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1.
Annu Int Conf IEEE Eng Med Biol Soc ; 2022: 4001-4004, 2022 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-36086215

##### RESUMO

The study aimed to develop a pulmonary circulatory system capable of high-speed 3D reconstruction of valve leaflets to elucidate the local hemodynamic characteristics in the valved conduits with bulging sinuses. Then a simultaneous measurement system for leaflet structure and pressure and flow characteristics was designed to obtain valve leaflet dynamic behaviour with different conduit structures. An image preprocessing method was established to obtain the three leaflets behaviour simultaneously for one sequence with two leaflets images from each pair of three high-speed cameras. Firstly, the multi-digital image correlation analyses were performed, and then the valve leaflet structure was measured under the static condition with fixed opening angles in the water-filled visualization chamber and the pulsatile flow tests simulating paediatric pulmonary flow conditions in the different types of conduit structures; with or without bulging sinuses. The results showed the maximum 3D reconstruction error to be around 0.06 mm. In the steady flow test, the evaluation of opening angles under the different flow rates conditions was achieved. In the pulsatile flow test, each leaflet's opening and closing behaviours were successfully reconstructed simultaneously at the high-frequency recording rate of 960fps. Therefore, the system developed in this study confirms the design evaluation method of an ePTFE valved conduit behaviour with leaflet structures interacting with local fluid dynamics in the vicinity of valves. Clinical Relevance- The system reveals the bulging sinus effects on ePTFE valve leaflet motion by the 3D reconstruction using multi-camera high-speed sequential imaging in vitro.

##### Assuntos
Próteses Valvulares Cardíacas , Politetrafluoretileno , Criança , Hemodinâmica , Humanos , Desenho de Prótese , Fluxo Pulsátil
2.
Med Eng Phys ; 106: 103834, 2022 08.
Artigo em Inglês | MEDLINE | ID: mdl-35926957

##### RESUMO

Arterio-Venous Fistulas (avf) are the most popular form of vascular access used for hemodialysis. However they continue to present complications leading to early and late failure. To understand the reasons for failure, it is necessary to analyze the hemodynamics involved. Wall shear stress (wss) is commonly studied in avfs as it often relates to cardiovascular disease, although there is dispute over whether high or low wss is detrimental to avf patency. The goal of this paper is to investigate velocity flow conditions in a rigid, patient-specific brachio-cephalic avf model in both steady flow (Re = 1817) and patient-specific pulsatile flow (Reav=1817, Remax=2233). Particle Image Velocimetry (piv) measurements were performed at the anastomosis to capture the complex 3D-3C flow present. The results from this study found regions of recirculation and high velocity fluctuations in the distal artery and proximal vein, and flow impingement at the anastomosis toe. Steady and pulsatile flow demonstrated similar flow features, possibly owed to the low pulsatility index. In addition, the recirculation zone did not vary along the waveform. The directional variability was seen to be the highest at the regions of recirculation and flow impingement suggesting regions of high transWSS while the coefficient of variation was greatest at the walls and in areas of flow separation indicating high temporal wall shear stress.

##### Assuntos
Derivação Arteriovenosa Cirúrgica , Fístula , Derivação Arteriovenosa Cirúrgica/métodos , Velocidade do Fluxo Sanguíneo , Hemodinâmica , Humanos , Fluxo Pulsátil , Diálise Renal
3.
Curr Opin Obstet Gynecol ; 34(5): 292-299, 2022 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-35895911

##### Assuntos
Nascimento Prematuro , Artéria Uterina , Cesárea , Feminino , Humanos , Lactente , Recém-Nascido , Valor Preditivo dos Testes , Gravidez , Resultado da Gravidez , Terceiro Trimestre da Gravidez , Fluxo Pulsátil , Ultrassonografia Pré-Natal
4.
Int J Cardiol ; 366: 80-81, 2022 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-35787432
5.
Can J Surg ; 65(4): E407-E416, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35790239

##### RESUMO

BACKGROUND: The benefits of using cadaveric humans in surgical training are well documented, and knowledge of the latest endovascular techniques is essential in the daily practice of vascular surgeons. Our study explores the feasibility of an affordable human cadaveric model with pulsatile and heated antegrade perfusion for reliable and reproducible endovascular or surgical simulation. METHODS: We undertook cannulation of 7 human cadavers embalmed in a saturated salt solution to create a left-to-right central perfusion with a heated solution, from the ascending thoracic aorta to the right atrium. To that end, we used surgically created carotidojugular and femorofemoral arteriovenous fistulas. Biomedical engineers designed a prototype pump for pulsatile circulation. We monitored invasive blood pressure and temperature. We used this model for training for endovascular thoracic aortic procedures and open vascular surgeries. RESULTS: The prototype pump achieved a pulsatile flow rate of 4.7 L/min. Effective cadaveric perfusion was achieved for several hours, not only with an arterioarterial pathway but also with arteriovenous circulation. The arterial pressures and in situ temperatures accurately restored vascular functions for life-like conditions. This new model made it possible to successfully perform thoracic endovascular aortic repair, subclavian artery stenting and simulation of abdominal open vascular trauma management. The saturated salt solution method and a specifically designed pump improved cost competitiveness. CONCLUSION: Endovascular simulation on human cadavers, optimized with the pulsatile and heated perfusion system, can be a dynamic adjunct for surgical training and familiarization with new devices. This reproducible teaching tool could be relevant in all surgery programs.

