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The Position Relationship Between the Opening of the Three Branches of the Aortic Arch and the Aortic Arch Axis in Normal People
Journal Pre-proof The position relationship between the opening of three branches of aortic arch and the aortic arch axis in normal people Zhenyi Zhan, Bo Li, Bailang Chen PII:
S0890-5096(20)30013-3
DOI:
https://doi.org/10.1016/j.avsg.2019.12.036
Reference:
AVSG 4848
To appear in:
Annals of Vascular Surgery
Received Date: 14 July 2019 Revised Date:
8 December 2019
Accepted Date: 14 December 2019
Please cite this article as: Zhan Z, Li B, Chen B, The position relationship between the opening of three branches of aortic arch and the aortic arch axis in normal people, Annals of Vascular Surgery (2020), doi: https://doi.org/10.1016/j.avsg.2019.12.036. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2020 Published by Elsevier Inc.
1
The position relationship between the opening of three branches of aortic
2
arch and the aortic arch axis in normal people
3
Zhenyi Zhan,1 Bo Li,2 Bailang Chen,2 Shenzhen, China
4
1 Fuwai Hospital,Chinese Academy of Medical Sciences,Shenzhen.
5
2 Division of Cardiovascular surgery, The seventh affiliated hospital of Sun
6
Yat-sen University, Shenzhen, China.
7
Correspondence to: Bailang Chen, Division of Cardiovascular surgery, The
8
seventh affiliated hospital of Sun Yat-sen Universitye.No. 628, Zhenyuan Road,
9
Guangming District, Shenzhen, China; E-mail: [email protected]
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
1
25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40
Abstract
Objective: To assess the position of three branches of the aortic arch in
41
normal people, to provide reference data for the customization of aortic arch stents
42
and simplified intraluminal treatment.
43
Methods: A total of 120 patients who underwent thoracic aorta computed
44
tomography angiography（CTA） examination in our institution were enrolled
45
according to a set inclusion and exclusion criteria from January 2018 to December
46
2018. Measurements were using the GEAW 4.6 workstation. The parameters recorded
47
were: the ratio of the distance from the point where the aortic branch opening
48
intersects the aortic arch to the anterior wall of the aorta to the cross-sectional
49
diameter of the aortic arch. Finally, the position relationship among the three branch
50
openings was determined.
51
Results: The position relationship among the three branches openings is divided into 2
52
three categories: Type I: Two of the branch openings are completely surrounded by
53
the boundary of the other branch. Type II: There is no inclusion relationship between
54
the three branch openings. Type III:
55
boundary of the other branch. In Type I there were 23 cases (19.2%); Type II, 37 cases
56
(30.8%); and Type III, 60 cases (50%). These three position relationship were not
57
significantly different between sexes and different ages (P > 0.05). These data was
58
used to design a possible stent model.
59
Conclusion This study reveals that the position of three aortic branches exhibits
60
distinct patterns divided into three types. Based on measurements of the opening
61
position of the three branches, the position relationship between the three branches
62
can be obtained, to provide a theoretical basis for the design of intraluminal stents and
63
application of the simplified intracavity thoracic endovascular aneurysm repair
64
（TEVAR）technology.
65
Key words: opening of three branches of aortic arch, aortic arch axis, CTA
One branch opening is surrounded by the
66 67
INTRODUCTION
68
The incidence of aortic arch disease has been increasing yearly due to several
69
factors including the high number of ageing population. The aortic dissection
70
aneurysm is characterized by acute onset and severe illness. These patients frequently
71
manifest several symptoms such as sudden severe pain, shock, and organ ischemia
72
which decrease health status and quality of life for patients
73
although technically possible, is often associated with relatively high surgical trauma,
74
postoperative mortality, and serious complications (including stroke and myocardial
75
infarction, etc.)[2]. As a result, less invasive endovascular approaches have been
76
designed which partially substitute traditional thoracotomy for the treatment of most
77
conditions of the thoracoabdominal aorta.
[1]
. Standard open repair,
78
However, due to the unique anatomical structure of the aortic arch, the use of
79
endovascular advances into the aortic arch repair have been limited by its tortuosity,
80
hemodynamic forces as well as the need to maintain perfusion to vital arch vessels[3].
81 82
Several methods have been used to treat diseases of the arch or ascending aorta, including hybrid surgery
[4]
, Fenestrated techniques 3
[5]
, "chimney" techniques,, and
[6-8]
83
implantation of branch grafts
. Branch grafts are often used to reconstruct
84
important branch vessels on the aortic arch. Given that these grafts have to be
85
customized long before they are
86
increases the mortality rate.
applied, this time lag greatly delays treatment and
87
Standard off-the-shelf devices would preclude this delay and reduce costs, but
88
require deeper understanding and mapping of the aortic arch geometry. Several
89
studies have described the anatomy of the aortic arch. For instance, studies have
90
reported the distance between the three branches of the aorta and the angular
91
relationship between the three branches and the aortic arch, which reflects the
92
positional relationship between the three branches and the aortic arch to some extent.
93
This study explored the anatomy of aortic arch from another perspective. Using a
94
commercially available software, we outlined the three arch vessels in patients
95
without aneurysms or dissections. The vascular imaging workstation was used to
96
observe the relationship between the three branches opening of the normal aortic arch.
97
This information was then applied to design a prototype stent model that can be
98
prospectively applied in a simulated manner to patients with arch aneurysm. The goal
99
of this study is to develop an arch endograft that would obviate the need for
100
customization in many cases.
101 102 103
Materials and Methods
104
Normal information
105
Patients who underwent thoracic aortic CT angiography (CTA) in our hospital
106
from January to December 2018 were enrolled in this study. The CTA examination
107
was performed in patients with chest pain, abdominal pain, and pain in the lower
108
back.
