Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 18 de 18
Filtrar
1.
J Clin Med ; 13(10)2024 May 12.
Artículo en Inglés | MEDLINE | ID: mdl-38792397

RESUMEN

Background: Joint pain has been recognized as one of the major causes of limitations in mobility, functional decline, and consequently declined quality of life in older adults. Hence, this study aimed to identify the predictors, protective factors, and adverse outcomes of joint pain in community-dwelling older adults. Methods: In this Long-term Research Grant Scheme-Towards Useful Ageing (LRGS-TUA) longitudinal study, a total of 1005 older participants aged 60 years and above who were successfully followed up after five years were included in the analysis. The participants self-reported their joint pain status at baseline and during the fifth year. Subsequently, the baseline characteristics were used to predict changes in joint pain status. Adverse outcomes related to joint pain were evaluated based on the participants' joint pain statuses. Results: Results showed that being female, having diabetes mellitus, and higher body mass index were associated with the incidence of joint pain. Meanwhile, increased intake of pantothenic acid and higher levels of blood albumin levels were associated with recovery from joint pain. Participants with persistent joint pain at baseline and follow-up showed higher levels of depression and disability compared to individuals who never experience any joint pain. However, participants who had recovered from joint pain did not differ significantly from those without joint pain at baseline and follow-up in these measures. Conclusions: By identifying the modifiable risk factors, factors associated with recovery, and adverse outcomes related to joint pain, this study adds to current evidence that may contribute to further management strategies for joint pain in older adults.

2.
Ann N Y Acad Sci ; 1531(1): 49-59, 2024 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-38084081

RESUMEN

This study aimed to examine the impact of diabetes and hypertension on retinal nerve fiber layer (RNFL) thickness components. Optical coherence tomography (OCT) measurements do not consider blood vessel contribution, which this study addressed. We hypothesized that diabetes and/or hypertension would lead to thinner RNFL versus controls due to the vascular component. OCT angiography was used to measure the RNFL in 121 controls, 50 diabetes patients, 371 hypertension patients, and 177 diabetes patients with hypertension. A novel technique separated the RNFL thickness into original (vascular component) and corrected (no vascular component) measurements. Diabetes-only (98 ± 1.7 µm; p = 0.002) and diabetes with hypertension (99 ± 0.8 µm; p = 0.001) patients had thinner original RNFL versus controls (102 ± 0.8 µm). No difference was seen between hypertension-only patients (101 ± 0.5 µm; p = 0.083) and controls. After removing the blood vessel component, diabetes/hypertension groups had thinner corrected RNFL versus controls (p = 0.024). Discrepancies in diabetes/hypertension patients were due to thicker retinal blood vessels within the RNFL thickness (p = 0.002). Our findings suggest that diabetes and/or hypertension independently contribute to neurodegenerative thinning of the RNFL, even in the absence of retinopathy. The differentiation of neuronal and vascular components in RNFL thickness measurements provided by the novel technique highlights the importance of considering vascular changes in individuals with these conditions.


Asunto(s)
Diabetes Mellitus , Hipertensión , Enfermedades de la Retina , Humanos , Células Ganglionares de la Retina , Fibras Nerviosas , Hipertensión/complicaciones , Tomografía de Coherencia Óptica/métodos
3.
PLoS One ; 18(9): e0292213, 2023.
Artículo en Inglés | MEDLINE | ID: mdl-37768943

