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  • 1
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    Development of an in vitro test procedure for the characterization of left atrial appendage occluder devices
    Walter de Gruyter GmbH ; 2019
    In:  Current Directions in Biomedical Engineering Vol. 5, No. 1 ( 2019-09-01), p. 461-463
    Details
    In: Current Directions in Biomedical Engineering, Walter de Gruyter GmbH, Vol. 5, No. 1 ( 2019-09-01), p. 461-463
    Abstract: The implantation of an occluder in the left atrial appendage (LAA) is an emerging therapy for the treatment of patients suffering from atrial fibrillation and with a contraindication to oral anticoagulation. The LAA occluder (LAAO) provides a reduction of the potential risk of strokes by thromboembolism. Currently, only a few CE-approved devices are available on the market and the number of clinical trials is comparatively low. Furthermore, there is currently no standardized test method available for testing functionality of the occluder, especially for testing safe anchorage and permeability. Therefore, the aim of this study is to establish an in vitro test method to prove anchorage mechanism and permeability regarding thromboembolism of the LAAO under physiological conditions. A standardized technical and fully parameterized silicone model of a LAA, based on studies of different morphologies and sizes, was developed. The LAA model was mounted onto the left atrial chamber of a commercial pulse duplicator system to simulate physiological hemodynamic conditions. The test was performed using the Watchman device (Boston Scientific, USA; size: 31 mm). The inner implantation diameter of the LAA model was designed according to a target compression of 10% for the Watchman device in the implanted configuration. Furthermore, thrombus-like particles (n=150, d=1,7±0,05 mm) were added to represent the flushing of thrombi out of the LAA after device implantation. Within several cycles it was confirmed that no particles were washed out of the LAA model with the implanted occluder leading to a full protection against thromboembolism. It could also be shown that the occluder is firmly anchored in the LAA. Pressure measurements with sensors in the left atrium and in the LAA distal to the occluder could also show that the occluder has no influence on the pressure conditions in the LAA.
    Type of Medium: Online Resource
    ISSN: 2364-5504
    URL: Article
    DOI: 10.1515/cdbme-2019-0116
    Language: English
    Publisher: Walter de Gruyter GmbH
    Publication Date: 2019
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  • 2
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    Acute drug transfer and particle release of drug coated balloons within a porcine in-vitro model
    Walter de Gruyter GmbH ; 2017
    In:  Current Directions in Biomedical Engineering Vol. 3, No. 2 ( 2017-09-26), p. 465-468
    Details
    In: Current Directions in Biomedical Engineering, Walter de Gruyter GmbH, Vol. 3, No. 2 ( 2017-09-26), p. 465-468
    Abstract: Drug coated balloons (DCB) are used in the therapy of coronary as well as peripheral artery disease. The success of drug transfer to the vessel wall depends on the excipient used in combination with paclitaxel as antiproliferative drug. Although in-vivo studies show very good results with this technology, there is a lack of in-vitro test methods for characterization of various DCB available on the market. This study describes a method to gain information about the drug transfer and the particle release of three different DCB based on cetylpyridinium salycate (Cetpyrsal), hyaluronic acid and iopromide within a porcine in-vitro model. The Cetpyrsal-based DCB showed promising results with the highest drug transfer while producing the lowest number of particles.
    Type of Medium: Online Resource
    ISSN: 2364-5504
    URL: Article
    DOI: 10.1515/cdbme-2017-0098
    Language: English
    Publisher: Walter de Gruyter GmbH
    Publication Date: 2017
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  • 3
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    Development of a microstent system for minimally invasive glaucoma surgery
    Walter de Gruyter GmbH ; 2017
    In:  Current Directions in Biomedical Engineering Vol. 3, No. 2 ( 2017-09-26), p. 779-781
    Details
    In: Current Directions in Biomedical Engineering, Walter de Gruyter GmbH, Vol. 3, No. 2 ( 2017-09-26), p. 779-781
    Abstract: Glaucoma is the leading cause of irreversible blindness worldwide. An increased intraocular pressure (IOP) is known as major risk factor. Currently, drainage devices that are implanted by means of minimally invasive glaucoma surgery (MIGS) represent a promising approach for IOP low-ering. Commercially available devices for MIGS suffer from unregulated drainage involving ocular hypotony. Further-more, long term drainage capability of current devices is limited by fibrotic encapsulation processes. Therefore, our group focusses on the development of a valved drug-eluting microstent for MIGS. Within the current work, we developed two alternative injector devices for minimally invasive mi-crostent implantation. Both injector devices were based on a cannula in which the microstent is loaded and a mandrel inside the cannula. Injector device A is designed to push the microstent out of the cannula and injector device B is de-signed to withdraw the cannula above the microstent. Manu-facturing of injector devices was conducted using rapid prototyping. Simplified polymeric microstents were manu-factured from polycarbonate based silicone elastomer. Simulated use was performed in a silicone eye model. The presented injector devices were suitable for minimally in-vasive ab interno microstent implantation into suprachoroidal space. Ongoing miniaturization of the microstent system will allow the use of a 22 G cannula in future ex vivo experiments.
