Hemodynamic Model Research Articles

An Image-Based Framework for the Analysis of the Murine Microvasculature: From Tissue Clarification to Computational Hemodynamics

The blood–brain barrier is a unique physiological structure acting as a filter for every molecule reaching the brain through the blood. For this reason, an effective pharmacologic treatment supplied to a patient by systemic circulation should first be capable of crossing the barrier. Standard cell cultures (or those based on microfluidic devices) and animal models have been used to study the human blood–brain barrier. Unfortunately, these tools have not yet reached a state of maturity because of the complexity of this physiological process aggravated by a high heterogeneity that is not easily recapitulated experimentally. In fact, the extensive research that has been performed and the preclinical trials carried out provided sometimes contradictory results, and the functionality of the barrier function is still not fully understood. In this study, we have combined tissue clarification, advanced microscopy and image analysis to develop a one-dimensional computational model of the microvasculature hemodynamics inside the mouse brain. This model can provide information about the flow regime, the pressure field and the wall shear stress among other fluid dynamics variables inside the barrier. Although it is a simplified model of the cerebral microvasculature, it allows a first insight on into the blood–brain barrier hemodynamics and offers several additional possibilities to systematically study the barrier microcirculatory processes.

Hall and ion slip effects on hybrid nanoparticles (Au-GO/blood) flow through a catheterized stenosed artery with thrombosis

Present paper deals with the effect of Hall and ion slips on MHD blood flow through a catheterized multi-stenosis artery with thrombosis. Blood is considered a base fluid, and the suspension of Au and GO nanoparticles are used to form the hybrid nano-blood suspension. The hemodynamic mathematical model is presented to mimic the blood flow inside the artery subjected to Joule heating, thermal radiation, Hall and ion slip effects. The effect of the shape of nanoparticles and the variable viscosity depending upon hematocrit is taken into account. The mathematical model is presented in a curvilinear coordinate system, and a mild stenosis assumption is used to get the closed-form solutions. The reduced governing equations are solved using the Crank Nicholson scheme with “MATLAB.” The effect of various pertinent parameters on flow patterns are illustrated graphically. It is observed that increasing the Hall and ion slips parameter causes the increment in the fluid velocity due to an enhancement in the cyclotron frequency of the particles. The hybrid nanoparticles Au-GO/blood has a higher temperature profile than pure blood and unitary nanoparticles, as the thermal conductivity increases with an increase in nanoparticle concentration. Scientists and clinical researchers may find the present study useful in understanding the various illness’s conditions, including cancers, infections, and the removal of blood clots. Furthermore, current research may be helpful in the biomedical area, such as magnetic resonance angiography (MRA), which creates an image of an artery to identify any abnormalities in the artery. The current findings are consistent with recent findings in earlier blood flow research studies.

Validation of a cerebral hemodynamic model with personalized calibration in patients with aneurysmal subarachnoid hemorrhage.

This study aims to validate a numerical model developed for assessing personalized circle of Willis (CoW) hemodynamics under pathological conditions. Based on 66 computed tomography angiography images, investigations were obtained from 43 acute aneurysmal subarachnoid hemorrhage (aSAH) patients from a local neurovascular center. The mean flow velocity of each artery in the CoW measured using transcranial Doppler (TCD) and simulated by the numerical model was obtained for comparison. The intraclass correlation coefficient (ICC) over all cerebral arteries for TCD and the numerical model was 0.88 (N = 561; 95% CI 0.84-0.90). In a subgroup of patients who had developed delayed cerebral ischemia (DCI), the ICC had decreased to 0.72 but remained constant with respect to changes in blood pressure, Fisher grade, and location of ruptured aneurysm. Our numerical model showed good agreement with TCD in assessing the flow velocity in the CoW of patients with aSAH. In conclusion, the proposed model can satisfactorily reproduce the cerebral hemodynamics under aSAH conditions by personalizing the numerical model with TCD measurements. Clinical trial registration: [http://www.trialregister.nl/], identifier [NL8114].