109
Exclusion criteria: (1) Patients diagnosed with arterial diseases such as aortic
110
aneurysm, aortic dissection, aortic wall hematoma, and aortic penetrating ulcer
111
affecting the thoracic aorta and/or aortic arch branch. (2) The parameters, range, and
112
image quality of the CT scan are not up to standard or the window width and window
113
position are not suitable, and intravascular lumen contrast agents are poorly filled. (3) 4
114
Patients with severe organic lesions in the chest or mediastinum causing changes in
115
aortic morphology. (4) Patients diagnosed with connective tissue diseases e.g., Marfan
116
syndrome. (5) Patients with aortic diseases after surgery. (6) The presence of
117
variations in the aortic arch branch.
118
Finally, 80 men and 40 women were enrolled. The age ranged from 16 to 89 years old,
119
with an average of (63 ± 14) years.
120
Method
121
Image processing software: GEAW4.6 workstation was used to reconfigure the
122
aorta from the raw data of the CT scans (US GE 64-row CT scanner). All CT scans
123
were acquired from 1-mm-thick cuts. The centerline tool was used to straighten the
124
aortic arch (Fig. 1). The three branch openings of the aortic arch were identified and
125
cross-sectional images were taken (Fig. 2).
126
From the cross-sectional view, the intersection of the three branches with the aortic
127
arch was marked (A,C in the figure). The vertical distance from the intersection to the
128
anterior wall of the aortic arch was measured (AB, CD in the figure). Subsequently,
129
the ratio of (AB, CD) to the cross-sectional diameter of the aortic arch (EF in the
130
figure 2) was calculated. For each branch vessel, the ratio was used to indicate the
131
position of the branch vessel opening on the aortic arch. For instance, AB divided by
132
EF equals K1, CD divided by EF equals K2. Therefore, we infer that the position of
133
this branch ranges from K1 to K2. For each branch vessel opening position, we
134
determined the range K1 to K2 (Fig. 3). The laws governing different opening ranges
135
of the three branch vessels were explored.
136
Analysis of the three branch opening data revealed a certain inclusion
137
relationship between the three branch openings. The branches were divided into three
138
types based on the number of branches in which branches are completely wrapped by
139
the boundaries of another branch. Type I: One of the branch boundaries completely
140
wraps around the other two branches. Type II: There is no inclusion relationship
141
between the three branches. Type III: One or two pairs of inclusion relationships
142
exists among the three branches (Fig. 4).
143 144
Statistical methods 5
145
Data are analyzed using SPSS 17.0 software. The measurement data are
146
expressed as x±s, the t-test was used for comparison between the two groups, the
147
one-way analysis of variance was used for comparison among groups, and the LSD-t
148
test was used to compare multiple groups. The count data were analyzed by
149
chi-square test. P<0.05 was considered statistically significant.
150
Outcomes
151
Vascular analysis of the three aortic branches was performed by 120 CT scans of
152
the thoracoabdominal aorta of 120 patients (mean age: 63 years; 80 men, 40 women).
153
All patients had type I aortic arches with three separate arch vessels, namely the
154
Brachiocephalic trunk（BCT）, Left common carotid artery （LCCA）, and Left
155
subclavian artery （LSA）. We found a certain inclusion relationship between the
156
three branch vessels. Among the three types of branch openings, 23 cases had type I,
157
accounting for 19.2%; 37 cases had type III, accounting for 30.8%; and 60 cases had
158
type III, accounting for 50%. However, further analysis revealed that there was no
159
significant difference between in these types among age or gender (Table 1). A
160
histogram showing the distribution of the three types of between different genders is
161
shown in Fig. 5. Table 2 shows that the three types of branch openings are not
162
significantly different among ages (Fig. 6). The data analysis revealed that type I and
163
type III accounted for nearly 70% of the total number of study subjects. For type III,
164
only one branch was surrounded by the boundary of another branch. Further analysis
165
showed that, for patients with type III, the branches that were not completely wrapped
166
were covered by > 70%. Since most populations of patients had type I or type III, we
167
envisage designing a stent model to block the closure of the aortic dissection while
168
avoiding the closure of the three branch vessels (Fig. 7). As shown in the figure, the
169
red part shows the stent for removing the film. Blood flows into the vessels of the
170
three branches from the bare stent portion. Based on the three-branch diameter
171
measurement. The L1 and L2 can be customized to several specifications based on the
172
existing data. For patients with aortic dissection fracture distant to the position of
173
three-branch region, this model can be used to efficiently seal the fracture. According
174
to the needs of the actual situation, We can put the chimney stent to better block the
175
dissection. After designing the specific stent, it can be applied to some patients with
176
Stanford A dissection requiring emergency surgery.
177 6
Table 1
178
Comparison of branch openings between male and female
Gender
I
II
III
Total
Male
14(15.3)
27(24.7)
39(40.0)
80(80.0)
Female
9(7.7)
10(12.3)
21(20.0)
40(40.0)
Total
23(23.0)
37(37.0)
60(60.0)
120(120.0)
179 180 181
P＞0.05 Indicates no statistically significant differences in the positional relationship of the three branches of the aortic arch between genders, as shown in Table 1.
182 183 184 185 186
Table 2 Comparison of branch openings among different age-groups
187
Age
I
II
III
Total
188
≤40
1(1.9)
4(3.1)
5(5.0)
10(10.0)
189
41-60
4(5.9)
9(9.6)
18(15.5)
31(31.0)
≥61
18(15.1)
24(24.4)
37(39.5)
79(79.0)
Total
23(23.0)
37(37.0)
60(60.0)
120(120.0)
P
190
＞
191
0.0
192
5
193
Ind
194
icat
195
es no significant differences in the classification of the position of the three branches
196
of the aortic arch in the three age-groups ≤40 years old, 41-60 years old, and ≥61
197
years old, as shown in Table 2.