RESUMEN

Contract appointment policy for newly graduated medical officers was implemented by the Ministry of Health Malaysia in 2016 to overcome the lack of permanent posts. Contract officers faced disadvantages in terms of salary, leave provision, and career prospects. A nationwide strike, Hartal Doktor Kontrak (HDK) was organised on 26th July 2021. Besides generating widespread public attention, HDK was also closely scrutinised by the medical fraternity and stakeholders. This content analysis aimed to explore how the medical fraternity and stakeholders viewed the strike as their perception would offer vital insights into the fundamental causes and viable solutions to the contract appointment policy. A qualitative content analysis of Facebook (FB) posts on the HDK strike was conducted from 1st June 2021 until 28th February 2022. A total of 182 FB posts were retrieved from stakeholders, medical fraternity groups, and medical key opinion personnel. Inductive coding was used in the thematic analysis to identify pertinent themes. Three main themes emerged: triggering factors, reactions to the strike, and outcomes of the strike. Factors that led to the strike included unequal treatment faced by contract officers, frustration with the government's lack of long-term solutions, and aggravation by the COVID-19 pandemic. In terms of reactions, there was a mixture of supportive and opposing voices. No substantial negative impact on the healthcare service resulted from the strike. Instead, it generated widespread attention that propelled the government into implementing solutions to prevent adverse short and long-term consequences. Various suggestions were proposed, including the reform of human resource planning and undergraduate medical education. The results highlight the importance of proactive systemic measures by the government to prevent further strikes that may jeopardise healthcare provision. In summary, social media was found to influence the progress and outcome of HDK, thus demonstrating the impact of media influence on similar issues.


Asunto(s)
COVID-19 , Medios de Comunicación Sociales , Humanos , Malasia , Pandemias , COVID-19/epidemiología , Percepción
4.
Ann N Y Acad Sci ; 1529(1): 72-83, 2023 11.
Artículo en Inglés | MEDLINE | ID: mdl-37656135

RESUMEN

Data on how retinal structural and vascular parameters jointly influence the diagnostic performance of detection of multiple sclerosis (MS) patients without optic neuritis (MSNON) are lacking. To investigate the diagnostic performance of structural and vascular changes to detect MSNON from controls, we performed a cross-sectional study of 76 eyes from 51 MS participants and 117 eyes from 71 healthy controls. Retinal macular ganglion cell complex (GCC), retinal nerve fiber layer (RNFL) thicknesses, and capillary densities from the superficial (SCP) and deep capillary plexuses (DCP) were obtained from the Cirrus AngioPlex. The best structural parameter for detecting MS was compensated RNFL from the optic nerve head (AUC = 0.85), followed by GCC from the macula (AUC = 0.79), while the best vascular parameter was the SCP (AUC = 0.66). Combining structural and vascular parameters improved the diagnostic performance for MS detection (AUC = 0.90; p<0.001). Including both structure and vasculature in the joint model considerably improved the discrimination between MSNON and normal controls compared to each parameter separately (p = 0.027). Combining optical coherence tomography (OCT)-derived structural metrics and vascular measurements from optical coherence tomography angiography (OCTA) improved the detection of MSNON. Further studies may be warranted to evaluate the clinical utility of OCT and OCTA parameters in the prediction of disease progression.


Asunto(s)
Esclerosis Múltiple , Humanos , Esclerosis Múltiple/diagnóstico por imagen , Estudios Transversales , Retina/diagnóstico por imagen , Células Ganglionares de la Retina , Progresión de la Enfermedad , Tomografía de Coherencia Óptica/métodos
5.
Leadersh Health Serv (Bradf Engl) ; ahead-of-print(ahead-of-print)2022 11 11.
Artículo en Inglés | MEDLINE | ID: mdl-36350129

RESUMEN

PURPOSE: Formal structured leadership training is increasingly incorporated as a regular fixture in developed nations to produce competent leaders to ensure the provision of quality patient care. However, most low- and middle-income countries (LMICs) rely on one-off external training opportunities for selected individuals as they lack the necessary resources to implement long-term training for a wider pool of potential health care leaders. This case study shares the establishment process of the Talent Grooming Programme for technical health care professionals (TGP), a three-year in-house leadership training programme specially targeted at potential health care leaders in Malaysia. DESIGN/METHODOLOGY/APPROACH: This case study aims to share a comprehensive overview of the ideation, conceptualisation and implementation of TGP. The authors also outlined its impact from the individual and organisational perspectives, besides highlighting the lessons learned and recommendations for the way forward. FINDINGS: TGP set out to deliver experiential learning focusing on formal training, workplace experiences, practical reflection and mentoring by supervisors and other esteemed leaders to fulfil the five competency domains of leadership, organisational governance, communication and relationship, professional values and personal values. The successes and challenges in TGP programme delivery, post-training assessment, outcome evaluation and programme sustainability were outlined. PRACTICAL IMPLICATIONS: The authors' experience in setting up TGP provided valuable learning points for other leadership development programme providers. As for any development programme, a continuous evaluation is vital to ensure its relevance and sustainability. ORIGINALITY/VALUE: Certain aspects of TGP establishment can be referenced and modified to adapt to country-specific settings for others to develop similar leadership programme, especially those in LMICs.