In-silico cardiovascular hemodynamic model to simulate the effect of physical exercise

Coronary heart disease (CHD) is a leading cause of death in developing countries. Lifestyle disorders are one of the precursors of CHD. Exercise-based cardiac health rehabilitation is often prescribed as a secondary prevention strategy to reduce the impact of CHD. To monitor the exercise’s impact on the cardiac parameters, a simulation platform is required to predict the cardiovascular parameters of an individual during exercise. So, in this paper, our objective is to model an in-silico cardiac platform to simulate the exercise effect on the cardiac parameters relevant to cardiac rehabilitation. The proposed framework encompasses a novel cardiovascular hemodynamic model for simulating an individual’s exercise condition using an ECG signal and the metabolic equivalent of task (MET) value approximated from a wearable device. The Neuromodulation parameters such as heart rate and cardiac compliances are estimated from the morphology of the ECG signal. The exercise modulated systemic resistances for the coupled hemodynamic model are assessed based on the MET values of the activity levels to meet additional blood demand during exercises. Effects of exercise on cardiac parameters are simulated on two open-source datasets for healthy subjects, namely Troika and Kaggle, and several hemodynamic parameters are evaluated. The model simulated blood pressure (BP) shows a correlation coefficient of 0.99 (for systolic BP) and 0.95 (for diastolic BP) with Kaggle data BP. The effect of exercise on a diseased heart is demonstrated through a case of silent ischemia. The proposed simulation platform is intended to be used for cardiac rehabilitation monitoring aid for both healthy and patients suffering from heart diseases, providing a cardiac care continuum.

Personalized computational estimation of relative change in coronary blood flow after percutaneous coronary intervention in short-term and long-term perspectives

Abstract Coronary artery disease is the leading cause of mortality worldwide, accounting for 12.8% of all deaths. Although the clinical benefits of treating stenosis with percutaneous coronary intervention (PCI) have been extensively demonstrated, residual myocardial ischemia remains in about 30–50% of patients even after a formally successful PCI. We apply previously developed and validated 1D model of haemodynamics, which distributes terminal hydraulic resistance based on the diameters of the parent vessels and Murray’s law by a recursive algorithm. In our new model the terminal resistance is decreased according to a transmural perfusion ratio increase. In contrast to our previous work we calculate the transmural perfusion ratio for personally defined zones. Thus, peripheral hydraulic resistance of myocardial perfusion is personalized based on patient data, whichwere extracted from computed tomography perfusion images. The model serves as a computational tool for simulating pre- to post-PCI changes in coronary haemodynamics of four patients. We simulate fractional flow reserve (FFR), coronary flow reserve (CFR), instantaneous wave-free ratio (iFR), average flow in selected arteries in hyperemic and rest conditions before PCI and after PCI immediately after the surgery (in a short-term) and in a long-term (several months) perspectives. We conclude that high FFR and iFR values in short-term and long-term perspectives are not necessary correlate with CFR improvement and long-term blood flow recovery in coronary arteries.

Current and Future Applications of Computational Fluid Dynamics in Coronary Artery Disease.

Hemodynamics interacts with the cellular components of human vessels, influencing function and healthy status. Locally acting hemodynamic forces have been associated-by a steadily increasing amount of scientific evidence-with nucleation and evolution of atherosclerotic plaques in several vascular regions, resulting in the formulation of the 'hemodynamic risk hypothesis' of the atherogenesis. At the level of coronary arteries, however, the complexity of both anatomy and physiology made the study of this vascular region particularly difficult for researchers. Developments in computational fluid dynamics (CFD) have recently allowed an accurate modelling of the intracoronary hemodynamics, thus offering physicians a unique tool for the investigation of this crucial human system by means of advanced mathematical simulations. The present review of CFD applications in coronary artery disease was set to concisely offer the medical reader the theoretical foundations of quantitative intravascular hemodynamics-reasoned schematically in the text in its basic (i.e., pressure and velocity) and derived quantities (e.g., fractional flow reserve, wall shear stress and helicity)-along with its current implications in clinical research. Moreover, attention was paid in classifying computational modelling derived from invasive and non-invasive imaging modalities with unbiased remarks on the advantages and limitations of each procedure. Finally, an extensive description-aided by explanatory figures and cross references to recent clinical findings-was presented on the role of near-wall hemodynamics, in terms of shear stress, and of intravascular flow complexity, in terms of helical flow.