198 199 200
Discuss Nowadays, the evolution of endoluminal repair technology has extended 7
201
endovascular treatment to the forbidden zone of the aortic arch. Currently, there are
202
three main endovascular techniques for TEVAR revascularization of the three
203
branches of aortic arch. These include the chimney technique, fenestrated and
204
branched stent grafts which are used to closing dissection involving the aortic arch[9].
205
These techniques have some shortcomings which need to be resolved to design
206
readily available off-the-shelf fenestrated or branched arch devices [10]. One of the
207
missing pieces precluding development of these grafts is an accurate and surgically
208
relevant mapping of the normal aortic arch.
209
The design of the standardized intraluminal stent requires precise understanding
210
of the aortic arch morphology, including the diameter and angle of the aortic arch as
211
well as the relative positional relationship of the three branches on the arch. In the
212
interventional treatment of aortic arch lesions, accurate information on aortic arch
213
morphology and branch variation information can help to guide the design, fabrication
214
and production of aortic large vessel stents, and contribute to the vascular
215
interventional treatment of diseases such as aortic dissection [11].
216
Previous studies mainly explored the positional relationship between the three
217
branches of the aorta and the aortic arch based on the distance between the three
218
branches and the angle between the three branches and the axis of the aortic arch, and
219
the relationship between the three has been established to some extent. Finlay et al[12]
220
showed that the distance from the aortic sinus to the brachiocephalic trunk, the left
221
common carotid artery, and the left subclavian artery were (69.9 ±11.8) mm, (8 1.7 ±
222
13.8) mm, (9 6 .6 ± 15 .8 ) mm, respectively. The distances from BCT to LCCA and
223
LCCA to LSA were (5.1 ± 1.5) mm and (10.9 ± 4. 4) mm, respectively. Yan et al [13]
224
reported that the distance between BCT and LCC was (4.39±2.49) mm, and the
225
distance between left common carotid artery and left subclavian artery was
226
(6.43±3.98). Accurate measurement of these parameters provide information for the
227
design of stents. The measurement values of these parameters vary among individuals.
228
Previous attempts to customize the aortic arch stent have been limited by the
229
variability of the three branches of the aortic arch. There could be fundamental rules
230
governing the geometry of the three branch openings, which require further
231
understanding. In this study, we measured the positional relationship between the
232
three branch openings of the aortic arch from a new perspective. We aimed to find the
233
potential positional relationship of the three branch openings, to provide a theoretical 8
234
basis for the design of intraluminal stent and application of the simplified intracavity
235
TEVAR technology.
236 237
Multidetector CT has become the most common method of evaluating thoracic vasculature
[14]
and the principal diagnostic method for assessment of thoracic aortic
[15]
238
abnormalities
. It has also been used to assess the morphology of the aortic arch.
239
In this study, we used the centerline tool to measure the position of the three branches
240
of the aortic arch on the cross-sectional image. Due to the curved structure of the
241
aortic arch, it is not easy to observe the position of the three branches. Thus, we used
242
this tool to resolve this problem.
243
Consequently, we found that there appears to be a certain relationship between
244
the three-branches. However, this relationship is not influenced by gender and age.
245
We attempted to develop a stent model that is suitable for most people. While sealing
246
the aortic dissection, care was taken to ensure that the blood flow in the three
247
branches is as smooth as possible. Of course, we assume that each patient has type I
248
branch opening. In this way, according to the existing three-branch diameter and the
249
distance between the branches, the window is fenestrated at the bracket to maximize
250
the fit of the three-branch area.
251
However, type I and type III patients are the majority. Our results showed that
252
this model can also be applied to patients with type III. For type III，although one of
253
the branches is not completely covered in the window opening area, most of the
254
people in this type have more than 70% area of the branch in this range, which is
255
sufficient because 70% of the area is sufficient for blood flow or guidewire to pass (If
256
you need to put the chimney stent through this small hole).
257
Numerous researchers have attempted to measure the diameter of the three
258
branches of the aortic arch. In a study by Finlay et al[12], the LSA diameters were
259
found to range from 9.3-17.6 mm with an average diameter of 13.5 mm. The
260
measured LCCA diameters ranged from 6.9-13.6 mm with an average of 10.1 mm,
261
and the BCT diameters ranged from 11.7-20.0 mm with an average of 15.7 mm. The
262
distance between LSA and LCCA ranged from 3.6-25.3 mm with an average of 10.9
263
mm. The distance between BCT and LCCA ranged from 2.3-10.9 mm with an average
264
of 5.1 mm. Guo et al[16] found that the innominate artery diameter was 13±2.0 mm,
265
the left common carotid artery was 8.7±1.5 mm, and the left subclavian artery was 9
266
10.7±1.7 mm. On the basis of these findings, we conclude that the BCT is the thickest,
267
and to cover all branches, our L1 value is determined by the BCT diameter. Similarly,
268
the value of L2 is determined by the distance between BCT and LSA. If data on the
269
branch diameter of a certain population and the distance between branches is available,
270
we can design stents for this group. Therefore, L1and L2 are set within a certain range,
271
upon which several specifications can be developed within this range to suit most
272
people (type I and type III) in this group.
273
Depending on the individual differences among the patients, different sizes of
274
window stents can be designed. When the stent is successfully released in the aortic
275
arch, it can cover the interlayer to the largest extent while avoiding the blockage of
276
important branches providing blood supply to ensure the smooth blood flow through
277
the branch. For some interlayers that are not covered by the bracket, we can use the
278
open part of the stent itself to place the chimney bracket to further block the interlayer,
279
if necessary. This approach is expected to achieve a complete intraluminal repair of
280
the aortic dissection through a customized stent, thus avoiding the huge damage
281
caused by thoracotomy.
