Physiological Pulsatile Flow Research Articles

Transitional turbulent flow in a stenosed coronary artery with a physiological pulsatile flow.

The turbulence in the blood flow, caused by plaque deposition on the arterial wall, increases by the combined effect of the complex plaque geometries and the pulsatile blood flow. The correlation between the plaque geometry, the pulsatile inlet flow and the induced turbulence in a constricted artery is investigated in this study. Pressure drop, flow velocity and wall shear stress are determined for stenosed coronary artery models with three different degrees of asymmetric stenosis and for different heart working conditions. A Computational Fluid Dynamics model, validated against experimental data published in the literature, was developed to simulate the blood pulsatile flow inside a stenosed coronary artery model. The transitional flow behaviour was quantified by investigation of the changes in the turbulence kinetic energy. It was shown that the separation starts from the side of the asymmetric stenosis and spreads to its opposite side further downstream. The results suggest that there is a high risk of the formation of a secondary stenosis at a downstream distance equal to 10 times of the artery diameter at the side and bottom regions of the first stenosis due to the existence of the recirculation zones and low shear stresses. Finally, a stenosed patient-specific coronary artery model was employed to illustrate the applicability of the obtained results for real geometry models. The results of this study provide a good prediction of pressure drop and blood flow rate, which can be applied in the investigation of the heart muscle workout and the required heart power.

Identification of viscoelastic properties of Dacron aortic grafts subjected to physiological pulsatile flow

In vascular surgery, most synthetic vascular grafts currently used for large vessels replacements are made of Dacron (polyethylene terephthalate; PET). In this study, the dynamic response of these synthetic arterial substitutes to physiological pulsatile conditions is investigated in depth. Experiments were performed on a mock circulatory loop developed to replicate physiological pulsatile pressure and flow. Two different models of Dacron grafts (branched and straight) were tested at various heart rate conditions. Results are presented in terms of cyclic axisymmetric diameter changes, hysteretic loops of the pressure-diameter change, and viscoelastic parameters, such as loss factor and storage modulus that are identified from the hysteresis loop. The amplitude of cyclic diameter change of the Dacron graft was found to be always below 0.2% for all the heart rates considered (from 57 to 187 bpm). The loss factor of the Dacron graft slightly increased with the heart rate; almost no effect of the pulse rate was observed on the storage modulus, which was identified to be around 100 MPa. Both glycerol-water mixture (i.e. the blood analogue fluid) and saline solution were used in the circulatory loop and results did not present significant differences between the two cases. This shows that the effect of the shear load on the dynamic response of Dacron grafts is negligible. A comparison between Dacron vascular implants and human thoracic aortas shows a large mismatch in their viscoelastic mechanical properties.

Reduction of Cerebral Emboli: In vitro Study with a Novel Cerebral Embolic Protection Device.

AimTo assess the efficacy of the TriGUARD 3™, a novel cerebral embolic protection (CEP) device in reducing cerebral embolization by deflecting embolic debris away from the cerebral circulation using a quantitative in vitro model.Methods and ResultsThis in vitro study assessed the ability of a cerebral embolic protection device to deflect embolic debris, by measuring the percent of particles and air bubbles, 200 µm and 300 µm in size, from entering the cerebral circulation compared to unprotected controls. A 3D printed silicone model of the ascending aorta, the aortic arch with its three major cerebral arteries and the descending aorta was connected to a custom-made simulator that mimics physiological pulsatile flow patterns of the left ventricle. Comparative analyses were used to assess the efficacy of the cerebral embolic protection device to deflect particles and air bubbles away from the major cerebral arteries. The percent of particles and air bubbles entering the major cerebral arteries was significantly lower with cerebral embolic protection compared to unprotected controls (p<0.0001). Cerebral protection resulted in 97.4–100% reduction in air bubble counts, and 97.4–97.8% reduction in particle counts compared to unprotected controls.ConclusionThis in vitro study used simulated physiologic flow conditions in an aortic arch model to demonstrate >97% efficacy of the TriGUARD 3 CEP device, in reducing cerebral embolization of particulate and air bubbles of 200 µm to 300 µm in size.