Sensitivity Analysis of a Mathematical Model Simulating the Post-Hepatectomy Hemodynamics Response

Recently a lumped-parameter model of the cardiovascular system was proposed to simulate the hemodynamics response to partial hepatectomy and evaluate the risk of portal hypertension (PHT) due to this surgery. Model parameters are tuned based on each patient data. This work focuses on a global sensitivity analysis (SA) study of such model to better understand the main drivers of the clinical outputs of interest. The analysis suggests which parameters should be considered patient-specific and which can be assumed constant without losing in accuracy in the predictions. While performing the SA, model outputs need to be constrained to physiological ranges. An innovative approach exploits the features of the polynomial chaos expansion method to reduce the overall computational cost. The computed results give new insights on how to improve the calibration of some model parameters. Moreover the final parameter distributions enable the creation of a virtual population available for future works. Although this work is focused on partial hepatectomy, the pipeline can be applied to other cardiovascular hemodynamics models to gain insights for patient-specific parameterization and to define a physiologically relevant virtual population.

Hemodynamic analysis of a curved artery based on microcirculation boundary.

Microcirculation plays a key role in regulating blood flow but is not considered in previous research of hemodynamics. A curved artery model is established to study its hemodynamic characteristics based on microcirculation boundary. The hemodynamic model of a curved artery is constructed and simulated by computational fluid dynamics. The curved artery model is simulated by fluid-structure interaction. At the same time, a porous medium is used to simulate microcirculation as the outlet boundary. The distribution characteristics of the blood flow velocity, the pressure and the wall shear stress in different sections at different time of the cardiac cycle are obtained. The results show that the velocities in curved arteries decrease and the pressures gradually increase. The blood flow velocity waveform and value are affected and they are sensitive to the microcirculation boundary. However, the pressure value is only affected by the microcirculation function. This work is useful for researchers to deeply understand the hemodynamic characteristics of curved arteries. There is important clinical significance to analyze the pathogenesis of cardiovascular disease considering microcirculation function and its coupling effect.

On the Effects of Boundary Conditions in One-Dimensional Models of Hemodynamics

The paper is devoted to the theoretical analysis of the effects of boundary conditions on the solutions of the system of one-dimensional (1D) hemodynamics. The integral inequalities, which realize the energy inequalities for the solutions of initial-boundary-value problems, are obtained. It is demonstrated that the unphysical unbounded solutions can take place for the case of bounded functions from boundary conditions. For the periodic boundary conditions, the integral estimation illustrates the correct behavior of the solution. For this case of boundary conditions, the effective Fourier method for the analytical solution is proposed. The analytical solutions, obtained by this approach, can be used for the comparison of different 1D blood-flow models. The results obtained in the paper allow for an the alternatively view of the stated boundary conditions and can explain some problems, which can arise in numerical simulations. They expand the possibilities of the application of analytical methods in the field of blood-flow simulation. The results can be useful for the specialists on blood-flow modeling.

Reducing Geometric Uncertainty in Computational Hemodynamics by Deep Learning-Assisted Parallel-Chain MCMC.

Computational hemodynamic modeling has been widely used in cardiovascular research and healthcare. However, the reliability of model predictions is largely dependent on the uncertainties of modeling parameters and boundary conditions, which should be carefully quantified and further reduced with available measurements. In this work, we focus on propagating and reducing the uncertainty of vascular geometries within a Bayesian framework. A novel deep learning (DL)-assisted parallel Markov chain Monte Carlo (MCMC) method is presented to enable efficient Bayesian posterior sampling and geometric uncertainty reduction. A DL model is built to approximate the geometry-to-hemodynamic map, which is trained actively using online data collected from parallel MCMC chains and utilized for early rejection of unlikely proposals to facilitate convergence with less expensive full-order model evaluations. Numerical studies on two-dimensional aortic flows are conducted to demonstrate the effectiveness and merit of the proposed method.

Numerical Model for Cerebrovascular Hemodynamics with Indocyanine Green Fluorescence Videoangiography.