282
Our study found that the positional relationship between the three branches of the
283
aortic arch is not irregular. We attempted to fenestrate on the stent without affecting
284
the blood flow through the three branches of the bow. At the same time, the stent
285
should not be too large. Otherwise, the fracture of the dissection cannot be blocked
286
sufficiently. On the other hand, the opening should not be too small to affect the blood
287
flow through the branches. The inclusion relationship between the aortic branches
288
identified in this study presents a theoretical basis for the development of suitable
289
fenestrated stents. According to our classification, the customized stent can better
290
make the opening area of the stent match the opening area of the three branches. This
291
method of producing standardized grafts will lower manufacturing costs and facilitate
292
the timely production of customized stent for clinical application.
293 294 295
CONCLUSIONS The development of standardized off-the-shelf aortic arch endografts will 10
296
reduce production costs and treatment delays that currently subject patients to
297
additional risk of adverse sequelae. The present study describes a stent model based
298
on the results of the study. Based on these findings, a prototype of an off-the-shelf
299
endograft is suggested that can now be evaluated, refined, and validated in future
300
studies.
301 302
Limitation
303
This study is based on a population of people with normal three-branch anatomy,
304
and did not cover the population of people with other variants of aortic branches. The
305
population used in this study comprise hospital-based patients. Patients who undergo
306
CTA examination for various reasons may carry some bias. In the future,
307
measurements and observations should be performed for non-hospital populations. In
308
addition, multi-center, multi-regional crowd data should be generated to
309
comprehensively analyze large populations.
310 311
CONFLICT STATEMENT
312 313
None.
314 315 316 317 318 319 320 321
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emergency surgery for acute aortic dissection type A:a comparison between young and elderly adults[J].
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Eur J Cardiothorac Surg, 2017,51(3):465-471.
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Hogendoorn W, Schlösser FJ, Moll FL, et al. Thoracic endovascular aortic repair with the chimney graft technique[J]. J Vasc Surg, 2013,58(2):502-511.
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Hongku K, Dias N, Sonesson B, et al. Techniques for aortic arch endovascular repair[J]. J Cardiovasc Surg
Zou J, Jiao Y, Zhang X, et al. Early- and Mid-term Results of the Chimney Technique in the Repair of Aortic Arch Pathologies[J]. Cardiovasc Intervent Radiol, 2016,39(11):1550-1556.
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Zhang H , Huang H , Zhang Y , et al. Comparison of Chimney Technique and Single-Branched Stent Graft
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for Treating Patients with Type B Aortic Dissections that Involved the Left Subclavian Artery[J].
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CardioVascular and Interventional Radiology, 2018(20).
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Milne CP, Amako M, Spear R, et al. Inner-Branched Endografts for the Treatment of Aortic Arch
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Aneurysms After Open Ascending Aortic Replacement for Type A Dissection[J]. Ann Thorac Surg,
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2016,102(6):2028-2035.
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Lioupis C , Corriveau M M , Mackenzie K S , et al. Treatment of Aortic Arch Aneurysms with a Modular
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Transfemoral Multibranched Stent Graft: Initial Experience[J]. European Journal of Vascular &
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Endovascular Surgery the Official Journal of the European Society for Vascular Surgery, 2012,
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43(5):525-532.
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[10]
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2007;19:188e92 [11]
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Finlay A, Johnson M, Forbes TL. Surgically relevant aortic arch mapping using computed tomography[J]. Ann Vasc Surg, 2012,26(4):483-490.
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Budhiraja V , Rastogi R , Jain V , et al. Anatomical Variations in the Branching Pattern of Human Aortic Arch: A Cadaveric Study from Central India[J]. ISRN Anatomy, 2013, 2013:1-5.
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Chuter TA, Schneider DB. Endovascular repair of the aortic arch. Perspect Vasc Surg Endovasc Ther
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Berko NS, Jain VR, Godelman A, et al. Variants and anomalies of thoracic vasculature on computed 12
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tomographic angiography in adults. J Comput Assist Tomogr 2009;33:523e8. [15]
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Turkvatan A, Buyukbayraktar FG, Olcer T, Cumhur T.Congenital anomalies of the aortic arch: evaluation with the use of multidetector computed tomography. Korean J Radiol 2009;10:176e84.
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358 359 360 361 362 363 364 365
Figure Legend
366
Fig. 1. Straightening of the aortic arch with the center line tool. From this side view,
367
the three branches of the aorta are clearly seen. The center point of the three branches
368
is used to make a cross-section
369
Fig. 2. The intersection (A, C) of the branch opening and the aortic arch is marked on
370
the cross-sectional image. The cross-sectional diameter is represented by EF. The line
371
passing through B, D is perpendicular to EF, and lines AB, CD are parallel to EF.
372
Fig. 3. Schematic diagram of the three branches of the aortic arch. Short lines are used
373
to indicate different three branch openings. The position and width of the openings of
374
different branches is defined in the figure.
375
Fig. 4. Classification of the three branch openings. Type I: Two of the branch
376
openings are completely surrounded by the boundary of the other branch. Type II:
377
There is no inclusion relationship between the three branch openings. Type III:
378
one branch opening is surrounded by the boundary of another branch.
379
Fig. 5. Different branch openings types have roughly the same trend between genders.
380
Fig. 6. Different branch openings types have roughly the same trend between different 13
Only
381
age-groups
382
Fig. 7 The red part shows the stent without film cover. L1 is the width
383
length.
384 385 386 387 388 389 390
14
and L2 is the
Table 1 Comparison of typing between male and female Gender I II III Total Male 14(15.3) 27(24.7) 39(40.0) 80(80.0) Female 9(7.7) 10(12.3) 21(20.0) 40(40.0) Total 23(23.0) 37(37.0) 60(60.0) 120(120.0) P＞0.05There was no statistically significant difference in the positional relationship of the three branches of the aortic arch in the gender group,as shown in Tables 1.
Table 2 Age ≤40 41-60 ≥61 Total
Comparison of typing in different age groups
I 1(1.9) 4(5.9) 18(15.1) 23(23.0)
II 4(3.1) 9(9.6) 24(24.4) 37(37.0)
III 5(5.0) 18(15.5) 37(39.5) 60(60.0)
Total 10(10.0) 31(31.0) 79(79.0) 120(120.0)
P＞0.05There were no significant differences in the classification of the position of the three branches of the aortic arch in the three age groups ≤40 years old, 41-60 years old, and ≥61 years old, as shown in Tables 2.
