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Non-obstructive general angioscopy is a modality to detect small areas in the aorta.
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All of the ulcer-like projections and entries were detected by non-obstructive general angioscopy.
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Based on the angioscopy findings, the range of the graft position was confirmed.
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Angioscopy was useful for observing the condition of the aortic intima.
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Angioscopy plays an important role to determine the precise position of the graft.
Abstract
Background
Non-obstructive general angioscopy is a powerful modality for detecting areas in the aorta with vulnerable plaque, which are difficult to visualize using conventional diagnostic tools such as computed tomography (CT). The aim of the present study was to clarify the efficacy and usefulness of aortic angioscopy in patients with chronic type B aortic dissection scheduled for thoracic endovascular repair (TEVAR).
Methods
Ten patients with chronic type B aortic dissection who underwent elective TEVAR were enrolled. Before starting the stent graft procedure, the aortic intima was observed by use of non-obstructive general angioscopy. Based on those findings, the range of the stent graft position was confirmed.
Results
In all patients, observations of the aortic intima with non-obstructive general angioscopy from a point just proximal of the descending aorta to the iliac artery were successful. At the proximal site, an entry site or ulcer-like projection was detected in all patients, while a small intimal tear or entry, or an irregular intima surface with a salmon-pink color were seen in some cases. In contrast, preoperative CT did not detect any such findings in the same locations. After confirming the position of the abnormal intima, we determined the position of the distal end of the stent graft. No complications considered to be related to aortic angioscopy were noted.
Conclusions
Non-obstructive general angioscopy is useful for observing the condition of the aortic intima, revealing abnormal conditions, and confirming a normal aortic intima in patients with chronic type B aortic dissection. This modality may play an important role in determining the precise position of a stent graft for a TEVAR procedure.
Recent advances in imaging modalities have led to their greater availability and increased use, particularly computed tomography (CT), while improvements in surgical and anesthetic techniques have resulted in better survival for patients with type A acute aortic dissection [
]. Such complications, especially those involving the descending thoracic aorta in type B aortic dissection cases or type A cases with a persistent false lumen that undergo surgery, are increasingly being managed by endovascular techniques [
Although conventional imaging modalities, such as CT, magnetic resonance imaging (MRI), and transesophageal echocardiography (TEE), have been used to diagnose aortic diseases, the ability to detect millimeter-sized plaques is limited due to relatively poor spatial resolution [
Early detection of vulnerable atherosclerotic plaque for risk reduction of acute aortic rupture and thromboemboli and atheroeombli using non-obstructive angioscopy.
]. Also, few modalities have the capability to fully detect intimal injury or vulnerable plaques in the aorta in vivo.
Non-obstructive general angioscopy is a powerful tool that has been found useful for detecting vulnerable plaques in the aorta, which are difficult to visualize using conventional diagnostic tools [
Early detection of vulnerable atherosclerotic plaque for risk reduction of acute aortic rupture and thromboemboli and atheroeombli using non-obstructive angioscopy.
] in patients has been shown. Thus, it is considered to have potential to reveal the etiology of aortic dissection.
The aim of the present study was to clarify the efficacy and usefulness of non-obstructive general angioscopy in patients with chronic type B aortic dissection scheduled for a thoracic endovascular repair (TEVAR). We present here detailed findings of the aortic intima in those patients revealed with this modality.
Patients and methods
Patient characteristics
Ten patients with chronic type B aortic dissection scheduled for elective TEVAR were enrolled in this study, after obtaining informed consent prior to the procedure. The study protocol was approved by the local ethics committee of Osaka Police Hospital.
The preoperative characteristics of the patient cohort are shown in Table 1. Seven were male and the mean age was 69 ± 13 years (range 46–84 years). Three patients had a previous aortic surgical procedure for acute aortic dissection, of whom one underwent total arch replacement with an open stent graft after the initial operation. The duration since previous surgery or onset of acute aortic dissection was from 15 days to 10 years (median 36 days). Indications for surgery included a remaining ulcer-like projection (ULP) in 6 patients and false lumen dilatation in 6. Two patients had a stent-induced new entry (SINE) and one a large entry.