##### Assuntos
Procedimentos Endovasculares , Cadáver , Humanos , Perfusão/métodos , Fluxo Pulsátil , Stents
6.
Neuroimage ; 258: 119362, 2022 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-35688316

##### RESUMO

Cerebrospinal fluid (CSF) provides physical protection to the central nervous system as well as an essential homeostatic environment for the normal functioning of neurons. Additionally, it has been proposed that the pulsatile movement of CSF may assist in glymphatic clearance of brain metabolic waste products implicated in neurodegeneration. In awake humans, CSF flow dynamics are thought to be driven primarily by cerebral blood volume fluctuations resulting from a number of mechanisms, including a passive vascular response to blood pressure variations associated with cardiac and respiratory cycles. Recent research has shown that mechanisms that rely on the action of vascular smooth muscle cells ("cerebrovascular activity") such as neuronal activity, changes in intravascular CO2, and autonomic activation from the brainstem, may lead to CSF pulsations as well. Nevertheless, the relative contribution of these mechanisms to CSF flow remains unclear. To investigate this further, we developed an MRI approach capable of disentangling and quantifying CSF flow components of different time scales associated with these mechanisms. This approach was evaluated on human control subjects (n = 12) performing intermittent voluntary deep inspirations, by determining peak flow velocities and displaced volumes between these mechanisms in the fourth ventricle. We found that peak flow velocities were similar between the different mechanisms, while displaced volumes per cycle were about a magnitude larger for deep inspirations. CSF flow velocity peaked at around 10.4 s (range 7.1-14.8 s, n = 12) following deep inspiration, consistent with known cerebrovascular activation delays for this autonomic challenge. These findings point to an important role of cerebrovascular activity in the genesis of CSF pulsations. Other regulatory triggers for cerebral blood flow such as autonomic arousal and orthostatic challenges may create major CSF pulsatile movement as well. Future quantitative comparison of these and possibly additional types of CSF pulsations with the proposed approach may help clarify the conditions that affect CSF flow dynamics.

##### Assuntos
Circulação Cerebrovascular , Imageamento por Ressonância Magnética , Encéfalo/fisiologia , Tronco Encefálico , Líquido Cefalorraquidiano/fisiologia , Circulação Cerebrovascular/fisiologia , Humanos , Fluxo Pulsátil/fisiologia
7.
Magn Reson Med ; 88(4): 1643-1658, 2022 10.
Artigo em Inglês | MEDLINE | ID: mdl-35754143

##### RESUMO

PURPOSE: Dual-velocity encoded (dual-venc or DV) 4D flow MRI achieves wide velocity dynamic range and velocity-to-noise ratio (VNR), enabling accurate neurovascular flow characterization. To reduce scan time, we present interleaved dual-venc 4D Flow with independently prescribed, prospectively undersampled spatial resolution of the high-venc (HV) acquisition: Variable Spatial Resolution Dual Venc (VSRDV). METHODS: A prototype VSRDV sequence was developed based on a Cartesian acquisition with eight-point phase encoding, combining PEAK-GRAPPA acceleration with zero-filling in phase and partition directions for HV. The VSRDV approach was optimized by varying z, the zero-filling fraction of HV relative to low-venc, between 0%-80% in vitro (realistic neurovascular model with pulsatile flow) and in vivo (n = 10 volunteers). Antialiasing precision, mean and peak velocity quantification accuracy, and test-retest reproducibility were assessed relative to reference images with equal-resolution HV and low venc (z = 0%). RESULTS: In vitro results for all z demonstrated an antialiasing true positive rate at least 95% for R PEAK - GRAPPA $${R}_{\mathrm{PEAK}-\mathrm{GRAPPA}}$$  = 2 and 5, with no linear relationship to z (p = 0.62 and 0.13, respectively). Bland-Altman analysis for z = 20%, 40%, 60%, or 80% versus z = 0% in vitro and in vivo demonstrated no bias >1% of venc in mean or peak velocity values at any R ZF $${R}_{\mathrm{ZF}}$$ . In vitro mean and peak velocity, and in vivo peak velocity, had limits of agreement within 15%. CONCLUSION: VSRDV allows up to 34.8% scan time reduction compared to PEAK-GRAPPA accelerated DV 4D Flow MRI, enabling large spatial coverage and dynamic range while maintaining VNR and velocity measurement accuracy.