S0890-5096(20)30013-3
DOI:
https://doi.org/10.1016/j.avsg.2019.12.036
Reference:
AVSG 4848
To appear in:
Annals of Vascular Surgery
Received Date: 14 July 2019 Revised Date:
8 December 2019
Accepted Date: 14 December 2019
Please cite this article as: Zhan Z, Li B, Chen B, The position relationship between the opening of three branches of aortic arch and the aortic arch axis in normal people, Annals of Vascular Surgery (2020), doi: https://doi.org/10.1016/j.avsg.2019.12.036. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2020 Published by Elsevier Inc.
1
The position relationship between the opening of three branches of aortic
2
arch and the aortic arch axis in normal people
3
Zhenyi Zhan,1 Bo Li,2 Bailang Chen,2 Shenzhen, China
4
1 Fuwai Hospital,Chinese Academy of Medical Sciences,Shenzhen.
5
2 Division of Cardiovascular surgery, The seventh affiliated hospital of Sun
6
Yat-sen University, Shenzhen, China.
7
Correspondence to: Bailang Chen, Division of Cardiovascular surgery, The
8
seventh affiliated hospital of Sun Yat-sen Universitye.No. 628, Zhenyuan Road,
9
Guangming District, Shenzhen, China; E-mail: [email protected]
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
1
25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40
Abstract
Objective: To assess the position of three branches of the aortic arch in
41
normal people, to provide reference data for the customization of aortic arch stents
42
and simplified intraluminal treatment.
43
Methods: A total of 120 patients who underwent thoracic aorta computed
44
tomography angiography（CTA） examination in our institution were enrolled
45
according to a set inclusion and exclusion criteria from January 2018 to December
46
2018. Measurements were using the GEAW 4.6 workstation. The parameters recorded
47
were: the ratio of the distance from the point where the aortic branch opening
48
intersects the aortic arch to the anterior wall of the aorta to the cross-sectional
49
diameter of the aortic arch. Finally, the position relationship among the three branch
50
openings was determined.
51
Results: The position relationship among the three branches openings is divided into 2
52
three categories: Type I: Two of the branch openings are completely surrounded by
53
the boundary of the other branch. Type II: There is no inclusion relationship between
54
the three branch openings. Type III:
55
boundary of the other branch. In Type I there were 23 cases (19.2%); Type II, 37 cases
56
(30.8%); and Type III, 60 cases (50%). These three position relationship were not
57
significantly different between sexes and different ages (P > 0.05). These data was
58
used to design a possible stent model.
59
Conclusion This study reveals that the position of three aortic branches exhibits
60
distinct patterns divided into three types. Based on measurements of the opening
61
position of the three branches, the position relationship between the three branches
62
can be obtained, to provide a theoretical basis for the design of intraluminal stents and
63
application of the simplified intracavity thoracic endovascular aneurysm repair
64
（TEVAR）technology.
65
Key words: opening of three branches of aortic arch, aortic arch axis, CTA
One branch opening is surrounded by the
66 67
INTRODUCTION
68
The incidence of aortic arch disease has been increasing yearly due to several
69
factors including the high number of ageing population. The aortic dissection
70
aneurysm is characterized by acute onset and severe illness. These patients frequently
71
manifest several symptoms such as sudden severe pain, shock, and organ ischemia
72
which decrease health status and quality of life for patients
73
although technically possible, is often associated with relatively high surgical trauma,
74
postoperative mortality, and serious complications (including stroke and myocardial
75
infarction, etc.)[2]. As a result, less invasive endovascular approaches have been
76
designed which partially substitute traditional thoracotomy for the treatment of most
77
conditions of the thoracoabdominal aorta.
[1]
. Standard open repair,
78
However, due to the unique anatomical structure of the aortic arch, the use of
79
endovascular advances into the aortic arch repair have been limited by its tortuosity,
80
hemodynamic forces as well as the need to maintain perfusion to vital arch vessels[3].
81 82
Several methods have been used to treat diseases of the arch or ascending aorta, including hybrid surgery
[4]
, Fenestrated techniques 3
[5]
, "chimney" techniques,, and
[6-8]
83
implantation of branch grafts
. Branch grafts are often used to reconstruct
84
important branch vessels on the aortic arch. Given that these grafts have to be
85
customized long before they are
86
increases the mortality rate.
applied, this time lag greatly delays treatment and
87
Standard off-the-shelf devices would preclude this delay and reduce costs, but
88
require deeper understanding and mapping of the aortic arch geometry. Several
89
studies have described the anatomy of the aortic arch. For instance, studies have
90
reported the distance between the three branches of the aorta and the angular
91
relationship between the three branches and the aortic arch, which reflects the
92
positional relationship between the three branches and the aortic arch to some extent.
93
This study explored the anatomy of aortic arch from another perspective. Using a
94
commercially available software, we outlined the three arch vessels in patients
95
without aneurysms or dissections. The vascular imaging workstation was used to
96
observe the relationship between the three branches opening of the normal aortic arch.
97
This information was then applied to design a prototype stent model that can be
98
prospectively applied in a simulated manner to patients with arch aneurysm. The goal
99
of this study is to develop an arch endograft that would obviate the need for
100
customization in many cases.
101 102 103
Materials and Methods
104
Normal information
105
Patients who underwent thoracic aortic CT angiography (CTA) in our hospital
106
from January to December 2018 were enrolled in this study. The CTA examination
107
was performed in patients with chest pain, abdominal pain, and pain in the lower
108
back.
