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1.
Ann Vasc Surg ; 98: 155-163, 2024 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-37805169

RESUMO

BACKGROUND: The stent-assisted balloon-induced intimal disruption and relamination (STABILISE) technique for treatment of type B dissection has shown promising clinical results at mid-term. Computational modeling is a way of noninvasively obtaining hemodynamic effects, such as pressure and wall shear stress, leading to a better understanding of potential benefits. Particular areas of interest are (1) the effect of intimal disruption and re-lamination and (2) the effect of the bare metal stent in the visceral aortic segment. METHODS: Single-center prospective case series. Data from 5 consecutive locally performed cases of STABILISE technique were analyzed. Included cases were type B aortic dissection with or without prior de-branching. The STABILISE procedure had to be performed without 30-day major complications. Preoperative and postoperative imaging data for each patient were transferred to the biomedical engineering team. Each case was reconstructed, meshed, and simulated with computational fluid dynamics using patient-specific data (heart rate, blood pressure, height, and weight). Hemodynamic parameters were then extracted from the simulations. RESULTS: In all cases, computational analysis showed for postoperative patients: (1) a drop in pressure difference between lumina and (2) lower wall shear stress effects, compared to their preoperative status. These observations were most pronounced in the visceral aortic segment. CONCLUSIONS: Computational modeling shows favourable changes in the flow dynamics of type B dissection treated using the STABILISE technique. This may suggest protective effects of this technique for long-term aortic healing and cicatrization.


Assuntos
Aneurisma da Aorta Torácica , Dissecção Aórtica , Implante de Prótese Vascular , Humanos , Resultado do Tratamento , Dissecção Aórtica/diagnóstico por imagem , Dissecção Aórtica/cirurgia , Aorta/cirurgia , Stents , Implante de Prótese Vascular/efeitos adversos , Implante de Prótese Vascular/métodos , Hemodinâmica , Aneurisma da Aorta Torácica/diagnóstico por imagem , Aneurisma da Aorta Torácica/cirurgia
2.
J Vasc Surg ; 75(4): 1181-1190.e5, 2022 04.
Artigo em Inglês | MEDLINE | ID: mdl-34742883

RESUMO

BACKGROUND: Improved risk stratification is a key priority for type B aortic dissection (TBAD). Partial false lumen thrombus morphology is an emerging predictor of complications. However, partial thrombosis is poorly defined, and its evaluation in clinical studies has been inconsistent. Thus, we aimed to characterize the hemodynamic pressure in TBAD and determine how the pressure relates to the false lumen thrombus morphology and clinical events. METHODS: The retrospective admission computed tomography angiograms of 69 patients with acute TBAD were used to construct three-dimensional computational models for simulation of cyclical blood flow and calculation of pressure. The patients were categorized by the false lumen thrombus morphology as minimal, extensive, proximal or distal thrombosis. Linear regression analysis was used to compare the luminal pressure difference between the true and false lumen for each morphology group. The effect of morphology classification on the incidence of acute complications within 14 days was studied using logistic regression adjusted for clinical parameters. A survival analysis for adverse aortic events at 1 year was also performed using Cox regression. RESULTS: Of the 69 patients, 44 had experienced acute complications and 45 had had an adverse aortic event at 1 year. The mean ± standard deviation age was 62.6 ± 12.6 years, and 75.4% were men. Compared with the patients with minimal thrombosis, those with proximal thrombosis had a reduced false lumen pressure by 10.1 mm Hg (95% confidence interval [CI], 4.3-15.9 mm Hg; P = .001). The patients who had not experienced an acute complication had had a reduced relative false lumen pressure (-6.35 mm Hg vs -0.62 mm Hg; P = .03). Proximal thrombosis was associated with fewer acute complications (odds ratio, 0.17; 95% CI, 0.04-0.60; P = .01) and 1-year adverse aortic events (hazard ratio, 0.36; 95% CI, 0.16-0.80; P = .01). CONCLUSIONS: We found that proximal false lumen thrombosis was a marker of reduced false lumen pressure. This might explain how proximal false lumen thrombosis appears to be protective of acute complications (eg, refractory hypertension or pain, aortic rupture, visceral or limb malperfusion, acute expansion) and adverse aortic events within the first year.


