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Department of Radiology, The First Affiliated Hospital of China Medical University, 155 Nanjing North Street, Shenyang 110001, Liaoning, PR ChinaLaboratory of Medical Imaging and Interventional Radiology, The First Affiliated Hospital of China Medical University, 155 Nanjing North Street, Shenyang 110001, Liaoning, PR China
Corresponding author. K. Xu, Department of Radiology, The First Affiliated Hospital of China Medical University, 155 Nanjing North Street, Shenyang 110001, Liaoning, PR China. Tel.: +86 24 8328 2999; fax: +86 24 8328 2997.
Affiliations
Department of Radiology, The First Affiliated Hospital of China Medical University, 155 Nanjing North Street, Shenyang 110001, Liaoning, PR ChinaLaboratory of Medical Imaging and Interventional Radiology, The First Affiliated Hospital of China Medical University, 155 Nanjing North Street, Shenyang 110001, Liaoning, PR China
Department of Radiology, The First Affiliated Hospital of China Medical University, 155 Nanjing North Street, Shenyang 110001, Liaoning, PR ChinaLaboratory of Medical Imaging and Interventional Radiology, The First Affiliated Hospital of China Medical University, 155 Nanjing North Street, Shenyang 110001, Liaoning, PR China
Department of Radiology, The First Affiliated Hospital of China Medical University, 155 Nanjing North Street, Shenyang 110001, Liaoning, PR ChinaDepartment of radiology, University Hospital, K.U. Leuven, Leuven 3000, Belgium
Department of Radiology, The First Affiliated Hospital of China Medical University, 155 Nanjing North Street, Shenyang 110001, Liaoning, PR ChinaLaboratory of Medical Imaging and Interventional Radiology, The First Affiliated Hospital of China Medical University, 155 Nanjing North Street, Shenyang 110001, Liaoning, PR China
To evaluate the feasibility and safety of a new unibody branched stent-graft for reconstruction of the canine aortic arch.
Materials and methods
Twenty adult hybrid dogs were used for the experiments. Ten dogs were implanted with single-branched stent-grafts; the other ten dogs were implanted with double-branched stent-grafts. The stent-grafts were implanted transluminally via the abdominal aorta. The branched limbs were caught and pulled into supra-aortic vessels using gooseneck snare wires introduced via the axillary arteries. The animals were euthanized 4 months after implantation.
Results
One of the ten dogs implanted with a single-branched stent-graft died from failure of the implantation procedure, and two of the ten dogs implanted with double-branched stent-grafts died from failure of the procedure and excessive blood loss. After month 4, the remaining unibody branched stent-grafts were patent and did not migrate.
Conclusions
This new unibody branched stent-graft could be used to reconstruct the aortic arch. This is a total endovascular technique, and compared to other branched stent-grafts appears to be safer and easier to implant.
The unibody branched stent-graft described in this paper could be used to reconstruct the aortic arch while preserving the three branch vessels. Compared to other branched stent-grafts, this version appears more versatile, while the implantation procedure appears to be simpler.
Introduction
Surgical repair is the traditional treatment for patients with thoracic aortic aneurysm. Despite recent advances in surgical techniques, surgical repair is still associated with high mortality and morbidity.
Endovascular aortic repair versus open surgical repair for descending thoracic aortic disease a systematic review and meta-analysis of comparative studies.
However, when the aortic arch is involved, endovascular repair can be very difficult. Some innovative studies on total endovascular repair have been conducted to reconstruct the aortic arch.
Feasibility of the Inoue single-branched stent-graft implantation for thoracic aortic aneurysm or dissection involving the left subclavian artery: short- to medium-term results in 17 patients.
However, up to now, these have been limited to animal studies and incidental case reports. Therefore, new techniques are still needed to overcome the challenges associated with treating arch pathologies. In this article, we describe a new unibody branched stent-graft applied for reconstruction of the canine aortic arch.
Materials and Methods
Stent-graft system
The stent-graft system used in this study consisted of a unibody branched stent-graft, a delivery system, and a gooseneck snare wire. Woven Dacron tubes were attached to multiple self-expanding stainless steel Z stents with 5-0 polypropylene sutures. The unibody single-branched stent-graft consisted of a main stent-graft and a branched limb for the left subclavian artery (LSA) (Fig. 1A). The unibody double-branched stent-graft consisted of a main stent-graft and two branched limbs for the innominate artery (IA) and the LSA, respectively (Fig. 1B). The first Z segment of the main stent-graft was bare. The branched limb and main stent-grafts were sewn together (Fig. 1). There was excess fabric (approximately 5 mm in length) between the branched limbs and the main stent-graft (Fig. 1) to increase the motion range of the branched limbs and the flexibility of the branched stent-grafts.