##### Assuntos
Imageamento Tridimensional , Imageamento por Ressonância Magnética , Velocidade do Fluxo Sanguíneo , Humanos , Imageamento Tridimensional/métodos , Imageamento por Ressonância Magnética/métodos , Imagens de Fantasmas , Fluxo Pulsátil , Reprodutibilidade dos Testes
8.
Analyst ; 147(13): 2953-2965, 2022 Jun 27.
Artigo em Inglês | MEDLINE | ID: mdl-35667121

##### RESUMO

The lymphatic vascular function is regulated by pulsatile shear stresses through signaling mediated by intracellular calcium [Ca2+]i. Further, the intracellular calcium dynamics mediates signaling between lymphatic endothelial cells (LECs) and muscle cells (LMCs), including the lymphatic tone and contractility. Although calcium signaling has been characterized on LEC monolayers under uniform or step changes in shear stress, these dynamics have not been revealed in LMCs under physiologically-relevant co-culture conditions with LECs or under pulsatile flow. In this study, a cylindrical organ-on-chip platform of the lymphatic vessel (Lymphangion-Chip) consisting of a lumen formed with axially-aligned LECs co-cultured with transversally wrapped layers of LMCs was exposed to step changes or pulsatile shear stress, as often experienced in vivo physiologically or pathologically. Through real-time analysis of intracellular calcium [Ca2+]i release, the device reveals the pulsatile shear-dependent biological coupling between LECs and LMCs. Upon step shear, both cell types undergo a relatively rapid rise in [Ca2+]i followed by a gradual decay. Importantly, under pulsatile flow, analysis of the calcium signal also reveals a secondary sinusoid within the LECs and LMCs that is very close to the flow frequency. Finally, LMCs directly influence the LEC calcium dynamics both under step changes in shear and under pulsatile flow, demonstrating a coupling of LEC-LMC signaling. In conclusion, the Lymphangion-Chip is able to illustrate that intracellular calcium [Ca2+]i in lymphatic vascular cells is dependent on pulsatile shear rate and therefore, serves as an analytical biomarker of mechanotransduction within LECs and LMCs, and functional consequences.

##### Assuntos
Cálcio , Células Endoteliais , Cálcio/metabolismo , Sinalização do Cálcio , Técnicas de Cocultura , Mecanotransdução Celular , Células Musculares/metabolismo , Fluxo Pulsátil
9.
Fetal Diagn Ther ; 49(4): 196-205, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35671735

##### RESUMO

INTRODUCTION: A controversy exists about the accuracy of the cerebroplacental ratio (CPR) for the prediction of cesarean section for intrapartum fetal compromise (CS-IFC). Our aim was to evaluate whether the interval to delivery modifies the accuracy of CPR either as a single marker or combined with estimated fetal weight centile (EFWc), type of labor onset (TLO), and other clinical variables. METHODS: This was a multicenter retrospective study of 5,193 women with singleton pregnancies who underwent an ultrasound scan at 35+0-41+0 weeks and gave birth within 1 month of examination, at any of the participating hospitals in Spain, UK, and Italy. CS-IFC was diagnosed in case of an abnormal intrapartum fetal heart rate or intrapartum fetal scalp pH <7.20, requiring urgent cesarean section. The diagnostic ability of CPR in multiples of the median (CPR MoM) was evaluated at different intervals to delivery, alone and combined with EFWc, TLO, and other pregnancy data such as maternal age, maternal body mass index, parity, and fetal sex, for the prediction of CS-IFC by means of ROC curves and logistic regression analysis. RESULTS: The predictive ability of CPR MoM for CS-IFC worsened with the interval to delivery. In general, the best prediction was obtained prior to labor and by adding information related to EFWc and TLO (AUC 0.71 [95% CI: 0.64-0.79], 0.73 [95% CI: 0.66-0.80], and 0.75 [95% CI: 0.69-0.81]; p < 0.0001). Addition of more clinical data did not improve prediction. In addition, results did not vary when only cases with spontaneous onset of labor were studied. CONCLUSION: CPR MoM prediction of CS-IFC at the end of pregnancy worsens with the interval to delivery. Accordingly, it should be done in the short term and considering EFWc and TLO.

##### Assuntos
Cesárea , Artérias Umbilicais , Feminino , Humanos , Artéria Cerebral Média/diagnóstico por imagem , Valor Preditivo dos Testes , Gravidez , Resultado da Gravidez , Fluxo Pulsátil/fisiologia , Estudos Retrospectivos , Ultrassonografia Pré-Natal/métodos , Artérias Umbilicais/diagnóstico por imagem
10.
Commun Biol ; 5(1): 582, 2022 06 14.
Artigo em Inglês | MEDLINE | ID: mdl-35701487

##### RESUMO

Theoretical models of retinal hemodynamics showed the modulation of retinal pulsatile patterns (RPPs) by heart rate (HR), yet in-vivo validation and scientific merit of this biological process is lacking. Such evidence is critical for result interpretation, study design, and (patho-)physiological modeling of human biology spanning applications in various medical specialties. In retinal hemodynamic video-recordings, we characterize the morphology of RPPs and assess the impact of modulation by HR or other variables. Principal component analysis isolated two RPPs, i.e., spontaneous venous pulsation (SVP) and optic cup pulsation (OCP). Heart rate modulated SVP and OCP morphology (pFDR < 0.05); age modulated SVP morphology (pFDR < 0.05). In addition, age and HR demonstrated the effect on between-group differences. This knowledge greatly affects future study designs, analyses of between-group differences in RPPs, and biophysical models investigating relationships between RPPs, intracranial, intraocular pressures, and cardiovascular physiology.

