Pulsatile Research Articles

Enhancing understanding of stent-induced deformation in MCA aneurysms: a hemodynamic study.

This article provides a comprehensive hemodynamic assessment of two endovascular techniques for treating cerebral aneurysms. Through finite volume simulations of pulsatile blood flow in saccular aneurysms, we evaluated hemodynamic factors under two coiling conditions with varying porosities and deformation stages to determine the most effective treatment for each case. Our analysis shows that stent and coiling treatments are more effective for aneurysms with smaller sac volumes. In particular, stent placement is found to be more effective than coiling for managing saccular aneurysms. The results indicate that stent-induced deformation effectively redirects the main blood flow, significantly lowering the risk of aneurysm rupture near the ostium. Obtained results emphasize the role of deformation and porosity in controlling wall shear stress, which is essential for understanding aneurysm progression and potential rupture risk.

Spectrally selective and interleaved water imaging and fat imaging (siWIFI).

To develop a novel imaging sequence that independently acquires water and fat images while being inherently insensitive to motion. The new sequence, termed spectrally selective and interleaved water imaging and fat imaging (siWIFI), uses a narrow bandwidth RF pulse for selective excitation of water and fat separately. The interleaved acquisition method ensures that the obtained water and fat images are inherently coregistered. A radial sampling strategy further reduces motion-induced artifacts. Phantoms with lipid concentrations ranging from 0% to 50% were scanned to measure fat fraction. Moreover, healthy volunteers were scanned to assess the in vivo feasibility of fat fraction measurement at the hip, knee, and liver. In vivo fat fraction measurements were compared with those from vendor-provided iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL) scans. Furthermore, a magnetization transfer (MT) preparation module was incorporated to demonstrate the feasibility of simultaneous measurement of fat fraction and MT ratio utilizing the siWIFI framework. The phantom fat fractions measured by siWIFI showed excellent correlation with lipid concentrations (R2 = 0.9995, p < 0.0001). In vivo studies demonstrated that the fat fractions obtained from siWIFI were comparable to those from IDEAL. Additionally, siWIFI demonstrates reduced motion artifacts from pulsatile flow in knee imaging compared to IDEAL scans and exhibits less sensitivity to respiratory motion in liver imaging compared to IDEAL scans without breath-hold. The knee imaging study demonstrated that MT-prepared siWIFI is capable of generating fat fraction and MT ratio maps simultaneously. The proposed siWIFI sequence allows selective water-fat imaging and quantification with reduced motion artifacts.

Abstract 4138558: The effect of pulsatile vs. non-pulsatile perfusion on hospital stay, ICU stay, and intubation time in patients undergoing cardiopulmonary bypass: A meta-analysis randomized controlled trials.

Background: Pulsatile perfusion is a developing technique that attempts to mimic the natural pulsatile flow of blood during cardiopulmonary bypass (CBP). Purpose: Our meta-analysis was done to evaluate the effects of pulsatile perfusion in CPB compared to non-pulsatile on hospital stay, ICU stay, and intubation time. Methods: Randomized control trials that evaluated the implementation of pulsatile perfusion during CPB were identified by a literature search of the following databases (PubMed, Web of Science, Scopus, Central, and Embase) up to February 2024. Results: Our search yielded 33 trials with 3174 patients, the analysis showed that pulsatile perfusion led to a significant decrease in hospital stay [MD = -1.38, 95% CI (-2.51, -0.25), P = 0.016], ICU stay [MD = -0.47, 95% CI (-0.82, -0.13), P = 0.007], intubation time [MD = -3.73, 95% CI (-5.42, -2.04), P &lt; 0.001]. However, no significant difference between the two regimens was detected in the adult subgroup when we performed sungroup analysis based on the age for hospital stay and ICU stay outcomes [MD = -0.31, 95% CI (-0.95, 0.33), P = 0.334] and [MD = -3.73, 95% CI (-5.42, -2.04), P &lt; 0.001] respectively. Conclusion: Pulsatile perfusion showed positive effects on hospital stay, ICU stay, and intubation time. However, there was no difference between the two methods on hospital and ICU stay in the adult’s subgroup. Also, the outcomes showed significant heterogeneity, which requires more robust RCTs to be conducted to increase the quality and the certainty of evidence.

