Blood Flow Hemodynamics Research Articles

Hemodynamics of a stenosed aortic valve: Effects of the geometry of the sinuses and the positions of the coronary ostia

Aortic valve stenosis is one of the most prevalent cardiovascular disease among adults worldwide. Stenosis of the aortic valve changes the hemodynamic parameters inside the aortic root which perpetuates aortic valve calcification and has been associated with the development of coronary artery atherosclerosis. Invasive studies have revealed that the geometry of the sinuses, as well as the locations of the coronary artery ostia, impact coronary blood flow hemodynamics, which has been associated with the development of coronary artery disease. The aim of this study is to elucidate this observed phenomenon, in which geometrical variations inside the aortic root and malfunctioning of the aortic valve because of the calcification not only affect the progression of the calcification but also lead to initiation of coronary artery atherosclerosis. A 2D fluid structure interaction model of the aortic valve was developed and simulated in ANSYS Fluent based on available echocardiography images in the literature. The model incorporates fluid structure interaction and employs the k − ω Menter's Shear Stress Transport (SST) turbulence model for the turbulent flow downstream of the leaflets. The effects of various diameters of the sinuses 25, 20.8, and 17.6 mm and positions of the coronary artery ostia (proximal, middle, and distal) on aortic root hemodynamics were investigated and parameters including transvalvular pressure gradient, valve orifice diameters, maximum jet velocity along the valve orifice area, and wall shear stresses on leaflets calculated. Results demonstrate that a severely calcified valve with the proximal coronary artery ostia witnesses a much higher transvalvular pressure gradient (approximately 10 times larger) compared to that for a healthy case. Moreover, the presence of the proximal coronary artery ostia for valves with diameters of the sinus 25 and 20.8 mm results in the reduction of the coronary blood flow and increase of the probability of coronary artery atherosclerosis.

3039 – YAP REGULATES HEMATOPOIETIC STEM CELL FORMATION IN RESPONSE TO THE BIOMECHANICAL FORCES OF BLOOD FLOW

Hematopoietic stem cells (HSCs) are born from cells in the dorsal aorta that adopt hematopoietic potential and commitment during development. Physical forces, namely wall shear stress (WSS) and cyclic stretch (CS), produced by hemodynamic blood flow are required to generate HSCs from arterial endothelium, but the mechanisms by which these forces are transduced into a "stemness" regulatory program remain unknown. Using a novel "dorsal-aorta-on-a-chip" microfluidic platform, we demonstrate that exposure to WSS and CS increases expression of the hematopoietic transcription factor RUNX1 in human CD34+ hemogenic endothelial cells derived from induced pluripotent stem cells. Notably, CS specifically induced activity of the YAP transcription factor, a mechanically-activated regulator of organ size and pluripotency. We corroborate these findings in a zebrafish model, and demonstrate that loss or gain of YAP function in vivo can blunt or augment the production of HSCs during definitive hematopoiesis. Importantly, we find that YAP is responsible for the maintenance, not initiation, of the hematopoietic program in newly specified hemogenic endothelial cells. Molecularly, we identify a stretch-induced, RhoGTPase-dependent mechanotransduction network controlling YAP nuclear availability to regulate RUNX1 expression, both in zebrafish and human cells. Moreover, we show that small molecule stimulation of RhoGTPases can rescue HSC production in zebrafish embryos with no flow, and enhance the hematopoietic potential of human iPSC-derived CD34+ endothelial cells grown in static culture. Together these findings uncover YAP as a transcriptional regulator of stem cell fate commitment during tissue morphogenesis, and suggest a pharmacologically amenable mechanotransduction pathway that could be exploited to improve the in vitro derivation of HSCs from human cells for therapeutic purposes.