##### Assuntos
Disco Óptico , Veia Retiniana , Frequência Cardíaca , Humanos , Pressão Intraocular , Fluxo Pulsátil/fisiologia , Veia Retiniana/fisiologia
11.
J Biomech Eng ; 144(11)2022 11 01.
Artigo em Inglês | MEDLINE | ID: mdl-35643820

##### RESUMO

Atherosclerosis in carotid arteries depends mostly on hemodynamic parameters, and any disturbances in pulsatile flows may alter the hemodynamic parameters extensively. Gas emboli are one such source that can hinder and disturb standard blood flow patterns and potentially lead to occlusions and ischemia. To understand how gas embolism affects carotid artery hemodynamics, numerical simulation of coupled Newtonian two-phase laminar flow with interface tracking are performed in an anatomical image-based geometry with flow conditions closely approximating physiological flows. Bubble behavior and Pulsatile flow field changes are quantified. Significant deviation from flow without gas embolism is observed leading to nonstandard flow distributions. Results show that gas embolism promotes complex spatio-temporal variations in the carotid artery hemodynamics leading to higher time averaged shear stress values and greater regions of high oscillatory shear index, implying higher probability of atherosclerosis incidence. Depending on contact angle, gas emboli were found to be lodged in carotid sinus or exiting the carotid artery, which can potentially cause abnormalities in blood pressures, heart rates, and ischemia in downstream vasculature, respectively.

##### Assuntos
Aterosclerose , Embolia Aérea , Velocidade do Fluxo Sanguíneo , Artérias Carótidas/fisiologia , Simulação por Computador , Hemodinâmica/fisiologia , Humanos , Modelos Cardiovasculares , Fluxo Pulsátil/fisiologia , Estresse Mecânico
12.
Ultrasound Obstet Gynecol ; 60(2): 207-214, 2022 08.
Artigo em Inglês | MEDLINE | ID: mdl-35502146

##### RESUMO

OBJECTIVE: Women with gestational diabetes mellitus (GDM) and/or hypertensive disorders of pregnancy (HDP) are at increased long-term cardiovascular risk. Mild cardiac functional alterations have been detected in women with GDM or HDP in midgestation, prior to clinical onset of the disease, but these functional alterations have not been found to be useful as screening tools. In contrast, increased impedance to peripheral blood flow, measured by echocardiography or ophthalmic artery Doppler, has been shown to provide incremental value to maternal characteristics for the prediction of pre-eclampsia. However, it is unknown whether similar changes can be detected in women at risk of GDM. In this study, we performed detailed cardiovascular phenotyping in a large, unselected population of women in midgestation to identify similarities and differences in cardiovascular adaptation in women who are at risk of GDM and/or HDP. METHODS: This was a prospective observational study in women attending for a routine hospital visit at 19 + 1 to 23 + 3 weeks' gestation. This visit included assessment of flow velocity waveforms from the maternal ophthalmic arteries, echocardiography for assessment of maternal cardiovascular function and measurement of uterine artery pulsatility index and serum placental growth factor (PlGF) for assessment of placental perfusion and function. The measured indices were converted to either multiples of the median (MoM) values or deviation from the median (delta) after adjusting for maternal characteristics and elements of medical history. Biomarker delta or MoM values in the GDM and HDP groups were compared with those in the unaffected group using 95% CI and t-tests. RESULTS: The study population of 5214 pregnancies contained 4429 (84.9%) that were unaffected by GDM or HDP, 509 (9.8%) complicated by GDM without HDP, 41 (0.8%) with GDM and HDP, and 235 (4.5%) with HDP without GDM. In HDP cases, with or without GDM, there was evidence of impaired placentation, with a decrease in PlGF, and increased impedance to flow in the peripheral circulation, suggested by an increase in ophthalmic artery peak systolic velocity (PSV) ratio, peripheral vascular resistance assessed on echocardiography and mean arterial pressure. In the GDM group without HDP, there was no evidence of altered placental perfusion or function and ophthalmic artery PSV ratio was not significantly different from that in the unaffected group; peripheral vascular resistance and mean arterial pressure were increased but to a lesser degree than in the HDP group. In the HDP group, there was an increase in global longitudinal systolic strain and slight increase in isovolumic relaxation time, while in the GDM group, there was an increase in mitral valve E/e', myocardial performance index and global longitudinal systolic strain. CONCLUSIONS: In midgestation, women who subsequently develop HDP or GDM have a mild subclinical reduction in left ventricular function. In HDP cases, with or without GDM, there is evidence of impaired placentation and all biomarkers of impedance to peripheral blood flow are consistently increased. In contrast, in the GDM group without HDP, biomarkers of placental function are normal and those of impedance to peripheral blood flow are either marginally increased or not significantly different from those in normal pregnancies. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.