Directional flow in perivascular networks: mixed finite elements for reduced-dimensional models on graphs

Flow of cerebrospinal fluid through perivascular pathways in and around the brain may play a crucial role in brain metabolite clearance. While the driving forces of such flows remain enigmatic, experiments have shown that pulsatility is central. In this work, we present a novel network model for simulating pulsatile fluid flow in perivascular networks, taking the form of a system of Stokes–Brinkman equations posed over a perivascular graph. We apply this model to study physiological questions concerning the mechanisms governing perivascular fluid flow in branching vascular networks. Notably, our findings reveal that even long wavelength arterial pulsations can induce directional flow in asymmetric, branching perivascular networks. In addition, we establish fundamental mathematical and numerical properties of these Stokes–Brinkman network models, with particular attention to increasing graph order and complexity. By introducing weighted norms, we show the well-posedness and stability of primal and dual variational formulations of these equations, and that of mixed finite element discretizations.

Semi-analytical solution for pressure-driven non-Newtonian flows in concentric annuli

Hemodynamics during cardiac catheterization can be modeled as non-Newtonian fluid flow within concentric annuli. Rapid and precise evaluation of flow rate variations is crucial for understanding the catheter's impact on local hemodynamics. We propose a general semi-analytical solution for flow rates in pressure-driven non-Newtonian flows within concentric annuli. This solution is suitable for commonly used non-Newtonian models. Validation using the Casson and Carreau–Yasuda models across various diameter ratios confirms the accuracy of the proposed solution, with a maximum relative error of 3.55%. It also reliably predicts time-averaged flow rates in pulsatile flows, with a maximum relative error of only 0.53%.

Vertical concentration distribution of fine settling particles in a pulsatile laminar open channel flow

Vertical concentration distribution of fine settling particles in a pulsatile laminar open channel flow

ГЕМОДИНАМИКА ГОЛОВНОГО МОЗГА У НОВОРОЖДЕННЫХ ОТ МАТЕРЕЙ С ФЕТОПЛАЦЕНТАРНОЙ НЕДОСТАТОЧНОСТЬЮ

Objective. To determine the state of brain structures and blood flow parameters in the ventricular system in newborns whose mothers suffered from placental insufficiency using neurosonography and Doppler ultrasound. Material and methods. The study involved 96 newborns from mothers with placental insufficiency (the main group) and 30 healthy newborns (the control group). The diagnostic tools included a neurosonographic assessment of the anterior and middle cranial fossae, as well as Doppler ultrasound of the anterior and middle cerebral arteries, vein of Galen blood flow velocity assessment, systolic/diastolic ratio (S/D), resistive index (Ri) and pulsatility index (PI). Results. The comparative analysis of blood flow in the anterior cerebral artery and the vein of Galen did not reveal statistically significant differences between the main and control groups. While examining the middle cerebral artery, despite the absence of statistically significant differences in blood flow velocities compared with the control group, resistive index (Ri), pulsatility index (Pi) and systolic/diastolic ratio (S/D) showed statistically significant differences. This indicates increased vascular resistance in newborns from the main group. Conclusion. It is essential to combine Doppler ultrasound and neurosonography in order to make an objective assessment of the state of the newborns central nervous system from mothers with placental insufficiency. The study revealed impairment of hemodynamics in the middle cerebral arteries pool in newborns from the main group. To assess cerebral hemodynamics, it is preferable to use the Ri, Pi and S/D indices.

