1
|
Ong CW, Ho P, Leo HL. Effects of Microporous Stent Graft on the Descending Aortic Aneurysm: A Patient-Specific Computational Fluid Dynamics Study. Artif Organs 2016; 40:E230-E240. [DOI: 10.1111/aor.12802] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Revised: 05/11/2016] [Accepted: 06/06/2016] [Indexed: 12/18/2022]
Affiliation(s)
- Chi-Wei Ong
- Department of Biomedical Engineering; National University of Singapore
| | - Pei Ho
- Department of Cardiac, Thoracic and Vascular Surgery; National University Health System; Singapore
| | - Hwa-Liang Leo
- Department of Biomedical Engineering; National University of Singapore
| |
Collapse
|
2
|
Hemodynamic Study of Flow Remodeling Stent Graft for the Treatment of Highly Angulated Abdominal Aortic Aneurysm. COMPUTATIONAL AND MATHEMATICAL METHODS IN MEDICINE 2016; 2016:3830123. [PMID: 27247612 PMCID: PMC4876205 DOI: 10.1155/2016/3830123] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Revised: 03/30/2016] [Accepted: 04/17/2016] [Indexed: 11/18/2022]
Abstract
This study investigates the effect of a novel flow remodeling stent graft (FRSG) on the hemodynamic characteristics in highly angulated abdominal aortic aneurysm based on computational fluid dynamics (CFD) approach. An idealized aortic aneurysm with varying aortic neck angulations was constructed and CFD simulations were performed on nonstented models and stented models with FRSG. The influence of FRSG intervention on the hemodynamic performance is analyzed and compared in terms of flow patterns, wall shear stress (WSS), and pressure distribution in the aneurysm. The findings showed that aortic neck angulations significantly influence the velocity flow field in nonstented models, with larger angulations shifting the mainstream blood flow towards the center of the aorta. By introducing FRSG treatment into the aneurysm, erratic flow recirculation pattern in the aneurysm sac diminishes while the average velocity magnitude in the aneurysm sac was reduced in the range of 39% to 53%. FRSG intervention protects the aneurysm against the impacts of high velocity concentrated flow and decreases wall shear stress by more than 50%. The simulation results highlighted that FRSG may effectively treat aneurysm with high aortic neck angulations via the mechanism of promoting thrombus formation and subsequently led to the resorption of the aneurysm.
Collapse
|
3
|
Occlusion of canine aneurysms using microporous self-expanding stent grafts: long-term follow-up. Clin Neurol Neurosurg 2014; 122:34-41. [PMID: 24908214 DOI: 10.1016/j.clineuro.2014.04.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2014] [Revised: 04/12/2014] [Accepted: 04/14/2014] [Indexed: 11/20/2022]
Abstract
PURPOSE The treatment of large or giant cerebral aneurysms by surgical and/or endovascular techniques is difficult and poses relatively high risks. Therefore, a microporous self-expanding (hybrid) stent graft composed of a thin, expandable, segmented polyurethane (SPU) membrane with micropores and a drug-delivery system was developed. MATERIALS AND METHODS A commercially available, self-expanding carotid stent was covered with a thin microporous SPU membrane fabricated by the dip-coating method and the excimer laser ablation technique, with an intraluminal coating of argatroban. Experimentally fabricated lateral-wall aneurysms in canine carotid arteries using venous pouches were occluded with the hybrid stent graft (bale-shaped pore density of 23.6%) on one side and a bare-metal stent on the other side without systemic antiplatelet therapy. RESULTS Angiography at 1, 6, and 12 months of stenting revealed that all arteries were patent without marked stenosis without systemic antiplatelet therapy. All aneurysms treated with hybrid stent grafts remained occluded throughout the 12-month period, while among those treated by bare-metal stents, 2 of 3 aneurysms were occluded at 6 months (67%) and only 1 of 3 aneurysms were occluded at 12 months (33%). Histology revealed that the novel hybrid stent graft had less intimal hyperplasia than the bare-metal stent. The hybrid stent graft was useful for the successful occlusion of these canine carotid aneurysms, even at 12 months. CONCLUSIONS The novel hybrid stent grafts are expected to overcome the disadvantages of fully covered stent grafts and simple bare-metal stents, while combining both their merits, and appear to be useful in the treatment of large or giant cerebral aneurysms.