Assuntos
Aneurisma da Aorta Torácica , Dissecção Aórtica , Ruptura Aórtica , Implante de Prótese Vascular , Procedimentos Endovasculares , Trombose , Idoso , Aorta , Ruptura Aórtica/etiologia , Implante de Prótese Vascular/efeitos adversos , Procedimentos Endovasculares/efeitos adversos , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Trombose/complicações , Trombose/etiologia , Resultado do Tratamento
3.
J Vasc Surg ; 71(5): 1789-1801.e3, 2020 05.
Artigo em Inglês | MEDLINE | ID: mdl-31831314

RESUMO

OBJECTIVE: New tools are urgently needed to help with surgical decision-making in type B aortic dissection (TBAD) that is uncomplicated at the time of initial presentation. This narrative review aims to answer the clinical question, Can computational modeling be used to predict risk in acute and chronic Stanford TBAD? METHODS: The review (PROSPERO 2018 CRD42018104472) focused on risk prediction in TBAD. A comprehensive search of the Ovid MEDLINE database, using terms related to computational modeling and aortic dissection, was conducted to find studies of any form published between 1998 and 2018. Cohort studies, case series, and case reports of adults (older than 18 years) with computed tomography or magnetic resonance imaging diagnosis of TBAD were included. Computational modeling was applied in all selected studies. RESULTS: There were 37 studies about computational modeling of TBAD identified from the search, and the findings were synthesized into a narrative review. Computational modeling can produce numerically calculated values of stresses, pressures, and flow velocities that are difficult to measure in vivo. Hemodynamic parameters-high or low wall shear stress, high pressure gradient between lumens during the cardiac cycle, and high false lumen flow rate-have been linked to the pathogenesis of branch malperfusion and aneurysm formation by numerous studies. Considering the major outcomes of end-organ failure, aortic rupture, and stabilization and remodeling, hypotheses have been generated about inter-relationships of measurable parameters in computational models with observable anatomic and pathologic changes, resulting in specific clinical outcomes. CONCLUSIONS: There is consistency in study findings about computational modeling in TBAD, although a limited number of patients have been analyzed using various techniques. The mechanistic patterns of association found in this narrative review should be investigated in larger cohort prospective studies to further refine our understanding. It highlights the importance of patient-specific computational hemodynamic parameters in clinical decision-making algorithms. The current challenge is to develop and to test a risk assessment method that can be used by clinicians for TBAD.


Assuntos
Dissecção Aórtica/patologia , Dissecção Aórtica/cirurgia , Simulação por Computador , Medição de Risco/métodos , Algoritmos , Humanos
4.
Arterioscler Thromb Vasc Biol ; 39(6): 1125-1136, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-31018660

RESUMO

Objective- Isolated common iliac artery aneurysms (CIAA) are rare. Their prognosis and influence on aortoiliac blood flow and remodeling are unclear. We evaluated the hypotheses that morphology at and distal to the aortic bifurcation, together with the associated hemodynamic changes, influence both the natural history of CIAA and proximal aortic remodeling. Approach and Results- Twenty-five isolated CIAAs (15 intact, 10 ruptured), in 23 patients were reconstructed and analyzed with computational fluid dynamics: all showed abnormal flow. Then we studied a series of 24 hypothetical aortoiliac geometries in silico with varying abdominal aortic deflection and aortic bifurcation angles: key findings were assessed in an independent validation cohort of 162 patients. Wall shear stress in isolated unilateral CIAAs was lower than the contralateral common iliac artery, 0.38±0.33 Pa versus 0.61±0.24 Pa, inversely associated with CIAA diameter ( P<0.001) and morphology (high shear stress in variants distal to a sharp kink). Rupture usually occurred in regions of elevated low and oscillatory shear with a wide aortic bifurcation angle. Abdominal aortas deflected towards the CIAA for most unilateral isolated CIAAs (14/21). In silico, wider bifurcation angles created high focal regions of low and oscillatory shear in the common iliac artery. The associations of unilateral CIAA with aortic deflection and common iliac artery diameter with bifurcation angle were confirmed in the validation cohort. Conclusions- Decreasing wall shear stress is strongly associated with CIAA progression (larger aneurysms and rupture), whereas abnormal blood flow in the CIAA seems to promote proximal aortic remodeling, with adaptive lateral deflection of the abdominal aorta towards the aneurysmal side.


Assuntos
Aneurisma Roto/fisiopatologia , Aorta Abdominal/fisiopatologia , Hemodinâmica , Aneurisma Ilíaco/fisiopatologia , Artéria Ilíaca/fisiopatologia , Remodelação Vascular , Adaptação Fisiológica , Aneurisma Roto/diagnóstico por imagem , Aorta Abdominal/diagnóstico por imagem , Simulação por Computador , Europa (Continente) , Feminino , Humanos , Hidrodinâmica , Aneurisma Ilíaco/diagnóstico por imagem , Artéria Ilíaca/diagnóstico por imagem , Masculino , Modelos Cardiovasculares , Estudos Retrospectivos , Estresse Mecânico
5.
Eur J Vasc Endovasc Surg ; 59(5): 786-793, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-31982309