Sex Difference In Cerebral Blood Flow During Exercise Hyperthermia

PURPOSE: Young healthy females are more prevalent to orthostatic hypotension compared to males. It is unknown if females show similar cerebral blood flow hemodynamics (middle cerebral artery, MCAvmean) compared to males during exercise hyperthermia. We tested the hypothesis that females have an attenuated MCAvmean response to exercising in hyperthermic conditions. METHODS: Twenty-two healthy active adults (7 day activity: 8620±3008 steps/day; VO2max: 49±10 mL/kg/min ) adults (11M/11F, 22.4±4.9y, 169±7.6cm, 68.3±13kg) exercised at similar metabolic heat production (M: 7.1±1.5 W/kg and F: 6.9±1.4 W/kg; P=0.32) for 60 min (cycle ergometer) in cool (24.0±0.00C; 14.4±3.6%Rh) and hot (42.3±0.20C; 27.9±5.5%Rh) conditions in random order with 7 days washout. MCAvmean absolute and percent change from rest, MCAvmean conductance (MCAvmeanCVC), cardiac output index (COi) and systemic vascular resistance index (SVRi), and the difference between conditions (hot minus cool) were examined by a mixed model 2-way repeated-measures analysis of variance for Interaction (I) and Main Effect (ME) for time and sex. Significance was set at P<0.05. RESULTS: Thermal (ΔTin, Cool: Δ0.5±0.10C, Hot: Δ1.5±0.60C; ME: condition; P<0.0001) and cardiovascular strain (ΔHR Cool: 58±15 b/min, Hot: 71±15 b/min; ME: condition; P<0.01) were similar between sex and increased in hot compared to cool condition. During the cool condition, absolute MCAvmean and MCAvmeanCVC were higher in females compared to males (ME: sex P<0.005). In contrast, MCAvmean and MCAvmeanCVC increased then decreased over time in hot compared to the cool condition (ME: time; P<0.0001). COi increased in hot compared to cool condition (ME: condition; P<0.008). Females had greater SVRi compared to males in both conditions (ME: sex; P<0.008). However, the %change and the difference between conditions, females compared to males had an attenuated MCAvmean (ME: sex; P<0.03) and MCAvmeanCVC (I: time × sex; P<0.01). CONCLUSIONS: These data indicate that sex differences exist for exercise cerebral blood flow. Females have higher MCAvmean in cool and have an attenuated MCAvmean response during exercise hyperthermia compared to males. This sex difference may be due to differences in blood pressure and systemic vascular resistance.

Technical Assessment of Ultrasonic Cerebral Tomosphygmography and New Scientific Evaluation of Its Clinical Interest for the Diagnosis of Electrohypersensitivity and Multiple Chemical Sensitivity.

Ultrasonic cerebral tomosphygmography (UCTS), also known as “encephaloscan”, is an ultrasound-based pulsatile echoencephalography for both functional and anatomical brain imaging investigations. Compared to classical imaging, UCTS makes it possible to locate precisely the spontaneous brain tissue pulsations that occur naturally in temporal lobes. Scientific publications have recently validated the scientific interest of UCTS technique but clinical use and industrial development of this ancient brain imaging technique has been stopped notably in France, not for scientific or technical reasons but due to a lack of financing support. UCTS should be fundamentally distinguished from transcranial Doppler ultrasonography (TDU), which, although it also uses pulsed ultrasounds, aims at studying the velocity of blood flow (hemodynamics) in the cerebral arteries by using Doppler effect, especially in the middle cerebral artery of both hemispheres. Instead, UCTS has the technical advantage of measuring and locating spontaneous brain tissue pulsations in temporal lobes. Recent scientific work has shown the possibility to make an objective diagnosis of electrohypersensitivity (EHS) and multiple chemical sensitivity (MCS) by using UCTS, in conjunction with TDU investigation and the detection of several biomarkers in the peripheral blood and urine of the patients. In this paper, we independently confirm the clinical interest of using UCTS for the diagnosis of EHS and MCS. Moreover, it has been shown that repetitive use of UCTS in EHS and/or MCS patients can contribute to the objective assessment of their therapeutic follow-up. Since classical CT scan and MRI are usually not contributive for the diagnosis and are poorly tolerated by these patients, UCTS should therefore be considered as one of the best imaging technique to be used for the diagnosis of these new disorders and the follow-up of patients.