A multimodal imaging approach to investigate retinal oxygen and vascular dynamics, and neural dysfunction in bietti crystalline dystrophy

BackgroundThis study aimed to explore retinal changes in Bietti crystalline dystrophy (BCD) patients, including retinal metabolism, blood flow, vascular remodeling, and pupillary light reflex (PLR) abnormalities. MethodsThis cross-sectional study included 120 eyes from BCD patients and 120 eyes from healthy controls, utilizing a multimodal imaging system (MEFIAS 3200, SYSEYE, Chongqing, China) to evaluate retinal oxygenation, blood flow, vascular structure, and PLR. Measurements included oxygen saturation, blood flow velocity, vessel diameters, and pulsatility metrics. PLR parameters were assessed under specific light stimuli. ResultsBCD patients demonstrated significantly higher retinal oxygen saturation and content, but lower oxygen utilization and metabolism compared to controls, with more pronounced declines in those over 40 years old. Vascular parameters revealed smaller external diameters and larger lumen diameters, indicating vascular remodeling. Retinal blood flow was lower, while the resistivity index was higher in BCD patients. Additionally, PLR abnormalities were noted, including reduced constriction amplitude, pupil constriction ratio, constriction duration, and maximum constriction velocity, along with prolonged latency were observed in BCD patients. ConclusionBCD patients had significant retinal and vascular changes, along with PLR impairments, especially in patients over 40. More targeted interventions should be focused in future research.

Changes in portal pulsatility index induced by a fluid challenge in patients with haemodynamic instability and systemic venous congestion: a prospective cohort study

BackgroundIt is uncertain whether fluid administration can improve patients with systemic venous congestion and haemodynamic instability. This study aimed to describe the changes in systemic venous congestion and peripheral perfusion parameters induced by a fluid challenge in these patients, and to analyse the influence of the fluid responsiveness status on these changes.MethodsThe study is a single-centre prospective cohort study of 36 critically ill ICU patients with haemodynamic instability and a maximum vena cava diameter ≥ 20 mm. Changes in cardiac index during a fluid challenge (4 mL/kg of lactated Ringer’s solution during 5 min) assessed by pulse contour analysis, central venous pressure, ultrasound systemic congestion parameters (portal venous flow pulsatility index, supra hepatic and intrarenal venous Doppler), and peripheral perfusion parameters (capillary refill time and peripheral perfusion index) were assessed in the overall population. All these data were compared between patients presenting a cardiac index increase > 10% during the fluid challenge (fluid responders) and the others (fluid non-responders).ResultsTwenty-eight (78%) patients were admitted for postoperative care following cardiac surgery; their mean ± SD left ventricular ejection fraction was 42 ± 9% and right ventricular dysfunction was found in at least 61% of the patients. The mean ± SD SOFA score was 9 ± 3. Thirteen (36%) patients were fluid responders. The fluid challenge administration induced a significant increase in portal pulsatility index, VExUS score, and central venous pressure without significant difference of these changes between fluid responders and non-responders. No significant change in perfusion parameters was observed.ConclusionFluid administration in patients with haemodynamic instability and systemic venous congestion worsens venous congestion regardless of the fluid responsiveness status, without improving perfusion parameters.

Evaluation of extra-corporeal membrane oxygenator cannulae in pulsatile and non-pulsatile pediatric mock circuits.

This study evaluated the hemodynamic performance of arterial and venous cannulae in a compliant pediatric extracorporeal membrane oxygenation (ECMO) mock circuit in pulsatile and non-pulsatile flow conditions. The ECMO setup consisted of an oxygenator, diagonal pump, and standardized-length arterial/venous tubing with pressure transducers. A validated left-heart mock loop was adapted to simulate pediatric conditions. The pulsatile flow was driven by a computer-controlled piston pump set at 120 bpm. A roller pump was used for non-pulsatile conditions. The circuit was primed with 40% glycerol-based solution. The cardiac output was set to 1 L/min and the aortic pressure to 40-50 mmHg. Four arterial cannulae (8Fr, 10Fr, 12Fr, 14Fr) and five venous cannulae (12Fr, 14Fr, 16Fr, 18Fr, 20Fr) (Medtronic, Inc., Minneapolis, MN, USA) were tested at increasing flow rate in 12 combinations. The pulsatile condition required lower ECMO pump speeds for all cannulae combinations at a given flow rate, inducing a significantly smaller increase of flow in the mock loop. Under non-pulsatile conditions, the aortic and arterial pressures in the cannulae were higher (p < 0.01) while no significant differences in pressure drop and pressure-flow characteristics (M-number) were observed. The total hemodynamic energy was higher in case of non-pulsatile flow (p < 0.01). Under non-pulsatile conditions, the system was characterized by overall higher pressures, resulting in higher support to the patient. The consequent increase of potential energy compensates for increases of kinetic energy, leading to a higher total hemodynamic energy. Pressure gradients and M number are independent of the testing conditions. Pulsatile testing conditions led to more physiological testing conditions, and it is recommended for ECMO testing.