Table 1Baseline characteristics of study patients.
Patient
Age
Sex
Initial type of aortic dissection
Previous operation
Duration from initial onset
Duration from previous operation
Preoperative findings
1
75
M
Type B
TAR + OS
66 days
26 days
SINE
Dilatation of false lumen
2
57
F
Type B
–
30 days
–
ULP
Dilatation of false lumen
3
46
M
Type A
Bentall + TAR + OS
46 days
46 days
Narrow false lumen
Dilation of false lumen
4
64
M
Type B
TEVAR
55 days
55 days
ULP
5
84
F
Type B
–
15 days
–
ULP
6
84
M
Type B
–
29 days
–
ULP
Dilatation of false lumen
7
72
M
Type B
TAR + OS
4 years 9 months
898 days
SINE
Dilatation of false lumen
8
80
M
Type B
–
36 days
–
ULP
9
69
F
Type B
–
10 years
–
Large entry
Dilatation of false lumen
10
57
M
Type B
–
36 days
–
ULP
TAR, total arch replacement; OS, open stent graft; SINE, stent-induced new entry; TEVAR, thoracic endovascular repair; ULP, ulcer-like projection; Bentall, Bentall procedure.
In all cases, after induction of general anesthesia, the femoral artery was exposed and an 8-French sheath inserted. Before starting the stent graft procedure, we observed the aortic intima using a non-obstructive general angioscopy system that consisted of a VISIBLE Fiber (FiberTech Co., Ltd., Tokyo, Japan), Fiber Imaging System FT-203F (FiberTech Co., Ltd.), and Console (Intertec Medicals Co., Ltd., Osaka, Japan). The tips of the fiber catheter, 4-French probing catheter, and 6-French guiding catheter were set at the same position just proximal of the descending aorta, then pulled back to the iliac artery. Images were recorded digitally and converted to movie files for on-site and off-line review. Non-obstructive general angioscopy provides a visual field following injection of low-molecular-weight dextran into the space between the 4-French probing catheter and fiber, with that also infused from the 6-French guiding catheter (dual infusion), allowing observation of the aortic intima from just proximal of the descending aorta to the iliac artery. Continuous aortic angioscopy observations for vessel-wide screening of the aorta are then performed while the 6-Fr guiding catheter is slowly pulled back and rotated.
After finishing the intima observations, a stent graft procedure was performed in a usual manner. Based on the findings obtained with non-obstructive general angioscopy, the range of the stent graft position was confirmed and then it was deployed. A Conformable Gore TAG Endoprosthesis (W.L. Gore & Associates, Flagstaff, AZ, USA) was used in the present cases.
Data were analyzed using the Statview 5.0 program (SAS Institute Inc., Cary, NC, USA). Results are expressed as the mean ± standard deviation.
Results
Outcomes
In all patients, successful observations of the aortic intima from just proximal of the descending aorta to the iliac artery were performed using non-obstructive general angioscopy (Table 2). An SINE or ULP was detected in all patients in the proximal and entry sites. Furthermore, a smooth white surface, yellow plaques with either a smooth or irregular surface, and intimal tear where blood was flowing out at the dissected site were visualized in the non-obstructive general angioscopic images. Near the tear, a salmon pink-colored intima was also observed.
Table 2Intraoperative findings and postoperative outcomes.