Collapse
|
4
|
Nishi S, Nakayama Y, Ishibashi-Ueda H, Yoshida M, Yonetani H. Treatment of rabbit carotid aneurysms by hybrid stents (microporous thin polyurethane-covered stents): preservation of side-branches. J Biomater Appl 2013; 28:1097-104. [PMID: 23887877 PMCID: PMC4025620 DOI: 10.1177/0885328213498293] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Objective We sought to determine the patency of normal arterial branches from the covered
segments of an artery after stenting. Background Most intracranial aneurysms occur at arterial branching points (bifurcations,
side-branches, or perforators). The post-stenting patency of normal arterial branches
from the covered segments of the artery is important. We have previously developed a
hybrid stent with micropores to prevent early parent artery occlusion by more early
endothelialization, and mid- to long-term parent artery stenosis by control of intimal
hyperplasia after aneurysm occlusion. Methods We created aneurysms in 10 rabbits by distal ligation and intraluminal incubation of
elastase within an endovascularly trapped proximal segment of the common carotid artery.
All animals were treated with hybrid stents having micropores. Four animals were
observed for one month and three each for three and 12 months. The patency of the
side-branches of the subclavian artery was evaluated angiographically and in some cases,
histologically. Results Aneurysms were completely occluded at all time points other than 12 months. The
subclavian artery and brachiocephalic artery were patent, without significant stenosis.
All the side-branches of the subclavian artery detected on the preoperative angiogram
remained patent at the final assessment. Conclusion The use of hybrid stents for aneurysm repair and side-branch patency seems to be
effective, as per the long-term results obtained in an animal model.
Collapse
Affiliation(s)
- Shogo Nishi
- 1Department of Neurosurgery, Neuro-Intervention, Spinal Surgery, Sapporo-Higashi Tokushukai Hospital, Sapporo, Hokkaido, Japan
| | | | | | | | | |
Collapse
|
5
|
Kodama T, Iwata H. Comparison of bare metal and statin-coated coils on rates of intra-aneurysmal tissue organization in a rat model of aneurysm. J Biomed Mater Res B Appl Biomater 2013; 101:656-62. [PMID: 23359484 DOI: 10.1002/jbm.b.32869] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2011] [Revised: 06/23/2012] [Accepted: 11/18/2012] [Indexed: 11/10/2022]
Abstract
Endovascular treatment of intracranial aneurysms with detachable coils has been accepted widely. Problems of coil compaction, recanalization and rare endothelialization at the aneurysm orifice are not yet solved. We investigated the efficacy of a simvastatin coating applied without any additional matrix to coils to accelerate thrombus organization in the cavity in a rat model of aneurysm. Twelve metal coils coated with simvastatin and 12 bare coils were inserted into the ligated external carotid arterial (ECA) sacs of rats. The ECA sacs were removed 2 or 4 weeks after the coils were implanted and examined by histology and immunohistochemical assay. The organized areas in the ECA sacs in the simvastatin group (73.6 ± 19.4%, 2 wk; 83.4 ± 11.1%, 4 wk) was significantly higher p = 0.003, 2 wk; p = 0.0004, 4 wk than the bare metal group at 2 and 4 weeks (20.5 ± 10.7%, 2 wk, p < 0.003; 37.4 ± 20.6%, 4 wk, p < 0.0004). Organized tissues that formed around the coils coated with simvastatin were characterized by an accumulation of cells positive for αSMA and collagen connective matrix. Tissues also were accompanied by marked formation of endothelium at the orifice of the ECA sac. We suggest that coating coils with simvastatin effectively accelerated organization within the aneurysms and endothelialization over the coil.