Computational analysis of pulsatile blood flow and heat transport dynamics in middle cerebral artery aneurysms in different body physiologies

This paper presents a comprehensive hemodynamic evaluation of two endovascular techniques for treating cerebral aneurysms. Using the finite volume method, we simulated pulsatile blood flow and heat transport dynamics in two saccular aneurysms of varying sizes and shapes. We assessed hemodynamic factors under two coiling conditions with different porosities and deformation stages to identify the most effective treatment for each case. Our computational analysis reveals that stent and coiling applications are more efficient for aneurysms with low-sac volume. Notably, stent placement proves to be more effective than coiling in treating saccular aneurysms. Our findings indicate that stent-induced deformation sufficiently diverts the main blood flow, thereby reducing the risk of aneurysm rupture near the ostium region.

Vascular complications in patients with peripheral veno-arterial extracorporeal membrane oxygenation: clinical-echocardiographic characteristics and predictors

Abstract Introduction Veno-arterial Extracorporeal membrane oxygenation (VA ECMO) is a salvage intervention in patients with cardiogenic shock (CS), and cardiac arrest (CA) refractory to standard therapies. Lower limb ischemia associated with peripheral VA ECMO is frequent, and is considered a serious complication with a significant impact on the morbidity and mortality. Purpose The aim of this study was to describe the clinical-echographic parameters and analyze predictors related to vascular complications in patients with peripheral VA ECMO. Methods The study was a single-center cohort analysis. It included all consecutive adult patients with peripheral femoro-femoral VA ECMO due to refractory cardiogenic shock (CS) or cardiac arrest (CA) between March 2014 and December 2022. Patients with central cannulation were excluded. The primary endpoint was evidence of vascular complications resulting in surgical intervention. A multivariate logistic regression model was used to adjust for variables of interest. Results The study included 83 patients (65± 12 years, 54% male). The main previous diagnosis was necrotic ischemic cardiomyopathy (33%), and the most frequent indication was postcardiotomy (40.9%), mainly in SCAI D (85.5%). Cardiopulmonary resuscitation was performed in 18.1%. Femoro-femoral cannulation was percutaneuos in 95.2%. Most patients had intra-aortic balloon pump (87.1%) and distal percutaneous cannula (88.8%). A total of 18 patients presented vascular complications (21.7%): 2 patients (11.1%) amputation, 5 patients (27.7%) compartment syndrome requiring fasciotomy, 9 patients (50.0%) thrombectomy, and 2 patients (11.1%) a surgical resolution post decannulation due to AV fistula. The median duration of VA ECMO was 5 days (IQR 2-8). Among the ultrasound variables, the systolic peak velocity (SPV) in the distal territory (tibioperoneal segment) had a median of 22 cm/sec (IQR 10-30). Pulsatile spectral Doppler flow in the cannulated limb was evidenced in 42 patients (50.6%) of total population, and only in 3 patients (16.6%) with vascular complications. The survival rate from VA ECMO was 57.8%, and the survival rate to discharge 42.1%. In-hospital mortality of patients with or without vascular complications did not show statistically significant differences (54.2 % vs 58.2 %, p= 0.26). After multivariate analysis, distal territory SPV less than 20 cm/sec (OR: 2.1, 95%CI: 1.3 – 12.1, p: 0.03), as well as history of previous vascular disease, were associated with a higher number of vascular complications (OR: 2.5, 95% CI: 1.5 – 10.1, P; 0.02). Conclusions Vascular complications in patients with femoro-femoral VA ECMO remain frequent and constitute an important cause of morbidity. Decreased peak systolic velocities in the cannulated tibio-peroneal territory, as well as a history of previous vascular disease were significantly associated with a higher rate of vascular complications.