Patient
Age
Sex
Findings of non-obstructive angioscopy
Findings not detected by preoperative CT
Postoperative findings
1
75
M
Direct visualization of SINE and false lumen, small re-entry, yellow plaque, erosion at descending aorta
Small re-entry at descending aorta
Closure of SINE
Diminished false lumen
2
57
F
Erosion/small re-entry at descending aorta
Erosion/small re-entry at descending aorta
Diminished false lumen
3
46
M
Several re-entry locations
Some re-entry locations
Expanded true lumen
4
64
M
Location of ULP
Some re-entry locations
Diminished ULP
Re-entry locations
5
84
F
Location of ULP
None
Diminished ULP
White smooth surface of other lesions
6
84
M
Location of ULP
None
Diminished ULP
White smooth surface of other lesions
7
72
M
Direct visualization of SINE, small re-entry, erosion at descending aorta
Small re-entry at descending aorta
Closure of SINE
Thrombosed false lumen
8
80
M
Location of ULP
None
Diminished ULP
White smooth surface of other lesions
Diminished false lumen
9
69
F
Location of ULP small re-entry, erosion at descending aorta
Small re-entry at descending aorta
Closure of entry
Thrombosed false lumen
10
57
M
Location of ULP
Small re-entry at descending aorta
Diminished ULP
White smooth surface of other lesions
Diminished false lumen
CT, computed tomography; SINE, stent-induced new entry; ULP, ulcer-like projection.
Following observation of the intima, a Conformable Gore TAG Endoprosthesis was deployed and a TEVAR procedure was successfully performed in all cases, and each patient had an uneventful recovery following the operation. Postoperative CT showed complete exclusion of the entry site or ULP. There were no complications considered to be related to the non-obstructive general angioscopy procedure.
Findings in patients without previous surgery
Following onset of primary type B acute aortic dissection, there were 6 patients with ULPs, while 1 patient had a large entry found 10 years after onset of type B acute aortic dissection. In those cases, all of the ULPs and 1 entry were detected by non-obstructive general angioscopy (Fig. 1, Supplemental Movie file 1), and the location of the ULP or entry was similar to that detected in CT. A white smooth surface was also visualized in areas where CT scanning showed only a smooth intima surface. Yellow plaques with either a smooth or irregular surface were also detected. In 3 patients, a small intimal tear or entry, erosion, and irregular intima surface with a salmon-pink color were found, which were not detected in the same locations by preoperative CT, which showed a smooth intima surface and no abnormal signs (Fig. 1). After detecting the position of the abnormal intima with non-obstructive general angioscopy, the initial plans for the stent graft were changed in regard to size, length, and position. Also, we were able to identify the site of aortic angioscopy by referencing the height of the vertebral body based on fluoroscopy findings and then determined the position of the distal end of the stent graft.
Fig. 1A sagittal image of computed tomography (CT) of aorta and a set of angioscopic images: ulcer-like projection in Patient 2 detected in a position similar to that shown in CT findings (left side), (b), (c). A smooth white surface was also seen in the area where CT scanning showed the intima with a smooth surface (left side), (a), (d). A smooth yellow surface was also detected (d). A small intimal tear, erosion, and irregular intima surface with a salmon-pink color were revealed, which were not visualized in the same location by preoperative CT (e), (f).
Postoperatively, the false lumen in all patients was thrombosed. After approximately 2 months, the false lumen had nearly disappeared in patients who experienced the initial acute aortic dissection within a 3-month period (Fig. 2).
Fig. 2(a) Preoperative computed tomography imaging of Patient 2 showing type B aortic dissection with an ulcer-like projection (ULP) at the proximal descending aorta, along with a thrombosed and dilated false lumen. (b) Postoperatively, the ULP was covered with a stent graft and the false lumen had shrunk. (c) After 11 months, the false lumen had disappeared.
Findings of patients who underwent TEVAR after total arch replacement with open stent graft
In 2 patients with an SINE who underwent total arch replacement with an open stent graft, non-obstructive general angioscopy provided direct visualization of the new entry, which revealed an intimal tear at the border between the stent graft and intima where blood was flowing out at the dissected site. The edge of the intimal tear was irregular and the surface was also irregular with a yellow color. Erosion of the intima and yellow plaque were also found, while a false lumen was seen beyond the entry (Fig. 3A, Supplemental Movie file 2).