##### Assuntos
Diabetes Gestacional , Hipertensão Induzida pela Gravidez , Pré-Eclâmpsia , Biomarcadores , Diabetes Gestacional/diagnóstico , Feminino , Idade Gestacional , Humanos , Hipertensão Induzida pela Gravidez/diagnóstico por imagem , Fenótipo , Placenta , Fator de Crescimento Placentário , Pré-Eclâmpsia/diagnóstico , Gravidez , Fluxo Pulsátil/fisiologia , Artéria Uterina
13.
PLoS One ; 17(5): e0262372, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35550626

##### RESUMO

BACKGROUND: The flow of physiologic fluids through organs and organs systems is an integral component of their function. The complex fluid dynamics in many organ systems are still not completely understood, and in-vivo measurements of flow rates and pressure provide a testament to the complexity of each flow system. Variability in in-vivo measurements and the lack of control over flow characteristics leave a lot to be desired for testing and evaluation of current modes of treatments as well as future innovations. In-vitro models are particularly ideal for studying neurological conditions such as hydrocephalus due to their complex pathophysiology and interactions with therapeutic measures. The following aims to present the reciprocating positive displacement pump, capable of inducing pulsating flow of a defined volume at a controlled beat rate and amplitude. While the other fluidic applications of the pump are currently under investigation, this study was focused on simulating the pulsating cerebrospinal fluid production across profiles with varying parameters. METHODS: Pumps were manufactured using 3D printed and injection molded parts. The pumps were powered by an Arduino-based board and proprietary software that controls the linear motion of the pumps to achieve the specified output rate at the desired pulsation rate and amplitude. A range of 0.01 [Formula: see text] to 0.7 [Formula: see text] was tested to evaluate the versatility of the pumps. The accuracy and precision of the pumps' output were evaluated by obtaining a total of 150 one-minute weight measurements of degassed deionized water per output rate across 15 pump channels. In addition, nine experiments were performed to evaluate the pumps' control over pulsation rate and amplitude. RESULTS: Volumetric analysis of a total of 1200 readings determined that the pumps achieved the target output volume rate with a mean absolute error of -0.001034283 [Formula: see text] across the specified domain. It was also determined that the pumps can maintain pulsatile flow at a user-specified beat rate and amplitude. CONCLUSION: The validation of this reciprocating positive displacement pump system allows for the future validation of novel designs to components used to treat hydrocephalus and other physiologic models involving pulsatile flow. Based on the promising results of these experiments at simulating pulsatile CSF flow, a benchtop model of human CSF production and distribution could be achieved through the incorporation of a chamber system and a compliance component.

##### Assuntos
Hidrocefalia , Hidrodinâmica , Humanos , Fluxo Pulsátil
14.
Int J Numer Method Biomed Eng ; 38(8): e3630, 2022 08.
Artigo em Inglês | MEDLINE | ID: mdl-35593678

##### RESUMO

The purpose of this paper is to demonstrate the importance of a compliant wall approach in modeling of non-Newtonian and non-physiological blood flows. A case study of a stenosed and symptomatic carotid bifurcation was considered to show the influence of the wall-resilience assumption on the flow parameters obtained with numerical simulations. Patient-specific data concerning the geometry and flow conditions were collected and used to carry out two-way coupled fluid structure interaction simulations of the pulsatile blood flow through carotid artery. The wall compliance was considered separately as related to the wall-elasticity and as associated with the reaction of the loose connective tissue surrounding the carotid bifurcation. The obtained hemodynamic parameters were compared to those which were found in rigid-wall simulations. The difference between the results obtained for rigid-wall and compliant-wall approaches for the peak-systolic area-averaged wall shear stress achieved 35%, whereas the difference between the time-averaged local vorticity and shear strain reached, respectively, 42% and 43%. The influence of the highly resilient wall on the monitored hemodynamic parameters was significant even if time-averaged values are compared, which suggests that these metrics are considerably overestimated if the wall compliance is not considered. Moreover, the findings show that the mechanical response of the loose connective tissue cannot be neglected in blood flow simulations. Additionally, this study indicates that stiffening of the arterial wall due to atherosclerosis significantly rises hemodynamic parameters. This explains the therapeutic benefits of surgical removal of plaque lesions formed in the carotid bifurcation (endarterectomy).

