Peripheral artery disease (P.A.D.) is a significant health issue in developed countries. Stenosis of an artery produces substantial changes in blood flow and, consecutively, in its hemodynamics. By simulating the stenosis (obstruction) - arterial environment, valuable insights are obtained. Various methodologies are used to simulate an arterial flow distribution. In this study, a 0D model using a printed circuit board (P.C.B.) is proposed. The model mimics a medium-sized single artery stenosis. Various degrees of stenosis are simulated. Results show that the P.C.B. model accurately predicts the hemodynamic changes produced by stenosis of a medium-sized artery. Also, the model is sensitive to the arterial wall stats. In conclusion, the P.C.B. design is a viable method for hemodynamic simula-tions. Moreover, to enhance the precision and intricacy of the simulation, the complexity and design of the P.C.B. must be augmented. Additionally, alongside subsequent computational fluid dynamics (C.F.D.) studies, the model will extract significant insights into the vascular dynamics of arterial stenosis

Arterial ageing is thought to cause a diastolic-to-systolic shift in the return time (RT) of backward waves to central arteries. However, current methods of estimating RT—inflection point, zero crossing, and foot methods—depend on a single waveform feature and produce systolic RT throughout life. We propose a novel centroid method that accounts for the entire backward pressure waveform and develop a ground truth RT (GTRT), which can be used in computational models to test the accuracy of RT estimation methods. Linear wave tracking was implemented in a one-dimensional systemic arterial tree model and GTRT was calculated as the amplitude-weighted mean RT of backward waves at the ascending aorta. Using a virtual cohort of 1200 patients, the centroid RT was closest to GTRT compared to the zero crossing, inflection point, and foot methods; mean differences (limits of agreement) were -8 (-47,30), vs -42 (-136,52), -78 (-305,149), and -197 (-379,-15) ms, respectively. The sensitivity of the methods to changes in RT was also assessed in ten sheep. A balloon catheter in the descending thoracic aorta was used to generate a backward-running pulse that arrived at the ascending aorta at different times during diastole or systole, allowing the “bulk” RT of the backward-running wave ensemble to be manipulated. Only the centroid method was sensitive to both diastolic and systolic changes in RT. We conclude that the accuracy and robustness of the centroid method make it most suitable for evaluating the diastolic-to-systolic shift in RT of backward waves with ageing.

It is yet unknown how the formation of aneurysm inside the human body occurs. Thus, the understanding and analysis of the Coanda effect will result in a better overview of the overall fluid mechanics that develops inside such a structure, leading not only to better treatment plans, but also to diminished postoperative risks. This paper presents how the fluid behaves in this situation, and takes into consideration how this physical phenomenon influences the hemodynamics inside numerous anatomical regions, located in the central nervous system, where aneurysms usually develop. Analyzing the three main areas in which cerebral aneurysms form the Coanda effect can potentially lead to the rupture of the aneurysm, by changing the blood flow trajectory, it should be taken into consideration when choosing a treatment plan, especially in postoperative care. In addition, there are other factors that can influence the evolution of an aneurysm such as shape, size, localization and the patient’s health condition. Understanding and analysis of the Coanda effect will result in a better overview of the overall fluid mechanics that develops inside such a structure, leading not only to better treatment plans, but also to diminished postoperative risks.

Background: The clinical impact of vasopressin in hemorrhagic shock remains largely unknown. Objective: This systematic review and meta-analysis was designed to investigate the effects of vasopressin receptor agonists during the resuscitation of hemorrhagic shock. Methods: A systematic search of PubMed (MEDLINE), Scopus, and PubMed Central was conducted for relevant articles. Preclinical (animal) and clinical studies were included. The primary objective was to investigate the correlation of vasopressin receptor agonist use with mortality and various hemodynamic parameters. Results: Data extraction was possible in 13 animal studies and two clinical studies. Differences in risk of mortality between patients who received a vasopressin receptor agonist were not statistically significant when compared to those who were not treated with such agents [RR (95%CI): 1.17 (0.67, 2.08); p=0.562; I2 = 50%]. The available data were insufficient to conduct a meta-analysis assessing the effect of vasopressin receptor agonists on hemodynamics. Drawing safe conclusions from animal studies was challenging, due to significant heterogeneity in terms of species and dosage of vasopressin receptor agonists across studies. Conclusions: Differences in risk of mortality between patients who received a vasopressin receptor agonist were not statistically significant when compared to those who were not treated with such agents after hemorrhagic shock.