The use of indocyanine green videoangiography (ICG-VA) to assess blood flow in the brain during cerebrovascular surgery has been increasing. Clinical studies on ICG-VA have predominantly focused on qualitative analysis. However, quantitative analysis numerical modelling for time profiling enables a more accurate evaluation of blood flow kinetics. In this study, we established a multiple exponential modified Gaussian (multi-EMG) model for quantitative ICG-VA to understand accurately the status of cerebral hemodynamics. We obtained clinical data of cerebral blood flow acquired the quantitative analysis ICG-VA during cerebrovascular surgery. Varied asymmetric peak functions were compared to find the most matching function form with clinical data by using a nonlinear regression algorithm. To verify the result of the nonlinear regression, the mode function was applied to various types of data. The proposed multi-EMG model is well fitted to the clinical data. Because the primary parameters-growth and decay rates, and peak center and heights-of the model are characteristics of model function, they provide accurate reference values for assessing cerebral hemodynamics in various conditions. In addition, the primary parameters can be estimated on the curves with partially missed data. The accuracy of the model estimation was verified by a repeated curve fitting method using manipulation of missing data. The multi-EMG model can possibly serve as a universal model for cerebral hemodynamics in a comparison with other asymmetric peak functions. According to the results, the model can be helpful for clinical research assessment of cerebrovascular hemodynamics in a clinical setting.

Patient-Specific Image-Based Computational Fluid Dynamics Analysis of Abdominal Aorta and Branches.

The complicated abdominal aorta and its branches are a portion of the circulatory system prone to developing atherosclerotic plaque and aneurysms. These disorders are closely connected to the changing blood flow environment that the area’s complicated architecture produces (between celiac artery and iliac artery bifurcation); this phenomenon is widespread at arterial bifurcations. Based on computed tomography angiography (CTA) scans, this current work offers a numerical analysis of a patient-specific reconstruction of the abdominal aorta and its branches to identify and emphasize the most likely areas to develop atherosclerosis. The simulations were run following the heart cycle and under physiological settings. The wall shear stress (WSS), velocity field, and streamlines were examined. According to the findings, complex flow is primarily present at the location of arterial bifurcations, where abnormal flow patterns create recirculation zones with low and fluctuating WSS (<0.5 Pa), which are known to affect endothelial homeostasis and cause adverse vessel remodeling. The study provides a patient-specific hemodynamic analysis model, which couples in vivo CT imaging with in silico simulation under physiological circumstances. The study offers quantitative data on the range fluctuations of important hemodynamic parameters, such as WSS and recirculation region expansion, which are directly linked to the onset and progression of atherosclerosis. The findings could also help drug targeting at this vascular level by understanding blood flow patterns in the abdominal aorta and its branches.

Fabricating a multi-component microfluidic system for exercise-induced endothelial cell mechanobiology guided by hemodynamic similarity

Generating precise in vivo arterial endothelial hemodynamic microenvironments using microfluidics is essential for exploring endothelial mechanobiology. However, a hemodynamic principle guiding the fabrication of microfluidic systems is still lacking. We propose a hemodynamic similarity principle for quickly obtaining the input impedance of the microfluidic system in vitro derived from that of the arterial system in vivo to precisely generate the desired endothelial hemodynamic microenvironments. First, based on the equivalent of blood pressure (BP) and wall shear stress (WSS) waveforms, we establish a hemodynamic similarity principle to efficiently map the input impedance in vivo to that in vitro, after which the multi-component microfluidic system is designed and fabricated using a lumped parameter hemodynamic model. Second, numerical simulation and experimental studies are carried out to validate the performance of the designed microfluidic system. Finally, the intracellular Ca2+ responses after exposure to different intensities of exercise-induced BP and WSS waveforms are measured to improve the reliability of EC mechanobiological studies using the designed microfluidic system. Overall, the proposed hemodynamic similarity principle can guide the fabrication of a multi-component microfluidic system for endothelial cell mechanobiology.

A predictive hemodynamic model based on risk factors for ruptured mirror aneurysms.