Collapse
Affiliation(s)
- Tomonobu Kodama
- Department of Reparative Materials, Institute for Frontier Medical Sciences, Kyoto University, Kyoto-city, Kyoto, Japan
| | | |
Collapse
|
6
|
Nishi S, Nakayama Y, Ishibashi-Ueda H, Okamoto Y, Yoshida M. Development of microporous self-expanding stent grafts for treating cerebral aneurysms: designing micropores to control intimal hyperplasia. J Artif Organs 2011; 14:348-56. [PMID: 21698514 DOI: 10.1007/s10047-011-0581-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2011] [Accepted: 06/01/2011] [Indexed: 11/30/2022]
Abstract
Treatment of large (diameter 12-25 mm) or giant (diameter >25 mm) cerebral aneurysms with a broad neck in the cranio-cervical area is difficult and carries relatively high risks, even with surgical and/or endovascular methods. To this end, we have been developing a high-performance, self-expanding stent graft which consists of a commercially available NiTi stent (diameter 5 mm, length 20 mm) initially covered with a thin microporous segmented polyurethane membrane fabricated by the dip-coating method. Micropores are then created by the excimer laser ablation technique, and the outer surface is coated with argatroban. There are 2 types of micropore patterns: circular-shaped pore type (pore: diameter 100 μm, opening ratio 12.6%) and the bale-shaped pore type (pore: size 100 × 268 μm, opening ratio 23.6%). This self-expanding stent graft was tested on side-wall aneurysms of both canine carotid arteries that were experimentally induced using the venous pouches from the external jugular veins, with the self-expanding stent graft on one side and a bare self-expanding stent on the other side. All carotid arteries were patent and free of marked stenosis after 1 month. All aneurysms were occluded by stent grafts, while patent in those treated with bare stents. Histologically, the stent grafts with bale-shaped micropores and a high opening ratio were associated with less intimal hyperplasia (187 ± 98 μm) than the bare stents (341 ± 146 μm) or the stent grafts with circular micropores and a low opening ratio (441 ± 129 μm). A pore ratio of 23.6% was found to control intimal growth.
Collapse
Affiliation(s)
- Shogo Nishi
- Department of Neurosurgery, Interventional Neurosurgery, and Spinal Surgery, Sapporo-Higashi Tokushukai Hospital, 14-3-1 Higashi, N33, Higashi-ku, Sapporo, Hokkaido 065-0033, Japan.
| | | | | | | | | |
Collapse
|
7
|
Treatment of carotid siphon aneurysms by use of the Willis stent graft: an angiographic and histopathological study. Eur Radiol 2010; 20:1974-84. [DOI: 10.1007/s00330-010-1738-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2009] [Revised: 11/24/2009] [Accepted: 12/16/2009] [Indexed: 10/19/2022]
|
8
|
Sato S, Nakayama Y, Matsuhashi T, Seiji K, Matsunaga K, Takasawa C, Ishibashi T, Zhou YM, Ishibashi-Ueda H, Okamoto Y, Asano H, Takahashi S. Evaluation of self-expandable, FK506-coated, covered stents in canine animal model. J Biomed Mater Res B Appl Biomater 2009; 90:647-52. [DOI: 10.1002/jbm.b.31330] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
9
|
Development of novel covered stents using salmon collagen. J Artif Organs 2009; 12:61-6. [DOI: 10.1007/s10047-008-0446-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2008] [Accepted: 11/27/2008] [Indexed: 10/21/2022]
|
10
|
Nishi S, Nakayama Y, Ishibashi-Ueda H, Okamoto Y, Kinoshita Y. High-performance self-expanding stent graft: development and application to experimental aneurysms. J Artif Organs 2009; 12:35-9. [DOI: 10.1007/s10047-008-0437-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2008] [Accepted: 09/24/2008] [Indexed: 10/21/2022]
|
11
|
Nakayama Y, Zhou YM, Ishibashi-Ueda H. Development of in vivo tissue-engineered autologous tissue-covered stents (biocovered stents). J Artif Organs 2007; 10:171-6. [PMID: 17846716 DOI: 10.1007/s10047-007-0376-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2006] [Accepted: 01/23/2007] [Indexed: 10/22/2022]
Abstract
Biocovered stents, which are stents covered with autologous membranous tissues, were developed by applying a novel concept based on in vivo tissue engineering. Balloon-expandable stents crimped on silicone rods as a mold (diameter: 2 mm) were embedded into dorsal subcutaneous pouches in rabbits. After 1 month, the struts of the stents were fully encapsulated with membranous connective tissues formed around the silicone rods. Upon removing the silicone rod, stents covered with tubular connective tissues, in which the struts were completely impregnated, were obtained as biocovered stents. These tissues were composed mainly of collagen and fibroblasts and had a thickness of less than approximately 200 microm with an excellent high burst strength of approximately 1000 mmHg. The luminal surface of the tissues was extremely flat and smooth. The stents could be mounted on balloon catheters with a hand crimping tool and could be expanded by inflation with little damage to the tissues. It is anticipated that these novel stents may greatly enhance early normal vascular reconstruction with high reliability, thereby reducing the rate of in-stent restenosis.
