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Aneurysm shrinkage after endovascular repair of aortic diseases
Journal of Clinical Imaging 30 (2006) 22 – 26
Aneurysm shrinkage after endovascular repair of aortic diseases Shao Hua Cheng a, Noriyuki Katoa,T, Takatsugu Shimonob, Hideto Shinpob, Masaki Ishidaa, Tadanori Hiranoc, Kan Takedaa a Department of Radiology, Mie University Hospital, 2-174 Edobashi, Tsu, Mie 514-8507, Japan Department of Thoracic and Cardiovascular Surgery, Mie University Hospital, 2-174 Edobashi, Tsu, 514-8507, Japan c Department of Radiology, Matsusaka Central General Hospital, 102 Kawai-cho Kobo, Matsusaka, Mie 515-8566, Japan b
Received 1 June 2005; accepted 10 July 2005
Abstract Background: There are two graft materials for endovascular repair of aortic diseases, i.e., polyester and expanded polytetrafluoroethylene (ePTFE). The latest reports have suggested that there is graft-specific difference in outcomes. The purpose of this article was to evaluate the difference in terms of aneurysm shrinkage. Patients and methods: Eighty-six patients who underwent endovascular repair of aortic diseases were included. Forty patients had true aortic aneurysms, 8 had aortic pseudoaneurysms, and 38 had aortic dissections. Eighteen patients with true aortic aneurysms were treated with stent grafts fabricated with polyester, while the other 68 patients, including 22 patients with true aneurysms, 8 patients with pseudoaneurysms, and 38 patients with aortic dissections, were treated with stent grafts fabricated with ePTFE. All patients were followed-up by computed tomography (CT) for more than 1 year. The mean follow-up term was 28 months. Computed tomography confirmed that there were sufficiently long necks, and the aneurysm or the entry tear was completely excluded without any endoleak in all patients. The diameter of the preoperative lesion was compared with that measured on follow-up CT at 1 year and at the end of the follow-up term. Increase or decrease in the diameter by more than 5 mm was defined as a significant diameter change. Results: Aneurysm shrinkage was observed in 40% of patients with true aneurysms, 88% of patients with pseudoaneurysms, and 55% of patients with aortic dissections at 1 year. There was no significant increase in patients with aneurysm shrinkage at the end of follow-up in any groups. In the case of true aortic aneurysms, shrinkage of aneurysms was observed more frequently with polyester-fabricated stent grafts (67%, 13/18) than with ePTFE-fabricated ones (18%, 4/22) at 1 year ( Pb.01). In contrast, expansion of aneurysms was observed only in patients treated with ePTFE (14%, 3/22). Shrinkage of the descending aorta was observed in 55% of patients with acute aortic dissections and 36% of patients with chronic aortic dissections. There was no case with aortic enlargement in either group. There was no significant difference between acute and chronic dissection in terms of shrinkage of the descending aorta. Conclusion: Expanded polytetrafluoroethylene appears to be effective for the treatment of pseudoaneurysms and aortic dissections. However, polyester seems to be more effective than ePTFE when true aneurysms are to be treated. D 2006 Elsevier Inc. All rights reserved. Keywords: Aorta, aneurysm; Aorta, dissection; Stents and prosthesis; Complications
1. Introduction Endovascular repair of aortic diseases has become an acceptable alternative to conventional open surgery. It has been applied to abdominal aortic aneurysms, thoracic aortic aneurysms, and aortic dissections [1– 4]. In terms of
T Corresponding author. Tel.: +81 59 231 5029; fax: +81 59 232 8066. E-mail address: [email protected] (N. Kato). 0899-7071/06/$ – see front matter D 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.clinimag.2005.07.032
immediate outcome, endovascular repair seems superior to surgical graft replacement [3,5]. However, it has been demonstrated that various problems including endoleaks, limb occlusion, and device failure can develop during longerterm follow-up of patients who underwent endovascular repair. The advantages of endovascular repair obtained with immediate outcome could be offset because of such late troubles [6–10]. Since the goal of aneurysm repair is to prevent aneurysm rupture, shrinkage of aneurysm sac after endovascular repair
S.H. Cheng et al. / Journal of Clinical Imaging 30 (2006) 22 – 26 Table 1 Aortic diseases and graft material used for their repair
Table 3 Aneurysm sac change with each graft material in the case of true aortic aneurysm
True aneurysm Disease TAA Graft
AAA
Pseudoaneurysm Dissection
Polyester ePTFE Polyester ePTFE ePTFE
Number 7
9
11
13
8
23
ePTFE 38
is deemed treatment success because it indicates sac depressurization. In contrast, aneurysm sac expansion, which is associated with endoleak or endotension, implies persistent pressurization and necessitates secondary intervention. It has been suggested by several reports that aneurysm sac change is dependent upon the type of stent grafts [11–13]. Among several types of stent grafts, ePTFE-fabricated stent grafts are reported to be strongly correlated with sac expansion [14]. However, previous reports compared devices used for atherosclerotic abdominal aortic aneurysms and did not include aortic diseases of other etiologies. The purpose of this study was to evaluate the efficacy of ePTFE-fabricated stent grafts in the treatment of true aortic aneurysms, pseudoaneurysms, and aortic dissections.