Analysis of Cerebrospinal Fluid Flowmetry in Evaluating the Efficiency of Endoscopic Third Ventriculostomy in Aqueductal Stenosis

Background: Endoscopic third ventriculostomy (ETV) approach was gaining popularity over shunt placement in obstructive hydrocephalus. Postoperative ETV assessment and patients follow up remains a matter of controversy and challenge to ensure efficiency and patency of ventriculostomy.Aim of the work: To assess whether cerebrospinal fluid (CSF) flow is restored after ETV and similarity to flow in normal aqueduct with patients clinical and ventricular size changes assessment.Patients and Methods: From April 2016 to April 2019, 30 patients with hydrocephalus due to aqueductal stenosis (AS) were treated with ETV. They were followed up for ventriculostomy patency within the 1st, 6th and 9th month after surgery and compared to 22 persons as a control group of normal aqueductal flow with phase contrast magnetic resonance imaging (PC MRI).Results: Twenty-three (23) patients restored pulsatile bidirectional pattern of CSF flow across the ventriculostomy similar to that of aqueductal flow. While one patient had no flow during the 1st follow up and 6 patients showed initial pulsatile flow then developed flow disturbance during the 2nd follow up period. Absolute stroke volume values showed significant statistical difference between ETV and control groups (p value < 0.001). The value of 85 μl showed sensitivity and specificity of 84.3% and 81.7%, respectively as a cutoff value of ETV efficiency.Conclusion: ETV is an efficient technique to restores the physiological pulsatile Cerebrospinal fluid flow. Absolute stroke volume was a good predictor of ETV efficiency.

Axisymmetric compact finite-difference lattice Boltzmann method for blood flow simulations.

An axisymmetric compact finite-difference lattice Boltzmann method is proposed to simulate both Newtonian and non-Newtonian flow of blood through a lumen. The curvature of the arteries could be accurately resolved using body-fitted mesh owing to the proposed finite-difference formulation. The axisymmetric nature of the flow, as well as the non-Newtonian nature of blood, are incorporated into the lattice Boltzmann equation using separate source terms. Using Chapman-Enskog expansion it is shown that the resulting lattice Boltzmann equation with these additional source terms recovers the macroscopic axisymmetric hydrodynamic equations. The solver is verified for (1) steady inflow of a Newtonian fluid through a stenosed lumen, (2) temporally developing pulsatile flow (Womersley flow) through a straight lumen with Newtonian fluid, and (3) steady inflow of a non-Newtonian fluid through a straight lumen. The solver is then applied to simulate the steady flow of a non-Newtonian fluid through a stenosed lumen, and it was found that a smaller recirculation zone and lower WSS values are obtained when compared with the flow of a Newtonian fluid. The capability of the solver to simulate spatially developing (velocity-driven) pulsatile flow is then demonstrated by simulating physiological pulsatile flow through an axisymmetric abdominal aortic aneurysm. From this simulation, the cycle-averaged wall shear stress is observed to have a steep gradient going from a minimum (negative) to a maximum (positive) value towards the distal end of the aneurysm, which is prone to the risk of rupture. An iterative procedure to select the geometric and flow parameters for unsteady inflow condition in the lattice Boltzmann method framework is demonstrated that accurately resolves all the timescales to achieve incompressibility. Overall, the present solver seems to be promising to simulate axisymmetric flow of blood with steady and pulsatile inflows while considering the blood rheology.

Comparative Study of Wall-Shear Stress at the Ascending Aorta for Different Mechanical Heart Valve Prostheses.

An experimental study is reported which investigates the wall shear stress (WSS) distribution in a transparent model of the human aorta comparing an St. Jude Medical (SJM) Regent bileaflet mechanical heart valve (BMHV) with the Lapeyre-Triflo FURTIVA trileaflet mechanical heart valve (TMHV) in physiological pulsatile flow. Elastic microcantilever structures, calibrated as micropillar WSS sensors by microparticle-image-velocimetry measurements, are applied to the wall along the ascending aorta (AAo). The peak WSS values in the BMHV are observed to be almost twice that of the values seen in the TMHV. Flow field analysis illuminates that these peaks are linked to the jet-like flows generated in the valves interacting with the aortic wall. Not only the magnitude but also the impact regions are specific for different valve designs. The side-orifice jets generated by the BMHV travel along the aortic wall in the AAo, impacting the wall throughout the AAo. However, the jets generated by TMHV impact further downstream in the AAo and results in a reduced WSS.

