11 research outputs found

    Biomedical applications of photo- and sono-activated Rose Bengal:a review

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    \u3cp\u3eObjective: The aim of this review is to discuss and compare the extensive range of biomedical applications of photo- and sono-activated Rose Bengal (RB). Background data: RB is a xanthene dye that due to its interesting photo- and sono-sensitive properties is gaining attention in the scientific field. Methods: This study is a literature review using the database PubMed. Results: As a photosensitizer, RB converts the triplet oxygen molecule into reactive oxygen species after irradiation with green light (532 nm). This mechanism allows for the use of photo-activated RB in photochemical tissue bonding, photodynamic therapy, antimicrobial therapy and cancer treatment, photothrombotic animal models, and other applications, including tissue engineering and treatment of tauopathies. As a sono-sensitive compound, RB is applied for sonodynamic therapy, cancer treatment, and antimicrobial therapy. Conclusions: This review outlines the versatility and effectiveness of photo- and sono-activated RB in numerous biomedical applications.\u3c/p\u3

    Development of an ex vivo aneurysm model for vascular device testing

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    \u3cp\u3eAn ex vivo aneurysm model that closely resembles the in vivo situation can provide an important tool for testing therapies. The model should mimic a variety of conditions, such as in vivo hemodynamics and native arterial structure and characteristics, avoiding animal experimentation.  Therefore, the aim of this study is to develop an ex vivo aneurysm model by vessel wall stiffening to be used to assess treatment strategies. Porcine carotid arteries from slaughterhouse animals were used to evaluate the acute effect of different concentrations of Rose Bengal on distensibility. This sono-sensitive compound was activated by several ultrasound frequencies, resulting in stiffening of the treated arteries of which the most effective combination was selected. In a pulsatile ex vivo vascular bioreactor treated and control porcine carotid arteries were subjected to physiological conditions for 10 days. During culture, hemodynamics showed increased mean pressure and decreased pulsatility in treated arteries compared to controls. Change in vessel morphology and significant increase of distal diameter was observed in the treated arteries but not in the controls. Histology of treated arteries revealed dissection-like lesions distally and aneurysm-like structure proximally. Finally, a stent graft was deployed in one treated artery and cultured demonstrating the feasibility of testing endovascular devices in the model. In conclusion, we developed an ex vivo model reproducing the onset of aneurysm formation. This could represent a promising tool for early stage device testing thereby reducing the need for animal studies.\u3c/p\u3

    Syllectometry : the effect of aggregometer geometry in the assessment of red blood cell shape recovery and aggregation

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    Syllectometry is a measuring method that is commonly used to assess red blood cell (RBC) aggregability. In syllectometry, light is incident on a layer of whole blood initially exposed to shear flow. The backscattered light is measured after abruptly stopping the driving mechanism. The resultant time-dependent intensity plot is called the syllectogram. Parameters that quantify RBC aggregability are obtained by analyzing the syllectogram. As we will show in this paper, the upstroke in the initial part of the syllectogram contains the information for measurement of RBC-shape recovery in whole blood as well. To estimate RBC-shape recovery, we extended the existing two-exponential mathematical representation of the syllectogram by a third exponent that describes the upstroke. To investigate the feasibility of RBC-shape recovery measurement from the upstroke, we derived an analytical model of the flow decay that follows after abruptly stopping the driving mechanism. The model reveals that for large gaps the flow decay may interfere with the true RBC-shape recovery process. These theoretical findings were confirmed by velocity measurements in a Couette-type aggregometer. Syllectograms obtained using large gaps differ in many respects from those obtained using small gaps. As predicted by our model large gaps show a prolonged apparent shape-recovery time-constant. Moreover, a delayed intensity peak, a reduced upstroke of the intensity peak and a considerable increase of the half-life parameter are observed. The aggregation indices for large gaps are lower than for small gaps. This paper yields a better understanding of the velocity and shear-rate decay following upon abruptly stopping the driving mechanism. A better mathematical representation of the syllectogram and recommendations for a maximum gap width enables both RBC-shape recovery and aggregation measurements in whole blood using syllectometry