2. Patients and methods Since July 1997 through March 2003, 124 patients with aortic diseases were treated with endovascular stent graft placement in our hospital. Eighty-eight patients were followed-up for at least 1 year. Among them, 86 patients in whom it was confirmed that there was no endoleak on follow-up CT were included in this study. The mean followup term was 28F17 months. Forty patients had true aortic aneurysms (Table 1). Eight patients had aortic pseudoaneurysms, including four dissecting aneurysms, two traumatic aneurysms, and two anastomotic aneurysms. Thirty-eight patients had aortic dissection, including 24 acute dissections and 14 chronic dissections. Eighteen patients with true aortic aneurysms were treated with stent grafts fabricated with polyester. Among them, 11 patients with abdominal aortic aneurysms were treated with Zenith (Cook, Bloomington, IN), while seven patients with thoracic aortic aneurysms were treated with a handmade device, which was fabricated with Z-stents (Cook) and polyester graft (UBE, Tokyo, Japan). The porosity of each
Graft
Pre
1 year
Latest
Polyester ePTFE
54F10 54F9
45F14T 52F11
44F13T 53F15
T Pb.01 vs. pre.
graft was 350 and 150 mL/cm2 per minute, respectively. The other 68 patients, including 22 patients with true aneurysms (thirteen patients with abdominal aortic aneurysms and nine patients with thoracic aortic aneurysms), 8 patients with pseudoaneurysms, and 38 patients with aortic dissections, were treated with a hand-made device, which was fabricated with Z-stents and expanded polytetrafluoroethylene (ePTFE) (Impra, Tempe, AZ). Expanded PTFE, which is originally 8 or 10 mm in diameter, was dilated with balloon catheters until the desired diameter was obtained. The ratio of the dilatation ranged from 3.1 to 4.0 compared to the original diameter of the graft. Initially, ePTFE-fabricated stent grafts were used in all patients at our institution. However, we have used them only in the case of pseudoaneurysms and aortic dissections since we experienced two cases of perigraft hygroma in the case of true aortic aneurysms as described below. All patients were followed-up by CT. Contrast-enhanced CT was obtained at two phases, i.e., early and late phases. The early- and late-phase images were obtained approximately 20 and 90 s after initiation of contrast medium injection at the rate of 5 mL/s. Computed tomography confirmed that there were sufficiently long necks, which were 2 cm or longer at the aorta and 1 cm or longer at the iliac artery in patients with aneurysms, and 1 cm or longer in patients with dissections. The maximal diameter of preoperative lesion was compared with that measured on 1-year follow-up CT and the latest follow-up CT. In the case of aortic dissections, the maximal diameter of the descending thoracic aorta was compared. Decrease or increase by 5 mm or more in diameter was considered as significant. Student’s t-test was used to compare the diameters. The percentage of patients whose aneurysm diameter shrank, did not change, or enlarged was
Table 2 Aneurysm sac change in each aortic disease Diseases
Pre
1 year
Latest
True aneurysm Pseudoaneurysm Dissection Acute Chronic
54F10 50F7 44F8 41F4 49F10
49F13T 37F7T 39F8T 36F5T 44F10
49F14T 36F7T 38F9T 36F6T 43F11T
T Pb.01 vs. pre.
Fig. 1. Aneurysm sac change in each aortic disease.
24
S.H. Cheng et al. / Journal of Clinical Imaging 30 (2006) 22 – 26
Fig. 4. Aneurysm sac change in true aortic aneurysm. Fig. 2. Fate of aneurysm in each aortic disease at 1 year.
3.2. Fate of aneurysm compared by v 2 test between polyester group and ePTFE group. In both comparisons, P value less than .05 was considered as significant.
3. Results 3.1. Aneurysm sac change The mean maximal diameter of aneurysms or descending thoracic aorta at 1 year after treatment and at the end of the follow-up significantly decreased in all groups (Table 2). As shown in Table 3, significant aneurysm shrinkage was observed with polyester, while the diameter of aneurysms did not reduce with ePTFE in the case of true aortic aneurysms. Among aortic dissections, the maximal diameter of the descending thoracic aorta significantly decreased in acute cases, while there was no significant decrease in chronic cases at 1 year. However, at the end of follow-up, significant decrease was observed in chronic cases as well as in acute cases. As shown schematically in Fig. 1, aneurysm shrinkage occurred in 1 year and did not significantly progress thereafter.