Hemodynamic characteristics of pulsatile blood flow through bifurcated stenosed carotid artery

Purpose Carotid artery is often associated with plaque deposition because of its shape and associated flow features. The shape of stenosed bifurcation is characterised by bifurcation angle (ß), planarity angle (α) and severity of stenosis (b). In the present work, three-dimensional numerical computations have been performed to analyse the effect of these geometrical parameters of carotid bifurcation on the characteristics of flow. Design/methodology/approach Governing equations of this study were solved using ANSYS Fluent 20.1 and the blood flow was considered as laminar, pulsatile and non-Newtonian. Instantaneous flow behaviour has been illustrated using vorticity, velocity and helicity contours, whereas the time-averaged wall shear stress ( τw¯) and oscillatory shear index (OSI) quantify the time-averaged behaviour. Findings The recirculation zone and secondary flow are ascertained to be stronger for higher bifurcation angle as compared to the lower bifurcation angle. Strength of the secondary flow is found to reduce with increase in α from 0° to 10°, whereas it grows as α varies from 10° to 20°. For higher bifurcation angles, τw¯ is lower than 2 Pa and OSI is greater than 0.2 on the outer walls. Similar observations were made for τw¯ and OSI distribution on bottom wall in non-planar cases, which predicted atherogenic locations. Originality/value The values for ß were taken as 30°, 45°, 60° and 75°, whereas for α, range of 0°–20° was chosen. The stenosis was considered on the outer wall of internal carotid artery and its severity was considered within the range of 0%–60%.

Reply Letter to “Pulsatile Flow During Venoarterial-Extracorporeal Membrane Oxygenation: A Topic in Need of Attention”

Reply Letter to “Pulsatile Flow During Venoarterial-Extracorporeal Membrane Oxygenation: A Topic in Need of Attention”

Pulsatile Flow During Venoarterial-Extracorporeal Membrane Oxygenation: A Topic in Need of Attention.

Pulsatile Flow During Venoarterial-Extracorporeal Membrane Oxygenation: A Topic in Need of Attention.

First diagnosis of severe coarctation of the aorta necessitation percutaneous intervention during pregnancy, a case report

Abstract Background Coarctation of the aorta (CoA) is a common congenital heart defect that affects about 3-4 in every 10,000 live births. Despite clear signs on clinical examination, the diagnosis is sometimes not made until adulthood. An increasing number of patients with CoA are reaching child-bearing age. Unrepaired CoA or severe recurrent stenosis during pregnancy is a significant concern, as it poses a high risk of maternal and foetal complications and even death. Case summary A 21-year-old women was referred to the cardiology department at 17 weeks’ gestation for management of arterial hypertension and unexplained systolic murmur. She had been diagnosed with hypertension elsewhere the year before presentation, but unfortunately this remained unexplored. She had been started on labetalol early in the pregnancy. Clinical examination showed a loud systolic heart murmur extending from parasternal to subclavicular and scapular areas. Pulses in the lower extremities were very weak and blood pressure was slightly elevated with a significant gradient between the upper and lower extremities. Echocardiography showed remarkable absence of pulsatile flow in the abdominal aorta and narrowing just distal to the subclavian artery with typical diastolic tail pattern on suprasternal imaging. Cardiac magnetic resonance confirmed the presence of a severe coarctation distal to the subclavian artery and presence of multiple collaterals allocating this patient in the extremely high-risk category with a risk of up to up 40-100% of maternal cardiac event during pregnancy. An extensive multidisciplinary team meeting was convened. After initial medical optimisation, increased claudication and signs of placental hypoperfusion necessitated an endovascular procedure under general anaesthesia at 23 weeks’ gestation. A Bentley BeGraft Plus stent (16x38 mm) was successfully placed. Postoperative ultrasound showed biphasic placental perfusion and normalisation of blood pressure and ankle-brachial indices. At 36 weeks’ gestation, the patient gave birth to a healthy child. Conclusion CoA should be considered in any young patient with arterial hypertension. Altered maternal haemodynamics during pregnancy resulted in severe symptomatic CoA and reduced placental flow necessitating percutaneous intervention during pregnancy. A multidisciplinary pregnancy heart team is essential for optimal treatment management in these high-risk patients.