Collapse
Affiliation(s)
- Yasuhide Nakayama
- Department of Bioengineering, Advanced Medical Engineering Center, National Cardiovascular Center Research Institute, 5-7-1 Fujishiro-dai, Suita 565-8565, Japan.
| | | | | |
Collapse
|
12
|
Watanabe T, Kanda K, Ishibashi-Ueda H, Yaku H, Nakayama Y. Development of biotube vascular grafts incorporating cuffs for easy implantation. J Artif Organs 2007; 10:10-5. [PMID: 17380291 DOI: 10.1007/s10047-006-0361-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2006] [Accepted: 09/28/2006] [Indexed: 10/23/2022]
Abstract
We are developing functional autologous tubular tissues, called biotubes, as ideal small-caliber vascular grafts that have growth potential without immunological rejection. In this study, to improve surgical handling, a novel biotube reinforced at the anastomosis regions was designed. Silicone rods, 2 mm in diameter and used as a mold, were covered with two pieces of short polyurethane sponge tubing as anastomotic reinforcement cuffs at both ends. After the assembly was placed into dorsal subcutaneous pouches in rabbits for 1 month, seamless biotubes incorporating the cuffs were obtained. The interstices and surfaces of the cuffs were impregnated and covered with connective tissues similar to those of the biotubes, mainly consisting of collagen and fibroblasts. Since the tubular shape of both ends was rigidly maintained, end-to-end anastomosis by conventional microsurgery techniques between biotubes and native carotid arteries was very easy. In preliminary autoimplantation studies, angiographic observation of up to 2 months duration showed no formation of aneurysms or rupturing.
Collapse
Affiliation(s)
- Taiji Watanabe
- Department of Bioengineering, Advanced Medical Engineering Center, National Cardiovascular Center Research Institute, 5-7-1 Fujishiro-Dai, Suita, Japan
| | | | | | | | | |
Collapse
|
13
|
Sato S, Nakayama Y, Miura Y, Okamoto Y, Asano H, Ishibashi-Ueda H, Zhou YM, Hayashida K, Matsuhashi T, Seiji K, Sato A, Yamada T, Takahashi S, Ishibashi T. Development of self-expandable covered stents. J Biomed Mater Res B Appl Biomater 2007; 83:345-53. [PMID: 17385230 DOI: 10.1002/jbm.b.30802] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
We newly developed self-expandable covered stents by combining two of our original technologies. Of these, the first is the dip-coating covering method that was developed previously for balloon-expandable stents; the other is the newly developed self-expandable Nitinol stents, namely, Sendai stents. The three types of covered stents with the expansion diameter of 4.5, 5.0, or 6.0 mm thus obtained had a laser-processed microporous elastomeric cover film (pore diameter: 100 microm, interpore distance: 250 microm). Although the film was extremely thin (approximately 15 microm), the film could be expanded without causing any damage, the strut was completely embedded within the film, and the luminal surface of the film was smooth and flat. Mechanical properties such as ideal flexibility to follow the shapes of arteries were almost retained even after covering. As appropriate drugs, the blood-contacting inner and tissue-contacting outer surfaces of the film were differentially coated with argatroban for antithrombogenicity or FK506 for anti-inflammation, respectively. The preliminary in vivo study indicated that the covered stents mounted in the delivery catheter were navigated and placed to appropriate position in the arteries, and permissible neointimal thickening after 1-month implantation was observed similarly in noncovered stents.