Patient Specific Diagnostics for cardiovascular diseases based on diagnostic imaging: an application to the aneurism of the ascending aorta

In the framework of a collaboration between clinicians and engineers (namely, the Department of Radiology of the Brotzu Hospital in Cagliari and the group of experimental hydraulics at DICAAR - University of Cagliari), methodologies for the application of the in vitro study of the cardiovascular fluid mechanics to the support of the physical interpretation of the diagnostic imaging data are being tested. To this aim, we set up a mock-loop able to reproduce the physiologic pulsatile flow and designed to host a replica of aortic root made of transparent silicon rubber. Then, we developed a procedure to obtain a transparent and compliant replica of a patient specific ascending aorta from diagnostic images. The patient specific aorta model can be inserted in the mock-loop to study the fluid dynamics by means of particle image velocimetry techniques. We compared the flow in three cases, corresponding to physiological conditions, mild and severe aortic root dilation, observing significant differences in the redirection of the transvalvular jet and vortex evolution in the aortic flow. The observed fluid dynamics differences may have relevant implications on the thromboembolism and vascular tissue damage potential.

Association Between Flow Acceleration in the Carotid Artery and Intracranial Aneurysms.

In physiologic pulsatile flow, velocity acceleration is an independent factor determining wall shear stress experienced by the vascular endothelium. The purpose of this study was to evaluate Doppler indices of systolic velocity acceleration in extracranial cerebral vessels and the occurrence of intracranial aneurysms. We reviewed medical records and 3.0-T brain magnetic resonance imaging with 3-dimensional time-of-flight magnetic resonance angiography of 1323 adults who underwent health checkups from June 2006 to November 2011, in whom 53 intracranial aneurysms were identified in 45 patients. Doppler ultrasound parameters of the carotid and vertebral arteries were analyzed in these 45 patients with aneurysms and compared with another 45 control participants matched for age and sex. We defined the maximum systolic acceleration (ACCmax ) as the maximum slope of the early phase of systolic acceleration on the Doppler waveform and the maximum acceleration index (AImax ) as the ratio of the ACCmax and peak systolic velocity. The Doppler analysis showed a significantly increased AImax and ACCmax in the common carotid artery (CCA), internal carotid artery, and vertebral artery in the aneurysm group. A cutoff 13.89 s-1 for the AImax of the CCA had sensitivity of 80% with a negative predictive value of 99% for intracranial aneurysms. This study suggests that the AImax of the CCA with a cutoff of 13.89 s-1 may be an alternative to 3-dimensional time-of-flight magnetic resonance angiography or computed tomographic angiography as a screening tool for intracranial aneurysms. Further prospective studies are needed to validate the diagnostic performance and cost-effectiveness of these indices for screening.

Analysis of blood flow energy characteristics of pulsatile and non-pulsatile flow during extracorporeal circulation

Objective: To analyze the magnitude of blood flow energy and characteristics of frequency domain between pulsatile flow and nonpulsatile flow during cardiopulmonary bypass and physiological flow. Methods: From January 2017 to December 2017, 60 cases of patients with mitral valve disease scheduled for mitral valve replacement or repair at Department of Cardiasurgery, Shanghai Chest Hospital, Shanghai Jiaotong University were randomly divided into 2 groups: pulsatile perfusion (PP) and non-pulsatile perfusion (NP). The magnitude of blood flow energy during pulsatile and non-pulsatile was calculated using energy equivalent pressure (EEP) and surplus hemodynamic energy (SHE) while fast Fourier transformation (FFT) was used to perform power spectral density analysis to identify the frequency domain characteristics between artificial and physiological flow (prior to CPB). The data was analyzed by analysis of variance or t test. Results: At the different time-points after occlusion, the EEP and SHE in PP group were respectively 1.52 to 1.62 and 2.03 to 2.22 times higher than NP at the distal of artery filter. The power density analysis revealed that the blood flow energy of physiological pulsatile flow patterns was within 40 Hz and the ratio of low frequency energy was more than 90% before clamp. The spectral energy ratio of low frequency decreased in both group compared with physiological flow was more obvious in NP group at the radial artery. The ratio of estimated value of power density of PP and NP groups analysis showed the corresponding 0 to 5 Hz, 0 to 10 Hz, 0 to 40 Hz frequency range values measured at the radial artery and filter were 9.51, 4.68, 3.59 and 3.87, 2.69, 2.38 respectively after occulusion. In each frequency range, the energy of PP is higher than that of NP, and the lower the frequency, the greater the difference. The ratio of estimated value of power density of PP and NP groups for the three frequencies measured at the radial artery before and after occlusion were 2.86, 2.83, 2.75 and 14.70, 12.74, 9.85 respectively, and decreased significantly in NP group and low frequency energy. The ratio of estimated value of power density of PP and NP groups under the three different frequencies measured at the radial artery and filter were 26.35, 33.15, 37.36 and 37.41, 54.18, 56.64 respectively, in the conduction process from filter to radial artery, energy exhaustion is significant, especially in group NP. Conclusions: The PP provides significantly more energy than the NP whereby the PP is closer to the physiological pulsatile on the energy frequency structure and attenuation characteristics, with mainly low frequency energy of 0 to 5 Hz and weak energy attenuation. The energy loss of non-pulsatile flow is obvious, especially the low frequency energy.