During the Renaissance, Leonardo Da Vinci was the first person to successfully detail the anatomy of the aortic root and its adjacent structures. Ever since, novel insights into morphology, function and their interplay have accumulated resulting in advanced knowledge on complex functional characteristics of the aortic valve (AV) and root. This shifted the vision from the AV as being a static structure towards that of a dynamic interconnected apparatus within the aortic root as a functional unit, exhibiting a complex interplay with adjacent structures via both humoral and mechanical stimuli. This paradigm shift has stimulated surgical treatment strategies of valvular disease that seek to recapitulate healthy AV function, whereby AV disease can no longer be seen as an isolated morphological pathology which needs to be replaced. As prostheses still cannot reproduce the complexity of human nature, treatment of diseased AVs, whether stenotic or insufficient, has tremendously evolved with a similar shift towards treatments options that are more hemodynamically centered such as the Ross procedure and valve-conserving surgery. Native AV and root components allow for an efficient Venturi effect over the valve to allow for optimal opening during the cardiac cycle, while also alleviating the left ventricle. Next to that, several receptors are present on native AV leaflets, enabling messenger pathways based on their interaction with blood and other shear-stress related stimuli. Many of these physiological and hemodynamical processes are under acknowledged but may hold important clues for innovative treatment strategies, or as potential novel targets for therapeutic agents that halt or reverse the process of valve degeneration. A structured overview of these pathways and their implications for cardiothoracic surgeons and cardiologists is lacking. As such, we provide an overview on embryology, hemodynamics, and messenger pathways of the healthy and diseased AV and its implications for clinical practice, by relating this knowledge to current treatment alternatives and clinical decision-making.

Diseases such as diabetes are known to reduce blood circulation in the capillaries and arterioles; however, there are no devices that can easily measure this on a daily basis. In this study, we developed a tool for measuring finger photoplethysmograms using green-light and near-infrared LEDs. We then conducted photoplethysmography on 25 diabetic inpatients/outpatients as well as 21 adult males and females who had not been diagnosed or treated for diabetes, hypertension, or cardiovascular disease (as a control group). In the diabetic patients, the inverse full width at half maximum velocity plethysmogram (1/FWHMVPG) tended to be smaller compared to the control group, and the delay in the green light a-wave peak relative to the near-infrared light a-wave peak in the acceleration plethysmogram was significantly increased. The results suggest that peripheral hemodynamics could be easily estimated at home using a photoplethysmography device mounted on a ring-wearable device.

Introduction: CT perfusion (CTP) is an alternative tool to assess cerebral hemodynamics in brain trauma. As traumatic acute subdural hematomas (ASH) are severe lesions commonly associated with poor outcome, we aimed to evaluate the brain hemodynamics in this population. Methods: Five patients admitted at the emergency department sustaining traumatic acute subdural hematoma were evaluated. Preoperative CTP was performed immediately after nonenhanced head CT scan. Postoperative CTP was performed in four patients. The outcome was assessed 6 months after surgery using the extended Glasgow Outcome Scale. Results: 4 male and 1 female were evaluated. Mean age was 46y (SD: 8.1). Mean preoperative midline brain shift was 10.1 mm (SD: 1.8). The main mechanism of trauma was falling (four patients). There was a general improvement in cerebral blood flow (CBF) after surgery from 23.9 (SD: 6.1) to 30.7 ml/100g/min, (SD: 5.1) and in mean transit time (MTT) from 7.3 (SD: 1.3) to 5.8s (SD:1.0), although it is not statistically significant (p=0.06 and p=0.06, respectively). There was still a reduction in the cerebral blood volume (CBV) media when compared to the value after surgery, from 2.63 (SD: 1.10) to 2.34 ml/100g (SD: 0.67), which is not statistically significant (p=0.31). Spearman correlation test of postoperative and preoperative CBF ratio with outcome was 0.94 (p=0.054). Only one patient died (three days after surgery). This patient was victim of car crash and had the highest preoperative MTT (9.97 seconds) and CBV (4.51 ml/100 g). Conclusion: Post-operative improvement of hemodynamic CTP parameters may be correlated with outcomes after ASH. Further studies with larger samples are required to confirm this hypothesis.