Fig. 3. Fate of aneurysm in each aortic disease at the end of follow-up.
Aneurysm shrinkage was observed in 16 (40%) patients with true aortic aneurysms at 1 year, while aneurysms enlarged in three patients (8%) (Fig. 2). Aneurysm shrinkage was observed in seven patients (88%) with pseudoaneurysms, and there was no patient with aneurysm expansion. Shrinkage of the descending thoracic aorta was observed in 21 patients (55%) with aortic dissections, and there was no patient either whose descending aorta expanded. The number of patients whose aneurysms or descending thoracic aorta shrank slightly increased in patients with true aneurysms or dissections at the end of the follow-up (Fig. 3). It did not change in acute cases, while it slightly increased in chronic cases. In terms of graft material, the diameter of true aneurysms significantly decreased with polyester, while there was no significant change with ePTFE either at 1 year or at the end of follow-up (Fig. 4). Aneurysm shrinkage was observed in 12 (67%) of 18 patients with polyester at 1 year, while it was observed in only four (18%) with ePTFE ( Pb.01) (Fig. 5). The percentage of aneurysm sac shrinkage increased in both groups at the end of the follow-up (Fig. 6). Aneurysm enlargement occurred only with ePTFE (14%, 3/22), and the percentage slightly increased at the end of follow-up (18%, 4/22). All
Fig. 5. Fate of true aortic aneurysm at 1 year.
S.H. Cheng et al. / Journal of Clinical Imaging 30 (2006) 22 – 26
25
gradually increased and reached more than 30%. No endoleak was observed in 67% of their patients. Although the number of patients is so small in our series, we experienced four similar cases. On the other hand, aneurysm shrinkage does occur even with ePTFE in some patients. Therefore, such other factor as hyperfibrinolysis might be affecting the fate of aneurysm [19,20]. Since modifications to alter permeability have been added to the Excluder, the mechanism may be elucidated in the near future. 4.2. Aneurysm sac change in the case of pseudoaneurysm Fig. 6. Fate of true aortic aneurysm at the end of follow-up.
four patients finally underwent surgical conversion. Among them, the cause of aneurysm expansion was intra-aneurysmal seroma in two patients, type I endotension in one patient, and type II endotension in one patient.
Although only ePTFE-fabricated stent grafts were used, aneurysm shrinkage was observed as frequently as 90% in the case of pseudoaneurysms, and there was no aneurysm enlargement in contrast to true aortic aneurysms. Provided the microporous feature of ePTFE is the only determinant of the aneurysm sac change, this fact cannot be explained. In addition to the various features of stent graft, the characteristics of the target lesion, i.e., the state of the aneurysm wall and surrounding tissue, are seemingly implicated.
4. Discussion 4.3. Aortic diameter change in the case of aortic dissection 4.1. Aneurysm sac change in the case of true aortic aneurysm Some authors have demonstrated that the type of stent grafts is closely correlated with aneurysm sac change [11–14]. The potential factors that could influence sac change are type of graft material and structure of the device [15–18]. Most previous reports have suggested that aneurysm shrinkage is least with ePTFE-fabricated stent grafts (Excluder) compared to polyester-fabricated ones. It is not surprising since there is a tendency that the most frequent endoleak was observed with Excluder. However, it is speculated that the difference in fabric permeability could greatly contribute to aneurysm sac change. That is, the thin microporous feature of ePTFE could not prevent the transudation of serous fluid into the aneurysm sac and could make perigraft hygroma or intraaneurysmal seroma [9,10]. The present study also showed similar results to the previous report. The mean diameter of true aortic aneurysms significantly decreased with polyester, while it did not with ePTFE. In addition, the percentage of aneurysm shrinkage was significantly larger with polyester than with ePTFE (63% vs. 18%, Pb.01). Since various other factors might be associated with aneurysm sac change in this study, no definitive conclusion can be derived. However, no case with endoleak was included, and the contribution of pressure transmission through the attachment site should be relatively low instead. Therefore, the difference could be attributed largely to the graft material itself. Recently, Cho et al. [18] reported aortic aneurysms that even enlarged after endovascular repair with the Excluder. In their series, the percentage of patients with aneurysm sac enlargement
It is well known that remodeling of the aorta occurs after endovascular repair of aortic dissection irrespective of whether acute or chronic [3,4]. Similarly, significant decrease of the descending thoracic aorta was observed in both acute and chronic dissections in the present study. However, the percentage of aortic diameter reduction was about 50% even in patients with acute dissection. The definition that change in size of 5 mm or more is significant should be contributing to this low percentage to some extent. Another contributing factor is pressurization to the false lumen of the descending thoracic aorta. Since more than half of patients with aortic dissections have natural fenestrations or reentries in the aorta or its branches below the diaphragm, blood pressure in the patent false lumen of the lower aorta could theoretically be transmitted to the thrombosed false lumen of the descending thoracic aorta. The percentage was only one third in patients with chronic dissection at 1 year, although there was no aortic enlargement, as well as with acute dissection. This is not surprising because the aortic wall is fibrotic and rigid compared to that of acute dissection in addition to pressurization to the false lumen from the lower aorta. Irrespective of acute or chronic dissections, the aortic diameter did not change in about half of the patients even at the end of followup. Implications of stable aorta are unknown. It could be a transient state before aortic enlargement, since all dissections were treated with ePTFE-fabricated stent grafts. However, we could expect an optimistic outcome in the case of aortic dissections, since there was no aortic enlargement during similar follow-up term to true aneurysms.