Asunto(s)
Países en Desarrollo , Liderazgo , Humanos , Animales , Aseo Animal , Malasia , Atención a la Salud
6.
Healthcare (Basel) ; 9(9)2021 Sep 14.
Artículo en Inglés | MEDLINE | ID: mdl-34574982

RESUMEN

Physician burnout has been recognized as a public health crisis. However, there is a paucity of burnout studies in the context of medical internship. We assessed the prevalence and relationship between various training characteristics, personal variables, resilience, and coping with burnout in a cross-sectional study involving 837 interns from ten hospitals across Malaysian healthcare system. The instrument package included demographic questions, the Connor-Davidson Resilience Scale, Brief COPE and the Copenhagen Burnout Inventory. A total of 754 (90.1%) interns completed the inventories. We found a high prevalence of personal-related (73.3%), work-related (69.1%), and patient-related (43.4%) burnout among Malaysian interns. Multivariable analysis showed female gender (odds ratio (OR):1.50; 95% confidence interval (CI): 1.02-2.20), prior work experience (OR: 1.56; 95% CI: 1.05-2.30), and irregular spirituality routines (OR: 1.97; 95% CI: 1.30-2.99) were associated with increased odds of personal-related burnout. Irregular spirituality routines (OR: 2.24; 95% CI: 1.49-3.37) were associated with work-related burnout, while living with other people (OR: 1.77; 95% CI: 1.15-2.73) was associated with patient-related burnout. Lower resilience levels and avoidant copings were associated with personal-, work-, and patient-related burnout. Burnout prevalence among interns is high. The findings support the value of individual-targeted alongside organizational-targeted intervention in burnout reduction. As burnout is prevalent in both years of internship training, ongoing burnout prevention and wellbeing measures are deemed necessary.

7.
Artículo en Inglés | MEDLINE | ID: mdl-34501637

RESUMEN

Strengthening the health systems through gaps identification is necessary to ensure sustainable improvements especially in facing a debilitating outbreak such as COVID-19. This study aims to explore public perspective on health systems' response towards COVID-19, and to identify gaps for health systems strengthening by leveraging on WHO health systems' building blocks. A qualitative study was conducted using open-ended questions survey among public followed by in-depth interviews with key informants. Opinions on Malaysia's health systems response towards COVID-19 were gathered. Data were exported to NVIVO version 12 and analysed using content analysis approach. The study identified various issues on health systems' response towards COVID-19, which were then mapped into health systems' building blocks. The study showed the gaps were embedded among complex interactions between the health systems building blocks. The leadership and governance building block had cross-cutting effects, and all building blocks influenced service deliveries. Understanding the complexities in fostering whole-systems strengthening through a holistic measure in facing an outbreak was paramount. Applying systems thinking in addressing gaps could help addressing the complexity at a macro level, including consideration of how an action implicates other building blocks and approaching the governance effort in a more adaptive manner to develop resilient systems.


Asunto(s)
COVID-19 , Brotes de Enfermedades , Programas de Gobierno , Humanos , Liderazgo , Salud Pública , SARS-CoV-2
8.
Asia Pac Psychiatry ; : e12417, 2020 Aug 26.
Artículo en Inglés | MEDLINE | ID: mdl-32964660