Cardiac function and blood flow hemodynamics assessment of zebrafish (Danio rerio) using high-speed video microscopy

BackgroundIn the last few decades, zebrafish (Danio rerio) were introduced as a model organism to investigate human diseases including cardiovascular and neuronal disorders. In most zebrafish investigations, cardiac function and blood flow hemodynamics need to be assessed to study the effects of the interference on the cardiovascular system. For heart function assessment, most important parameters include heart rate, cardiac output, ejection fraction, fractional area change, and fractional shortening. MethodsA 10 s high-speed video of beating heart and flowing blood within major vessels of zebrafish that are less than 5 days post fertilization (dpf) were recorded via a stereo microscope equipped with a high speed camera. The videos were analyzed using MicroZebraLab and image J software for the assessment of cardiac function. ResultsUsing the technique described here, we were able to simply yet effectively assess cardiac function and blood flow dynamics of normal zebrafish embryos. We believe that the practical method presented here will help cardiac researchers using the zebrafish as a model to examine cardiac function by using tools that could be available in their laboratory.

The improvement of the shear stress and oscillatory shear index of coronary arteries during Enhanced External Counterpulsation in patients with coronary heart disease.

Enhanced External Counterpulsation (EECP) can chronically relieve ischemic chest pain and improve the prognosis of coronary heart disease (CHD). Despite its role in mitigating heart complications, EECP and the mechanisms behind its therapeutic nature, such as its effects on blood flow hemodynamics, are still not fully understood. This study aims to elucidate the effect of EECP on significant hemodynamic parameters in the coronary arterial tree. A finite volume method was used in conjunction with the inlet pressure wave (surrogated by the measured aortic pressure) before and during EECP and outlet flow resistance, assuming the blood as newtonian fluid. The time-average wall shear stress (TAWSS) and oscillatory shear index (OSI) were determined from the flow field. Regardless of the degree of vascular stenosis, hemodynamic conditions and flow patterns could be improved during EECP. In comparison with the original tree, the tree with a severe stenosis (75% area stenosis) demonstrated more significant improvement in hemodynamic conditions and flow patterns during EECP, with surface area ratio of TAWSS risk area (SAR-TAWSS) reduced from 12.3% to 6.7% (vs. SAR-TAWSS reduced from 7.2% to 5.6% in the original tree) and surface area ratio of OSI risk area (SAR-OSI) reduced from 6.8% to 2.5% (vs. SAR-OSI of both 0% before and during EECP in the original tree because of mild stenosis). Moreover, it was also shown that small ratio of diastolic pressure (D) and systolic pressure (S) (D/S) could only improve the hemodynamic condition mildly. The SAR-TAWSS reduction ratio significantly increased as D/S became larger. A key finding of the study was that the improvement of hemodynamic conditions along the LMCA trees during EECP became more significant with the increase of D/S and the severity degree of stenoses at the bifurcation site. These findings have important implications on EECP as adjuvant therapy before or after percutaneous coronary intervention (PCI) in patients with diffuse atherosclerosis.

A phase 2 randomised controlled trial of serelaxin to lower portal pressure in cirrhosis (STOPP)