    Validation of a fluid-structure interaction model of a heart valve using the dynamic mesh method in fluent

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    Simulations of coupled problems such as fluid-structure interaction (FSI) are becoming more and more important for engineering purposes. This is particularly true when modeling the aortic valve, where the FSI between the blood and the valve determines the valve movement and the valvular hemodynamics. Nevertheless only a few studies are focusing on the opening and closing behavior during the ejection phase (systole). In this paper, we present the validation of a FSI model using the dynamic mesh method of Fluent for the two-dimensional (2D) simulation of mechanical heart valves during the ejection phase of the cardiac cycle. The FSI model is successfully validated by comparing simulation results to experimental data obtained from in vitro studies using a CCD camera

    Evaluation of a fictitious domain method for predicting dynamic response of mechanical heart valves

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    Flow phenomena around heart valves are important for the motion of the valve leaflets, hence the dynamics of the valve. This work presents an evaluation of a two-dimensional moving rigid heart valve, in which a fictitious domain method is used to describe fluid–structure interaction. Valve motion and fluid flow around the valve were computed for several Reynolds and Strouhal numbers. Particle Image Velocimetry measurements in an in vitro experimental set-up were performed to validate the computational results. The influences of variations of the flow-pulse, expressed in Reynolds and Strouhal number, are well predicted by the computational method. As the fictitious domain method can readily be applied to fully three-dimensional fluid–structure interaction problems, this study indicates that this method is well suited for the analysis of valve dynamics and ventricular flow in physiologically realistic geometries

    Attenuated cardiac function degradation in ex vivo pig hearts

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    \u3cp\u3eIsolated hearts offer the opportunity to evaluate heart function, treatments, and diagnostic tools without in vivo factor interference. However, the early loss of cardiac function and edema occur over time and do limit the duration of the experiment. This research focuses on delaying these limitations using optimal blood control. This study examines whether blood conditioning by means of the combination of blood predilution and hemodialysis can significantly reduce cardiac function degradation. Slaughterhouse porcine hearts were revived in the PhysioHeartℱ platform to restore physiological cardiac performance. Twelve hearts were divided into a control group and a dialysis group; in the latter group, hemodialysis was attached to the blood reservoir. Cardiac hemodynamics and blood parameters were recorded and evaluated. Blood conditioning significantly reduced the loss of cardiac pump function (control group vs dialysis group, −14.9 ± 6.3%/h vs −9.7 ± 2.7%/h) and loss of cardiac output (control group vs dialysis group, −11.8 ± 3.4%/h vs −5.9 ± 2.0%/h). Hemodialysis resulted in physiological and stable blood parameters, whereas in the control group ions reached pathological values, while interstitial edema still occurred. The combination of blood predilution and hemodialysis significantly attenuated ex vivo cardiac function degradation and delayed the loss of cardiac hemodynamics. We hypothesized that besides electrolyte and metabolic control, the hemodialysis-accompanied increase in hematocrit resulted in improved oxygen transport. This could have temporarily compensated the deleterious effect of an increased oxygen-diffusion distance due to edema in the dialysis group and resulted in less progression of cell decay. Clinically validated measures delaying edema might improve the effectiveness of the PhysioHeartℱ platform.\u3c/p\u3

    Beating heart porcine high-fidelity simulator for the training of edge-to-edge mitral valve repair

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    \u3cp\u3eTranscatheter treatment of structural heart disease is becoming an everyday reality for an increasing number of surgeons, and effective training modalities for basic guide-wire skills, catheter handling, and periprocedural imaging are of growing relevance. In this video tutorial we present a beating-heart porcine model used as a high-fidelity training simulator for transcatheter cardiac valve procedures.  We demonstrate a complete transcatheter edge-to-edge mitral valve repair procedure, including periprocedural imaging, clip deployment, and quality control. Various mitral valve pathologies can be simulated, including the demonstrated leaflet prolapse. Trainees practice clip navigation within the left atrium, transmitral passage, and clip orientation as well as grasping mitral valve leaflets to treat mitral regurgitation.  Periprocedural imaging is achieved via epicardial echocardiography and left ventricular cardioscopy, and these imaging modalities are also relied on to guide surgeons during the simulations, as required. The beating heart model enables realistic demonstration of the hemodynamic consequences of valve repair, and we believe that this simulator represents a valuable adjunct to surgical training.\u3c/p\u3