##### Assuntos
Artérias Carótidas , Modelos Cardiovasculares , Velocidade do Fluxo Sanguíneo , Artérias Carótidas/fisiologia , Tecido Conjuntivo , Constrição Patológica , Hemodinâmica/fisiologia , Humanos , Fluxo Pulsátil , Estresse Mecânico
15.
Am J Physiol Regul Integr Comp Physiol ; 323(1): R59-R67, 2022 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-35503236

##### RESUMO

Teaching traditionally asserts that the arterial pressure pulse is dampened across the capillary bed to the extent that pulsatility is nonexistent in the venous circulation of the lower limbs. Herein, we present evidence of transmission of arterial pulsations across the capillary network into perforator veins in the lower limbs of healthy, heat-stressed humans. Perforator veins are connections from the superficial veins that drain into the deep veins. When assessed using ultrasound at rest, they infrequently demonstrate flow, and a pulsatile flow waveform is not described. We investigated perforator vein pulsatility in 10 young, healthy volunteers who underwent passive heating by +2°C core body temperature via a hot-water-perfused suit, and 5 who also underwent active heating by +2°C via low-intensity cycling while wearing the hot-water-perfused suit. At +0.5°C increments in temperature, blood velocity in an ankle perforator vein was measured using duplex ultrasound. In all perforators with heating, sustained flow was demonstrated, with a pulsatile waveform that was synchronous with the cardiac cycle. The maximum velocity was 30 ± 13 cm/s with passive heating and approximately half with active heating (P = 0.04). The small veins of the skin at the ankle also demonstrated increased perfusion with pulsatility, seen with low-velocity microvascular imaging technology. We consider explanations for this pulsatility and conclude that it is propagated from the arterial inflow through the skin microcirculation as a result of increased dilatation and flow volume and that this is a normal response to increased skin blood flow.

##### Assuntos
Perna (Membro) , Extremidade Inferior , Velocidade do Fluxo Sanguíneo/fisiologia , Humanos , Perna (Membro)/irrigação sanguínea , Fluxo Pulsátil , Água
16.
Artif Organs ; 46(9): 1833-1846, 2022 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-35524699

##### RESUMO

BACKGROUND: Mechanical heart valves (MHV) and its fluid dynamics inside a pulsatile pediatric ventricular assist device (PVAD) can be associated with blood degradation. In this article, flow structures are analyzed and compared by an experimental investigation on the effect of bileaflet MHV positioned at varying angles in the inlet port orifice of a PVAD. METHODS: Time-resolved particle image velocimetry was applied to characterize the internal flow of the device. St Jude Medical bileaftlet valves were used on the inlet orifice and positioned at 0°, 15°, 30°, 45°, 60°, and 90° in relation to the centerline of the device. Three planes with bidimensional velocity magnitude fields were considered in the analysis with visualization of diastolic jets, device wall washing patterns and flow circulation during emptying or systole of the pump. Also, the washing vortex area, and vertical velocity probabilities of regurgitant flows in the inlet valve were evaluated. RESULTS: The results show that a variation in the angle of the MHV at the inlet port produced distinct velocities, fluid structures, and regurgitant flow probabilities within the device. MHV positioned at an angle of 0° generated the strongest inlet jet, larger vortex area during filling, more prominent outgoing flow, and less regurgitation compared to the angles studied. The presence of unfavorable fluid structures, such as small vortices, and/or sudden flow structure interruption, and/or regurgitation, were identified at 45° and 90° angles. CONCLUSIONS: The 0° inlet angle had better outcomes than other angles due to its consistency in the multiple parameters analyzed.

##### Assuntos
Próteses Valvulares Cardíacas , Coração Auxiliar , Baías , Velocidade do Fluxo Sanguíneo , Criança , Humanos , Modelos Cardiovasculares , Desenho de Prótese , Fluxo Pulsátil
17.
ASAIO J ; 68(7): 925-931, 2022 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-35544445

##### RESUMO

Durable continuous-flow left ventricular assist devices (cfLVADs) demonstrate superior survival, cardiac functional status, and overall quality of life compared to medical therapy alone in advanced heart failure. Previous studies have not considered the impact arterial compliance may have on pump performance or developed arterial pressure. This study assessed the impact of alterations in arterial compliance, preload, and afterload on continuous-flow pump function and measured hemodynamics using an in-vitro pulsatile mock circulatory loop. Decreased arterial compliance was associated with a significant increase in arterial pressure pulsatility which was not evident in the flow pulsatility, as displayed in pump flow waveforms. There were marked changes in the pump flow waveforms due to the significant alteration in the aortoventricular gradient during diastole according to the changes in compliance. This study demonstrates that changes in systemic blood pressure, afterload, and left ventricular contractility each significantly affects the flow waveform. The association of hypertension with lower aortic compliance results in markedly decreased diastolic flow rates which may be important in contributing to a greater risk of adverse events under cfLVAD support.