Three-dimensional biomechanics of coronary arteries

The focus of this paper is to model and simulate the nonlinear dynamics of atherosclerotic coronary arteries as a tool to predict the initiation of heart attack. A dynamic three-dimensional visco/hyperelastic fluid–structure interaction model of an atherosclerotic coronary artery is developed by means of the finite element method (FEM) using ANSYS. Simulations are undertaken using the model to examine the risk of plaque rupture with the following parameters taken into account with varying levels of stenosis: physiological pulsatile blood flow; tapered shape of the artery; viscoelasticity and hyperelasticity of the artery wall; effect of the motion of the heart; active artery muscle contraction; the lipid core inside the plaque; three layers of the artery wall; non-Newtonian characteristics of the blood flow; and micro-calcification; this paper is the first to incorporate all these effects. The generated model can potentially be used as a predictive tool for plaque rupture to identify the conditions that are high risk for atherosclerosis plaque rupture.

Long-Term Durability Test for the Left Ventricular Assist System EVAHEART under the Physiologic Pulsatile Load.

The EVAHEART Left Ventricular Assist System (LVAS) was designed for the long-term support of a patient with severe heart failure. It has an original water lubrication system for seal and bearing and wear on these parts was considered one of its critical failure modes. A durability test focusing on wear was designed herein. We developed a mock loop, which generates a physiologic pulsatile flow and is sufficiently durable for a long-term test. The pulsatile load and the low fluid viscosity enable the creation of a severe condition for the mechanical seal. A total of 18 EVAHEART blood pumps completed 2 years of operation under the pulsatile condition without any failure. It indicated the EVAHEART blood pump had a greater than 90% reliability with a 88% confidence level. The test was continued with six blood pumps and achieved an average of 8.6 years, which was longer than the longest clinical use in Japan. The test result showed that no catastrophic, critical, marginal, or minor failures of the blood pump or their symptoms were observed. The seal performance was maintained after the test. Moreover, the surface roughness did not change, which showed any burn or abnormal wear occurred. The original water lubrication system equipped in EVAHEART LVAS prevent severe wear on the seal and the bearing, and it can be used in the bridge to transplant and destination therapy.

Effect of pulsatile blood flow on LDL transport in arterial layers

Considering the pulsatile nature of blood flow, the transport of low density lipoprotein (LDL) species in the arterial wall has been numerically analysed. A straight axi-symmetric arterial segment with four arterial porous layers vis. endothelium, intima, internal elastic lamina and media has been taken into consideration. These layers are considered porous in nature. For modelling the fluid flow in the lumen and the arterial wall, Navier-Stokes equation and Darcy's equation have been used respectively. The solute flow modelling in the lumen and in the arterial wall has been done by using convection-diffusion equation and convection-diffusion-reaction equation respectively. Simple pulsatile and physiological pulsatile model of blood flow have been considered in the present analysis. The present study shows that the physiological pulsatile flow is having more impact on the radial filtration velocity at lumen-endothelium interface than that of the case for simple pulsatile nature of flow. Therefore, the possibility of enhancement in solute transport in the arterial wall is more in case of physiological pulsatile nature of flow.