RESUMO

OBJECTIVE: Isolated common iliac artery aneurysms (CIAAs) are uncommon, and evidence concerning their development, progression, and management is weak. The objective was to describe the morphology and haemodynamics of isolated CIAAs in a retrospective study. METHODS: Initially, a series of 25 isolated CIAAs (15 intact, 10 ruptured) in 23 patients were gathered from multiple centres, reconstructed from computed tomography, and then morphologically classified and analysed with computational fluid dynamics. The morphological classification was applied in a separate, consecutive cohort of 162 patients assessed for elective aorto-iliac intervention, in which 55 patients had intact CIAAs. RESULTS: In the isolated CIAA cohort, three distinct morphologies were identified: complex (involving a bifurcation); fusiform; and kinked (distal to a sharp bend in the CIA), with mean diameters of 90.3, 48.3, and 31.7 mm, and mean time averaged wall shear stresses of 0.16, 0.31, and 0.71 Pa, respectively (both analysis of variance p values < .001). Kinked cases vs. fusiform cases had less thrombus and favourable haemodynamics similar to the non-aneurysmal contralateral common iliac artery (CIA). Ruptured isolated CIAAs were large (mean diameter 87.5 mm, range 55.5-138.0 mm) and predominantly complex. The mean CIA length for aneurysmal arteries was greatest in kinked cases followed by complex and fusiform (100.8 mm, 91.1 mm, and 80.6 mm, respectively). The morphological classification was readily applicable to a separate elective patient cohort. CONCLUSION: A new morphological categorisation of CIAAs is proposed. Potentially this is associated with both haemodynamics and clinical course. Further research is required to determine whether the kinked CIAA is protected haemodynamically from aneurysm progression and to establish the wider applicability of the categorisation presented.


Assuntos
Hemodinâmica , Aneurisma Ilíaco/classificação , Aneurisma Ilíaco/fisiopatologia , Estudos de Coortes , Progressão da Doença , Feminino , Humanos , Processamento de Imagem Assistida por Computador , Masculino , Estudos Retrospectivos
6.
Eur J Vasc Endovasc Surg ; 60(2): 194-200, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32571654

RESUMO

OBJECTIVE: There is controversy about the role of pre-emptive thoracic endovascular aortic repair (TEVAR) in uncomplicated type B aortic dissection (TBAD). The aim was to understand expert opinions and the factors influencing decision making. METHODS: In 2018, surgeons from Australia/New Zealand (ANZ) and Europe (EUR) were contacted to participate in an online survey which comprised questions about preferences for pre-emptive TEVAR, followed by five case scenarios, and two ranking questions for anatomical and technical risk factors respectively. Case 1 was designed to favour TEVAR in a hypertensive patient with partial false lumen thrombosis and large diameter (aortic ≥ 40 mm, false lumen ≥ 22 mm). Case 2 had no risk factors mandating TEVAR, according to current evidence. Cases 3, 4, and 5 were designed to test one risk factor respectively, large entry tear on the inner aortic curvature (≥10 mm), partial false lumen thrombosis, and large diameter alone. RESULTS: There were 75 responses, 42 from EUR and 33 from ANZ. Almost half of surgeons (49.3%) endorsed pre-emptive TEVAR with 82.3% preferring to perform TEVAR in the subacute phase. In Case 1 and 5, 58.3% and 52.8% of surgeons respectively chose TEVAR, the highest rates obtained in the survey. Cases 1 and 5 included large diameters ≥40 mm, which were ranked the highest in importance when surgeons considered anatomical risk factors. Surgeons who recommend pre-emptive TEVAR were more likely to choose TEVAR in both Case 1 (83.3% vs. 33.3%, p < .001, 95% CI 27.6%-65.8%) and Case 5 (69.4% vs. 38.2%, p = .008, 95% CI 8.2%-50.0%). CONCLUSION: In this survey about uncomplicated TBAD, about half of surgeons recommended pre-emptive TEVAR in selected cases. The surgeon's predisposition towards intervention and large diameters appear to be the most influential factors in decision making. These findings underline the uncertainty in today's practice and emphasise the need for better predictive tools.