4D-Flow MRI and Vector Ultrasound in the In-Vitro Evaluation of Surgical Aortic Heart Valves - a Pilot Study.

The aim of this study was the initial investigation of 4D-Flow MRI and Vector Ultrasound as novel imaging techniques in the in-vitro analysis of hemodynamics in anatomical models. Specifically, by looking at the hemodynamic performance of state-of-the-art surgical heart valves in a 3D-printed aortic arch. The mock circulatory loop simulated physiological, pulsatile flow. Two mechanical and three biological aortic valves prostheses were compared in a 3D-printed aortic arch. 4D magnetic resonance imaging and vector flow Doppler ultrasound served as imaging methods. Hemodynamic parameters such as wall shear stress, flow velocities and pressure gradients were analyzed. The flow analysis revealed characteristic flow-patterns in the 3D-printed aortic arch. The blood-flow in the arch presented complex patterns, including the formation of helixes and vortices. Higher proximal peak velocities and lower flow volumes were found for biological valves. The mock circulatory loop in combination with modern radiological imaging provides a sufficient basis for the hemodynamic comparison of aortic valves.

Flow enhancement produced by a pulsatile flow of shear-thinning fluids in circular and concentric annular tubes

Although the analysis of the flow enhancement of non-Newtonian fluids produced by pulsatile flows through tubes is common in the literature, the case of Carreau fluid has not been analyzed, which is the aim of this work. This study determines the flow enhancement caused by the pulsatile fluid flow through (a) a circular tube and (b) a concentric annular tube. We show that the flow rate enhancement of the shear-thinning fluid is controlled by the Carreau number Cu, the Womersley number Wo, the fluid power-law index n, the ratio between the outer and inner radii κ, a parameter β that represents the ratio between the infinite and zero-shear viscosities, and the amplitude of the oscillatory signal ɛ. In both cases (a) and (b), a numerical solution of the start-up of the hydrodynamic is evaluated. With the aid of the velocity solution, the volumetric flow rate is determined under periodic conditions after the initial transient has vanished. Then, the fractional increase in the mean flow rate I due to the pulsatile pressure gradient is calculated. Furthermore, an asymptotic solution for small, intermediate, and very large values of the Carreau number is performed to provide physical insight into flow enhancement.

A General Scaling Law of Vascular Tree: Optimal Principle of Bifurcations in Pulsatile Flow

A General Scaling Law of Vascular Tree: Optimal Principle of Bifurcations in Pulsatile Flow

A computational study of the influence of wavy arteries and veins on hemodynamic characteristics in an unsteady state

The present work is focused on the study of hemodynamic characteristics for tortuous arteries/veins in a pulsatile flow. This work is an extension of an earlier work by the author, which reported the hemodynamic characteristics in a steady flow situation. It is a well-known fact that various geometric parameters affect the hemodynamics, such as the diameter of vessels, the diameter of mother and daughter tubes in bifurcation, the angle between them, and their relative magnitudes. This paper is focused on the effect of tortuosity produced in straight and bifurcating tubes under pulsatile flow conditions. A heartbeat rate of 120 bpm is considered for pulsation, covering one cycle of systole and diastole. The measure of tortuosity is defined by the varying pitch and the amplitude. The present analysis is carried out computationally using ANSYS. Results are presented through secondary flow streamline, velocity profile, and its effect on wall shear stress. Key findings are that secondary vortices are observed in the bifurcated model and counter-rotating vortices are observed in the wavy tube geometry. The velocity distribution is asymmetric in the case of the plain bifurcation geometry. In the case of the wavy tube and bifurcated geometry, there is a shift in peak velocity from the inner to the outer wall, depending on the crest and trough positions of the tortuous vein. Relative change in magnitude of velocity for wavy tube depends on the depth and pitch of wavy wall of the tortuous tube. The velocity reduces with an increase in time step for unsteady flow.