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S.H. Cheng et al. / Journal of Clinical Imaging 30 (2006) 22 – 26
4.4. Limitations of the study The present study has several limitations. First, the number of patients is extremely small and follow-up term is short. However, there are similar tendencies to previous reports with larger series in terms of the fact that aneurysm shrinkage is less with ePTFE than with polyester. Second, although two kinds of polyester graft were used and two kinds of true aortic aneurysms, i.e., thoracic aortic aneurysm and abdominal aortic aneurysm, were treated, the results were brought together. This could confound appreciation of the data. Third, there remains the possibility that pressure transmission through the attachment site might contribute to aneurysm enlargement as experienced in one patient in our series. Finally, exact evaluation of ePTFE compared to polyester in the case of aortic dissections is impossible because no polyester-fabricated stent grafts were used. Therefore, the mechanism of relatively high percentage of patients with stable aorta can only be speculated. In conclusion, ePTFE may be effective in the endovascular repair of pseudoaneurysms. In the case of aortic dissections, ePTFE seems to be effective in that it is not linked to secondary intervention following aortic enlargement, although further investigation is mandatory. Polyester should be preferable when true aortic aneurysms are to be treated as far as thin ePTFE as used in the present stuff is used.
[6]
[7] [8]
[9]
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[14]
[15]
References [1] Parodi JC, Palmaz JC, Barone HD. Transfemoral intraluminal graft implantation for abdominal aortic aneurysms. Ann Vasc Surg 1991; 5:491 – 9. [2] Dake MD, Miller DC, Semba CP, Mitchell RS, Walker PJ, Liddell RP. Transluminal placement of endovascular stent-grafts for the treatment of descending thoracic aortic aneurysms. N Engl J Med 1994;331:1729 – 34. [3] Nienaber CA, Fattori R, Lund G, Dieckmann C, Wolf W, von Kodolitsch Y, Nicolas V, Pierangeli A. Nonsurgical reconstruction of thoracic aortic dissection by stent-graft placement. N Engl J Med 1999; 340:1539 – 45. [4] Dake MD, Kato N, Mitchell RS, Semba CP, Razavi MK, Shimono T, Hirano T, Takeda K, Yada I, Miller DC. Endovascular stent-graft placement for the treatment of acute aortic dissection. N Engl J Med 1999;340:1546 – 52. [5] Prinssen M, Verhoeven ELG, Buth J, Cuypers PWM, van Sambeek MRHM, Balm R, Buskens E, Grobbee DE, Blankensteijn JD.