Assuntos
Aneurisma da Aorta Torácica/cirurgia , Dissecção Aórtica/cirurgia , Implante de Prótese Vascular , Tomada de Decisão Clínica , Procedimentos Endovasculares , Padrões de Prática Médica , Cirurgiões , Dissecção Aórtica/diagnóstico por imagem , Aneurisma da Aorta Torácica/diagnóstico por imagem , Austrália , Prótese Vascular , Implante de Prótese Vascular/efeitos adversos , Implante de Prótese Vascular/instrumentação , Procedimentos Endovasculares/efeitos adversos , Procedimentos Endovasculares/instrumentação , Europa (Continente) , Pesquisas sobre Atenção à Saúde , Nível de Saúde , Disparidades em Assistência à Saúde , Humanos , Nova Zelândia , Seleção de Pacientes , Fatores de Risco , Stents , Resultado do Tratamento
7.
Eur J Vasc Endovasc Surg ; 60(3): 365-373, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32253165

RESUMO

OBJECTIVE: To test whether aneurysm biomechanical ratio (ABR; a dimensionless ratio of wall stress and wall strength) can predict aneurysm related events. METHODS: In a prospective multicentre clinical study of 295 patients with an abdominal aortic aneurysm (AAA; diameter ≥ 40 mm), three dimensional reconstruction and computational biomechanical analyses were used to compute ABR at baseline. Participants were followed for at least two years and the primary end point was the composite of aneurysm rupture or repair. RESULTS: The majority were male (87%), current or former smokers (86%), most (72%) had hypertension (mean ± standard deviation [SD] systolic blood pressure 140 ± 22 mmHg), and mean ± SD baseline diameter was 49.0 ± 6.9 mm. Mean ± SD ABR was 0.49 ± 0.27. Participants were followed up for a mean ± SD of 848 ± 379 days and rupture (n = 13) or repair (n = 102) occurred in 115 (39%) cases. The number of repairs increased across tertiles of ABR: low (n = 24), medium (n = 34), and high ABR (n = 44) (p = .010). Rupture or repair occurred more frequently in those with higher ABR (log rank p = .009) and ABR was independently predictive of this outcome after adjusting for diameter and other clinical risk factors, including sex and smoking (hazard ratio 1.41; 95% confidence interval 1.09-1.83 [p = .010]). CONCLUSION: It has been shown that biomechanical ABR is a strong independent predictor of AAA rupture or repair in a model incorporating known risk factors, including diameter. Determining ABR at baseline could help guide the management of patients with AAA.


Assuntos
Aorta Abdominal/fisiopatologia , Aneurisma da Aorta Abdominal/fisiopatologia , Ruptura Aórtica/etiologia , Hemodinâmica , Modelos Cardiovasculares , Modelagem Computacional Específica para o Paciente , Idoso , Idoso de 80 Anos ou mais , Aorta Abdominal/diagnóstico por imagem , Aorta Abdominal/cirurgia , Aneurisma da Aorta Abdominal/complicações , Aneurisma da Aorta Abdominal/diagnóstico por imagem , Aneurisma da Aorta Abdominal/cirurgia , Ruptura Aórtica/diagnóstico por imagem , Ruptura Aórtica/fisiopatologia , Ruptura Aórtica/cirurgia , Aortografia , Fenômenos Biomecânicos , Angiografia por Tomografia Computadorizada , Progressão da Doença , Feminino , Humanos , Angiografia por Ressonância Magnética , Masculino , Valor Preditivo dos Testes , Prognóstico , Estudos Prospectivos , Medição de Risco , Fatores de Risco , Estresse Mecânico , Fatores de Tempo , Procedimentos Cirúrgicos Vasculares
9.
NPJ Microgravity ; 10(1): 7, 2024 Jan 13.
Artigo em Inglês | MEDLINE | ID: mdl-38218868

RESUMO

We investigated variations in haemodynamics in response to simulated microgravity across a semi-subject-specific three-dimensional (3D) continuous arterial network connecting the heart to the eye using computational fluid dynamics (CFD) simulations. Using this model we simulated pulsatile blood flow in an upright Earth gravity case and a simulated microgravity case. Under simulated microgravity, regional time-averaged wall shear stress (TAWSS) increased and oscillatory shear index (OSI) decreased in upper body arteries, whilst the opposite was observed in the lower body. Between cases, uniform changes in TAWSS and OSI were found in the retina across diameters. This work demonstrates that 3D CFD simulations can be performed across continuously connected networks of small and large arteries. Simulated results exhibited similarities to low dimensional spaceflight simulations and measured data-specifically that blood flow and shear stress decrease towards the lower limbs and increase towards the cerebrovasculature and eyes in response to simulated microgravity, relative to an upright position in Earth gravity.