RESUMEN

INTRODUCTION: The prevalence of psychological distress is increasing worldwide. Stressful working environments and high expectations in medical practice put doctors at high risk of depression, anxiety, and stress, especially among medical interns. Effective coping strategies may reduce psychological distress in the clinical setting. This study aimed to determine the prevalence of psychological distress and its association with coping strategies among medical interns in Malaysia. METHOD: A total of 431 medical interns at 26 Malaysian Ministry of Health hospitals participated in this cross-sectional study in 2017. Self-administered questionnaires consisting of sociodemographic characteristics, items from DASS and BRIEF COPE were used. Descriptive analysis was done followed by further analysis with chi-square and Spearman correlation tests. RESULTS: The prevalence of stress, anxiety, and depression was 29.7%, 39.9%, and 26.2%, with a significantly higher prevalence among female and younger interns. Three-quarters of them (73.1%) applied problem-focused strategies as the main coping mechanism. Emotion-focused coping strategies showed a significant but weak correlation with anxiety and stress whereas avoidance-based coping strategies were significantly correlated with depression, anxiety, and stress. DISCUSSION: Medical internship is a highly grueling period. Besides emphasizing clinical competency, internship training should also impart the practice of healthy coping mechanisms. The vulnerable groups of females and younger interns should be taught positive coping skills so that they are empowered to handle any stressors on their personal and professional lives. Optimum psychological wellbeing of the medical interns can improve the overall work performance and quality of care for patients.

9.
Am J Physiol Heart Circ Physiol ; 317(6): H1312-H1327, 2019 12 01.
Artículo en Inglés | MEDLINE | ID: mdl-31603355

RESUMEN

The deteriorating nature of severe functional tricuspid regurgitation (FTR) has led to the heightened interest in this pathology. However, therapies are heterogeneous and an ideal technique is uncertain. The hemodynamic impact on the cardiac chamber following therapeutic repairs has not been well studied, while its analysis could be used to predict the treatment success. In this study, the hemodynamics of the right ventricle (RV) after 1) clover edge-to-edge tricuspid repair, and 2) double orifice tricuspid repair was evaluated in three right heart models using an ex vivo pulsatile platform emulating severe FTR with the aid of stereoscopic particle image velocimetry. Although all repairs substantially reduced tricuspid regurgitant area, they resulted in a more than 50% reduction in diastolic tricuspid valve (TV) opening area. Splitting the TV orifice into multiple smaller orifices by both repairs eliminated the ring-shaped vortical structure inside the RV observed in FTR cases. Postrepair RV domain was mostly occupied with irregular vortical features and isolated vortex residuals. Moreover, vortical features varied among repair samples, indicating enhanced sensitivity of RV flow to postrepair TV morphology. Compared with clover repair, double orifice subjected the RV to enhanced swirling motions and exposed more regions to vortical motions, potentially indicating better rinsing and lower risk of mural thrombus formation. Double orifice repair increased the levels of RV mean kinetic energy and viscous energy loss than those observed in clover repair, although the impact of these on the cardiac efficiency remains unclear. These preliminary insights could be used to improve future treatment design and planning.NEW & NOTEWORTHY While clover and double orifice tricuspid repairs markedly improved leaflet coaptation, they substantially reduced diastolic tricuspid opening area. Postrepair right ventricle (RV) exhibited specific hemodynamic traits, including the loss of ring-shaped vortical structure and the enhanced sensitivity of RV flow to postrepair tricuspid valve morphology. Compared with clover technique, double orifice repair led to higher swirling motions in the RV domain, which could indicate lower risk of mural thrombus formation.


Asunto(s)
Anuloplastia de la Válvula Cardíaca/métodos , Hemodinámica , Modelos Cardiovasculares , Insuficiencia de la Válvula Tricúspide/fisiopatología , Válvula Tricúspide/fisiopatología , Animales , Anuloplastia de la Válvula Cardíaca/efectos adversos , Anuloplastia de la Válvula Cardíaca/instrumentación , Prótesis Valvulares Cardíacas/efectos adversos , Prótesis Valvulares Cardíacas/clasificación , Ventrículos Cardíacos/fisiopatología , Humanos , Modelación Específica para el Paciente , Porcinos , Válvula Tricúspide/cirugía , Insuficiencia de la Válvula Tricúspide/cirugía
10.
Sci Rep ; 9(1): 11504, 2019 08 08.
Artículo en Inglés | MEDLINE | ID: mdl-31395907