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A randomized trial comparing conventional and endovascular repair of abdominal aortic aneurysm. N Engl J Med 2004;351:1607 – 18. Arko FER, Lee WA, Hill BB, Cipriano P, Forgaty TJ, Zarins CK. Increased flexibility of AneuRx stent-graft reduces need for secondary intervention after endovascular aneurysm repair. J Endovasc Ther 2001; 8:583 – 91. Makaroun MS. The Ancure endografting system7 an update. J Vasc Surg 2001;33:S129 – 34. Beebe HG, Cronenwett JL, Katzen BT, Brewster DC, Green RM, Vanguard ET. Results of an aortic endograft trial: impact of device failure beyond 12 months. J Vasc Surg 2001;33:S55 – S63. Kato N, Shimono T, Hirano T, Mizumoto T, Suzuki T, Ishida M, Fujii H, Yada I, Takeda K. Aneurysm expansion after stent-graft placement in the absence of endoleak. J Vasc Interv Radiol 2002;13:321 – 6. Risberg B, Delle M, Eriksson E, Klingenstierna H, Lfnn L. Aneurysm sac hygroma: a cause of endotension. J Endovasc Ther 2001;8:447 – 53. Bertges DJ, Chow K, Wyers MC, Landsittel D, Frydrynch AV, Stavropoulos W, Tan WA, Rhee RY, Fillinger MF, Fairman RM, Makaroun MS. Abdominal aortic aneurysm size regression after endovascular repair is endograft dependent. J Vasc Surg 2003;37: 716 – 23. Ouriel K, Clair DG, Greenberg RK, Lyden SP, O’hara PJ, Sarac TP, Srivastava SD, Butler B, Sampram EK. Endovascular repair of abdominal aortic aneurysms: device-specific outcome. J Vasc Surg 2003;37:991 – 8. Greenberg RK, Deaton D, Sullivan T, Walker E, Lyden SP, Srivastava SD, Ouriel K, Ivanc T, Burton T, Mayo J. Variable sac behavior after endovascular repair of abdominal aortic aneurysm: analysis of core laboratory data. J Vasc Surg 2004;39:95 – 101. Singer-Ranger R, Adiseshiah M. Differing morphological changes following endovascular AAA repair using balloon-expandable or selfexpanding endografts. J Endovasc Ther 2000;7:479 – 85. Harris P, Brennan J, Martin J, Goudl D, Bakran A, Gilling-Smith G, Buth J, Gevers E, White D. Longitudinal aneurysm shrinkage following aortic aneurysm repair: a source of intermediate and late complications. J Endovasc Surg 1999;6:11 – 6. Franco T, Zajko A, Federle M, Makaroun M. Endovascular repair of the abdominal aortic aneurysm with the Ancure endograft: CT followup of perigraft flow and aneurysm size at 6 months. J Vasc Interv Radiol 2000;11:429 – 35. Matsumura JS, Ryu RK, Ouriel K. Identification and implications of transgraft microleaks after endovascular repair of aortic aneurysms. J Vasc Surg 2001;34:190 – 7. Cho JS, Dillavou ED, Rhee RY, Makaroun MS. Late abdominal aortic aneurysm enlargement after endovascular repair with the Excluder device. J Vasc Surg 2004;39:1236 – 42. Adolph R, Vorp DA, Steed DL, Webster MW, Kameneva MV, Watkins SC. Cellular content and permeability of intraluminal thrombus in abdominal aortic aneurysm. J Vasc Surg 1997;25:916 – 26. Lorelli DR, Jean-Claude JM, Fox CJ, Clyne J, Seabrook GR, Towne JB. Response of plasma matrix metalloproteinase-9 to conventional abdominal aortic aneurysm repair or endovascular exclusion: implications for endoleak. J Vasc Surg 2002;35:916 – 22.
Aneurysm shrinkage after endovascular repair of aortic diseases Shao Hua Cheng a, Noriyuki Katoa,T, Takatsugu Shimonob, Hideto Shinpob, Masaki Ishidaa, Tadanori Hiranoc, Kan Takedaa a Department of Radiology, Mie University Hospital, 2-174 Edobashi, Tsu, Mie 514-8507, Japan Department of Thoracic and Cardiovascular Surgery, Mie University Hospital, 2-174 Edobashi, Tsu, 514-8507, Japan c Department of Radiology, Matsusaka Central General Hospital, 102 Kawai-cho Kobo, Matsusaka, Mie 515-8566, Japan b
Received 1 June 2005; accepted 10 July 2005
Abstract Background: There are two graft materials for endovascular repair of aortic diseases, i.e., polyester and expanded polytetrafluoroethylene (ePTFE). The latest reports have suggested that there is graft-specific difference in outcomes. The purpose of this article was to evaluate the difference in terms of aneurysm shrinkage. Patients and methods: Eighty-six patients who underwent endovascular repair of aortic diseases were included. Forty patients had true aortic aneurysms, 8 had aortic pseudoaneurysms, and 38 had aortic dissections. Eighteen patients with true aortic aneurysms were treated with stent grafts fabricated with polyester, while the other 68 patients, including 22 patients with true aneurysms, 8 patients with pseudoaneurysms, and 38 patients with aortic dissections, were treated with stent grafts fabricated with ePTFE. All patients were followed-up by computed tomography (CT) for more than 1 year. The mean follow-up term was 28 months. Computed tomography confirmed that there were sufficiently long necks, and the aneurysm or the entry tear was completely excluded without any endoleak in all patients. The diameter