10.
Biomech Model Mechanobiol ; 23(1): 255-269, 2024 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-37805938

RESUMO

Cerebrovascular haemodynamics are sensitive to multiple physiological stimuli that require synergistic response to maintain adequate perfusion. Understanding haemodynamic changes within cerebral arteries is important to inform how the brain regulates perfusion; however, methods for direct measurement of cerebral haemodynamics in these environments are challenging. The aim of this study was to assess velocity waveform metrics obtained using transcranial Doppler (TCD) with flow-conserving subject-specific three-dimensional (3D) simulations using computational fluid dynamics (CFD). Twelve healthy participants underwent head and neck imaging with 3 T magnetic resonance angiography. Velocity waveforms in the middle cerebral artery were measured with TCD ultrasound, while diameter and velocity were measured using duplex ultrasound in the internal carotid and vertebral arteries to calculate incoming cerebral flow at rest, during hypercapnia and exercise. CFD simulations were developed for each condition, with velocity waveform metrics extracted in the same insonation region as TCD. Exposure to stimuli induced significant changes in cardiorespiratory measures across all participants. Measured absolute TCD velocities were significantly higher than those calculated from CFD (P range < 0.001-0.004), and these data were not correlated across conditions (r range 0.030-0.377, P range 0.227-0.925). However, relative changes in systolic and time-averaged velocity from resting levels exhibited significant positive correlations when the distinct techniques were compared (r range 0.577-0.770, P range 0.003-0.049). Our data indicate that while absolute measures of cerebral velocity differ between TCD and 3D CFD simulation, physiological changes from resting levels in systolic and time-averaged velocity are significantly correlated between techniques.


Assuntos
Artérias Cerebrais , Hidrodinâmica , Humanos , Artérias Cerebrais/diagnóstico por imagem , Ultrassonografia Doppler Transcraniana/métodos , Encéfalo/diagnóstico por imagem , Encéfalo/irrigação sanguínea , Angiografia por Ressonância Magnética/métodos , Velocidade do Fluxo Sanguíneo/fisiologia , Circulação Cerebrovascular/fisiologia
11.
Trends Biotechnol ; 42(5): 612-630, 2024 May.
Artigo em Inglês | MEDLINE | ID: mdl-38238246

RESUMO

3D printing technologies have the potential to revolutionize the manufacture of heart valves through the ability to create bespoke, complex constructs. In light of recent technological advances, we review the progress made towards 3D printing of heart valves, focusing on studies that have utilised these technologies beyond manufacturing patient-specific moulds. We first overview the key requirements of a heart valve to assess functionality. We then present the 3D printing technologies used to engineer heart valves. By referencing International Organisation for Standardisation (ISO) Standard 5840 (Cardiovascular implants - Cardiac valve prostheses), we provide insight into the achieved functionality of these valves. Overall, 3D printing promises to have a significant positive impact on the creation of artificial heart valves and potentially unlock full complex functionality.


Assuntos
Próteses Valvulares Cardíacas , Impressão Tridimensional , Humanos , Valvas Cardíacas , Desenho de Prótese/métodos , Engenharia Tecidual/métodos
12.
Cardiovasc Eng Technol ; 13(6): 816-828, 2022 12.
Artigo em Inglês | MEDLINE | ID: mdl-35419664

RESUMO

PURPOSE: Arterial shear forces may promote the embolization of clotted blood from the surface of thrombi, displacing particles that may occlude vasculature, with increased risk of physiological complications and mortality. Thromboemboli may also collide in vivo to form metastable aggregates that increase vessel occlusion likelihood. METHODS: A micromechanical force (MMF) apparatus was modified for aqueous applications to study clot-liquid interfacial phenomena between clotted porcine blood particles suspended in modified continuous phases. The MMF measurement is based on visual observation of particle-particle separation, where Hooke's Law is applied to calculate separation force. This technique has previously been deployed to study solid-fluid interfacial phenomena in oil and gas pipelines, providing fundamental insight to cohesive and adhesive properties between solids in multiphase flow systems. RESULTS: This manuscript introduces distributed inter-particle separation force properties as a function of governing physio-chemical parameters; pre-load (contact) force, contact time, and bulk phase chemical modification. In each experimental campaign, the hysteresis and distributed force properties were analysed, to derive insight as to the governing mechanism of cohesion between particles. Porcine serum, porcine albumin and pharmaceutical agents (alteplase, tranexamic acid and hydrolysed aspirin) reduced the measurement by an order of magnitude from the baseline measurement-the apparatus provides a platform to study how surface-active chemistries impact the solid-fluid interface. CONCLUSION: These results provide new insight to potential mechanisms of macroscopic thromboembolic aggregation via particles cohering in the vascular system-data that can be directly applied to computational simulations to predict particle fate, better informing the mechanistic developments of embolic occlusion.