RESUMEN

There has been a resurgence of interest in the treatment of severe functional tricuspid regurgitation (FTR) due to the awareness of its poor outcomes and potential percutaneous therapies. Kay bicuspidization has been adapted in percutaneous therapies but its clinical outcome remains uncertain. The present study evaluates the efficacy of Kay repair in a novel ex vivo pulsatile system. Porcine tricuspid valve (TV) (n = 3) was extracted and incorporated into a patient-specific silicon right ventricle (RV) emulating severe FTR, on which Kay repair was subsequently performed. TV area metrics and RV hemodynamic assessment by means of stereo-scopic particle image velocimetry were quantified in both FTR and post-repair conditions. Bicuspidization led to significant increase in cardiac output although the overall increment due to this approach alone was generally small, possibly due to existence of residual TR and the large reduction in TV opening area. Kinetic energy and viscous loss levels were increased post-repair, especially during diastolic filling. Main vortex structures generally maintained post-procedural. However, there was enhanced swirling motion in larger RV domain. Although this might reduce mural-thrombus risk, the relatively more complex vortex phenomenon likely resulted in elevated viscous loss observed and may potentially impact long-term adaptation. The RV hemodynamic alteration after tricuspid repair could be used to predict the success of these future transcatheter solutions.


Asunto(s)
Insuficiencia de la Válvula Tricúspide/cirugía , Válvula Tricúspide/cirugía , Animales , Femenino , Humanos , Masculino , Porcinos
11.
PLoS One ; 14(1): e0210780, 2019.
Artículo en Inglés | MEDLINE | ID: mdl-30699210

RESUMEN

The expanded polytetrafluoroethylene (ePTFE) heart valve can serve as a viable option for prosthetic aortic valve. In this study, an ePTFE bi-leaflet valve design for aortic valve replacement (AVR) is presented, and the performance of the proposed valve was assessed numerically and experimentally. The valve was designed using CAE software. The dynamic behavior of the newly designed bi-leaflet valve under time-varying physiological pressure loading was first investigated by using commercial finite element code. Then, in-vitro tests were performed to validate the simulation and to assess the hemodynamic performance of the proposed design. A tri-leaflet ePTFE valve was tested in-vitro under the same conditions as a reference. The maximum leaflet coaptation area of the bi-leaflet valve during diastole was 216.3 mm2. When fully closed, no leakage gap was observed and the free edges of the molded valve formed S-shaped lines. The maximum Von Mises stress during a full cardiac cycle was 4.20 MPa. The dynamic performance of the bi-leaflet valve was validated by the in-vitro test under physiological aortic pressure pulse. The effective orifice area (EOA), mean pressure gradient, regurgitant volume, leakage volume and energy loss of the proposed valve were 3.14 cm2, 8.74 mmHg, 5.93 ml/beat, 1.55 ml/beat and 98.99 mJ, respectively. This study reports a novel bi-leaflet valve design for AVR. The performance of the proposed valve was numerically and experimentally assessed. Compared with the reference valve, the proposed design exhibited better structural and hemodynamic performances, which improved valve competency. Moreover, the performance of the bi-leaflet design is comparable to commercialized valves available on the market. The results of the present study provide a viable option for the future clinical applications.


Asunto(s)
Válvula Aórtica , Prótesis Valvulares Cardíacas , Diseño de Prótesis , Presión Arterial , Simulación por Computador , Diseño Asistido por Computadora , Circulación Coronaria , Análisis de Elementos Finitos , Hemodinámica , Humanos , Imagenología Tridimensional , Técnicas In Vitro , Modelos Cardiovasculares , Politetrafluoroetileno , Estrés Mecánico
12.
Med Eng Phys ; 54: 1-13, 2018 04.
Artículo en Inglés | MEDLINE | ID: mdl-29454583

RESUMEN

Intra-ventricular flow dynamics has recently emerged as an important evaluation and diagnosis tool in different cardiovascular conditions. The formation of vortex pattern during the cardiac cycle has been suggested to play important epigenetic and energy-modulation roles in cardiac remodelling, adaptations and mal-adaptations. In this new perspective, flow alterations due to different cardiovascular procedures can affect the long-term outcome of those procedures. Especially, repairs and replacements performed on atrioventricular valves are likely to exert direct impact on intra-ventricular flow pattern. In this review, current consensus around the roles of vortex dynamics in cardiac function is discussed. An overview of physiological vortex patterns found in healthy left and right ventricles as well as post-operative ventricular flow phenomenon owing to different atrioventricular valvular procedures are reviewed, followed by the summary of different vortex identification schemes used to characterise intraventricular flow. This paper also emphasises on future research directions towards a comprehensive understanding of intra-cardiac flow and its clinical relevance. The knowledge could encourage more effective pre-operative planning and better outcomes for current clinical practices.