BackgroundIn preclinical models, recombinant human relaxin-2 (serelaxin) had anti-fibrotic effects and ameliorated portal hypertension (PH). A small exploratory study in patients with cirrhosis also suggested that serelaxin could reduce portal pressure.MethodsIn a phase 2, double-blind, randomised controlled study conducted in a single centre (Royal Infirmary of Edinburgh, UK), male and female adult participants with cirrhosis and clinically significant PH (CSPH; hepatic venous pressure gradient (HVPG) > 10 mmHg) were enrolled. Participants were allocated to serelaxin or placebo in a 3:1 ratio. The placebo was matched to serelaxin on appearance and administration protocol to create and maintain blinding. The primary endpoint was the change from baseline in fasting HVPG after 2 h of peripheral i.v. serelaxin infusion (80 μg/kg/day for 60 min followed by 30 μg/kg/day for at least 60 min). Secondary endpoints included the change from baseline in hepatic blood flow and systemic haemodynamics (cardiac index, systemic vascular resistance index and aortic pulse wave velocity). Short-term safety and tolerability of serelaxin were assessed.ResultsA total of 17 participants were screened, 15 were randomised and 11 completed the study (n = 9 serelaxin, n = 2 placebo). Reasons for withdrawal were baseline HVPG < 10 mmHg (n = 2) and technical failure (n = 2). The trial ended early due to manufacturer discontinuation of the study drug. The median age was 56 (range 43–69) years and 73% of participants were male. Alcohol was the commonest cirrhosis aetiology (n = 10). Participants had a median Model for End-Stage Liver Disease score of 10 (range 6–14). The mean baseline HVPG was 16.3 (range 10.3–21.7) mmHg. Individual responses were variable, but overall there was no statistically significant change in HVPG after 2 h of i.v. serelaxin (arithmetic mean of difference ± SD was 0.4 ± 3.5 mmHg (95% CI –2.3, 3.1; p = 0.76)). There were also no substantial changes from baseline in hepatic or systemic haemodynamics. We recorded 12 adverse events in 7 participants treated with serelaxin; none were significant, and most were unrelated to the investigational medicinal product. There were no serious adverse events.ConclusionIn a small randomised, phase 2, proof-of-concept study in patients with cirrhosis and CSPH, serelaxin infusion was safe and well-tolerated but had a neutral effect on HVPG.Trial registrationClinicalTrials.gov, NCT02669875. Registered on 1 February 2016.

Changes in Vertebral Artery Blood Flow in Different Head Positions and Post–Cervical Manipulative Therapy

ObjectiveThe objective of this study was to investigate the hemodynamics of blood flow through the V3 region of the vertebral artery contralateral to the side manipulated during different rotary head positions and post–cervical spinal manipulation. MethodsThis quasi-experimental study was performed on 25 healthy, asymptomatic participants, both male and female, between 20 and 30 years of age. Each participant presented with a C0/C1 or C1/C2 cervical facet restriction (as determined by motion palpation). Participation was voluntary, and participants had no symptoms of vertebrobasilar artery insufficiency or contraindications to cervical spinal manipulation. Doppler ultrasound was used to measure vertebral artery blood flow (V3 region) hemodynamics, contralateral side of manipulation, as close to C1/C2 region as possible in 4 positions of cervical rotation (neutral, 45°, maximum, and post-manipulation neutral). Doppler ultrasound parameters included peak systolic flow velocity, end diastolic flow velocity, mean flow velocity, vessel diameter, and flow rate. The nonparametric Friedman test was used for analysis across each head and neck position, and post manipulation. ResultsNo clinical or statistically significant results (P > .05) were found for any of the hemodynamic parameters in any of the head positions. ConclusionsHemodynamic measurements of the V3 region of the vertebral artery do not show significant changes in the measured head positions or following manipulation of the upper cervical spine in patients without pre-existing risk factors.

Vascular Complications of Splenectomy in a Patient with Gastric Dieulafoy-like Lesions in Left-sided Portal Hypertension Secondary to Splenic Vein and Artery Thrombosis

Due to lower clinical significance, the management of Dieulafoy and Dieulafoy-like lesions is less commonly reported than the management of their impending venous equivalent, variceal bleeding. Though Dieulafoy and Dieulafoy-like lesions are often benign, they can become life-threatening in certain clinical scenarios, especially with substantial changes in hemodynamic blood flow, which results in hemorrhage. Post-procedural hemodynamic blood flow should be carefully monitored in patients who receive procedures that drastically alter hemodynamic flow pressures. Factoring in the presence of Dieulafoy and Dieulafoy-like lesions might deepen the complexity of an intuitive surgical or interventional procedure for an experienced operator, and should, therefore, involve the cooperative effort between surgical, interventional, and diagnostic services to appropriately manage the patients. The case we present demonstrates the dire consequences of a routine splenectomy when a considerable change in hemodynamic pressure across benign Dieulafoy-like lesions occurs in a patient with both splenic artery and venous thrombosis.