ObjectivesTo identify hemodynamic risk factors for intracranial aneurysm rupture and establish a predictive model to aid evaluation.MethodsWe analyzed the hemodynamic parameters of 91 pairs of ruptured mirror aneurysms. A conditional univariate analysis was used for the continuous variables. A conditional multivariate logistic regression analysis was performed to identify the independent risk factors. Differences where p < 0.05 were statistically significant. A predictive model was established based on independent risk factors. Odds ratios (ORs) were used to score points. The validation cohort consisted of 189 aneurysms. Receiver operating characteristic curves were generated to determine the cutoff values and area under the curves (AUCs) of the predictive model and independent risk factors.ResultsThe conditional multivariate logistic analysis showed that the low shear area (LSA) (OR = 70.322, p = 0.044, CI = 1.112–4,445.256), mean combined hemodynamic parameter (CHP) (>0.087) (OR = 3.171, p = 0.034, CI = 1.089–9.236), and wall shear stress gradient (WSSG) ratio (>893.180) (OR = 5.740, p = 0.003, CI = 1.950–16.898) were independent risk factors. A prediction model was established: 23*LSA + 1*CHP mean (>0.087: yes = 1, no = 0) + 2 * WSSG ratio (>893.180: yes = 1, no = 0). The AUC values of the predictive model, LSA, mean CHP (>0.087), and WSSG ratio (>893.180) were 0.748, 0.700, 0.654, and 0.703, respectively. The predictive model and LSA cutoff values were 1.283 and 0.016, respectively. In the validation cohort, the predictive model, LSA, CHP (>0.087), and WSSG ratio (>893.180) were 0.736, 0.702, 0.689, and 0.706, respectively.ConclusionsLSA, CHP (>0.087), and WSSG ratio (>893.180) were independent risk factors for aneurysm rupture. Our predictive model could aid practical evaluation.

Data-driven computational models of ventricular-arterial hemodynamics in pediatric pulmonary arterial hypertension.

Pulmonary arterial hypertension (PAH) is a complex disease involving increased resistance in the pulmonary arteries and subsequent right ventricular (RV) remodeling. Ventricular-arterial interactions are fundamental to PAH pathophysiology but are rarely captured in computational models. It is important to identify metrics that capture and quantify these interactions to inform our understanding of this disease as well as potentially facilitate patient stratification. Towards this end, we developed and calibrated two multi-scale high-resolution closed-loop computational models using open-source software: a high-resolution arterial model implemented using CRIMSON, and a high-resolution ventricular model implemented using FEniCS. Models were constructed with clinical data including non-invasive imaging and invasive hemodynamic measurements from a cohort of pediatric PAH patients. A contribution of this work is the discussion of inconsistencies in anatomical and hemodynamic data routinely acquired in PAH patients. We proposed and implemented strategies to mitigate these inconsistencies, and subsequently use this data to inform and calibrate computational models of the ventricles and large arteries. Computational models based on adjusted clinical data were calibrated until the simulated results for the high-resolution arterial models matched within 10% of adjusted data consisting of pressure and flow, whereas the high-resolution ventricular models were calibrated until simulation results matched adjusted data of volume and pressure waveforms within 10%. A statistical analysis was performed to correlate numerous data-derived and model-derived metrics with clinically assessed disease severity. Several model-derived metrics were strongly correlated with clinically assessed disease severity, suggesting that computational models may aid in assessing PAH severity.

Assessment of fetal circulation and mechanisms of heart adaptation during umbilical cord compression: An experimental model in fetal sheep

Perinatal asphyxia is a serious health issue with long-term neurologic morbidities. Cerebral lesions are induced by low cardiac output which occurs often during labour without reliable predictive factors. To assess hemodynamic changes during umbilical cord (UC) compression in fetal sheep. Experimental study on chronically instrumented sheep fetuses (surgery at 131 days of gestation, term = 141 days). Under general anesthesia, a hysterotomy is performed. An aortic catheter is inserted via the axillary artery for blood sampling, and a 6 Fr. Sheath is introduced to the left ventricle (LV) through the right carotid artery under pressures and echocardiographic control. Then a 5 Fr. Transonic PV loop catheter (EMKA Technologies, France) is inserted through the sheath into the LV, and the sheath is withdrawn towards the aorta to allow permanent measurement of the aortic pressure. A 16 mm inflatable occlusion device is placed around the UC (OC16, California, USA). Series of complete occlusion of the UC are done with progressive increasing duration to simulate labour. LV pressures and volumes are registered continuously. Pressure-volume loops and blood samples are analyzed before during and after the occlusions. During the first experimentations, short occlusions did not induce significant modifications. Longer occlusions induced progressive systolic and diastolic disorders which appeared before the metabolic acidosis ( Fig. 1 ). Knowledge of foetal heart adaptation could be interesting to prevent neurologic lesions. This hemodynamic model could also be applied in other situations such as congenital diaphragmatic hernia, pulmonary hypertension or aortic coartation.