Assuntos
Água , Suínos , Animais , Tamanho da Partícula , Água/química
13.
J Vasc Access ; : 11297298221127760, 2022 Oct 24.
Artigo em Inglês | MEDLINE | ID: mdl-36281219

RESUMO

BACKGROUND: Peripheral intravenous catheters (PIVCs) are the most commonly used invasive medical device, yet despite best efforts by end-users, PIVCs experience unacceptably high early failure rates. We aimed to design a new PIVC that reduces the early failure rate of in-dwelling PIVCs and we conducted preliminary tests to assess its efficacy and safety in a porcine model of intravenous access. METHODS: We used computer-aided design and simulation to create a PIVC with a ramped tip geometry, which directs the infused fluid away from the vein wall; we called the design the FloRamp™. We created FloRamp prototypes (test device) and tested them against a market-leading device (BD Insyte™; control device) in a highly-controlled setting with five insertion sites per device in four pigs. We measured resistance to infusion and visual infusion phlebitis (VIP) every 6 h and terminated the experiment at 48 h. Veins were harvested for histology and seven pathological markers were assessed. RESULTS: Computer simulations showed that the optimum FloRamp tip reduced maximum endothelial shear stress by 60%, from 12.7 Pa to 5.1 Pa, compared to a typical PIVC tip and improved the infusion dynamics of saline in the blood stream. In the animal study, we found that 2/5 of the control devices were occluded after 24 h, whereas all test devices remained patent and functional. The FloRamp created less resistance to infusion (0.73 ± 0.81 vs 0.47 ± 0.50, p = 0.06) and lower VIP scores (0.60 ± 0.93 vs 0.31 ± 0.70, p = 0.09) than the control device, although neither findings were significantly different. Histopathology revealed that 5/7 of the assessed markers were lower in veins with the FloRamp. CONCLUSIONS: Herein we report preliminary assessment of a novel PIVC design, which could be advantageous in clinical settings through decreased device occlusion and reduced early failure rates.

15.
Arterioscler Thromb Vasc Biol ; 30(9): 1687-94, 2010 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-20508202

RESUMO

Abdominal aortic aneurysm (AAA) rupture remains a significant cause of death in the developed world. Current treatment approaches rely heavily on the size of the aneurysm to decide on the most appropriate time for clinical intervention and treatment. However, in recent years, several alternative rupture risk indicators have been proposed. This brief review examines some of these new approaches to AAA rupture risk assessment, from both numeric and experimental aspects and also what the future may hold for AAA rupture risk. Although numerically predicted wall stress, finite element analysis rupture index, rupture potential index, severity parameter, and geometric factors, such as asymmetry, have all been developed and show promise in possibly helping to predict AAA rupture risk, validation of these tools remains a significant challenge. Validation of biomechanics-based rupture indicators may be feasible by combining in vitro modeling of realistic AAA analogues with both retrospective and prospective monitoring and modeling of AAA cases. Peak wall stress is arguably the primary result obtained from numeric analyses; however, as the majority of ruptures occur in the posterior and posterior-lateral regions, the role of posterior wall stress has also recently been highlighted as potentially significant. It is also known that wall stress alone is not enough to cause rupture, as wall strength plays an equal role. Therefore, should a biomechanics-based rupture risk be implemented? There have been some significant steps, both numerically and experimentally, toward answering this and other questions relating to AAA rupture risk prediction, yet regardless of the efforts that are under way in several laboratories, the introduction of a numerically predicted rupture risk parameter into the clinicians' decision-making process may still be quite some time away.


Assuntos
Aneurisma da Aorta Abdominal/complicações , Ruptura Aórtica/etiologia , Aneurisma da Aorta Abdominal/diagnóstico , Aneurisma da Aorta Abdominal/fisiopatologia , Ruptura Aórtica/diagnóstico , Ruptura Aórtica/fisiopatologia , Fenômenos Biomecânicos , Simulação por Computador , Progressão da Doença , Análise de Elementos Finitos , Humanos , Modelos Cardiovasculares , Análise Numérica Assistida por Computador , Reprodutibilidade dos Testes , Medição de Risco , Fatores de Risco , Índice de Gravidade de Doença , Estresse Mecânico
16.
Artif Intell Med ; 116: 102072, 2021 06.
Artigo em Inglês | MEDLINE | ID: mdl-34020750