Determining the optimal blood flow restriction protocol for maximising muscle hypertrophy and strength, pressure and cuff width: A mini-review

Low load resistance training accompanied by blood flow restriction (BFR) has been established as a training modality to induce hypertrophy and strength adaptations. Throughout the BFR-literature, several protocols have emerged with a vast difference among manipulations regarding limb occlusion pressure and the use of different cuff sizes. The aim of this review is to summarise the research underpinning the stimulus regarding alterations in occlusion pressure and the use of different cuff widths, thus investigate whether an optimal protocol is evident. While the focal point of BFR-literature supports the efficiency of several BFR-protocols, no uniform BFR-protocol are located in the literature to maximise muscle hypertrophy and strength. However, an optimal limb occlusion pressure is crucial to achieve venous blood pooling, thus induce a significant stimulus to the muscle, and should be individualised and likely applied relative to the maximum arterial occlusion pressure. Quantification of the optimal pressure range is currently a disputed topic, with no conclusive evidence leading to the most efficient range of applied pressure. Regarding cuff widths, applying an absolute or relative pressure, and their implications regarding the hemodynamics of blood flow should be considered by the researchers. The author would highlight that future BFR studies should be conducted to shed light on the determinants underpinning the protocol to optimise muscle hypertrophy and strength through BFR resistance training, which could have an important ramification through its increasing use in clinical settings and athletic development.

Transcranial doppler methods in the assessment of cerebral vasomotor reactivity

Introduction. Transcranial Doppler is the only non-invasive neuroimaging modality in the diagnosis and monitoring of various neurovascular diseases. Apart from assessing cerebral hemodynamics of blood flow in the basal brain arteries, transcranial Doppler provides physiological data and anatomical images. Quantification analysis of vasomotor reactivity. Various transcranial Doppler methods evaluate cerebral vasomotor reactivity, providing important information on the properties of arterioles under induced hemodynamic conditions. Exogenous and endogenous vasoactive stimuli of different potency (apnea, acetazolamide, carbon dioxide, L-arginine) are most commonly used, making transcranial Doppler a prognostic indicator of future ischemic events. This article reviews principles of various transcranial Doppler methods in the evaluation of vasomotor reactivity, emphasizing their advantages and disadvantages. Transcranial Doppler in the field of reduced vasomotor reactivity. Evaluation of vasomotor reactivity has a role in the prediction of future ischemic events, evaluation of revascularization effect after carotid endarterectomy, but also in the increasingly significant choice of the right time to perform it. In recent years, transcranial Doppler methods have found application in other areas of dysfunctional cerebral hemodynamics: dementia, hypertension, migraines, and sepsis. Conclusion. Due to an excellent temporal resolution, non-invasive approach, good cost-benefit ratio, bedside monitoring, relative simplicity in terms of interpretation and performance, and portability, transcranial Doppler in vasomotor reactivity may be the ideal tool in the evaluation of cerebral hemodynamics, arterial perfusion integrity and collateral capacity.

Future Directions in Coronary CT Angiography: CT-Fractional Flow Reserve, Plaque Vulnerability, and Quantitative Plaque Assessment.