Asunto(s)
Función Atrial , Procedimientos Quirúrgicos Cardíacos , Válvulas Cardíacas/cirugía , Hemodinámica , Periodo Posoperatorio , Función Ventricular , Procedimientos Quirúrgicos Cardíacos/instrumentación , Humanos
13.
Artif Organs ; 42(2): E13-E28, 2018 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-28891078

RESUMEN

The concept of heterotopic implantation of transcatheter tricuspid valve is new and has shown promising results thus far. While the Reynolds shear stress values measured in the vicinity of this valve are relatively low, the values at some time points are higher than the threshold of platelet activation. Hence, in this study, we aim to reduce these values with an innovative stent design. It was shown that the Reynolds shear stress values measured were lower than those of valves made of generic stent design and the maximum Reynolds shear stress values in the vicinity of the valves was very low (∼10 dynes/cm2 ). The results also depicted the interesting flow phenomenon of this non-physiological treatment approach. Thus, this study has shown that bicaval valves could potentially be considered as a minimally invasive option to treat tricuspid regurgitation and valve design improvements could reduce the flow disturbances that were observed.


Asunto(s)
Prótesis Valvulares Cardíacas , Diseño de Prótesis , Insuficiencia de la Válvula Tricúspide/cirugía , Prótesis Valvulares Cardíacas/efectos adversos , Implantación de Prótesis de Válvulas Cardíacas , Hemodinámica , Humanos , Modelos Cardiovasculares , Stents/efectos adversos , Estrés Mecánico , Trombosis/etiología , Válvula Tricúspide/anatomía & histología , Válvula Tricúspide/fisiopatología , Válvula Tricúspide/cirugía , Insuficiencia de la Válvula Tricúspide/fisiopatología
14.
Med Eng Phys ; 50: 1-11, 2017 12.
Artículo en Inglés | MEDLINE | ID: mdl-29102273

RESUMEN

There has not been much progress in the development of transcatheter tricuspid valves to treat tricuspid regurgitation because of the difficulty in anchoring a stented valve onto the complex tricuspid annulus. Hence, the concept of heterotopic implantation of the transcatheter tricuspid valve onto the cavo-atrial junction was proposed. However, to date there has been no detailed in vitro investigation of the hemodynamic performance of this new device. The study utilises both 2-D and 3-D particle image velocimetry (PIV) to interrogate the flow patterns in the vicinity of the extra-cardiac tricuspid valves in an in vitro physiological flow loop, specifically at four measurement locations in the cavo-atrial anatomy. Comparison of the 2-D and 3-D PIV results revealed that accuracy of 2-D PIV would be acceptable at time point and at measurement locations where the velocity was mostly planar with minimal or low out-of-plane flow such as at the outlet of the superior vena cava valve at the point of valve closure. The results also showed that the RSS in the vicinity of the valves were relatively low (∼150 dynes/cm2) with the exception of that in the leakage jet at the upstream of the valve. The leakage in the leaflets could be a result of the use of aortic valve leaflets which was more suited for the higher pressured environment of the left side of the heart. The stent design could also be customised for implantation in the vena cava. In summary, these issues could be eradicated with improvements to the leaflet and stent design which would enhance the haemodynamics of the post-implantation flow performance.


Asunto(s)
Prótesis Valvulares Cardíacas , Hemodinámica , Reología , Humanos , Imagenología Tridimensional , Diseño de Prótesis , Estrés Mecánico , Insuficiencia de la Válvula Tricúspide/terapia
15.
Cardiovasc Eng Technol ; 8(4): 401-418, 2017 12.
Artículo en Inglés | MEDLINE | ID: mdl-28852976