Fig. 3(A) Direct visualization of a stent-induced new entry (SINE) was obtained (a)–(h). An intimal tear was present at the border between the stent graft and intima where blood was flowing out at the dissected site (d)–(g). The edge of the intimal tear was irregular (e) and had an irregular yellow surface (f). Intima erosion and yellow plaque were found (g). A false lumen was also seen beyond the entry (h). (B) From the edge of the stent graft to the descending aorta, angioscopy showed several findings, including a smooth white surface (i), yellow intima with a smooth surface (j), yellow plaque and red erosion (k), and a small re-entry point where blood was flowing out at the dissected site (l)–(n). Those were not seen in preoperative computed tomography images.
From the edge of the stent graft to the descending aorta, aortic angioscopy revealed several unique findings, such as a smooth white surface, yellow intima with regular surface, yellow plaque, and red erosion, as well as a small point of re-entry where blood was flowing out at the dissected site, which were not detected in preoperative CT images (Fig. 3B). The distal end of the stent graft was determined according to the location of the small re-entry or intima erosion, and identified using the location of the tip of the angioscope by referencing the height of the vertebral body. For this case, we initially planned to use a short stent graft to cover the SINE site. However, after finding the small entry at the distal level, we changed the initial plan and instead used a longer graft. Postoperative findings showed that the SINE and distal entry site were covered with the stent graft and the false lumen had shrunk. Findings obtained after 1 year showed that the false lumen had disappeared (Fig. 4).
Fig. 4(a) Preoperative computed tomography image of Patient 1 showing a type B aortic dissection with a stent-induced new entry (SINE) at the end of an open stent graft and patent dilated false lumen. (b) Postoperatively, the SINE was covered with a stent graft and the false lumen had shrunk. (c) After 1 year, the false lumen had disappeared.
In 1 patient with a narrow true lumen, several small points of entry were noted in the area of the descending aorta and abdominal aorta, while visceral branches were also detected. As compared to the other cases, the true lumen was narrow.
Discussion
In the current study, we analyzed use of non-obstructive general angioscopy in patients with chronic type B aortic dissection as a tool for determining the position of the entry site or abnormal intima. Various findings, such as a white smooth surface, yellow plaques with either a smooth or an irregular surface, and the intimal tear where blood was flowing out at the dissected site, were noted, which may provide useful insight regarding the pathology of acute aortic dissection. Furthermore, we applied this modality to treat cases of type B aortic dissection during TEVAR. To the best of our knowledge, there are no previous reports of the use of non-obstructive general angioscopy as a treatment modality, which we found useful for diagnosis as well as treatment. Thus, the findings of our study are considered to be important.
When left untreated, acute aortic dissection has been reported to be associated with high rates of mortality, 10% in type B and 50% in type A patients [
Early detection of vulnerable atherosclerotic plaque for risk reduction of acute aortic rupture and thromboemboli and atheroeombli using non-obstructive angioscopy.
]. Another study found that the survival rate was not different between patients with an aortic dissection with a patent pseudo-lumen and those with a thrombosed lumen [
Endovascular versus open repair of abdominal aortic aneurysm in 15-years’ follow-up of the UK endovascular aneurysm repair trial 1 (EVAR trial 1): a randomised controlled trial.
]. Recently, early management of the entry site, especially closure of the point of entry or re-entry, has been shown important for prevention of later complications, with entry closure a possible radical treatment for patients with type B aortic dissection [
Five-year results from the Study of Thoracic Aortic Type B Dissection Using Endoluminal Repair (STABLE I) study of endovascular treatment of complicated type B aortic dissection using a composite device design.
]. Appropriate entry closure is mandatory for effective treatment of such cases using TEVAR.