    Type of Medium: Online Resource
    ISSN: 2364-5504
    URL: Article
    DOI: 10.1515/cdbme-2017-0164
    Language: English
    Publisher: Walter de Gruyter GmbH
    Publication Date: 2017
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  • 4
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    Usage of different vessel models in a flow-through cell: in vitro study of a novel coated balloon catheter
    Royal Society of Chemistry (RSC) ; 2015
    In:  RSC Advances Vol. 5, No. 15 ( 2015), p. 11604-11610
    Details
    In: RSC Advances, Royal Society of Chemistry (RSC), Vol. 5, No. 15 ( 2015), p. 11604-11610
    Type of Medium: Online Resource
    ISSN: 2046-2069
    URL: Article
    DOI: 10.1039/C4RA12524J
    Language: English
    Publisher: Royal Society of Chemistry (RSC)
    Publication Date: 2015
    detail.hit.zdb_id: 2623224-8
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  • 5
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    Correlating Coating Characteristics with the Performance of Drug-Coated Balloons – A Comparative In Vitro Investigation of Own Established Hydrogel- and Ionic Liquid-Based Coating Matrices
    Public Library of Science (PLoS) ; 2015
    In:  PLOS ONE Vol. 10, No. 3 ( 2015-3-3), p. e0116080-
    Details
    In: PLOS ONE, Public Library of Science (PLoS), Vol. 10, No. 3 ( 2015-3-3), p. e0116080-
    Type of Medium: Online Resource
    ISSN: 1932-6203
    URL: Article
    URL: Article
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    URL: Article
    DOI: 10.1371/journal.pone.0116080
    DOI: 10.1371/journal.pone.0116080.g001
    DOI: 10.1371/journal.pone.0116080.g002
    DOI: 10.1371/journal.pone.0116080.g003
    DOI: 10.1371/journal.pone.0116080.g004
    DOI: 10.1371/journal.pone.0116080.g005
    DOI: 10.1371/journal.pone.0116080.t001
    DOI: 10.1371/journal.pone.0116080.s001
    Language: English
    Publisher: Public Library of Science (PLoS)
    Publication Date: 2015
    detail.hit.zdb_id: 2267670-3
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  • 6
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    Medical Device Regulation and current challenges for the implementation of new technologies
    Walter de Gruyter GmbH ; 2020
    In:  Current Directions in Biomedical Engineering Vol. 6, No. 3 ( 2020-09-01), p. 334-337
    Details
    In: Current Directions in Biomedical Engineering, Walter de Gruyter GmbH, Vol. 6, No. 3 ( 2020-09-01), p. 334-337
    Abstract: The European Parliament and the European Council on May 26, 2017 decided to introduce the new regulatory framework for medical devices. The transitional period of the so called Medical Device Regulation (EU 2017/745, MDR) should end on May 26, 2020. Currently the European Commission is working on a proposal to postpone the application for one year to relieve pressure from all stakeholders allowing them to fully focus on priorities related to the coronavirus crisis. From this date or most likely from May 26, 2021, manufacturers must present a CE-certificate according to the new MDR requirements not only for novel medical devices, but also for approved medical devices which are already on the market. The MDR will significantly complicate the process of bringing medical devices into market due to the increased requirements for the CE-certification process, particularly concerning increased documentation effort. This involves a risk for the translation of innovative products due to an overload of the overall system (manufacturers, Notified Bodies, experts) and might lead to shrinkage of the product range of existing products. Thankfully, adaption of transitional periods, special regulations, extensions of deadlines and most probably postponement of the MDR application date will ensure that there will be no gaps in medical supply that endanger patients. Establishing and keeping the relevant regulatory expertise up to date and devoting the necessary financial, time and human resources that is the biggest immediate challenge the medium-sized medical technology sector is facing in the near future. The current article, written about one month before the initially expected end of the first transition period on May 26, 2020, summarized the main aspects of the current state of MDR implementation with respect to regulatory novelties, the current legal basis in Germany, transition periods and changes in the requirements of CE-certification relevant technical documentation. Furthermore, challenges for existing and innovative medical devices were shortly discussed using a new stent based therapy of the proximal Fallopian tubal stenosis and transcatheter aortic valve implantation as two examples.