Figure 1The unibody branched stent-graft. (A) The single-branched stent-graft consists of a branched limb for the left subclavian artery (LSA) and the main stent-graft. The first Z segment of the main stent-graft is bare. (B) The double-branched stent-graft consists of two branched limbs and the main stent-graft. The first limb is for the innominate artery (IA) and the second limb is for the LSA. The first Z segment of the main stent-graft is bare.
The supra-aortic vessels of canines are composed of the LSA and the IA, the latter giving rise to bilateral carotid arteries and the right subclavian artery. Although the structure of the canine aortic arch differs slightly from that of humans, it is still an ideal substitute model for the study of any new branched stent-graft system, due to the suitable diameter of the artery and tolerance of canines to surgical trauma. Before designing the branched stent-graft, the diameters of the aortic arch and the supra-aortic vessels were measured using computed tomography angiography (CTA). The diameters of the main stent-graft and the branched limb were usually oversized by 10–20% to achieve effective sealing. The main stent-graft was 20–25 mm in diameter and 70–90 mm in length. The branched limb was 10–15 mm in diameter and 15–20 mm in length. The anatomic variability of the IA and LSA of canines is relatively limited. Therefore the distance between the branched limbs was not designed for individual dogs and. was 5 mm.
The delivery system consisted of a detachable sleeve and a delivery sheath. The detachable sleeve is designed to constrain the branched limb and was composed of a Dacron sleeve, a metal hook, and a traction wire (Fig. 2). The diameter of the Dacron sleeve was 4–6 mm. The hook, located at the tip of the Dacron sleeve, facilitates the capture of the detachable sleeve using the gooseneck snare wire. The traction wire, in the cavity of the detachable sleeve, ensures that the detachable sleeve cannot be accidentally detached from the folded branched limb during implantation. The delivery sheath has a top-cap opening backward, which is designed to constrain the bare segment. The traction wire of the detachable sleeve can pass through the delivery sheath and be fixed outside the handle (Fig. 3). The delivery sheath is 20–22 F in diameter.
Figure 2Photograph of the detachable sleeve, consisting of a metal hook, a Dacron sleeve, a traction wire, and a fixing device.
Figure 3Line drawings of the vertical section of the delivery system. (a) The delivery system of the single-branched stent-graft consists of a top-cap opening backward, an outer sheath, and a detachable sleeve. The traction wire of the detachable sleeve passes through the delivery system, and its end is fixed outside the handle of the delivery system using the fixing device. (b) The delivery system of the double-branched stent-graft, with two detachable sleeves, is similar to the single-branched stent-graft.
The detachable sleeve was passed through the main stent-graft and the branched limb from the distal end of the main stent-graft. The branched limb was folded into the Dacron sleeve. The bare segment of the main stent-graft was folded into the top-cap (Fig. 4A). Then the entire stent-graft was mounted into the outer sheath of the delivery system, and the traction wire was tightened and fixed using the fixing device (Fig. 4B). The assembly of the double-branched stent-graft was similar to that of the single-branched stent-graft.
Figure 4Assembly of the stent-graft system. (A) The top-cap folds the bare segment of the main stent-graft, the detachable sleeve folds the branched limb, and the outer sheath constrains the whole branched stent-graft. (B) Line drawing of the assembled stent-graft system. The bare Z segment of the main stent-graft is constrained into the top-cap, the branched limb is folded into the detachable sleeve, and the whole stent-graft is folded into the outer sheath.
Twenty adult hybrid dogs (25–35 kg) were used for the experiments. Single-branched stent-grafts were implanted in 10 dogs and double-branched stent-grafts were implanted in a further 10. All of the animals were cared for in accordance with guidelines approved by the Experimental Animal Care committee of China Medical University. Under general anesthesia and mechanical ventilation, the dogs were fixed in a supine position. Venous access was established through the left great saphenous vein.
A left axillary longitudinal incision was made, and the left axillary arteryisolated. Heparin (intravenous injection, 200 U/kg) was administered. An 8F long sheath was advanced to the orifice of the LSA through the left axillary artery under the guidance of fluoroscopy. A gooseneck snare wire (Cook Medical Inc., Bloomington, USA) was then introduced through the 8F sheath.