of the preoperative lesion was compared with that measured on follow-up CT at 1 year and at the end of the follow-up term. Increase or decrease in the diameter by more than 5 mm was defined as a significant diameter change. Results: Aneurysm shrinkage was observed in 40% of patients with true aneurysms, 88% of patients with pseudoaneurysms, and 55% of patients with aortic dissections at 1 year. There was no significant increase in patients with aneurysm shrinkage at the end of follow-up in any groups. In the case of true aortic aneurysms, shrinkage of aneurysms was observed more frequently with polyester-fabricated stent grafts (67%, 13/18) than with ePTFE-fabricated ones (18%, 4/22) at 1 year ( Pb.01). In contrast, expansion of aneurysms was observed only in patients treated with ePTFE (14%, 3/22). Shrinkage of the descending aorta was observed in 55% of patients with acute aortic dissections and 36% of patients with chronic aortic dissections. There was no case with aortic enlargement in either group. There was no significant difference between acute and chronic dissection in terms of shrinkage of the descending aorta. Conclusion: Expanded polytetrafluoroethylene appears to be effective for the treatment of pseudoaneurysms and aortic dissections. However, polyester seems to be more effective than ePTFE when true aneurysms are to be treated. D 2006 Elsevier Inc. All rights reserved. Keywords: Aorta, aneurysm; Aorta, dissection; Stents and prosthesis; Complications
1. Introduction Endovascular repair of aortic diseases has become an acceptable alternative to conventional open surgery. It has been applied to abdominal aortic aneurysms, thoracic aortic aneurysms, and aortic dissections [1– 4]. In terms of
T Corresponding author. Tel.: +81 59 231 5029; fax: +81 59 232 8066. E-mail address: [email protected] (N. Kato). 0899-7071/06/$ – see front matter D 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.clinimag.2005.07.032
immediate outcome, endovascular repair seems superior to surgical graft replacement [3,5]. However, it has been demonstrated that various problems including endoleaks, limb occlusion, and device failure can develop during longerterm follow-up of patients who underwent endovascular repair. The advantages of endovascular repair obtained with immediate outcome could be offset because of such late troubles [6–10]. Since the goal of aneurysm repair is to prevent aneurysm rupture, shrinkage of aneurysm sac after endovascular repair
S.H. Cheng et al. / Journal of Clinical Imaging 30 (2006) 22 – 26 Table 1 Aortic diseases and graft material used for their repair
Table 3 Aneurysm sac change with each graft material in the case of true aortic aneurysm
True aneurysm Disease TAA Graft
AAA
Pseudoaneurysm Dissection
Polyester ePTFE Polyester ePTFE ePTFE
Number 7
9
11
13
8
23
ePTFE 38
is deemed treatment success because it indicates sac depressurization. In contrast, aneurysm sac expansion, which is associated with endoleak or endotension, implies persistent pressurization and necessitates secondary intervention. It has been suggested by several reports that aneurysm sac change is dependent upon the type of stent grafts [11–13]. Among several types of stent grafts, ePTFE-fabricated stent grafts are reported to be strongly correlated with sac expansion [14]. However, previous reports compared devices used for atherosclerotic abdominal aortic aneurysms and did not include aortic diseases of other etiologies. The purpose of this study was to evaluate the efficacy of ePTFE-fabricated stent grafts in the treatment of true aortic aneurysms, pseudoaneurysms, and aortic dissections.
2. Patients and methods Since July 1997 through March 2003, 124 patients with aortic diseases were treated with endovascular stent graft placement in our hospital. Eighty-eight patients were followed-up for at least 1 year. Among them, 86 patients in whom it was confirmed that there was no endoleak on follow-up CT were included in this study. The mean followup term was 28F17 months. Forty patients had true aortic aneurysms (Table 1). Eight patients had aortic pseudoaneurysms, including four dissecting aneurysms, two traumatic aneurysms, and two anastomotic aneurysms. Thirty-eight patients had aortic dissection, including 24 acute dissections and 14 chronic dissections. Eighteen patients with true aortic aneurysms were treated with stent grafts fabricated with polyester. Among them, 11 patients with abdominal aortic aneurysms were treated with Zenith (Cook, Bloomington, IN), while seven patients with thoracic aortic aneurysms were treated with a handmade device, which was fabricated with Z-stents (Cook) and polyester graft (UBE, Tokyo, Japan). The porosity of each
Graft
Pre
1 year
Latest
Polyester ePTFE
54F10 54F9
45F14T 52F11
44F13T 53F15
T Pb.01 vs. pre.