RESUMEN

The increased understanding of right heart diseases has led to more aggressive interventions to manage functional tricuspid regurgitation (FTR). In some cases of FTR, prosthetic valve replacement is typically considered when concomitant organic components or significant geometrical distortions are involved in the pathology of the tricuspid valve. However, little is known of the performance of current devices in the right heart circulation. In this study, a novel in vitro mock circulatory system that incorporated a realistic tricuspid valve apparatus in a patient-specific silicon right ventricle (RV) was designed and fabricated. The system was calibrated to emulate severe FTR, enabling the investigation of RV hemodynamics in pre- and post-implantation of tri-leaflet tissue implant and bi-leaflet mechanical implant. 2D particle imaging velocimetry was performed to visualize flow and quantify relevant hemodynamic parameters. While our results showed all prosthetic implants improved cardiac output, these implants also subjected the RV to increased turbulence level. Our study also revealed that the implants did not create the optimal behavior of fluid transfer in the RV as we expected. Among the implants tested, tissue implant created the most dominant vortices, which persisted throughout diastole; its observed strong negative vortex could lead to increase energy expenditure due to undesired fluid direction. In contrast, both native valve and mechanical implant had both weaker vortex formation as well as more significant vortex dissipation. Interestingly, the vortex dissipation of native valve was associated with streamlined flow pattern that tended towards the pulmonary outlet, while the mechanical implant generated more regions of flow stagnation within the RV. These findings heighten the imperative to improve designs of current heart valves to be used in the right circulation.


Asunto(s)
Implantación de Prótesis de Válvulas Cardíacas/métodos , Ventrículos Cardíacos/fisiopatología , Insuficiencia de la Válvula Tricúspide/cirugía , Función Ventricular/fisiología , Animales , Calibración , Diseño de Equipo , Prótesis Valvulares Cardíacas , Implantación de Prótesis de Válvulas Cardíacas/instrumentación , Hemodinámica , Humanos , Modelos Cardiovasculares , Reología , Resistencia al Corte , Porcinos , Insuficiencia de la Válvula Tricúspide/sangre
16.
Comput Methods Biomech Biomed Engin ; 20(1): 85-93, 2017 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-27328413

RESUMEN

Arterio-venous grafts (AVGs), the second best option as long-term vascular access for hemodialysis, face major issues of stenosis mainly due to development of intimal hyperplasia at the venous anastomosis which is linked to unfavorable hemodynamic conditions. We have investigated computationally the utility of a coupled sequential venous anastomotic design to replace conventional end-to-side (ETS) venous anastomosis, in order to improve the hemodynamic environment and consequently enhance the patency of AVGs. Two complete vascular access models with the conventional and the proposed venous anastomosis configurations were constructed. Three-dimensional, pulsatile blood flow through the models was simulated, and wall shear stress (WSS)-based hemodynamic parameters were calculated and compared between the two models. Simulation results demonstrated that the proposed anastomotic design provides: (i) a more uniform and smooth flow at the ETS anastomosis, without flow impingement and stagnation point on the artery bed and vortex formation in the heel region of the ETS anastomosis; (ii) more uniform distribution of WSS and substantially lower WSS gradients on the venous wall; and (iii) a spare route for the blood flow to the vein, to avoid re-operation in case of stenosis. The distinctive hemodynamic advantages observed in the proposed anastomotic design can enhance the patency of AVGs.


Asunto(s)
Derivación Arteriovenosa Quirúrgica/métodos , Flujo Pulsátil , Diálisis Renal , Arterias/fisiología , Simulación por Computador , Humanos , Hiperplasia/patología , Modelos Biológicos , Estrés Mecánico , Túnica Íntima/patología
17.
Cardiovasc Eng Technol ; 7(3): 254-69, 2016 09.
Artículo en Inglés | MEDLINE | ID: mdl-27357300

