| 1. |
- Roos, Håkan, 1967, et al.
(författare)
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Displacement Forces in Iliac Landing Zones and Stent Graft Interconnections in Endovascular Aortic Repair: An Experimental Study
- 2014
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Ingår i: European Journal of Vascular and Endovascular Surgery. - : Elsevier BV. - 1078-5884 .- 1532-2165. ; 47:3, s. 262-267
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: Stent graft migration influences the long-term durability of endovascular aortic repair. Flow-induced displacement forces acting on the attachment zones may contribute to migration. Proximal fixation of aortic stent grafts has been improved by using hooks, while distal fixation and stent graft interconnections depend on self-expansion forces only. We hypothesized that flow-induced displacement forces would be significant at the distal end, and would correlate with graft movements. Methods: As part of an experimental study, an iliac limb stent graft was inserted in a pulsatile flow model similar to aortic invivo conditions, and fixed-mounted at its proximal and distal ends to strain gauge load cells. Peak displacement forces at both ends and pulsatile graft movement were recorded at different graft angulations (0-90°), perfusion pressures (145/80, 170/90, or 195/100mmHg), and stroke frequencies (60-100b.p.m.). Results: Flow-induced forces were of the same magnitude at the proximal and distal end of the stent graft (peak 1.8N). Both the forces and graft movement increased with angulation and perfusion pressure, but not with stroke rate. Graft movement reached a maximum of 0.29±0.01mm per stroke despite fixed ends. There were strong correlations between proximal and distal displacement forces (r=0.97, p<.001), and between displacement forces and graft movement (r=0.98, p<.001). Conclusions: Pulsatile flow through a tubular untapered stent graft causes forces of similar magnitude at both ends and induces pulsatile graft movements in its unsupported mid-section. Peak forces are close to those previously reported to be required to extract a stent graft. The forces and movements increase with increasing graft angulation and perfusion pressure. Improved anchoring of the distal end of stent grafts may be considered. © 2013 European Society for Vascular Surgery.
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| 2. |
- Jämstorp, Erik, et al.
(författare)
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Release of antithrombotic drugs from alginate gel beads
- 2010
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Ingår i: Current Drug Delivery. - : Bentham Science Publishers Ltd.. - 1567-2018 .- 1875-5704. ; 7:4, s. 297-302
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the present work was to evaluate alginate hydrogels in the form of spherical beads as carrier for antithrombotic drugs for future use in artificial grafts. The ionotropic gelation technique was employed to prepare beads from the L. hyperborea stipe of alginate with two different alginate concentrations and two different guluronic to manuronic acid ratios. The beads were loaded, via soaking, with three different types of low molecular weight model molecules representing drugs with antithrombotic action and their release characteristics were subsequently evaluated. The entire release process of the negatively charged model drugs under study (Salicylic acid and Hirudin), was found to be governed by diffusion, while additional electrostatic interactions between drug molecule and alginate matrix was indicated to influence the release rate of the analyzed positively charged drug molecule (Dipyridamole). It was found that the alginate hydrogel matrix imposed a decrease of the drug diffusion rate on the molecules under study as compared to the corresponding diffusion rates in water. All diffusion coefficients decreased slightly with increasing concentration of alginate and with increasing guluronic to manuronic acid ratio. The results show on the potential use of alginate gel beads when developing vehicles for release of low molecular weight antithrombotic drugs.
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| 3. |
- Inci, Kamuran, et al.
(författare)
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Air bubbles are released by thoracic endograft deployment: An in vitro experimental study
- 2016
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Ingår i: SAGE Open Medicine. - : SAGE Publications. - 2050-3121. ; 4
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: Embolic stroke is a dreaded complication of thoracic endovascular aortic repair. The prevailing theory about its cause is that particulate debris from atherosclerotic lesions in the aortic wall are dislodged by endovascular instruments and embolize to the brain. An alternative source of embolism might be air trapped in the endograft delivery system. The aim of this experimental study was to determine whether air is released during deployment of a thoracic endograft. Methods: In an experimental benchtop study, eight thoracic endografts (five Medtronic Valiant Thoracic and three Gore TAG) were deployed in a water-filled transparent container drained from air. Endografts were prepared and deployed according to their instructions for use. Deployment was filmed and the volume of air released was collected and measured in a calibrated syringe. Results: Air was released from all the endografts examined. Air volumes ranged from 0.1 to 0.3 mL for Medtronic Valiant Thoracic and from <0.025 to 0.04 mL for Gore TAG. The largest bubbles had a diameter of approximately 3 mm and came from the proximal end of the Medtronic Valiant device. Conclusion: Air bubbles are released from thoracic endografts during deployment. Air embolism may be an alternative cause of stroke during thoracic endovascular aortic repair.
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| 4. |
- Roos, Håkan, 1967, et al.
(författare)
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Displacement Forces in Stent Grafts: Influence of Diameter Variation and Curvature Asymmetry
- 2016
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Ingår i: European Journal of Vascular and Endovascular Surgery. - : Elsevier BV. - 1078-5884 .- 1532-2165. ; 52:2, s. 150-156
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: Long-term durability after endovascular aortic repair is influenced by stent graft migration causing types I and III endoleaks. Flow induced displacement forces have been shown to have the potential to cause migration. In this study, the influence of the distal diameter of iliac limb stent grafts and the shape of graft curvature on flow induced displacement forces, were investigated. Methods: In an experimental pulsatile flow model mimicking aortic conditions in vivo, flow induced displacement forces at the proximal and distal ends of iliac limb stent grafts were studied at different angles (0-90 degrees) and perfusion pressures (145/80, 170/90, 195/100 mmHg). Bell-bottomed, tapered, and non-tapered stent grafts and also asymmetric stent graft curvatures at 90 bend were studied. Measurements of graft movement were performed at all studied angulations and graft shapes. Results: For all stent graft diameters, flow induced displacement forces increased with higher pressure and increased stent graft angulation. Forces in the bell-bottom graft were considerably higher than in tapered and non-tapered grafts, with a markedly elevated peak force at the distal end (proximal end, 2.3 +/- 0.06 N and distal end, 6.9 +/- 0.05 N compared with 1.7 +/- 0.08 N and 1.6 +/- 0.08 N in non-tapered grafts; p <.001 both). Peak forces in tapered and non-tapered grafts were not significantly different between the proximal and distal end. In asymmetric stent graft curvatures, a significant increase in displacement forces was observed in the attachment zone that was closest to the stent graft bend. Graft movement increased with greater displacement forces. Conclusion: Flow induced displacement forces in iliac limb stent grafts are significant and are influenced by distal stent graft diameter and the shape of the graft curvature. The displacement forces are particularly high at the large distal end of bell-bottom grafts. Wide iliac arteries treated with bell-bottom stent grafts may require more vigilant surveillance and improved stent graft fixation.
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| 5. |
- Starnberg, Karin, et al.
(författare)
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Revision of the troponin T release mechanism from damaged human myocardium.
- 2014
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Ingår i: Clinical chemistry. - : Oxford University Press (OUP). - 1530-8561 .- 0009-9147. ; 60:8, s. 1098-104
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Tidskriftsartikel (refereegranskat)abstract
- Cardiac troponin T (cTnT) is released from damaged heart tissue in patients with acute myocardial infarction. It is presumed that most cTnT is tightly bound and released following the degradation of myofibrils in necrotic cardiomyocytes, resulting in sustained increases in circulating cTnT. Evidence of a large irreversibly bound fraction is based on the inability to extract most cTnT from cardiac tissue in cold low-salt extraction buffers.
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