    Type of Medium: Online Resource
    ISSN: 2364-5504
    URL: Article
    DOI: 10.1515/cdbme-2020-3086
    Language: English
    Publisher: Walter de Gruyter GmbH
    Publication Date: 2020
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  • 7
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    Transcatheter mitral valve repair devices - in vitro studies on the influence of device-width on mitral regurgitation
    Walter de Gruyter GmbH ; 2020
    In:  Current Directions in Biomedical Engineering Vol. 6, No. 3 ( 2020-09-01), p. 217-220
    Details
    In: Current Directions in Biomedical Engineering, Walter de Gruyter GmbH, Vol. 6, No. 3 ( 2020-09-01), p. 217-220
    Abstract: Mitral regurgitation (MR) is the most prevalent valvulopathy in the USA and the second most prevalent valvulopathy in Europe. Despite excellent clinical results of surgical mitral valve repair (SMVR), transcatheter-based mitral valve repair (MVR) procedures emerged as a feasible treatment option for surgically inoperable or high-risk patients suffering from clinically relevant MR. The current study investigates the impact of device-induced coaptationwidth on the hydrodynamic performance of insufficient mitral valves (MV) during left ventricular (LV) systole. A non-calcified, pathological MV model (MVM) featuring a D-shaped MV annulus with an area of 7.6 cm2 and a flail gap in the A2-P2 region was employed in an experimental setup. Pressure gradient-volumetric flow rate (Δp-Q) relations were investigated for steady-state backward flow with transvalvular pressure gradients ranging from (0.75 ≤ Δp ≤ 177.36) mmHg. Glycerol-water mixture (36 % (v/v) glycerol in water) at 37 °C with a density of (1 098.2 ± 1.3) kg·m-3 and a dynamic viscosity of 3.5 mPa∙s was used as circulatory fluid. In order to determine the impact of the width of transcatheter MVR devices during LV-systole Δp-Q relations were investigated for three MVM-configurations: (i) MVM without MVR device, (ii) MVM with one MVR device and (iii) MVM with two MVR devices implanted in the A2-P2 region. The MVR devices were manufactured from steel sheets with a thickness of 0.2 mm and feature arm lengths of 9.0 mm and a width of 5.0 mm. The conducted investigations show that the implantation of MVR devices in the A2-P2 region prevents the manifestation of an A2-P2 flail gap and thereby effectively reduces the retrograde blood flow during the LV-systole by 13 % with one MVR device and 27 % with two MVR devices implanted. Thus, the application of two MVR devices with a combined device-induced width of 10 mm results in a better MR reduction than the implantation of one MVR device with a device-induced width of 5 mm.
    Type of Medium: Online Resource
    ISSN: 2364-5504
    URL: Article
    DOI: 10.1515/cdbme-2020-3055
    Language: English
    Publisher: Walter de Gruyter GmbH
    Publication Date: 2020
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  • 8
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    Investigations of flow alteration of commissural misalignment of TAVR using Particle Image Velocimetry
    Walter de Gruyter GmbH ; 2020
    In:  Current Directions in Biomedical Engineering Vol. 6, No. 3 ( 2020-09-01), p. 159-163
    Details
    In: Current Directions in Biomedical Engineering, Walter de Gruyter GmbH, Vol. 6, No. 3 ( 2020-09-01), p. 159-163
    Abstract: Due to the raising number of TAVR implantations (transcatheter aortic valve replacement), tests for durability and prevention of associated diseases are becoming increasingly important. Not only the anatomy but also the positioning of the TAVR is decisive for its clinical performance. A misalignment in the circumferential direction can influence the flow in the sinus and thus inhibit the blood supply of the coronary arteries and influence the thrombosis potential. Therefore, the modification of the flow field is investigated in this study. For the characterization of the flow fields the measuring method of digital particle image velocimetry is used. A hydraulic circulation model is used to generate physiological flow and pressure conditions. Additionally, an aortic root model with Sinus Valsalvae, which represents the implantation environment, was developed. A prototype of a TAVR was implanted aligned to the commissure lines of the native valve leaflets on the one hand, and misaligned by 60 degree to the commissure of the native valves on the other hand. By determining the velocity vector fields, it could be shown that implantation of the TAVR with a commissureal misalignment influences the flow around the leaflets. A comparison of the flow fields shows that different recirculation areas occur. This is also indicated by a comparison of the mean velocities in the sinus and the observed shear rates. The influence of the altered flow field on the thrombosis and hemolysis potential should be investigated in future studies.