Coronary computed tomography angiography (CCTA) is a well-validated and noninvasive imaging modality for the assessment of coronary artery disease (CAD) in patients with stable ischemic heart disease and acute coronary syndromes (ACSs). CCTA not only delineates the anatomy of the heart and coronary arteries in detail, but also allows for intra- and extraluminal imaging of coronary arteries. Emerging technologies have promoted new CCTA applications, resulting in a comprehensive assessment of coronary plaques and their clinical significance. The application of computational fluid dynamics to CCTA resulted in a robust tool for noninvasive assessment of coronary blood flow hemodynamics and determination of hemodynamically significant stenosis. Detailed evaluation of plaque morphology and identification of high-risk plaque features by CCTA have been confirmed as predictors of future outcomes, identifying patients at risk for ACSs. With quantitative coronary plaque assessment, the progression of the CAD or the response to therapy could be monitored by CCTA. The aim of this article is to review the future directions of emerging applications in CCTA, such as computed tomography (CT)-fractional flow reserve, imaging of vulnerable plaque features, and quantitative plaque imaging. We will also briefly discuss novel methods appearing in the coronary imaging scenario, such as machine learning, radiomics, and spectral CT.

Untangling the co-effects of oriented nanotopography and sustained anticoagulation in a biomimetic intima on neovessel remodeling

Constructing a small-diameter artificial blood vessel with biological functions and mechanical compliance comparable to native tissues is still a major challenge in vascular tissue engineering. To address the issues of severe thrombosis and unsatisfactory long-term patency in small-diameter vascular grafts, herein we designed a specifically biomimetic intima with an oriented nanotopographical structure and covalently immobilized anticoagulant molecules. The mixture of heparinized silk fibroin (SF-Hep) and polycaprolactone (PCL) was used to produce oriented inner layer and pure PCL was used to fabricate vertically porous outer layer by a two-step cross-electrospinning. Our findings showed that the immobilized heparin significantly influenced adherence and activation of platelets while the oriented nanotopography mainly manipulated the elongation and aligned growth of endothelial cells as well as hemodynamics of blood flow. More importantly, two factors of the oriented structure and anticoagulation presented the obviously synergistic effects on rapid endothelialization, long-term patency and remodeling of neovessel. Consequently, the current study successfully combined biochemical induction of heparin molecule and biophysical stimulation of oriented nanotopography to create an off-the-shelf small-diameter vascular graft with excellent antithrombosis in the early stage and long-term patency in the late stage.

Knee extension with blood flow restriction: Impact of cuff pressure on hemodynamics.

Blood flow restriction (BFR) exercise has emerged as a method of increasing muscle size and strength with low intensity resistance training. While the cuff pressures used during BFR are typically a percentage of resting arterial occlusion pressure (AOP), the impact these cuff pressures have on blood flow during lower body exercise is unknown. To determine how various cuff pressures impact blood flow and tissue perfusion during exercise. Eleven healthy male participants completed four sets of knee extension (30 reps per set at 30% max torque) with 0%, 60%, 80%, and 100% of arterial occlusion pressure (AOP) was applied to the proximal portion of the thigh. Femoral artery blood flow, tissue oxygenation, and central hemodynamics were continuously recorded before, during, and after exercise. Electromyography (EMG) amplitude was recorded from the vastus lateralis during exercise. Blood flow increased during exercise compared to rest across all cuff pressures (p < 0.001), however compared to 0%, the absolute blood flow was reduced by 34 ± 17%, 45 ± 22%, and 72 ± 19% for 60, 80, and 100% AOP, respectively. Furthermore, each cuff pressure resulted in similar relative changes in blood flow before, during, and after exercise. During exercise, tissue saturation index (TSI) decreased as cuff pressure increased (p ≤ 0.005) with the exception of 80 to 100% AOP. Deoxyhemoglobin increased (p ≤ 0.001) with cuff pressure. Our data indicate that while BFR knee extension elicits an absolute hyperemic response at cuff pressures up to 100% resting AOP, the relative reductions in blood flow are consistent across rest, exercise and recovery.