##### Assuntos
Insuficiência Cardíaca , Coração Auxiliar , Insuficiência Cardíaca/cirurgia , Ventrículos do Coração , Coração Auxiliar/efeitos adversos , Hemodinâmica , Humanos , Modelos Cardiovasculares , Fluxo Pulsátil/fisiologia , Qualidade de Vida , Função Ventricular Esquerda/fisiologia
18.
Ultrasound Obstet Gynecol ; 60(2): 185-191, 2022 08.
Artigo em Inglês | MEDLINE | ID: mdl-35441764

##### RESUMO

OBJECTIVES: Preterm birth (PTB) is a major public health problem worldwide. It can occur spontaneously or be medically indicated for obstetric complications, such as pre-eclampsia (PE) or fetal growth restriction. The main objective of this study was to investigate whether there is a shared uteroplacental etiology in the first trimester of pregnancy across PTB subtypes. METHODS: This was a retrospective cohort study of singleton pregnancies that underwent screening for preterm PE as part of their routine first-trimester ultrasound assessment at a tertiary center in London, UK, between March 2018 and December 2020. Screening for preterm PE was performed using the Fetal Medicine Foundation algorithm, which includes maternal factors, mean arterial pressure (MAP), uterine artery pulsatility index (UtA-PI) and pregnancy-associated plasma protein-A (PAPP-A). Women with a risk of ≥ 1 in 50 for preterm PE were classified as high risk and offered prophylactic aspirin (150 mg once a day) and serial ultrasound assessments. The following delivery outcomes were evaluated: PTB < 37 weeks, iatrogenic PTB (iPTB) and spontaneous PTB (sPTB). Logistic regression analyses were performed to assess the association of PTB, iPTB and sPTB with an increased risk of preterm PE. A model for prediction of PTB < 37 weeks and < 33 weeks was developed and its performance was compared with that of an existing model in the literature. RESULTS: A total of 11 437 women were included in the study, of whom 475 (4.2%) had PTB. Of these, 308 (64.8%) were sPTB and 167 (35.2%) were iPTB. Patients with PTB had a higher body mass index, were more likely to be of black or Asian ethnicity, be smokers, have pregestational hypertension or diabetes, or have a history of previous PTB. They also had higher MAP (87.7 vs 86.0 mmHg, P < 0.0001), higher UtA-PI multiples of the median (MoM) (0.99 vs 0.92, P < 0.0001) and lower PAPP-A MoM (0.89 vs 1.08, P < 0.0001) compared to women with a term birth. In women at high risk of PE, the odds ratio for iPTB was 6.0 (95% CI, 4.29-8.43; P < 0.0001) and that for sPTB was 2.0 (95% CI, 1.46-2.86; P < 0.0001). A prediction model for PTB < 37 weeks and < 33 weeks, developed based on this cohort, included previous PTB, black ethnicity, chronic hypertension, diabetes mellitus, PAPP-A MoM and UtA-PI MoM. The performance of the model was similar to that of an existing first-trimester prediction model for PTB < 33 weeks (area under the curve, 0.704 (95% CI, 0.653-0.754) vs 0.694 (95% CI, 0.643-0.746)). CONCLUSIONS: Increased first-trimester risk for uteroplacental dysfunction was associated with both iPTB and sPTB, implying a shared etiological pathway. The same factors used to predict PE risk show acceptable discrimination to predict PTB at < 33 weeks. Women at high risk of uteroplacental dysfunction may warrant additional monitoring and management for an increased risk of sPTB. © 2022 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

##### Assuntos
Hipertensão , Pré-Eclâmpsia , Nascimento Prematuro , Biomarcadores , Feminino , Humanos , Recém-Nascido , Fator de Crescimento Placentário , Gravidez , Primeiro Trimestre da Gravidez , Proteína Plasmática A Associada à Gravidez/metabolismo , Nascimento Prematuro/etiologia , Fluxo Pulsátil , Estudos Retrospectivos , Artéria Uterina/diagnóstico por imagem
19.
Ultrasound Obstet Gynecol ; 60(2): 200-206, 2022 08.
Artigo em Inglês | MEDLINE | ID: mdl-35468236