A midline abdominal incision was then performed. The end of the abdominal aorta was isolated. Two elastic slings were placed around the aorta to prevent excessive intra-operative blood loss. Using the Seldinger technique, the abdominal aorta was punctured, and a stiff guide wire (Lunderquist; Cook Inc., Indianapolis, USA) was introduced through the puncture needle. Under fluoroscopic guidance, the delivery system was introduced and advanced over the stiff guide wire until the hook of the detachable sleeve reached the orifice of the LSA. The outer sheath of the delivery system was then withdrawn to the distal end of the second Z stent of the main stent-graft in order to release the detachable sleeve. The gooseneck snare wire was stretched out to catch the hook of the detachable sleeve and then used to pull it into the LSA (Figs. 5a and 6a ). The bare stent of the main stent-graft was then released by pushing the central shaft of the delivery system forward (Figs. 5b and 6b). Sequentially, the main stent-graft was released by withdrawing the outer sheath (Figs. 5c and 6b). Removing the fixing device, the branched limb was released by pulling the detachable sleeve out through the long sheath (Figs. 5d and 6c). Angiography was then performed upon removal of the delivery sheath (Fig. 6d). Finally, the long sheath was removed, the left axillary artery was ligatured, and all incisions were closed. All dogs were given penicillin (intramuscular injection, 1.6 million U/day) for the following three days.
Figure 5Line drawing of implantation procedure for the single-branched stent-graft. (a) The hook is caught and pulled into the LSA using the gooseneck snare wire introduced from the left axillary artery. (b) The bare segment of the main stent-graft is released from the top-cap by pushing the central core of the delivery system forward. (c) The main stent-graft is released by retracting the outer sheath. (d) The branched limb is released by pulling the detachable sleeve out through the long sheath.
Figure 6Implantation procedure for the single-branched stent-graft. (a) The hook is caught and pulled into the LSA using the gooseneck snare wire introduced from the left axillary artery. (b) The bare segment of the main stent-graft is released from the top-cap by pushing the central core of the delivery system forward, and the main stent-graft is released by retracting the outer sheath. (c) The branched limb is released by pulling the detachable sleeve out through the long sheath. (d) Angiography was performed. The branched stent-graft implanted successfully and is patent.
The double-branched stent-graft was implanted in a manner similar to that of the single-branched stent-graft. Two gooseneck snare wires were introduced via both axillary arteries. Each detachable sleeve was caught and pulled into the supra-aortic vessels by the gooseneck snare wires (Fig. 7a). The bare stent and the main stent-graft were released as in the single-branched stent-graft (Fig. 7b). Then the branched limbs were individually released by pulling the detachable sleeves out through the long sheaths (Fig. 7c), and angiography was again performed (Fig. 7d).
Figure 7Implantation procedure for the double-branched stent-graft. (a) The hooks of the two detachable sleeves are caught and pulled into the IA and the LSA, one by one, using the two gooseneck wires introduced from bilateral axillary arteries. (b) The bare segment of the main stent-graft is released from the top-cap by pushing the central core of the delivery system forward, and the main stent-graft is released by retracting the outer sheath. (c) The branched limbs are released by pulling the detachable sleeves out through the long sheath. (d) Angiography was performed. The branched stent-graft implanted successfully and is patent.
Among the ten animals implanted with single-branched stent-grafts, one dog was euthanized due to the unsuccessful capture of the hook to deploy the branched limb. Autopsy revealed that the hook of the detachable sleeve was retracted into the Dacron sleeve. Among the ten dogs implanted with the double-branched stent-grafts, one died due to excessive blood loss (1500 ml) from the incision of the abdominal aorta, the other was euthanized due to the failure in catching the hook of the second detachable sleeve. Autopsy revealed that the hook of the second detachable sleeve stretched into the Dacron sleeve of the first detachable sleeve. Both of the two unsuccessful implantation procedures occurred in the early stages of this project. The retraction of the hook into the sleeve was overcome by completely filling the Dacron sleeves with folded branched limbs after decreasing the diameter of the sleeves to 4–6 mm.
The average operation time, measured from the incision of the skin to surgical closure of the abdominal wall was 210 min (180–240 min); the average fluoroscopy time was 45 min (30–60 min); the average contrast load was 100 ml (75–125 ml); and with the exception of the dog dying from excessive blood loss, the average blood loss for the other animals was 200 ml (150–450 ml).
The surviving animals were followed for four months. No organ infarction, paraplegia, or serious infection occurred during the follow-up period. Before the dogs were euthanized, a further CTA was performed. This confirmed that; (i) all the stent-grafts were patent and had not migrated, (ii) there was no fractures of the Z stents (Fig. 8) and (iii) the stent-graft was incorporated into the thoracic aorta. The inner surface of the stent-graft was smooth suggesting satisfactory neo-intimal coverage. There was no thrombus in the lumen of the stent-graft (Fig. 9).