Effects of different non-Newtonian models on unsteady blood flow hemodynamics in patient-specific arterial models with in-vivo validation

The aim of this study is to demonstrate the implications of using different blood rheological models in the simulation of blood flow dynamics in atherosclerotic coronary arteries. Computational fluid dynamics simulation was performed using three-dimensional (3D) patient-specific models of diseased left anterior descending (LAD) coronary arteries with varying degrees of stenosis severity. The three-dimensional arterial models were reconstructed from 3D quantitative coronary angiography, and input flow conditions were prescribed with blood flow conditions measured in-vivo. Different blood viscosity models were used for the simulations, and they include Newtonian and also non-Newtonian models such as Bingham, Carreau, Carreau-Yasuda, Casson, modified Casson, Cross, modified Cross, simplified Cross, Herschel Bulkley, Kuang-Luo (K-L), PowellErying, modified PowellErying, Power-law, Quemada and Walburn-Schneck models. Results from this study show that the time-averaged velocity at the centre of the arteries produced in the CFD simulations that uses the Carreau, modified Casson or Quemada blood viscosity models corresponded exceptionally well with the clinical measurements regardless of stenosis severities and hence, highlights the usefulness of these models to determine the potential determinants of blood vessel wall integrity such as dynamic blood viscosity, blood velocity and wall shear stress.

CAR 5. Carotid Flow Volume Measurement in Doppler Ultrasound as a New Look at the Diagnosis of Internal Carotid Artery Stenosis

Blood flow velocity criteria in the diagnosis of carotid stenosis are well defined; however, there are no reference values concerning blood flow volume. The objective of this work covered assessment of blood flow volume in the internal carotid artery (ICA), external carotid artery (ECA), and vertebral artery (VA) in healthy volunteers and asymptomatic patients with carotid artery disease older than 65 years with the aim of implementation of blood flow volume measurements in clinical assessment of patients with carotid artery disease. There were 303 patients without history of neurologic symptoms included in the examination. The group of 123 healthy volunteers older than 65 years, without comorbidities that may alter cerebral blood flow volume, were examined to determine reference flow volume values in the ICA, ECA, and VA. The flow parameters in this group were compared with the flow in 56 healthy volunteers younger than 65 years. To determine the influence of ICA stenosis on cerebral blood flow volume, the group of 124 patients older than 65 years with asymptomatic ICA stenosis without comorbidities that might influence hemodynamics of blood flow were examined. In all patients, an extensive Doppler ultrasound examination with measurement of blood flow volume in the ICA, ECA, and VA was performed. Cerebral blood flow volume reference values in patients older than 65 years were determined. Gradual decline in cerebral blood flow, caused mainly by the significant reduction of ICA flow volume, was observed in healthy volunteers. A decline in the peak systolic and end-diastolic velocities in the ICA and the peak systolic velocity in the ECA was observed. Two subgroups with ICA stenosis and flow volume changes were identified: patients with compensatory elevation of blood flow volume and those without compensation whose flow volume was lower than reference values. The latter subgroup contained mainly patients with >50% ICA stenosis. Among asymptomatic patients with significant ICA stenosis, there is a subgroup without compensatory elevation of blood flow volume. Those patients may be more vulnerable to cerebral ischemia and featured with increased risk of ischemic stroke.

Effect of L-Arginine Therapy on Vasospasm: Experimental Study in Rats

Cerebral vasospasm occurring after subarachnoid hemorrhage is a serious cause of morbidity. Cerebral vasospasm-related studies aim to prevent complications after subarachnoid hemorrhage. Nitric oxide affects brain blood flow and local vascular hemodynamics. L-arginine is used in the synthesis of nitric oxide, and hence we have investigated the efficacy of L-arginine treatment by using femoral artery vasospasm model. Twenty-four male Sprague-Dawley rats have been divided into 3 groups as vasospasm, vasospasm+ L-arginine, and control. In this study, we have preferred the "Rat Femoral Artery Vasospasm Model" described by Okada etal. Rats in the vasospasm+ L-arginine group were given 300 mg/kg L-arginine for 7 days. At the end of the study, all samples of rat femoral arteries have been dissected and examined microscopically for histopathologic analysis. Statistical analysis was performed using Kruskal-Wallis and Mann-Whitney U tests, and P < 0.05 value was considered statistically significant. L-arginine treatment reduced the morphometric changes such as irregularity of the elastic lamina, disruption of the endothelial cells, vacuolization, and hemorrhages that are caused by vasospasm. When the wall thickness and lumen diameter measurements were evaluated statistically, significant improvement was observed in the vasospasm+ L-arginine group compared with the vasospasm group (P < 0.01). In our study, the use of L-arginine, as a nitric oxide substrate, improved the experimental vasospasm in rats. Therefore we think that L-arginine therapy can be used in the prevention and treatment of cerebral vasospasm after subarachnoid hemorrhage.