RESUMO

The segmentation and analysis of coronary arteries from intravascular optical coherence tomography (IVOCT) is an important aspect of diagnosing and managing coronary artery disease. Current image processing methods are hindered by the time needed to generate expert-labelled datasets and the potential for bias during the analysis. Therefore, automated, robust, unbiased and timely geometry extraction from IVOCT, using image processing, would be beneficial to clinicians. With clinical application in mind, we aim to develop a model with a small memory footprint that is fast at inference time without sacrificing segmentation quality. Using a large IVOCT dataset of 12,011 expert-labelled images from 22 patients, we construct a new deep learning method based on capsules which automatically produces lumen segmentations. Our dataset contains images with both blood and light artefacts (22.8 %), as well as metallic (23.1 %) and bioresorbable stents (2.5 %). We split the dataset into a training (70 %), validation (20 %) and test (10 %) set and rigorously investigate design variations with respect to upsampling regimes and input selection. We show that our developments lead to a model, DeepCap, that is on par with state-of-the-art machine learning methods in terms of segmentation quality and robustness, while using as little as 12 % of the parameters. This enables DeepCap to have per image inference times up to 70 % faster on GPU and up to 95 % faster on CPU compared to other state-of-the-art models. DeepCap is a robust automated segmentation tool that can aid clinicians to extract unbiased geometrical data from IVOCT.


Assuntos
Doença da Artéria Coronariana , Tomografia de Coerência Óptica , Algoritmos , Cápsulas , Doença da Artéria Coronariana/diagnóstico por imagem , Humanos
17.
Ann Biomed Eng ; 49(9): 2183-2195, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-33646497

RESUMO

The placenta uniquely develops to orchestrate maternal adaptations and support fetal growth and development. The expansion of the feto-placental vascular network, in part, underpins function. However it is unclear how vascular development is synergistically influenced by hemodynamics and how impairment may lead to fetal growth restriction (FGR). Here, we present a robust framework consisting of ex vivo placental casting, imaging and computational fluid dynamics of rat feto-placental networks where we investigate inlet (steady and transient) and outlet (zero-pressure, Murray's Law, asymmetric fractal trees and porous blocks) boundary conditions in a model of growth-restriction. We show that the Murray's Law flow-split boundary condition is not always appropriate and that mean steady-state inlet conditions produce comparable results to transient flow. However, we conclude that transient simulations should be adopted as they provide a larger amount of valuable data, a necessity to bridge the current knowledge gap in placental biomechanics. We also show preliminary data on changes in flow, shear stress, and flow deceleration between control and growth-restricted feto-placental networks. Our proposed framework provides a standardized approach for structural and hemodynamic analysis of feto-placental vasculature and has the potential to enhance our understanding of placental function.


Assuntos
Artérias/fisiologia , Retardo do Crescimento Fetal/fisiopatologia , Placenta/irrigação sanguínea , Animais , Artérias/diagnóstico por imagem , Feminino , Hemodinâmica , Interpretação de Imagem Assistida por Computador , Placenta/diagnóstico por imagem , Circulação Placentária , Gravidez , Ratos Wistar , Microtomografia por Raio-X
18.
Circ Cardiovasc Imaging ; 14(12): 1112-1121, 2021 12.
Artigo em Inglês | MEDLINE | ID: mdl-34875845

RESUMO

BACKGROUND: Low shear stress has been implicated in abdominal aortic aneurysm (AAA) expansion and clinical events. We tested the hypothesis that low shear stress in AAA at baseline is a marker of expansion rate and future aneurysm-related events. METHODS: Patients were imaged with computed tomography angiography at baseline and followed up every 6 months >24 months with ultrasound measurements of maximum diameter. From baseline computed tomography angiography, we reconstructed 3-dimensional models for automated computational fluid dynamics simulations and computed luminal shear stress. The primary composite end point was aneurysm repair and/or rupture, and the secondary end point was aneurysm expansion rate. RESULTS: We included 295 patients with median AAA diameter of 49 mm (interquartile range, 43-54 mm) and median follow-up of 914 (interquartile range, 670-1112) days. There were 114 (39%) aneurysm-related events, with 13 AAA ruptures and 98 repairs (one rupture was repaired). Patients with low shear stress (<0.4 Pa) experienced a higher number of aneurysm-related events (44%) compared with medium (0.4-0.6 Pa; 27%) and high (>0.6 Pa; 29%) shear stress groups (P=0.010). This association was independent of known risk factors (adjusted hazard ratio, 1.72 [95% CI, 1.08-2.73]; P=0.023). Low shear stress was also independently associated with AAA expansion rate (ß=+0.28 mm/y [95% CI, 0.02-0.53]; P=0.037). CONCLUSIONS: We show for the first time that low shear stress (<0.4 Pa) at baseline is associated with both AAA expansion and future aneurysm-related events. Aneurysms within the lowest tertile of shear stress, versus those with higher shear stress, were more likely to rupture or reach thresholds for elective repair. Larger prospective validation trials are needed to confirm these findings and translate them into clinical management.