Figure 8CTA image of the stent-graft 4 months after implantation. The branched stent-graft is patent and has not migrated. The Z stents have not fractured.
Figure 9Tissue specimens excised 4 months after implantation. The inner lumen of the stent-graft is covered by neo-intima and is as smooth as the aorta.
Endovascular aortic repair versus open surgical repair for descending thoracic aortic disease a systematic review and meta-analysis of comparative studies.
However, whre the aortic arch is involved, total endovascular repair can be very difficult. Some endovascular techniques that have been used to overcome this challenge include the fenestration technique, the chimney technique, and the branched stent-graft technique.
Feasibility of the Inoue single-branched stent-graft implantation for thoracic aortic aneurysm or dissection involving the left subclavian artery: short- to medium-term results in 17 patients.
Branched stent-grafts can be classified as modular and unibody. Modular branched stent-grafts are assembled in vivo from several components, while the unibody branched stent-graft is inserted as an integral device.
Lioupis et al reported the same treatment with a modular branched stent-graft, which consisted of a fenestrated stent-graft for the aortic arch and three stent-grafts for the supra-aortic vessels.
Our branched stent-grafts had a unibody design; the branched limbs and the main stent-graft were sutured together and thus the risks of component separation and type Ⅲ endoleak were much lower than with modular stent-grafts. No fracture of the stent-graft or type Ⅲ endoleak occurred in the study.
Our unibody branched stent-graft might be used to reconstruct the human aortic arch. The single-branched stent-graft could be used to reconstruct the distal aortic arch (preserving the LSA), while the double-branched stent-graft could be used to preserve the left common carotid artery (LCCA) and the LSA. Alternatively, the double-branched stent-graft could be used to reconstruct the total aortic arch by preserving the IA and LCCA and occluding the LSA.
Inoue et al reconstructed the human aortic arch with a unibody branched stent-graft for the first time in 1999.
The implantation procedure of the Inoue stent-graft was rather complicated, and the risk of cerebral embolisation was higher. Wei et al and Lioupis et al reported the reconstruction of the aortic arch with a modular branched stent-graft in 2009 and 2012, respectively.12, 14 The components of their stent-grafts were implanted one by one. Our device was implanted as a whole device. Additionally, the partially deployed stent-graft can be moved to facilitate the capture of the hooks, and there was no case of hook retraction into the Dacron sleeve after the diameter of the Dacron sleeve was decreased. Thus the catch of the hook was easy. The remaining manipulations were the same as with the straight stent-graft.
Our stent-graft was folded more tightly during the implantation procedure, compared to the Inoue stent-graft.
The risk of thrombosis in the stent-graft was lower. No organ infarction occurred in our experiment. The traction wire ensured that the branched limb could not be accidentally released from the detachable sleeve during the implantation procedure. Therefore, the deployment of our stent-graft was safer and easier, compared to other branched stent-grafts.
The inherent limitation to unibody branched stent-grafts is their suboptimal flexibility.
The excess fabric between the branched limbs and the main stent-graft increased its flexibility to some extent. But the unibody branched stent-graft still should be custom-made for apparent anatomic variability. Another limitation of this study is that the delivery system has to be introduced via the abdominal aorta in canines. The diameter of the delivery system will be decreased before it is used in humans. Additionally, this was a feasibility study for the new unibody branched stent-graft. Fatigue testing was not performed in the experiment.
In conclusion, the new unibody branched stent-graft could be used to reconstruct the aortic arch. This graft is advantageous because it is a total endovascular technique, and compared to other branched stent-grafts appears to be much safer and easier to implant. Further research is still needed before final clinical application.
Conflict of Interest
None declared.
Funding
This work was supported by the State Science and Technology Support Program of China [No. 2007BAI05B04] and the European Commission project Asia-Link CfP 2006-EuropeAid/123738/C/ACT/Multi-Proposal [No. 128-498/111].
Acknowledgements
We appreciate Dr. Fei Wang, Department of Psychiatry, Yale University School of Medicine, New Haven, USA, for giving valuable comments.
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Selective antegrade cerebral perfusion attenuates brain metabolic deficit in aortic arch surgery a prospective randomized trial.
Endovascular aortic repair versus open surgical repair for descending thoracic aortic disease a systematic review and meta-analysis of comparative studies.
Feasibility of the Inoue single-branched stent-graft implantation for thoracic aortic aneurysm or dissection involving the left subclavian artery: short- to medium-term results in 17 patients.
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