Spontaneous coronary collateral recruitment in patients with recurrent ST elevation myocardial infarction (STEMI).

The spontaneous recruitment of acute coronary collaterals in the setting of an ST elevation myocardial infarction (STEMI) is seen frequently in those patients undergoing primary percutaneous coronary intervention (pPCI) and is associated with improved clinical outcomes. However, it is unknown whether in patients who present with a recurrent STEMI, the degree of collateral recruitment remains the same as in the index procedure. We reviewed all patients presenting to our tertiary centre with a STEMI undergoing primary or rescue percutaneous coronary intervention (PCI) from July 2010 until December 2018. We identified patients who presented with a recurrent STEMI following their index procedure. We defined patients with poor collateral recruitment as Rentrop grade 0 or 1, whilst patients with robust collateral recruitment as Rentrop grade 2 or 3. Of the 1795 patients who were identified, there were 27 cases in 25 patients who presented with a repeat STEMI following their index procedure. The median time between cases was 12.8days (IQR 2.3-589.5days). Compared to the index case, there was no statistically significant difference in the degree of collateral recruitment in recurrent presentations (Z = -0.378, p = 0.70). In those patients presenting more than 6months following the index procedure, the median time between cases was 654.5days (IQR 479.5-1151.9). There was no difference in the degree of collateral recruitment in recurrent presentations (Z = 0.000, p = 1.0). Cases which had poorer collateral recruitment in recurrent presentations were less likely to be current smokers (0% vs 50%, p < 0.001) and less likely to have diabetes (0% vs 27.3%, p < 0.05) The recruitment of spontaneous coronary collaterals remains constant in recurrent STEMI presentations suggesting an innate biological process rather than merely a manifestation of alteration of haemodynamic blood flow. Further investigations to identify these processes is required.

Связь эндотелина-1 с ведущими показателями портального кровотока и центральной гемодинамики при циррозах печени

Связь эндотелина-1 с ведущими показателями портального кровотока и центральной гемодинамики при циррозах печени

Performance analysis of the transcatheter aortic valve implantation on blood flow hemodynamics: An optical imaging-based in vitro study.

Cardiac implants may have a strong influence on the hemodynamics of the circulatory system. In this study, we aimed at investigating the impact of transcatheter aortic valve implantation (TAVI) devices on blood flow patterns that develop in the ascending aorta under physiological flow conditions in vitro. For this purpose, a noninvasive optical measurement tool, three-dimensional particle tracking velocimetry (3D-PTV), was used in a realistic compliant silicone aortic model. The performance and the influence of two TAVIs and one surgical valve on the aortic flow were investigated. Our results showed that valve design and materials may have a distinct influence on relevant hemodynamic properties, namely kinetic energy, production of turbulence, and shear stresses in the ascending aorta. All properties varied considerably between the different valve models. We found that the total aortic regurgitation composed of the closing volume, transvalvular and paravalvular leakages varied for the three valves investigated. Furthermore, peak mean kinetic energy (MKE) ranged from 61 to 116 J/m3 , whereas peak turbulent kinetic energy (TKE) ranged from 23 to 36 J/m3 . The analysis of shear showed that all the three studied devices had minimal overall risk for thrombus formation. We conclude that the characteristics and material designs of TAVI devices have strong influences on the hemodynamics in the ascending aorta.