graft was 350 and 150 mL/cm2 per minute, respectively. The other 68 patients, including 22 patients with true aneurysms (thirteen patients with abdominal aortic aneurysms and nine patients with thoracic aortic aneurysms), 8 patients with pseudoaneurysms, and 38 patients with aortic dissections, were treated with a hand-made device, which was fabricated with Z-stents and expanded polytetrafluoroethylene (ePTFE) (Impra, Tempe, AZ). Expanded PTFE, which is originally 8 or 10 mm in diameter, was dilated with balloon catheters until the desired diameter was obtained. The ratio of the dilatation ranged from 3.1 to 4.0 compared to the original diameter of the graft. Initially, ePTFE-fabricated stent grafts were used in all patients at our institution. However, we have used them only in the case of pseudoaneurysms and aortic dissections since we experienced two cases of perigraft hygroma in the case of true aortic aneurysms as described below. All patients were followed-up by CT. Contrast-enhanced CT was obtained at two phases, i.e., early and late phases. The early- and late-phase images were obtained approximately 20 and 90 s after initiation of contrast medium injection at the rate of 5 mL/s. Computed tomography confirmed that there were sufficiently long necks, which were 2 cm or longer at the aorta and 1 cm or longer at the iliac artery in patients with aneurysms, and 1 cm or longer in patients with dissections. The maximal diameter of preoperative lesion was compared with that measured on 1-year follow-up CT and the latest follow-up CT. In the case of aortic dissections, the maximal diameter of the descending thoracic aorta was compared. Decrease or increase by 5 mm or more in diameter was considered as significant. Student’s t-test was used to compare the diameters. The percentage of patients whose aneurysm diameter shrank, did not change, or enlarged was
Table 2 Aneurysm sac change in each aortic disease Diseases
Pre
1 year
Latest
True aneurysm Pseudoaneurysm Dissection Acute Chronic
54F10 50F7 44F8 41F4 49F10
49F13T 37F7T 39F8T 36F5T 44F10
49F14T 36F7T 38F9T 36F6T 43F11T
T Pb.01 vs. pre.
Fig. 1. Aneurysm sac change in each aortic disease.
24
S.H. Cheng et al. / Journal of Clinical Imaging 30 (2006) 22 – 26
Fig. 4. Aneurysm sac change in true aortic aneurysm. Fig. 2. Fate of aneurysm in each aortic disease at 1 year.
3.2. Fate of aneurysm compared by v 2 test between polyester group and ePTFE group. In both comparisons, P value less than .05 was considered as significant.
3. Results 3.1. Aneurysm sac change The mean maximal diameter of aneurysms or descending thoracic aorta at 1 year after treatment and at the end of the follow-up significantly decreased in all groups (Table 2). As shown in Table 3, significant aneurysm shrinkage was observed with polyester, while the diameter of aneurysms did not reduce with ePTFE in the case of true aortic aneurysms. Among aortic dissections, the maximal diameter of the descending thoracic aorta significantly decreased in acute cases, while there was no significant decrease in chronic cases at 1 year. However, at the end of follow-up, significant decrease was observed in chronic cases as well as in acute cases. As shown schematically in Fig. 1, aneurysm shrinkage occurred in 1 year and did not significantly progress thereafter.
Fig. 3. Fate of aneurysm in each aortic disease at the end of follow-up.
Aneurysm shrinkage was observed in 16 (40%) patients with true aortic aneurysms at 1 year, while aneurysms enlarged in three patients (8%) (Fig. 2). Aneurysm shrinkage was observed in seven patients (88%) with pseudoaneurysms, and there was no patient with aneurysm expansion. Shrinkage of the descending thoracic aorta was observed in 21 patients (55%) with aortic dissections, and there was no patient either whose descending aorta expanded. The number of patients whose aneurysms or descending thoracic aorta shrank slightly increased in patients with true aneurysms or dissections at the end of the follow-up (Fig. 3). It did not change in acute cases, while it slightly increased in chronic cases. In terms of graft material, the diameter of true aneurysms significantly decreased with polyester, while there was no significant change with ePTFE either at 1 year or at the end of follow-up (Fig. 4). Aneurysm shrinkage was observed in 12 (67%) of 18 patients with polyester at 1 year, while it was observed in only four (18%) with ePTFE ( Pb.01) (Fig. 5). The percentage of aneurysm sac shrinkage increased in both groups at the end of the follow-up (Fig. 6). Aneurysm enlargement occurred only with ePTFE (14%, 3/22), and the percentage slightly increased at the end of follow-up (18%, 4/22). All
Fig. 5. Fate of true aortic aneurysm at 1 year.
S.H. Cheng et al. / Journal of Clinical Imaging 30 (2006) 22 – 26
25
gradually increased and reached more than 30%. No endoleak was observed in 67% of their patients. Although the number of patients is so small in our series, we experienced four similar cases. On the other hand, aneurysm shrinkage does occur even with ePTFE in some patients. Therefore, such other factor as hyperfibrinolysis might be affecting the fate of aneurysm [19,20]. Since modifications to alter permeability have been added to the Excluder, the mechanism may be elucidated in the near future. 4.2. Aneurysm sac change in the case of pseudoaneurysm Fig. 6. Fate of true aortic aneurysm at the end of follow-up.
four patients finally underwent surgical conversion. Among them, the cause of aneurysm expansion was intra-aneurysmal seroma in two patients, type I endotension in one patient, and type II endotension in one patient.