    Intracoronary hypothermia for acute myocardial infarction in the isolated beating pig heart

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    \u3cp\u3eHypothermia may attenuate reperfusion injury and thereby improve acute myocardial infarction therapy. Systemic cooling trials failed to reduce infarct size, perhaps because the target temperature was not reached fast enough. The use of selective intracoronary hypothermia combined with intracoronary temperature monitoring allows for titrating to target temperature and optimizing the cooling rate. We aimed to the test the feasibility of intracoronary cooling for controlled, selective myocardial hypothermia in an isolated beating pig heart. In five porcine hearts the left anterior descending artery (LAD) was occluded by an over-the-wire balloon (OTWB). After occlusion, saline at 22°C was infused through the OTWB lumen for 5 minutes into the infarct area at a rate of 30 ml/min. Thereafter the balloon was deflated but infusion continued with saline at 4°C for 5 minutes. Distal coronary temperature was continuously monitored by a pressure/temperature guidewire. Myocardial temperature at several locations in the infarct and control areas was recorded using needle thermistors. In the occlusion phase, coronary temperature decreased by 11.4°C (range 9.4-12.5°C). Myocardial temperature throughout the infarct area decreased by 5.1°C (range 1.8-8.1°C) within three minutes. During the reperfusion phase, coronary temperature decreased by 6.2°C (range 4.1-10.3°C) and myocardial temperature decreased by 4.5°C (range 1.5-7.4°C). Myocardial temperature outside the infarct area was not affected. In the isolated beating pig heart with acute occlusion of the LAD, we were able to rapidly “induce, maintain, and control” a stable intracoronary and myocardial target temperature of at least 4°C below body temperature without side effects and using standard PCI equipment, justifying further studies of this technique in humans.\u3c/p\u3

    Characteristics of surgical prosthetic heart valves and problems around labelling:a document from the European Association for Cardio-Thoracic Surgery (EACTS)– the Society of Thoracic Surgeons (STS)– American Association for Thoracic Surgery (AATS) valve labelling task force

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    \u3cp\u3eIntraoperative surgical prosthetic heart valve (SHV) choice is a key determinant of successful surgery and positive postoperative outcomes. Currently, many controversies exist around the sizing and labelling of SHVs rendering the comparison of different valves difficult. To explore solutions, an expert Valve Labelling Task Force was jointly initiated by the European Association for Cardio-Thoracic Surgery (EACTS), The Society of Thoracic Surgeons (STS) and the American Association for Thoracic Surgery (AATS). The EACTS–STS–AATS Valve Labelling Task Force, comprising cardiac surgeons, cardiologists, engineers, regulators and representatives from the International Organization for Standardization (ISO) and major valve manufacturers, held its first in-person meeting in February 2018 in Paris, France. This article was derived from the meeting's discussions. The Task Force identified the following areas for improvement and clarification: reporting of physical dimensions and characteristics of SHVs determining and labelling of SHV size, in vivo and in vitro testing and reporting of SHV hemodynamic performance and thrombogenicity. Furthermore, a thorough understanding of the regulatory background and the role of the applicable ISO standards, together with close cooperation between all stakeholders (including regulatory and standard-setting bodies), is necessary to improve the current situation. Cardiac surgeons should be provided with appropriate information to allow for optimal SHV choice. This first article from the EACTS–STS–AATS Valve Labelling Task Force summarizes the background of SHV sizing and labelling and identifies the most important elements where further standardization is necessary.\u3c/p\u3
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