109
Exclusion criteria: (1) Patients diagnosed with arterial diseases such as aortic
110
aneurysm, aortic dissection, aortic wall hematoma, and aortic penetrating ulcer
111
affecting the thoracic aorta and/or aortic arch branch. (2) The parameters, range, and
112
image quality of the CT scan are not up to standard or the window width and window
113
position are not suitable, and intravascular lumen contrast agents are poorly filled. (3) 4
114
Patients with severe organic lesions in the chest or mediastinum causing changes in
115
aortic morphology. (4) Patients diagnosed with connective tissue diseases e.g., Marfan
116
syndrome. (5) Patients with aortic diseases after surgery. (6) The presence of
117
variations in the aortic arch branch.
118
Finally, 80 men and 40 women were enrolled. The age ranged from 16 to 89 years old,
119
with an average of (63 ± 14) years.
120
Method
121
Image processing software: GEAW4.6 workstation was used to reconfigure the
122
aorta from the raw data of the CT scans (US GE 64-row CT scanner). All CT scans
123
were acquired from 1-mm-thick cuts. The centerline tool was used to straighten the
124
aortic arch (Fig. 1). The three branch openings of the aortic arch were identified and
125
cross-sectional images were taken (Fig. 2).
126
From the cross-sectional view, the intersection of the three branches with the aortic
127
arch was marked (A,C in the figure). The vertical distance from the intersection to the
128
anterior wall of the aortic arch was measured (AB, CD in the figure). Subsequently,
129
the ratio of (AB, CD) to the cross-sectional diameter of the aortic arch (EF in the
130
figure 2) was calculated. For each branch vessel, the ratio was used to indicate the
131
position of the branch vessel opening on the aortic arch. For instance, AB divided by
132
EF equals K1, CD divided by EF equals K2. Therefore, we infer that the position of
133
this branch ranges from K1 to K2. For each branch vessel opening position, we
134
determined the range K1 to K2 (Fig. 3). The laws governing different opening ranges
135
of the three branch vessels were explored.
136
Analysis of the three branch opening data revealed a certain inclusion
137
relationship between the three branch openings. The branches were divided into three
138
types based on the number of branches in which branches are completely wrapped by
139
the boundaries of another branch. Type I: One of the branch boundaries completely
140
wraps around the other two branches. Type II: There is no inclusion relationship
141
between the three branches. Type III: One or two pairs of inclusion relationships
142
exists among the three branches (Fig. 4).
143 144
Statistical methods 5
145
Data are analyzed using SPSS 17.0 software. The measurement data are
146
expressed as x±s, the t-test was used for comparison between the two groups, the
147
one-way analysis of variance was used for comparison among groups, and the LSD-t
148
test was used to compare multiple groups. The count data were analyzed by
149
chi-square test. P<0.05 was considered statistically significant.
150
Outcomes
151
Vascular analysis of the three aortic branches was performed by 120 CT scans of
152
the thoracoabdominal aorta of 120 patients (mean age: 63 years; 80 men, 40 women).
153
All patients had type I aortic arches with three separate arch vessels, namely the
154
Brachiocephalic trunk（BCT）, Left common carotid artery （LCCA）, and Left
155
subclavian artery （LSA）. We found a certain inclusion relationship between the
156
three branch vessels. Among the three types of branch openings, 23 cases had type I,
157
accounting for 19.2%; 37 cases had type III, accounting for 30.8%; and 60 cases had
158
type III, accounting for 50%. However, further analysis revealed that there was no
159
significant difference between in these types among age or gender (Table 1). A
160
histogram showing the distribution of the three types of between different genders is
161
shown in Fig. 5. Table 2 shows that the three types of branch openings are not
162
significantly different among ages (Fig. 6). The data analysis revealed that type I and
163
type III accounted for nearly 70% of the total number of study subjects. For type III,
164
only one branch was surrounded by the boundary of another branch. Further analysis
165
showed that, for patients with type III, the branches that were not completely wrapped
166
were covered by > 70%. Since most populations of patients had type I or type III, we
167
envisage designing a stent model to block the closure of the aortic dissection while
168
avoiding the closure of the three branch vessels (Fig. 7). As shown in the figure, the
169
red part shows the stent for removing the film. Blood flows into the vessels of the
170
three branches from the bare stent portion. Based on the three-branch diameter
171
measurement. The L1 and L2 can be customized to several specifications based on the
172
existing data. For patients with aortic dissection fracture distant to the position of
173
three-branch region, this model can be used to efficiently seal the fracture. According
174
to the needs of the actual situation, We can put the chimney stent to better block the
175
dissection. After designing the specific stent, it can be applied to some patients with
176
Stanford A dissection requiring emergency surgery.
177 6
Table 1
178
Comparison of branch openings between male and female
Gender
I
II
III
Total
Male
14(15.3)
27(24.7)
39(40.0)
80(80.0)
Female
9(7.7)
10(12.3)
21(20.0)
40(40.0)
Total
23(23.0)
37(37.0)
60(60.0)
120(120.0)
179 180 181
P＞0.05 Indicates no statistically significant differences in the positional relationship of the three branches of the aortic arch between genders, as shown in Table 1.
182 183 184 185 186
Table 2 Comparison of branch openings among different age-groups
187
Age
I
II
III
Total
188
≤40
1(1.9)
4(3.1)
5(5.0)
10(10.0)
189
41-60
4(5.9)
9(9.6)
18(15.5)
31(31.0)
≥61
18(15.1)
24(24.4)
37(39.5)
79(79.0)
Total
23(23.0)
37(37.0)
60(60.0)
120(120.0)
P
190
＞
191
0.0
192
5
193
Ind
194
icat
195
es no significant differences in the classification of the position of the three branches
196
of the aortic arch in the three age-groups ≤40 years old, 41-60 years old, and ≥61
197
years old, as shown in Table 2.
198 199 200
Discuss Nowadays, the evolution of endoluminal repair technology has extended 7
201
endovascular treatment to the forbidden zone of the aortic arch. Currently, there are
202
three main endovascular techniques for TEVAR revascularization of the three
203
branches of aortic arch. These include the chimney technique, fenestrated and
204
branched stent grafts which are used to closing dissection involving the aortic arch[9].