Although only ePTFE-fabricated stent grafts were used, aneurysm shrinkage was observed as frequently as 90% in the case of pseudoaneurysms, and there was no aneurysm enlargement in contrast to true aortic aneurysms. Provided the microporous feature of ePTFE is the only determinant of the aneurysm sac change, this fact cannot be explained. In addition to the various features of stent graft, the characteristics of the target lesion, i.e., the state of the aneurysm wall and surrounding tissue, are seemingly implicated.
4. Discussion 4.3. Aortic diameter change in the case of aortic dissection 4.1. Aneurysm sac change in the case of true aortic aneurysm Some authors have demonstrated that the type of stent grafts is closely correlated with aneurysm sac change [11–14]. The potential factors that could influence sac change are type of graft material and structure of the device [15–18]. Most previous reports have suggested that aneurysm shrinkage is least with ePTFE-fabricated stent grafts (Excluder) compared to polyester-fabricated ones. It is not surprising since there is a tendency that the most frequent endoleak was observed with Excluder. However, it is speculated that the difference in fabric permeability could greatly contribute to aneurysm sac change. That is, the thin microporous feature of ePTFE could not prevent the transudation of serous fluid into the aneurysm sac and could make perigraft hygroma or intraaneurysmal seroma [9,10]. The present study also showed similar results to the previous report. The mean diameter of true aortic aneurysms significantly decreased with polyester, while it did not with ePTFE. In addition, the percentage of aneurysm shrinkage was significantly larger with polyester than with ePTFE (63% vs. 18%, Pb.01). Since various other factors might be associated with aneurysm sac change in this study, no definitive conclusion can be derived. However, no case with endoleak was included, and the contribution of pressure transmission through the attachment site should be relatively low instead. Therefore, the difference could be attributed largely to the graft material itself. Recently, Cho et al. [18] reported aortic aneurysms that even enlarged after endovascular repair with the Excluder. In their series, the percentage of patients with aneurysm sac enlargement
It is well known that remodeling of the aorta occurs after endovascular repair of aortic dissection irrespective of whether acute or chronic [3,4]. Similarly, significant decrease of the descending thoracic aorta was observed in both acute and chronic dissections in the present study. However, the percentage of aortic diameter reduction was about 50% even in patients with acute dissection. The definition that change in size of 5 mm or more is significant should be contributing to this low percentage to some extent. Another contributing factor is pressurization to the false lumen of the descending thoracic aorta. Since more than half of patients with aortic dissections have natural fenestrations or reentries in the aorta or its branches below the diaphragm, blood pressure in the patent false lumen of the lower aorta could theoretically be transmitted to the thrombosed false lumen of the descending thoracic aorta. The percentage was only one third in patients with chronic dissection at 1 year, although there was no aortic enlargement, as well as with acute dissection. This is not surprising because the aortic wall is fibrotic and rigid compared to that of acute dissection in addition to pressurization to the false lumen from the lower aorta. Irrespective of acute or chronic dissections, the aortic diameter did not change in about half of the patients even at the end of followup. Implications of stable aorta are unknown. It could be a transient state before aortic enlargement, since all dissections were treated with ePTFE-fabricated stent grafts. However, we could expect an optimistic outcome in the case of aortic dissections, since there was no aortic enlargement during similar follow-up term to true aneurysms.
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4.4. Limitations of the study The present study has several limitations. First, the number of patients is extremely small and follow-up term is short. However, there are similar tendencies to previous reports with larger series in terms of the fact that aneurysm shrinkage is less with ePTFE than with polyester. Second, although two kinds of polyester graft were used and two kinds of true aortic aneurysms, i.e., thoracic aortic aneurysm and abdominal aortic aneurysm, were treated, the results were brought together. This could confound appreciation of the data. Third, there remains the possibility that pressure transmission through the attachment site might contribute to aneurysm enlargement as experienced in one patient in our series. Finally, exact evaluation of ePTFE compared to polyester in the case of aortic dissections is impossible because no polyester-fabricated stent grafts were used. Therefore, the mechanism of relatively high percentage of patients with stable aorta can only be speculated. In conclusion, ePTFE may be effective in the endovascular repair of pseudoaneurysms. In the case of aortic dissections, ePTFE seems to be effective in that it is not linked to secondary intervention following aortic enlargement, although further investigation is mandatory. Polyester should be preferable when true aortic aneurysms are to be treated as far as thin ePTFE as used in the present stuff is used.
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