Abstract: Background: Non-invasive acquistion of beat-to-beat pulse transit time (PTT) via piezoelectric/piezocapacitive sensors (PES/PCS) may expand perioperative hemodynamic monitoring. This study evaluated the ability for PTT via PES/PCS to correlate with systolic, diastolic, and mean invasive blood pressure (SBPIBP, DBPIBP, and MAPIBP) and to detect SBPIBP fluctuations. Methods: PES/PCS and IBP measurements were performed in 20 patients undergoing abdominal, urological, and cardiac surgery. A Pearson’s correlation analysis (r) between 1/PTT and IBP was performed. The predictive ability of 1/PTT with changes in SBPIBP was determined by area under the curve (reported as AUC, sensitivity, specificity). Results: Significant correlations between 1/PTT and SBPIBP were found for PES (r=0.64) and PCS (r=0.55) (p<0.01), as well as MAPIBP/DBPIBP for PES (r=0.6/0.55) and PCS (r=0.5/0.45) (p<0.05). A 7% decrease in 1/PTTPES predicted a 30% SBPIBP decrease(0.82, 0.76, 0.76), while a 5.6% increase predicted a 30% SBPIBP increase (0.75, 0.7, 0.68). A 6.6% decrease in 1/PTTPCS detected a 30% SBPIBP decrease (0.81, 0.72, 0.8), while a 4.8% 1/PTTPCS increase detected a 30% SBPIBP increase (0.73, 0.64, 0.68). Conclusions: Non-invasive beat-to-beat PTT via PES/PCS demonstrated significant correlations with IBP and detected significant changes in SBPIBP. Thus PES/PCS as a novel sensor technology may augment intraoperative hemodynamic monitoring during major surgery.

Hyperleptinemia potentiates the effects of many atherogenic factors, such as inflammation, platelet aggregation, migration, hypertrophy, proliferation of vascular smooth muscle cells, and endothelial cell dysfunction. The present study analysed the effects of long-term hyperleptinemia in an in vivo myocardial ischemia-reperfusion model to demonstrate whether the in vivo deleterious effect also affects cardiac structure and function. Rats by were subcutaneously administered leptin for 8 days to estimate the involvement of the JAK/STAT pathway. Data from 58 male Wistar rats were included in the final analysis. Myocardial infarction (MI) was modelled by the 30-minute ligation of the main left coronary artery followed by 120-minute reperfusion. Hemodynamic measurements, electrocardiography monitoring, echocardiography, myocardial infarct size and area at risk, blood biochemical parameters, leptin, IL-6, TNF-alpha, FGF-21, and cardiomyocyte morphology were measured. Statistical analyses were performed using IBM SPSS Statistics v.26. Seven-day hyperleptinemia in rats led to increased an blood pressure and heart rate, myocardial hypertrophy, impaired LV function, an increased frequency of ischemic arrhythmias, dyslipidaemia, systemic inflammation, and an increased size of induced myocardial infarction. The blockade of the JAK/STAT signalling pathway effectively reversed the negative effects of leptin, including increased blood pressure and total cholesterol.

Imaging of the ocular vasculature can provide new insights into the pathophysiology of ocular diseases. This study proposes a novel high-frequency super-resolution ultrasound localization microscopy (SRULM) technique and evaluates its ability to measure in vivo perfusion changes in the rat eye at elevated intraocular pressure (IOP). A 38.4 MHz center frequency linear array transducer on a VisualSonics Vevo F2 imaging platform was used to collect high frame rate (1 kHz) radiofrequency data of the posterior rat eye following systemic microbubble contrast injection. Following clutter and spatiotemporal non-local means filtering, individual microbubbles were localized and tracked. The microbubble tracks were accumulated over 10,000 frames to generate vascular images quantifying perfusion velocity and direction. Experiments were performed using physiologic relevant controlled flow states for algorithm validation and subsequently performed in vivo on the rat eye at 10 mm Hg IOP increments from 10 to 60 mm Hg. The posterior vasculature of the rat eye, including the ophthalmic artery, long posterior ciliary arteries and their branches, central retinal artery and retinal arterioles and venules were successfully visualized, and velocities quantified at each IOP level. Significant reductions in arterial flow were measured as IOP was elevated. High-frequency SRULM can be used to visualize and quantify perfusion velocity of the rat eye in both the retrobulbar and intraocular vasculature simultaneously. The ability to detect ocular perfusion changes throughout the depth of the eye may help elucidate the role ischemia has in the pathophysiology of ocular diseases such as glaucoma.

The contribution of genetic and environmental factors to the pathophysiology of cerebral aneurysms in monozygotic twins is under-reported and presents ambiguous arguments. The morphology and hemodynamics of neurovascular arteries in a pair of monozygotic twins (MTs) were investigated to reveal the underlying mechanisms. Four arterial models were reconstructed for the twin A-right brain and left brain, twin B-left brain, and B-left brain without anterior cerebral arteries based on preclinical scanned information. Subsequently, the dimensions, configurations and outlined curves of the three-perspective geometries were compared between the MTs. Adopting an in-vitro validated numerical cerebral aneurysm model, hemodynamic patterns were investigated and compared in the MT models, respectively. Morphological comparisons of the MTs show the size and shape of cerebral arteries exist significant differences, despite of the expected genetic similarities. These differences can be attributed to variations during embryological development and external environmental influences. Qualitatively and generally, numerical results indicate the MTs have some hemodynamic similarities (e.g., time-averaged pressure (TAP) distributions (~13400 Pa), and oscillatory shear index (0~0.49), but present significant differences in specific local arteries due to morphological variances. Specifically, the difference in the volumetric blood flow rate in corresponding arteries between the MTs is from 16% (smallest) in anterior choroidal artery (AChA) to 221% (largest) in the ophthalmic artery (OphA), varying with specific compared arteries. Also, the registered hemodynamic indicators, such as the maximum time-averaged wall shear stress (TWSS) (53.6 Pa vs. 37.8 Pa), and different local OSI distributions were observed between the MTs. The findings revealed that morphological variations in MTs could be generated by embryological and environmental factors, thus assuming they share the identical morphology in cardiovascular and neurovascular systems may lead to significant misevaluations in hemodynamics quantifications and further lesions.