##### RESUMO

OBJECTIVE: To assess whether pregnancy-associated plasma protein-A (PAPP-A) alters or provides equivalent screening performance as placental growth factor (PlGF) when screening for preterm pre-eclampsia (PE) at 11-13 weeks of gestation. METHODS: This was a secondary analysis of a non-intervention screening study of 6546 singleton pregnancies that were screened prospectively for preterm PE in the first trimester between December 2016 and June 2018. Patient-specific risks for preterm PE were estimated by maternal history, mean arterial pressure (MAP), uterine artery pulsatility index (UtA-PI), PlGF and PAPP-A. A competing-risks model with biomarkers expressed as multiples of the median was used. All women and clinicians were blinded to the risk for preterm PE. The performance of screening for preterm PE using PlGF vs PAPP-A vs both PAPP-A and PlGF was assessed by comparing areas under the receiver-operating-characteristics (AUC) curves. McNemar's test was used to compare detection rate at a fixed false-positive rate (FPR) of 10%. RESULTS: PlGF and PAPP-A were measured in 6546 women, of whom 37 developed preterm PE. The AUC and detection rate at 10% FPR using PlGF in combination with maternal history, MAP and UtA-PI were 0.854 and 59.46%, respectively. The respective values were 0.813 and 51.35% when replacing PlGF with PAPP-A and 0.855 and 59.46% when using both PAPP-A and PlGF. Statistically non-significant differences were noted in AUC when replacing PlGF with PAPP-A (ΔAUC, 0.04; P = 0.095) and when using both PAPP-A and PlGF (ΔAUC, 0.002; P = 0.423). However, on an individual case basis, screening using PlGF in conjunction with maternal history, MAP and UtA-PI identified three (8.1%) additional pregnancies that developed preterm PE and that were not identified when replacing PlGF with PAPP-A. Screening using PAPP-A in addition to maternal history and other biomarkers did not identify any additional pregnancies. CONCLUSION: On an individual case basis, adoption of a screening strategy that uses PAPP-A instead of PlGF results in reduced detection of preterm PE, consistent with previous literature. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.

##### Assuntos
Pré-Eclâmpsia , Proteína Plasmática A Associada à Gravidez , Biomarcadores , Feminino , Humanos , Recém-Nascido , Fator de Crescimento Placentário , Gravidez , Primeiro Trimestre da Gravidez , Fluxo Pulsátil , Artéria Uterina/diagnóstico por imagem
20.
Ultrasound Obstet Gynecol ; 60(1): 52-58, 2022 07.
Artigo em Inglês | MEDLINE | ID: mdl-35441758

##### RESUMO

OBJECTIVES: First, to explore hemodynamic differences between pregnancies delivering a small-for-gestational-age (SGA) neonate in the absence of hypertensive disorders and those that develop pre-eclampsia (PE) or gestational hypertension (GH), by comparing the ophthalmic artery peak systolic velocity (PSV) ratio and first (PSV1) and second (PSV2) PSV at 19-23 weeks' gestation, and second, to compare these pregnancies for markers of placental perfusion and function. METHODS: This was a prospective observational study in women attending for a routine hospital visit at 19 + 1 to 23 + 3 weeks' gestation. This visit included recording of maternal demographic characteristics and medical history, ultrasound examination for assessment of fetal anatomy and growth, and measurement of maternal ophthalmic artery PSV ratio, PSV1, PSV2, mean arterial pressure (MAP), uterine artery pulsatility index (UtA-PI) and serum placental growth factor (PlGF). The values of PSV ratio, PSV1, PSV2, MAP, UtA-PI and PlGF were converted to multiples of the median (MoM) or deltas. Mean MoMs or deltas of these biomarkers in the SGA, PE and GH groups were compared with those in the unaffected group. The definition of SGA was birth weight below the 10th percentile in the absence of PE or GH. RESULTS: The study population of 5214 pregnancies contained 4375 (83.9%) that were unaffected by SGA, PE or GH, 563 (10.8%) complicated by SGA, 157 (3.0%) with PE and 119 (2.3%) with GH. There were three main findings of the study. First, in the SGA, PE and GH groups, compared with unaffected pregnancies, the PSV ratio delta, PSV2 MoM, MAP MoM and UtA-PI MoM were increased and PlGF MoM was decreased; however, the magnitude of most changes was smaller in the SGA group than in PE and GH groups. Second, in the PE and GH groups, but not in the SGA group, PSV1 MoM was increased. Third, in general, in the pathological pregnancies, the magnitude of deviation of biomarkers from unaffected pregnancies was greater for those delivering at < 37 than at ≥ 37 weeks' gestation. CONCLUSION: In mid-gestation, pregnancies that subsequently develop hypertensive disorders and those delivering a SGA neonate, compared with unaffected pregnancies, have abnormal uteroplacental measurements and increased maternal ophthalmic artery PSV ratio. These data suggest similar pathophysiology in the two conditions, with evidence of placental dysfunction and increased peripheral vascular resistance, but the magnitude of abnormalities is greater in hypertensive disorders. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.

##### Assuntos
Hipertensão Induzida pela Gravidez , Pré-Eclâmpsia , Biomarcadores , Feminino , Retardo do Crescimento Fetal/diagnóstico por imagem , Idade Gestacional , Humanos , Hipertensão Induzida pela Gravidez/diagnóstico por imagem , Recém-Nascido , Artéria Oftálmica/diagnóstico por imagem , Placenta/diagnóstico por imagem , Fator de Crescimento Placentário , Pré-Eclâmpsia/diagnóstico , Gravidez , Terceiro Trimestre da Gravidez , Fluxo Pulsátil/fisiologia , Ultrassonografia Pré-Natal , Artéria Uterina/diagnóstico por imagem , Receptor 1 de Fatores de Crescimento do Endotélio Vascular
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