205
These techniques have some shortcomings which need to be resolved to design
206
readily available off-the-shelf fenestrated or branched arch devices [10]. One of the
207
missing pieces precluding development of these grafts is an accurate and surgically
208
relevant mapping of the normal aortic arch.
209
The design of the standardized intraluminal stent requires precise understanding
210
of the aortic arch morphology, including the diameter and angle of the aortic arch as
211
well as the relative positional relationship of the three branches on the arch. In the
212
interventional treatment of aortic arch lesions, accurate information on aortic arch
213
morphology and branch variation information can help to guide the design, fabrication
214
and production of aortic large vessel stents, and contribute to the vascular
215
interventional treatment of diseases such as aortic dissection [11].
216
Previous studies mainly explored the positional relationship between the three
217
branches of the aorta and the aortic arch based on the distance between the three
218
branches and the angle between the three branches and the axis of the aortic arch, and
219
the relationship between the three has been established to some extent. Finlay et al[12]
220
showed that the distance from the aortic sinus to the brachiocephalic trunk, the left
221
common carotid artery, and the left subclavian artery were (69.9 ±11.8) mm, (8 1.7 ±
222
13.8) mm, (9 6 .6 ± 15 .8 ) mm, respectively. The distances from BCT to LCCA and
223
LCCA to LSA were (5.1 ± 1.5) mm and (10.9 ± 4. 4) mm, respectively. Yan et al [13]
224
reported that the distance between BCT and LCC was (4.39±2.49) mm, and the
225
distance between left common carotid artery and left subclavian artery was
226
(6.43±3.98). Accurate measurement of these parameters provide information for the
227
design of stents. The measurement values of these parameters vary among individuals.
228
Previous attempts to customize the aortic arch stent have been limited by the
229
variability of the three branches of the aortic arch. There could be fundamental rules
230
governing the geometry of the three branch openings, which require further
231
understanding. In this study, we measured the positional relationship between the
232
three branch openings of the aortic arch from a new perspective. We aimed to find the
233
potential positional relationship of the three branch openings, to provide a theoretical 8
234
basis for the design of intraluminal stent and application of the simplified intracavity
235
TEVAR technology.
236 237
Multidetector CT has become the most common method of evaluating thoracic vasculature
[14]
and the principal diagnostic method for assessment of thoracic aortic
[15]
238
abnormalities
. It has also been used to assess the morphology of the aortic arch.
239
In this study, we used the centerline tool to measure the position of the three branches
240
of the aortic arch on the cross-sectional image. Due to the curved structure of the
241
aortic arch, it is not easy to observe the position of the three branches. Thus, we used
242
this tool to resolve this problem.
243
Consequently, we found that there appears to be a certain relationship between
244
the three-branches. However, this relationship is not influenced by gender and age.
245
We attempted to develop a stent model that is suitable for most people. While sealing
246
the aortic dissection, care was taken to ensure that the blood flow in the three
247
branches is as smooth as possible. Of course, we assume that each patient has type I
248
branch opening. In this way, according to the existing three-branch diameter and the
249
distance between the branches, the window is fenestrated at the bracket to maximize
250
the fit of the three-branch area.
251
However, type I and type III patients are the majority. Our results showed that
252
this model can also be applied to patients with type III. For type III，although one of
253
the branches is not completely covered in the window opening area, most of the
254
people in this type have more than 70% area of the branch in this range, which is
255
sufficient because 70% of the area is sufficient for blood flow or guidewire to pass (If
256
you need to put the chimney stent through this small hole).
257
Numerous researchers have attempted to measure the diameter of the three
258
branches of the aortic arch. In a study by Finlay et al[12], the LSA diameters were
259
found to range from 9.3-17.6 mm with an average diameter of 13.5 mm. The
260
measured LCCA diameters ranged from 6.9-13.6 mm with an average of 10.1 mm,
261
and the BCT diameters ranged from 11.7-20.0 mm with an average of 15.7 mm. The
262
distance between LSA and LCCA ranged from 3.6-25.3 mm with an average of 10.9
263
mm. The distance between BCT and LCCA ranged from 2.3-10.9 mm with an average
264
of 5.1 mm. Guo et al[16] found that the innominate artery diameter was 13±2.0 mm,
265
the left common carotid artery was 8.7±1.5 mm, and the left subclavian artery was 9
266
10.7±1.7 mm. On the basis of these findings, we conclude that the BCT is the thickest,
267
and to cover all branches, our L1 value is determined by the BCT diameter. Similarly,
268
the value of L2 is determined by the distance between BCT and LSA. If data on the
269
branch diameter of a certain population and the distance between branches is available,
270
we can design stents for this group. Therefore, L1and L2 are set within a certain range,
271
upon which several specifications can be developed within this range to suit most
272
people (type I and type III) in this group.
273
Depending on the individual differences among the patients, different sizes of
274
window stents can be designed. When the stent is successfully released in the aortic
275
arch, it can cover the interlayer to the largest extent while avoiding the blockage of
276
important branches providing blood supply to ensure the smooth blood flow through
277
the branch. For some interlayers that are not covered by the bracket, we can use the
278
open part of the stent itself to place the chimney bracket to further block the interlayer,
279
if necessary. This approach is expected to achieve a complete intraluminal repair of
280
the aortic dissection through a customized stent, thus avoiding the huge damage
281
caused by thoracotomy.
282
Our study found that the positional relationship between the three branches of the
283
aortic arch is not irregular. We attempted to fenestrate on the stent without affecting
284
the blood flow through the three branches of the bow. At the same time, the stent
285
should not be too large. Otherwise, the fracture of the dissection cannot be blocked
286
sufficiently. On the other hand, the opening should not be too small to affect the blood
287
flow through the branches. The inclusion relationship between the aortic branches
288
identified in this study presents a theoretical basis for the development of suitable
289
fenestrated stents. According to our classification, the customized stent can better
290
make the opening area of the stent match the opening area of the three branches. This
291
method of producing standardized grafts will lower manufacturing costs and facilitate
292
the timely production of customized stent for clinical application.