RESUMEN

Heterotopic implantation of transcatheter tricuspid valve is a new treatment option for tricuspid regurgitation. Transcatheter tricuspid valves are implanted onto the cavoatrial junction in order to avoid the challenging task of anchoring the valve onto the complex tricuspid valve annulus. However, little is known about optimum extent of oversizing of the valved stent in a vena cava. In this study, we implanted valves of the same diameter onto the larger sized inferior vena cava (IVC) and a smaller sized superior vena cava (SVC). The valve in the IVC was oversized by 10.7% while the valve in the SVC was oversized by 21.6%. Finite element analysis was performed (i) to assess the strain on the nitinol stent during manufacturing and deployment; (ii) the stents were deployed in a patient-specific vena cava model and the intramural stress of the vena cava was calculated computationally. These valves were fabricated and placed in a silicone model of a patient-specific right atrium which was part of a mock circulatory system that emulated the patho-physiological flow rate and pressure of a patient with tricuspid regurgitation. Flow measurements were conducted by particle image velocimetry (PIV). It was found that the maximum crimping strain on the nitinol stent was 6.85% which was lower than the critical threshold of 10%. The maximum stress on the vena cava was located at the spot where the hooks met the wall. The maximum stress on the IVC was 0.5098 MPa while the maximum stress on the SVC was 0.7 MPa. The maximum Reynolds shear stress (mRSS) in the vena cava was found to be higher in the IVC than SVC with the highest mRSS being 1741 dynes/cm(2) found in the region of high flow during the peak flow phase. The overtly oversized valve in the SVC did not cause flow disturbances and exhibited mostly laminar flows. The mRSS at the downstream of the vena cava valve and the middle of the atrium remained at low magnitudes. However, velocity fluctuations were high in the IVC in all the time points measured. In conclusion, oversizing the valve may assist anchorage; yet, careful consideration should be taken in choosing the extent of oversizing as it may lead to adverse effects.


Asunto(s)
Implantación de Prótesis de Válvulas Cardíacas/instrumentación , Hemodinámica/fisiología , Modelos Cardiovasculares , Modelación Específica para el Paciente , Stents , Válvula Tricúspide/fisiología , Fenómenos Biomecánicos , Análisis de Elementos Finitos , Humanos , Masculino , Diseño de Prótesis , Reología , Válvula Tricúspide/cirugía , Insuficiencia de la Válvula Tricúspide/cirugía , Venas Cavas/fisiología
18.
Artif Organs ; 39(9): 803-14, 2015 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-25920812

RESUMEN

Severe tricuspid regurgitation (TR) is life-threatening but is often undertreated. Many patients with severe TR are denied heart valve replacement surgery because their old age or comorbidities predispose them to a higher risk of surgical complications associated with open-heart surgery. With the advent of transcatheter technology, it is now possible to deliver the valve to the desired location without the need for open-heart surgery. However, presently, there is no commercially available transcatheter tricuspid valve. This may be due to the complex tricuspid valve anatomy, which lacks an anchorage zone for the percutaneous valves. In view of this drawback, we have recently developed and tested two percutaneous caval heart valves that are designed to deploy at the vena cava and atrium junction. The hemodynamic characteristics of these valves are tested in a mock circulatory system with patient-specific silicone atrium and vena cava, which emulates the physiological pressure and flow conditions at the right side of the human heart. Particle imaging velocimetry results showed that flow velocity and the associated Reynolds shear stress (RSS) and the turbulent kinetic energy (TKE) downstream of the valves increased after the implantation of the valves. A maximum flow velocity of 0.94 m/s was observed at the region downstream of the percutaneous valve at the superior vena cava (SVC). Maximum RSS value of 2076.1 dynes/cm(2) was observed downstream of the valve at the inferior vena cava during the deceleration phase while maximum TKE measured was 572.6 J/m(3) at the upstream of the valve in the SVC during the peak flow phase. While these values appear high, they are significantly lower than those reported in prosthetic mitral and aortic valves. Hence, caval stented valves can be potentially considered as a minimally invasive option to treat TR.


Asunto(s)
Atrios Cardíacos/cirugía , Implantación de Prótesis de Válvulas Cardíacas , Prótesis Valvulares Cardíacas , Hemodinámica , Procedimientos Quirúrgicos Mínimamente Invasivos , Venas Cavas/cirugía , Función Atrial , Diseño de Equipo , Implantación de Prótesis de Válvulas Cardíacas/instrumentación , Implantación de Prótesis de Válvulas Cardíacas/métodos , Humanos , Masculino , Procedimientos Quirúrgicos Mínimamente Invasivos/instrumentación , Procedimientos Quirúrgicos Mínimamente Invasivos/métodos , Venas Cavas/fisiología
SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA
...