    Type of Medium: Online Resource
    ISSN: 2364-5504
    URL: Article
    DOI: 10.1515/cdbme-2020-3041
    Language: English
    Publisher: Walter de Gruyter GmbH
    Publication Date: 2020
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  • 9
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    Impact of aortic annulus geometry according to ISO 5840:2019 (draft) on hydrodynamic performance of transcatheter aortic valve prostheses
    Walter de Gruyter GmbH ; 2020
    In:  Current Directions in Biomedical Engineering Vol. 6, No. 3 ( 2020-09-01), p. 454-457
    Details
    In: Current Directions in Biomedical Engineering, Walter de Gruyter GmbH, Vol. 6, No. 3 ( 2020-09-01), p. 454-457
    Abstract: To assess the hydrodynamic performance of transcatheter aortic valve prostheses (TAVP), in vitro test using pulse duplicators is required. Test conditions as well as minimum performance criteria are specified in ISO 5840- 3:2013 and ISO 5840-3:2019-draft. In the 2019 published draft, modifications regarding hydrodynamic testing are proposed. Among others, the geometrical configuration of the fixation has changed, with the intention to improve the anatomical representation as well as the comparability of results from different test laboratories. We analyzed the consequences of altered annulus fixations regarding native leaflets as well as a step in the proximal area of the protheses to prevent their migration. The analyses were conducted with regard to the degree of calcification of the annulus ring on hydrodynamic parameters. By using 3D stereolithography printing technology, molds for casting of silicone elastomer of annulus models with and without native leaflets were manufactured. A modular system enabled us to use the same annulus ring to model the degree of calcification as well as different step sizes. We performed in vitro hydrodynamic testing according to ISO 5840-3:2019-draft of a selfexpandable valve prototype with porcine pericardial leaflets by using a commercially available pulse duplicator system. As expected, regurgitation increases with increasing degree of calcification, whereby the use of a step has no influence on the backflow of fluid during diastole. The effective orifice area (EOA) of the valve showed a clear tendency with respect to radial protrusion of the step. The EOA decreased as the radial protrusion increased. We also present a suggestion to prevent migration without affecting the general test results, by using a novel step design. We also found that the novel annulus model with native leaflet drastically reduced the regurgitation.
    Type of Medium: Online Resource
    ISSN: 2364-5504
    URL: Article
    DOI: 10.1515/cdbme-2020-3117
    Language: English
    Publisher: Walter de Gruyter GmbH
    Publication Date: 2020
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  • 10
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    Quantification of noncircular stent expansion after TAVR into a pathological annulus and its impact on paravalvular leakage
    Walter de Gruyter GmbH ; 2021
    In:  Current Directions in Biomedical Engineering Vol. 7, No. 2 ( 2021-10-01), p. 597-600
    Details
    In: Current Directions in Biomedical Engineering, Walter de Gruyter GmbH, Vol. 7, No. 2 ( 2021-10-01), p. 597-600
    Abstract: Patients undergoing transcatheter aortic valve replacement (TAVR) may suffer severe clinical complications, caused by paravalvular leakage (PVL) which is defined as leakage between TAVR and aortic annulus. PVL is often facilitated by a severely calcified annulus. This limits the expansion of a self-expandable TAVR stent. To assess TAVR performance in terms of leakage, measurement of regurgitation fraction in a pathophysiological annulus is recommended according to ISO 5840. For this purpose, a configuration of a circular annulus with a calcification nodule has been proposed in the recently published ISO 5840. The impact of the proposed pathophysiological annulus model on the expansion of self-expandable TAVR stents and on the regurgitation fraction was investigated in this study. For this purpose, two commercially available selfexpandable TAVRs (Evolut R and Portico) were implanted in a calcified annulus model. Circular expansion of the TAVR stents was investigated based on μCT scans of the implanted TAVR. The calcification-induced area in which retrograde flow can occur during diastole was detected. These results were then compared with the experimentally determined regurgitation fraction obtained from pulse duplicator tests. The results of the μCT scans showed a continuous leakage area in the region of the annulus for the Evolut R compared to a locally larger leakage area of the Portico, which, however, reattaches to the annulus in the distal inflow region. The hydrodynamic measurements confirmed a smaller leakage in the pathological annulus for the Portico. In summary, it can be assumed that a continuous leakage area in the TAVR stent inflow region encourages the PVL of TAVR.
    Type of Medium: Online Resource
    ISSN: 2364-5504
    URL: Article
    DOI: 10.1515/cdbme-2021-2152
    Language: English
    Publisher: Walter de Gruyter GmbH
    Publication Date: 2021
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