Emerging of cardiovascular metal stent: a review on drug-eluting stent towards the utilisation of herbal coating

Metal stents used in the treatment of percutaneous coronary intervention (PCI) have revolutionized in treating atherosclerosis disease. Starting from the emergence of bare metal stent (BMS), this stent has been progressively developed into drug-eluting stent (DES) and biodegradable stent. By focusing on DES, various drugs have been used to coat metal stent with the aims to overcome in-stent restenosis and stent thrombosis. Therefore, the utilisation of various drugs and polymers as coating materials was reviewed in this study to identify possible alternative to overcome the current DES problems. Even though, both complications of BMS are covered successfully by DES, however, DES projects long term complications of delayed endotheliasation, delayed wound healing and late stent thrombosis. Another alternative of herb coating on DES is considered to be a potential approach in improving endotheliasation and retarding smooth muscle cells proliferation to accelerate wound healing and to prevent late stent thrombosis

Numerical Study of a Left Ventricular Assist Device (LVAD) With Different Blade Heights and Tip Clearances

One treatment modality for heart failure is to employ a mechanical heart assist device to increase blood flow to peripheral organs. There are various kinds of axial and centrifugal type mechanical pumps available for implantation depending on patient condition. Axial pumps are smaller in size comparatively, although centrifugal pumps have the advantages of lower rotational speed as well as better maintaining any native blood flow pulsatility. This work presents the results of the numerical study of the centrifugal blood pump configured as a Left Ventricular Assist Device (LVAD). The pump design utilized standard industrial centrifugal pump design principles but applied to smaller sized blood pumps. Flow characteristics are modelled using 3-dimensional steady state models operating at design speed of 2000 rpm using Newtonian blood properties for the fluid. Two design parameters of the pump are studied, the impeller blade height and tip clearance resulting in nine model variants. Analysis includes the hydrodynamic performance of the pump and the flow characteristics in the pump. A haemolysis prediction model quantifying red blood cell stress from exposure time and shear stress was used for quantitative predictions of haemolysis within the blood pump. Blood damage estimation was calculated along each path-line and averaged to a single value. By using a ranked selection method, the model with the 15 mm blade height and 800 µm tip clearance was selected as the preferred configuration with Haemolysis Index of 0.01 mmHg, efficiency of 58% at 104 mmHg outlet pressure

Effects of elasticity on wall shear stress in patient-specific aneurysm of cerebral artery

The behavior of wall shear stress (WSS) was previously reported in a deformable aneurysm model using fluid-structure interactions. However, these findings have not been validated. In the present study, we examined the effect of elasticity (i.e. , deformation) on wall shear stress inside a cerebral aneurysm at the apex of a bifurcation using particle image velocimetry in vitro. The flow model simulated a human patient-specific aneurysm at the apex of the bifurcation of the middle cerebral artery. Flow characteristics by wall elasticity were examined for both elastic and non-deformable aneurysm models with pulsatile blood flow. The absolute temporally- and spatially-averaged WSS along the bleb wall was smaller in the elastic model than that in the non-deformable model. This small WSS may be related to attenuation of the WSS. Further, the WSS gradient had a finite value near the stagnation point of the aneurysm dome. Finally, the WSS gradient near the stagnation point was slightly smaller in the elastic model than that in the non-deformable model. These data suggest that elasticity of the aneurysm wall can affect the progression and rupture of aneurysms via hemodynamic stress

Flow behaviour in normal and Meniere's disease of endolymphatic fluid inside the inner ear

Meniere's disease is a rare disorder that affects the inner ear which might be more severe if not treated. This is due to fluctuating pressure of the fluid in the endolymphatic sac and dysfunction of cochlea which causing the stretching of vestibular membrane. However, the pattern of the flow recirculation in endolymphatic region is still not fully understood. Thus, this study aims to investigate the correlation between the increasing volume of endolymphatic fluid and flow characteristics such as velocity, pressure and wall shear stress. Three dimensional model of simplified endolymphatic region is modeled using computer aided design (CAD) software and simulated using computational fluid dynamic (CFD) software. There are three different models are investigated; normal (N) model, Meniere's disease model with less severity (M1) and Meniere's disease model with high severity (M2). From the observed, the pressure drop between inlet and outlet of inner ear becomes decreases as the outlet pressure along with endolymphatic volume increases. However, constant flow rate imposed at the inlet of endolymphatic showing the lowest velocity. Flow recirculation near to endolymphatic region is occurred as the volume in endolympathic increases. Overall, high velocity is monitored near to cochlear duct, ductus reuniens and endolymphatic duct. Hence, these areas show high distributions of wall shear stress (WSS) that indicating a high probability of endolymphatic wall membrane dilation. Thus, more severe conditions of Meniere's disease, more complex of flow characteristic is occurred. This phenomenon presenting high probability of rupture is predicted at the certain area in the anatomy of vestibular system

