area of the true lumen instead of the traditional diameter measurement.
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