For this purpose, it is important to identify the entry position. Usually, CT is used to assess the entry site, while enhanced CT is able to show atherosclerotic lesions with aortic wall thickening and an entry tear. Thus, enhanced CT is necessary to visualize the global image of the aorta. However, in our study, it was not able to detect the existence of thrombi or ruptured plaques, and it may not be adequate for detection of a small entry site or intima injury, because CT has a spatial resolution limited to 500 μm [
]. Other disadvantages of CT are that the obtained images are static and tissue characterization is only based on CT values, while the intimal surface of the aorta cannot be visualized. A recent reported noted that virtual intravascular endoscopy is useful to reveal the entry shape and spatial relationship of the flaps [
]. However, with virtual intravascular endoscopy, axial images with a section thickness of 1 mm obtained during an optimal cardiac phase are transferred to the workstation for post-processing. To overcome those limitations, non-obstructive general angioscopy is a useful modality because of its spatial resolution of 150 μm [
] and suitability for observing local lesions, as this modality can reveal details related to aortic atherosclerosis that are difficult to observe with conventional CT, MRI, and TEE. In the present study, interesting findings noted included a white smooth surface, yellow plaques with either a smooth or irregular surface, plaque ruptures, erosion with a red thrombus, and entry tears. Those findings are compatible with previous studies [
Early detection of vulnerable atherosclerotic plaque for risk reduction of acute aortic rupture and thromboemboli and atheroeombli using non-obstructive angioscopy.
], thus we consider that aortic angioscopy may be helpful for not only diagnosing aortic disease but also clarifying related mechanisms. Previous studies have indicated that one of the possible initial steps in aortic dissection is rupture of the vasa vasorum, thus giving rise to an intramural hemorrhage, followed by dissection and intimal tearing [
]. They speculated that the subintimal blood flow was from a plaque injury, and the salmon-pink colored intima might be consistent with blood flow or an assembly of tiny bleeds due to disruption between the intima and subintima. Therefore, we consider that our findings obtained with non-obstructive general angioscopy are related to aortic dissection, although additional investigations are needed to confirm the relationship between those findings and the etiology of aortic dissection. Another advantage of non-obstructive general angioscopy is an ability to detect an entry tear and intimal injury with direct observation, and record these as both images and videos. Surgeons can then view the surface of the aneurysm at the location where an operation is required, making this modality convenient for use during TEVAR. Furthermore, a change in the initial length of the stent graft is helpful to surgeons in order to cover the entry site and preserve as many intercostal arteries as possible by checking the precise position of the small entry. We consider that angioscopy is effective for patients with back pain but without an aortic dissection detected by CT scanning, because we found several small lesions suspected to be an entry site that were not detected by CT.
Paraplegia or paraparesis is a catastrophic complication of TEVAR performed for type B aortic dissection [
]. Various risk factors have been reported, including length of the stent graft, blood pressure, elevated spinal cord pressure, and previous abdominal aortic operation [
]. Some studies have also noted that a staged TEVAR might be better than a single-stage procedure that covers the entire descending aorta from the point of prevention of spinal cord injury [
]. At our institution, we prefer to perform a staged operation and the distal end of the stent graft is usually above the Th8 vertebra level, because a longer stent graft is a risk factor for paraplegia. On the other hand, it is important to cover the entry as much as possible during TEVAR. We consider that our method is useful to obtain a good balance between potential complications and treatment effect. By precisely detecting the position of the possible entry or re-entry site, it is possible to plan whether to preserve or sacrifice the level of the intercostal artery. When the re-entry point must be covered below the Th8 level, various prevention methods are available for spinal cord injury, such as high blood pressure and spinal drainage, as well as others. As a result, none in this series experienced paraplegia. In several of the present cases, we detected a small re-entry point at the descending aorta that was not visualized by preoperative CT, making it possible to precisely and efficiently determine the distal end of the stent graft. In those cases, postoperative CT showed a shrunk or diminished false lumen. Another emerging factor involved in the pathogenesis of spinal cord injury during TEVAR is atheroembolism caused by dislodgement of aortic plaque due to manipulation of a large stent graft. Previous reports have suggested that subclinical embolisms are frequently present during TEVAR. However, because the tip diameter used for angioscopy is very small (0.75 mm) and a 6 Fr. catheter is utilized for observations, the non-obstructive angioscopy procedure itself is not considered to be a cause of further embolism during a TEVAR procedure. In fact, a previous study of 324 cases that underwent non-obstructive angioscopy reported that no complications including embolism occurred [
Early detection of vulnerable atherosclerotic plaque for risk reduction of acute aortic rupture and thromboemboli and atheroeombli using non-obstructive angioscopy.