Recent trends for practical rehabilitation robotics, current challenges and the future

This paper presents and studies various selected literature primarily from conference proceedings, journals and clinical tests of the robotic, mechatronics, neurology and biomedical engineering of rehabilitation robotic systems. The present paper focuses of three main categories: types of rehabilitation robots, key technologies with current issues and future challenges. Literature on fundamental research with some examples from commercialized robots and new robot development projects related to rehabilitation are introduced. Most of the commercialized robots presented in this paper are well known especially to robotics engineers and scholars in the robotic field, but are less known to humanities scholars. The field of rehabilitation robot research is expanding; in light of this, some of the current issues and future challenges in rehabilitation robot engineering are recalled, examined and clarified with future directions. This paper is concluded with some recommendations with respect to rehabilitation robots

The effect of spiral inducing chamber to left ventricular assist device outflow cannula

The rise of heart failure in the setting of shortage heart donor had brought to the emergence of development of left ventricular assist device (LVAD). However, patients are still encountering severe complications such as stroke and device thrombosis due to the hemodynamic changes. This study aimed to compare the hemodynamic characteristic between the standard and spiral LVAD outflow cannula. Two different anastomosis sites (2cm and 3cm) from sino-tubular junction are used and a spiral inducing chamber is attached to the cannula to promote spiral flow. The result showed that spiral LVAD cannula exhibit a lower output velocity with 37% percentage difference and lower region of low WSS value

Electrospun Combination of Peppermint Oil and Copper Sulphate with Conducive Physico-Chemical properties for Wound Dressing Applications

The ultimate goal in tissue engineering is to fabricate a scaffold which could mimic the native tissue structure. In this work, the physicochemical and biocompatibility properties of electrospun composites based on polyurethane (PU) with added pepper mint (PM) oil and copper sulphate (CuSO4) were investigated. Field Emission Electron microscope (FESEM) study depicted the increase in mean fiber diameter for PU/PM and decrease in fiber diameter for PU/PM/CuSO4 compared to the pristine PU. Fourier transform infrared spectroscopy (FTIR) analysis revealed the formation of a hydrogen bond for the fabricated composites as identified by an alteration in PU peak intensity. Contact angle analysis presented the hydrophobic nature of pristine PU and PU/PM while the PU/PM/CuSO4 showed hydrophilic behavior. Atomic force microscopy (AFM) analysis revealed the increase in the surface roughness for the PU/PM while PU/PM/CuSO4 showed a decrease in surface roughness compared to the pristine PU. Blood compatibility studies showed improved blood clotting time and less toxic behavior for the developed composites than the pristine PU. Finally, the cell viability of the fabricated composite was higher than the pristine PU as indicated in the MTS assay. Hence, the fabricated wound dressing composite based on PU with added PM and CuSO4 rendered a better physicochemical and biocompatible nature, making it suitable for wound healing applications

Non-invasive treatment for coronary in-stent restenosis via wireless revascularization with nitinol active stent

This paper reports a novel shape memory alloy (SMA) nitinol type active stent for non-invasive restenosis treatment, which operates using a radiofrequency (RF) electro-thermo-mechanical actuation technique for wireless revascularization. The developed stent is equipped with a capacitive pressure sensor for in-artery blood pressure measurement and can provide multiple expansion to restore the blood pressure flow. The device design, working principle, fabrication, and characterization of the nitinol active stent are reported in this work. The wireless monitoring feature is achieved via peak shifting in the reflection coefficient of the S11 parameter. The active stent with initial diameter and resonant frequency of 2 mm and 315 MHz, respectively, is expanded uniformly in stages up to 4.2 mm in diameter when excited with an RF power of ∼30 W for 320 s. The active stent is delivered and deployed ex vivo inside the left coronary artery of a cervine heart. The stented cervine heart before and after wireless actuation is inspected via penetration of X-rays. Endoscopic images reveal the expansion of the stent strut profile within the lumen of the stented artery. The active stent expands in stages up to 3.7 mm in diameter to scaffold the cervine coronary artery after excited with an RF power of 46.7 W. The achievable wireless revascularization capability eradicates the necessity of reintervention and repeat stenting procedure, whereas real-time wireless monitoring provides rapid indication of in-artery re-narrowing occurrence