293 294 295
CONCLUSIONS The development of standardized off-the-shelf aortic arch endografts will 10
296
reduce production costs and treatment delays that currently subject patients to
297
additional risk of adverse sequelae. The present study describes a stent model based
298
on the results of the study. Based on these findings, a prototype of an off-the-shelf
299
endograft is suggested that can now be evaluated, refined, and validated in future
300
studies.
301 302
Limitation
303
This study is based on a population of people with normal three-branch anatomy,
304
and did not cover the population of people with other variants of aortic branches. The
305
population used in this study comprise hospital-based patients. Patients who undergo
306
CTA examination for various reasons may carry some bias. In the future,
307
measurements and observations should be performed for non-hospital populations. In
308
addition, multi-center, multi-regional crowd data should be generated to
309
comprehensively analyze large populations.
310 311
CONFLICT STATEMENT
312 313
None.
314 315 316 317 318 319 320 321
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emergency surgery for acute aortic dissection type A:a comparison between young and elderly adults[J].
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Hogendoorn W, Schlösser FJ, Moll FL, et al. Thoracic endovascular aortic repair with the chimney graft technique[J]. J Vasc Surg, 2013,58(2):502-511.
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Hongku K, Dias N, Sonesson B, et al. Techniques for aortic arch endovascular repair[J]. J Cardiovasc Surg
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Zhang H , Huang H , Zhang Y , et al. Comparison of Chimney Technique and Single-Branched Stent Graft
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for Treating Patients with Type B Aortic Dissections that Involved the Left Subclavian Artery[J].
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CardioVascular and Interventional Radiology, 2018(20).
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Milne CP, Amako M, Spear R, et al. Inner-Branched Endografts for the Treatment of Aortic Arch
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Aneurysms After Open Ascending Aortic Replacement for Type A Dissection[J]. Ann Thorac Surg,
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2016,102(6):2028-2035.
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Lioupis C , Corriveau M M , Mackenzie K S , et al. Treatment of Aortic Arch Aneurysms with a Modular
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Transfemoral Multibranched Stent Graft: Initial Experience[J]. European Journal of Vascular &
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Endovascular Surgery the Official Journal of the European Society for Vascular Surgery, 2012,
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43(5):525-532.
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[10]
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2007;19:188e92 [11]
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Finlay A, Johnson M, Forbes TL. Surgically relevant aortic arch mapping using computed tomography[J]. Ann Vasc Surg, 2012,26(4):483-490.
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Budhiraja V , Rastogi R , Jain V , et al. Anatomical Variations in the Branching Pattern of Human Aortic Arch: A Cadaveric Study from Central India[J]. ISRN Anatomy, 2013, 2013:1-5.
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Chuter TA, Schneider DB. Endovascular repair of the aortic arch. Perspect Vasc Surg Endovasc Ther
Yan Yu. Aortic arch morphology related to endovascular treatment of thoracic aorta. (01) ,2013. (in chinese).
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Berko NS, Jain VR, Godelman A, et al. Variants and anomalies of thoracic vasculature on computed 12
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tomographic angiography in adults. J Comput Assist Tomogr 2009;33:523e8. [15]
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Turkvatan A, Buyukbayraktar FG, Olcer T, Cumhur T.Congenital anomalies of the aortic arch: evaluation with the use of multidetector computed tomography. Korean J Radiol 2009;10:176e84.
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358 359 360 361 362 363 364 365
Figure Legend
366
Fig. 1. Straightening of the aortic arch with the center line tool. From this side view,
367
the three branches of the aorta are clearly seen. The center point of the three branches
368
is used to make a cross-section
369
Fig. 2. The intersection (A, C) of the branch opening and the aortic arch is marked on
370
the cross-sectional image. The cross-sectional diameter is represented by EF. The line
371
passing through B, D is perpendicular to EF, and lines AB, CD are parallel to EF.
372
Fig. 3. Schematic diagram of the three branches of the aortic arch. Short lines are used
373
to indicate different three branch openings. The position and width of the openings of
374
different branches is defined in the figure.
375
Fig. 4. Classification of the three branch openings. Type I: Two of the branch
376
openings are completely surrounded by the boundary of the other branch. Type II:
377
There is no inclusion relationship between the three branch openings. Type III:
378
one branch opening is surrounded by the boundary of another branch.
379
Fig. 5. Different branch openings types have roughly the same trend between genders.
380
Fig. 6. Different branch openings types have roughly the same trend between different 13
Only
381
age-groups
382
Fig. 7 The red part shows the stent without film cover. L1 is the width
383
length.
384 385 386 387 388 389 390
14
and L2 is the
Table 1 Comparison of typing between male and female Gender I II III Total Male 14(15.3) 27(24.7) 39(40.0) 80(80.0) Female 9(7.7) 10(12.3) 21(20.0) 40(40.0) Total 23(23.0) 37(37.0) 60(60.0) 120(120.0) P＞0.05There was no statistically significant difference in the positional relationship of the three branches of the aortic arch in the gender group,as shown in Tables 1.
Table 2 Age ≤40 41-60 ≥61 Total
Comparison of typing in different age groups
I 1(1.9) 4(5.9) 18(15.1) 23(23.0)
II 4(3.1) 9(9.6) 24(24.4) 37(37.0)
III 5(5.0) 18(15.5) 37(39.5) 60(60.0)
Total 10(10.0) 31(31.0) 79(79.0) 120(120.0)
P＞0.05There were no significant differences in the classification of the position of the three branches of the aortic arch in the three age groups ≤40 years old, 41-60 years old, and ≥61 years old, as shown in Tables 2.