Assuntos
Aneurisma da Aorta Abdominal/diagnóstico por imagem , Aneurisma da Aorta Abdominal/fisiopatologia , Ruptura Aórtica/diagnóstico por imagem , Angiografia por Tomografia Computadorizada/métodos , Ultrassonografia/métodos , Idoso , Idoso de 80 Anos ou mais , Aorta Abdominal/diagnóstico por imagem , Aorta Abdominal/fisiopatologia , Aneurisma da Aorta Abdominal/complicações , Ruptura Aórtica/etiologia , Ruptura Aórtica/fisiopatologia , Progressão da Doença , Feminino , Seguimentos , Humanos , Masculino , Estresse Mecânico
19.
ANZ J Surg ; 90(12): 2425-2433, 2020 12.
Artigo em Inglês | MEDLINE | ID: mdl-32893461

RESUMO

BACKGROUND: The best management of acute uncomplicated type B aortic dissection is currently a controversial area. Recent advances in endovascular intervention have begun to establish pre-emptive thoracic endovascular aortic repair as a potential strategy. A review about the management for type B aortic dissection has been conducted. METHODS: A narrative review consisting of 157 original articles, meta-analyses and guidelines was conducted. The findings were synthesized and summarized using 70 articles. RESULTS: There are clear guidelines directing surgical management of acute complicated type B aortic dissection. However, the best management of acute uncomplicated disease is more ambiguous, which is especially concerning in a condition which is associated with significant morbidity and mortality. Medical management alone is generally favoured. Endovascular intervention is now being considered by some surgeons, but it can be technically difficult, while exposing the patient to potential surgical risks. CONCLUSIONS: Clinical and anatomical risk factors have been identified to help vascular surgeons make decisions about treatment in acute uncomplicated type B aortic dissection. New endovascular strategies are being developed to reduce surgical risk and address technical challenges. Registry data should be used to support future best management.


Assuntos
Aneurisma da Aorta Torácica , Dissecção Aórtica , Implante de Prótese Vascular , Procedimentos Endovasculares , Doença Aguda , Dissecção Aórtica/diagnóstico por imagem , Dissecção Aórtica/cirurgia , Aneurisma da Aorta Torácica/diagnóstico , Aneurisma da Aorta Torácica/cirurgia , Humanos , Fatores de Risco , Resultado do Tratamento
20.
J Appl Physiol (1985) ; 129(5): 1024-1032, 2020 11 01.
Artigo em Inglês | MEDLINE | ID: mdl-32881618

RESUMO

There is acknowledged variability in the Circle of Willis (CoW) in the general population, yet the structure and function relationship of the cerebrovasculature is poorly understood. We aimed to demonstrate the feasibility of combining high-resolution imaging techniques and computational fluid dynamics (CFD) to describe cerebrovascular structure and function in vivo. We tested our methodology by examining the null hypothesis that monozygotic twins (18-30 yr) would exhibit similar CoW structure and function. Six twin pairs underwent 3T magnetic resonance angiography of the head and neck and B-mode Doppler ultrasound for velocity and diameter recordings in the vertebral and internal carotid arteries under three conditions (rest, hypercapnia, and exercise). Artery diameter, length, tortuosity, and bifurcation angle were assessed in regions of interest of the CoW. We simulated hemodynamics to determine the cardiac-cycle time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), and relative residence time (RRT). We observed low and insignificant intraclass correlations (ICC) between twins in all regions for diameter (ICC range 0.000-0.657, P > 0.05), two of four regions for length (ICC range 0.355-0.368, P > 0.05), all regions for tortuosity (ICC range 0.270-0.505, P > 0.05), and all bifurcation angles (ICC range 0.000-0.547, P > 0.05). Similarly, no significant correlations were apparent for cerebral blood flow or CFD-derived measures of TAWSS, OSI, and RRT, at rest or in response to hypercapnia or exercise. Therefore, differences exist in CoW structure and associated shear stress in response to physiological stimulation. These data suggest that the structure, function, and health of cerebrovascular arteries are not primarily genetically dependent.NEW & NOTEWORTHY There is acknowledged variability in the Circle of Willis in the general population, yet the structure and function relationship of the cerebrovasculature is poorly understood. Using a combination of magnetic resonance imaging, high-resolution Doppler ultrasound, and computational fluid dynamic modeling, we show that monozygotic twins exhibit differences in cerebrovascular structure and function when exposed to physiological stimuli. These data suggest that the morphology, function, and health of cerebrovascular arteries are not primarily genetically determined.


Assuntos
Hidrodinâmica , Gêmeos Monozigóticos , Velocidade do Fluxo Sanguíneo , Circulação Cerebrovascular , Simulação por Computador , Hemodinâmica , Humanos , Modelos Cardiovasculares , Imagem Multimodal
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