Early Diagnosis of Intracranial Internal Carotid Artery Stenosis Using Extracranial Hemodynamic Indices from Carotid Doppler Ultrasound.

Atherosclerotic intracranial internal carotid artery stenosis (IICAS) is a leading cause of strokes. Due to the limitations of major cerebral imaging techniques, the early diagnosis of IICAS remains challenging. Clinical studies have revealed that arterial stenosis may have complicated effects on the blood flow’s velocity from a distance. Therefore, based on a patient-specific one-dimensional hemodynamic model, we quantitatively investigated the effects of IICAS on extracranial internal carotid artery (ICA) flow velocity waveforms to identify sensitive hemodynamic indices for IICAS diagnoses. Classical hemodynamic indices, including the peak systolic velocity (PSV), end-diastolic velocity (EDV), and resistive index (RI), were calculated on the basis of simulations with and without IICAS. In addition, the first harmonic ratio (FHR), which is defined as the ratio between the first harmonic amplitude and the sum of the amplitudes of the 1st–20th order harmonics, was proposed to evaluate flow waveform patterns. To investigate the diagnostic performance of the indices, we included 52 patients with mild-to-moderate IICAS (<70%) in a case–control study and considered 24 patients without stenosis as controls. The simulation analyses revealed that the existence of IICAS dramatically increased the FHR and decreased the PSV and EDV in the same patient. Statistical analyses showed that the average PSV, EDV, and RI were lower in the stenosis group than in the control group; however, there were no significant differences (p > 0.05) between the two groups, except for the PSV of the right ICA (p = 0.011). The FHR was significantly higher in the stenosis group than in the control group (p < 0.001), with superior diagnostic performance. Taken together, the FHR is a promising index for the early diagnosis of IICAS using carotid Doppler ultrasound methods.

An Arterial Compliance Sensor for Cuffless Blood Pressure Estimation Based on Piezoelectric and Optical Signals.

Objective: Blood pressure (BP) data can influence therapeutic decisions for some patients, while non-invasive devices that continuously monitor BP can provide patients with a more comprehensive BP assessment. Therefore, this study proposes a multi-sensor-based small cuffless BP monitoring device that integrates a piezoelectric sensor array and an optical sensor, which can monitor the patient’s physiological signals from the radial artery. Method: Based on the Moens–Korteweg (MK) equation of the hemodynamic model, pulse wave velocity (PWV) can be correlated with arterial compliance and BP can be estimated. Therefore, the novel method proposed in this study involves using a piezoelectric sensor array to measure the PWV and an optical sensor to measure the photoplethysmography (PPG) intensity ratio (PIR) signal to estimate the participant’s arterial parameters. The parameters measured by multiple sensors were combined to estimate BP based on the P–β model derived from the MK equation. Result: We recruited 20 participants for the BP monitoring experiment to compare the performance of the BP estimation method with the regression model and the P–β model method with arterial compliance. We then compared the estimated BP with a reference device for validation. The results are presented as the error mean ± standard deviation (SD). Based on the regression model method, systolic blood pressure (SBP) was 0.32 ± 5.94, diastolic blood pressure (DBP) was 2.17 ± 6.22, and mean arterial pressure (MAP) was 1.55 ± 5.83. The results of the P–β model method were as follows: SBP was 0.75 ± 3.9, DBP was 1.1 ± 3.12, and MAP was 0.49 ± 2.82. Conclusion: According to the results of our proposed small cuffless BP monitoring device, both methods of estimating BP conform to ANSI/AAMI/ISO 81060-2:20181_5.2.4.1.2 criterion 1 and 2, and using arterial parameters to calibrate the MK equation model can improve BP estimate accuracy. In the future, our proposed device can provide patients with a convenient and comfortable BP monitoring solution. Since the device is small, it can be used in a public place without attracting other people’s attention, thereby effectively improving the patient’s right to privacy, and increasing their willingness to use it.

Doppler evaluation of hepatic hemodynamics after living donor liver transplantation in infants.