]. To the best of our knowledge, these are the first reported cases in which non-obstructive general angioscopy was applied for planning the surgical procedure and also used as a tool during the operation. We consider this modality to be helpful for not only diagnosis of aortic disease, but also determination of treatment range and positioning during TEVAR. Also, taking into account the importance of findings related to aortic dissection, we consider that angioscopy should be performed by an aortic team comprising both cardiologists and cardiovascular surgeons.
This study has several limitations. First, this is a retrospective report of a single-center trial with a small number of cases that only revealed preliminary results of the efficacy of non-obstructive general angioscopy. Therefore, to confirm the effect of this modality for treatment of patients with other types of aortic dissection, a prospective multi-center trial is necessary to provide more reliable evidence. However, we found that non-obstructive general angioscopy is useful for observing the condition of the aortic intima, revealing abnormal conditions, and confirming a normal aortic intima in patients with chronic type B aortic dissection. From this point of view, our findings are important, because no other reports regarding non-obstructive angioscopy and TEVAR have been presented. Second, using aortic angioscopy findings, it was difficult to evaluate the global image of the aorta, such as the diameter of the aortic aneurysm or existence of a false lumen for aortic dissection, because only the vascular lumen surface was visualized [
Early detection of vulnerable atherosclerotic plaque for risk reduction of acute aortic rupture and thromboemboli and atheroeombli using non-obstructive angioscopy.
]. Therefore, we consider use of enhanced CT necessary to provide global imaging of the aorta. Finally, aortic angioscopy is an invasive procedure, although careful use by a trained examiner should cause few serious complications [
Angioscopic evaluation of atherosclerotic plaques: validation by histomorphologic analysis and association with stable and unstable coronary syndromes.
]. Indeed, we experienced no complications related to non-obstructive general angioscopy in the present patients.
Conclusion
Non-obstructive general angioscopy was shown to be useful for observing the condition of the aortic intima, location of abnormal findings, and normal aortic intima in patients with chronic type B aortic dissection. This modality may play an important role to determine the precise position of the stent graft during a TEVAR procedure as well as clarification of the mechanisms of aortic diseases.
Disclosures
There are no conflicts of interest to declare in regard to this study.
Appendix A. Supplementary data
The following are Supplementary data to this article:
Early detection of vulnerable atherosclerotic plaque for risk reduction of acute aortic rupture and thromboemboli and atheroeombli using non-obstructive angioscopy.
Endovascular versus open repair of abdominal aortic aneurysm in 15-years’ follow-up of the UK endovascular aneurysm repair trial 1 (EVAR trial 1): a randomised controlled trial.
Five-year results from the Study of Thoracic Aortic Type B Dissection Using Endoluminal Repair (STABLE I) study of endovascular treatment of complicated type B aortic dissection using a composite device design.
Angioscopic evaluation of atherosclerotic plaques: validation by histomorphologic analysis and association with stable and unstable coronary syndromes.
Angioscopy is the only imaging device that can visualize the vessel surface morphology in a living body as full-color, three-dimensional images in real time, and provide elucidations regarding a mechanism of acute coronary syndrome, development of atherosclerosis and stent healing [1–3]. The useful of angioscopy in the coronary artery has been abundant, and moreover the aortic evaluation with non-obstructive angioscopy has received much attention recently as an innovative application, whose procedure method has already been established well [4].
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