Background: The term “Long COVID” is commonly used to describe persisting symptoms after acute COVID‑19. Until now, proposed mechanisms for the explanation of Long COVID have not related quantitative measurements to basic laws. In this work, a common framework for the Long COVID pathophysiological mechanism is presented, based on the blood supply deprivation and the flow diffusion equation. Methods: Case-control studies with statistically significant differences between cases (post-COVID patients) and controls, from multiple tissues and geographical areas, were gathered and tabulated. Microvascular loss (ML) was quantified by vessel density reduction (VDR), foveal avascular zone enlargement (FAZE), capillary density reduction (CDR), and percentage of perfused vessels reduction (PPVR). Both ML and hemodynamic decrease (HD), were incorporated in the tissue blood supply reduction (SR) estimation. Results: ML data were found from 763 post-COVID patients with an average VDR, FAZE, CDR, and PPVR of 16%, 31%, 14%, and 21%, respectively. The average HD from 72 post-COVID patients was 37%. The estimated SR for multiple tissues with data from 634 post-COVID patients reached a sizeable 47%. This large SR creates conditions of lower mass diffusion rates, hypoxia, and undernutrition, which at a multi-tissue level, for a long time, can explain the wide variety of the Long COVID symptoms. Conclusions: Disruption of peripheral tissue blood supply by the contribution of both ML and HD is proposed here to be the principal cause of the mechanism leading to Long COVID symptoms.

Objective: To evaluate the clinical efficacy of antibiotic bone cement plus lateral bone repositioning for severe diabetic foot and its impact on wound healing rate. Methods: Sixty patients with hemodialysis anemia admitted to the endocrinology department of our hospital from July 2020 to July 2021 were included and randomly assigned to receive antibiotic bone cement plus lateral bone repositioning (observation group) or vacuum sealing drainage (VSD) (control group). Outcome measures included skin temperature of the affected limb, ankle-brachial index, sensory threshold, foot wound healing, dorsalis pedis artery hemodynamics, lower limb function and clinical efficacy. Results: Antibiotic bone cement plus lateral bone repositioning resulted in significantly higher treatment efficiency and transcutaneous partial pressure of oxygen, smaller wound, and lower trauma pH versus VSD, suggesting that antibiotic bone cement plus lateral bone repositioning contributes to potentiating the treatment efficacy and reducing the foot ulcer trauma, thereby facilitating rapid recovery. Patients given antibiotic bone cement plus lateral bone repositioning had larger vascular internal diameter and blood flow and better sensory conduction velocity of the common peroneal nerve and the motor conduction velocity of the tibial nerve versus those given VSD, indicating its vascular and neurological benefits. Conclusion: Antibiotic bone cement plus lateral bone repositioning enhances the treatment efficiency, boosts trauma healing, and promotes postoperative functional recovery of patients.

The beating heart is subject to intrinsic mechanical factors, exerted by contraction of the myocardium (stretch and strain) and fluid forces of the enclosed blood (wall shear stress). The earliest contractions of the heart occur already in the 10-somite stage in the tubular as yet unsegmented heart. With development the looping heart becomes asymmetric providing varying diameters and curvatures resulting in unequal flow profiles. These flow profiles exert various wall shear stresses and as a consequence different expression patterns of shear responsive genes. In this paper we investigate the morphological changes of the heart after changes the blood flow by ligation of the right vitelline vein in a model chicken embryo and analyze the extended expression in the endocardial cushions of the shear responsive gene Tgfbeta receptor III. A major phenomenon is the diminished endocardial-mesenchymal transition resulting in hypoplastic (even absence of) atrioventricular and outflow tract endocardial cushions, that might be lethal in early phases. The surviving embryos exhibit several cardiac malformations including ventricular septal defects and malformed semilunar valves related to a malposition of the aortopulmonary septum and the enclosed neural crest cells. We discuss the results in the light of the interactions between several shear stress responsive signaling pathways including Vegf, Notch, Pdgf, Klf2, eNos, Endothelin and Tgfβ/Bmp/Smad.