Collapse
Affiliation(s)
- Sachiko Sato
- Department of Diagnostic Radiology, Graduate School of Medicine, Tohoku University, 1-1 Seiryo, Sendai, Miyagi 980-8574, Japan
| | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
14
|
Nakayama Y, Masuda T. Development of a polymeric matrix metalloproteinase inhibitor as a bioactive stent coating material for prevention of restenosis. J Biomed Mater Res B Appl Biomater 2006; 80:260-7. [PMID: 16767737 DOI: 10.1002/jbm.b.30592] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Drug-eluting stents have been developed to prevent restenosis derived from excessive growth of smooth muscle cells (SMCs) after stenting. In almost every case, however, less- or non-biocompatible polymers were selected for the platform material for impregnating drugs on the stent strut. Consideration was given principally to the physical properties of the polymers, such as their adhesion to the strut and the drug dispersibility in the polymeric matrix. In this study, we designed a matrix metalloproteinase inhibitor (MMPI)-derivatized hydrophobic polymer (PMMPI) for use as a bioactive material for stent coating. This was a copolymer of n-butylmethacrylate and a vinyl monomer of synthetic MMPI (N-Hydroxy-5-carboxyethylcarbonyloxy-2(S)-methy-4(S)-(4-phenoxybenzoyl)amino-pentanamide: ONO-M11-335) with a molecular weight of about 32,000 and MMPI content of 45 per molecule. The precursor of the MMPI monomer produced significant activity in temporally inhibiting SMC proliferation without any cellular damage. After coating with the PMMPI, adhesion and proliferation of SMCs were manifestly prevented even when a small amount of MMPI was released from the polymer. The MMPI-immobilized surface may thus be effective for inhibiting both adhesion and proliferation of SMCs, which is the first step toward in vivo experimentation. It is very much expected that coating stent struts with PMMPI containing an appropriate combination of impregnated drugs will provide a powerful tool for prevention of restenosis with little cytotoxicity.
Collapse
Affiliation(s)
- Yasuhide Nakayama
- Department of Bioengineering, Advanced Medical Engineering Center, National Cardiovascular Center Research Institute, 5-7-1 Fujishiro-dai, Suita, Osaka 565-8565, Japan.
| | | |
Collapse
|
15
|
Duncan IC, Fourie PA. Initial experience with intracranial stent-graft use. Technical notes. Interv Neuroradiol 2005; 11:131-9. [PMID: 20584492 DOI: 10.1177/159101990501100203] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2005] [Accepted: 04/30/2005] [Indexed: 11/15/2022] Open
Abstract
SUMMARY We describe our initial experience with the placement of two premounted balloon expandable intracranial Jostent stent-grafts within the intracavernous internal carotid artery for the treatment of a symptomatic large intracavernous aneurysm in one case and a post-traumatic caroticocavernous fistula in the second. Among the initial technical complications we encountered were stent-graft migration and rapidly progressive intragraft thrombosis, with delayed sealing of the stent-graft coverings and exclusion of the pathologies relating to the use of abciximab in both cases. Despite these initial problems both cases had excellent short-term clinical outcomes with angiographic exclusion of both lesions by day three and good clinical and angiographic outcomes at one and two months respectively.
Collapse
Affiliation(s)
- I C Duncan
- Unitas Interventional Unit; Lyttelton, South Africa -
| | | |
Collapse
|