Objective: The aim of this study was to explore the hemodynamic changes of hepatic artery and portal vein detected by Doppler ultrasound (DU) in infants who underwent living donor liver transplantation (LDLT). Methods: The data of 41 infant patients (22 Males, 19 Females, median age of 5 months) were collected in the Children’s Hospital affiliated to the Chongqing Medical University from May 2018 to December 2019. The patients underwent left lateral segment LDLT (LLS -LDLT) because of biliary atresia (BA). Hemodynamic parameters, including the peak systolic velocity (PSV), resistivity index (RI) of the hepatic artery (HA), portal vein velocity (PVV), and portal vein flow (PVF) were recorded from Doppler ultrasound on the day before the operation, and on the 1st, the 7th, the 14th and the 30th day after LDLT procedures. The changes of PSVHA, RIHA, PVV and PVF before and on the 1st day after transplantation were analyzed by paired t-test. The comparison of the data between different postoperative time points were assessed by ANOVA. Results: Compared with the parameters measured before LDLT, PSVHA, and RIHA decreased, and PVV and PVF increased significantly (p < 0.001) on the 1st day after LLS-LDLT. As for PSV, there was no significant difference between the 7th day and the 1st day after transplantation (POD7 VS POD1, p = 0.167) while there was a substantial difference between the 14th, 30th and 1st day after LT (POD14 vs. POD1, p = 0.003) (POD30 vs. POD1, p < 0.001). And there was a significant difference between the 14th, 30th, and 7th days after LT (POD14 vs. POD7, p = 0.014) (POD30 vs. POD7, p < 0.001). There was no significant difference between 30th and 14th after transplantation (POD30 vs. POD14, p = 0.092). As for RIHA and PVV, the decrease was slow within the first month after the operation, and there was no significant difference at different times. Conclusion: We have identified major hepatic flow changes that occurred in 41 infants who underwent LLS -LDLT due to BA. The data could be used for future studies of LDLT in infants including hemodynamic modeling, liver regeneration and clinical management.

Framework for patient-specific simulation of hemodynamics in heart failure with counterpulsation support.

Despite being responsible for half of heart failure-related hospitalizations, heart failure with preserved ejection fraction (HFpEF) has limited evidence-based treatment options. Currently, a substantial clinical issue is that the disease etiology is very heterogenous with no patient-specific treatment options. Modeling can provide a framework for evaluating alternative treatment strategies. Counterpulsation strategies have the capacity to improve left ventricular diastolic filling by reducing systolic blood pressure and augmenting the diastolic pressure that drives coronary perfusion. Here, we propose a framework for testing the effectiveness of a soft robotic extra-aortic counterpulsation strategy using a patient-specific closed-loop hemodynamic lumped parameter model of a patient with HFpEF. The soft robotic device prototype was characterized experimentally in a physiologically pressurized (50–150 mmHg) soft silicone vessel and modeled as a combination of a pressure source and a capacitance. The patient-specific model was created using open-source software and validated against hemodynamics obtained by imaging of a patient (male, 87 years, HR = 60 bpm) with HFpEF. The impact of actuation timing on the flows and pressures as well as systolic function was analyzed. Good agreement between the patient-specific model and patient data was achieved with relative errors below 5% in all categories except for the diastolic aortic root pressure and the end systolic volume. The most effective reduction in systolic pressure compared to baseline (147 vs. 141 mmHg) was achieved when actuating 350 ms before systole. In this case, flow splits were preserved, and cardiac output was increased (5.17 vs. 5.34 L/min), resulting in increased blood flow to the coronaries (0.15 vs. 0.16 L/min). Both arterial elastance (0.77 vs. 0.74 mmHg/mL) and stroke work (11.8 vs. 10.6 kJ) were decreased compared to baseline, however left atrial pressure increased (11.2 vs. 11.5 mmHg). A higher actuation pressure is associated with higher systolic pressure reduction and slightly higher coronary flow. The soft robotic device prototype achieves reduced systolic pressure, reduced stroke work, slightly increased coronary perfusion, but increased left atrial pressures in HFpEF patients. In future work, the framework could include additional physiological mechanisms, a larger patient cohort with HFpEF, and testing against clinically used devices.