Pulsatile Non-Newtonian Fluid Flows in a Model Aneurysm with Oscillating Wall

This research presents a numerical simulation of an unsteady two-dimensional channel flow of Newtonian, and some non-Newtonian fluids using the finite volume method. The walls of the geometry oscillate sinusoidally with time. We have used the Cartesian curvilinear coordinates to handle complex geometries, i.e., arterial stents and bulges and the governing Navier-Stokes equations have been modified accordingly. Physiological pulsatile flow has been used at the inlet to characterize four different non-Newtonian models, i.e., the (i) Carreau, (ii) Cross, (iii) Modified-Casson and (iv) Quemada. We have presented the numerical results in terms of wall shear stress (WSS), pressure distribution as well as the streamlines and discussed the hemodynamic behaviors for laminar and laminar to turbulent transitional flow conditions. An increase of wall shear stress and a decrease in wall pressure are significantly observed at the stenosis throat for high Reynolds number and highly stenosed arteries. Likewise, the flow recirculation also increases if the narrowing level and the Reynolds number increases in the dilated region which eventually leads the stream to experience a transition to turbulence at $Re= 750$. The results for the fluid flow through an aneurysm just after a stenosis with oscillating wall are novel in the literature.

New Technology Mimics Physiologic Pulsatile Flow During Cardiopulmonary Bypass.

The VentriFlo True Pulse Pump (Design Mentor, Inc., Pelham, NH, USA) is the first blood pump designed to mimic human arterial waveforms in a standard oxygenation circuit. Our aim was to demonstrate the feasibility and safety of this pump in preparation for future studies to determine possible clinical advantages. We studied four piglets (41.4-46.2 kg): three with an implanted VentriFlo pulsatile pump and one with the nonpulsatile ROTAFLOW pump (MAQUET Holding B.V. & Co. KG, Rastatt, Germany) as a control. Hemodynamics was monitored during 6-h cardiopulmonary bypass (CPB) support and for 2 h after weaning off CPB. The VentriFlo demonstrated physiologic arterial waveforms with arterial pulse pressure of 24.6 ± 5.7 mm Hg. Pump flows (2.0 ± 0.1 L/min in ROTAFLOW; 1.9 ± 0.1 L/min in VentriFlo) and plasma free hemoglobin levels (27.9 ± 12.5 mg/dL in ROTAFLOW; 28.5 ± 14.2 mg/dL in VentriFlo) were also comparable, but systemic O2 extraction (as measured by arterial minus venous O2 saturation) registered slightly higher with the VentriFlo (63.2 ± 6.9%) than the ROTAFLOW (55.4 ± 6.5%). Histological findings showed no evidence of ischemic changes or thromboembolism. This pilot study demonstrated that the VentriFlo system generated pulsatile flow and maintained adequate perfusion of all organs during prolonged CPB.

Effects of blood flow dynamics on autologous pericardial degeneration in reconstructed pulmonary arteries.

To clarify the risk factors for abnormal degeneration of autologous pericardium, the mechanical stress on the endothelial tissue caused by turbulent blood flow in the pulmonary artery (PA) reconstructed with autologous pericardium and major aortopulmonary collateral arteries was assumed in pulmonary atresia and ventricular septal defect. Patient-specific PA models were created for 6 patients based on their past computed tomography images taken after unifocalization of major aortopulmonary collateral arteries. Computational fluid dynamics models were created to simulate the physiological pulsatile flow including the peripheral reflection wave, characteristic impedance and autonomous regulation system. Flow streamline, wall shear stress (WSS) and the oscillatory shear index (OSI) were calculated from the simulated result. PA degeneration was evaluated with the computed tomography images before the intracardiac repair. Regions with physiological high WSS had fewer abnormal changes. Excessively high WSS was often detected at the anastomosis site of the reconstructed PA, and intimal thickening was found in these regions during intracardiac repair. Regions with high OSI and low WSS had dilated change within several months. In 1 patient, in particular, detached vortex flow occurred at the rectangular angle anastomosis site of the right PA in flow streamline, resulting in high OSI and low WSS with abnormal enlargement in the pericardium. Endothelial stress caused by blood flow would affect the degeneration of autologous pericardium and major aortopulmonary collateral arteries in the reconstructed PA. High OSI and low WSS might induce enlargement or dilatation, and excessively high WSS in the anastomosis site might induce intimal thickening.

Small diameter vascular graft with fibroblast cells and electrospun poly (L-lactide-co-ε-caprolactone) scaffolds: Cell Matrix Engineering

Electrospun scaffolds have been widely used in tissue engineering due to their similar structure to native extracellular matrices (ECM). However, one of the obstacles limiting the application of electrospun scaffolds for tissue engineering is the nano-sized pores, which inhibit cell infiltration into the scaffolds. To overcome this limitation, we approached to make layers which are consisted of cells onto the electrospun sheet and then tubular structure was constructed by rolling. We called this as ‘Cell Matrix Engineering’ because the electrospun sheets were combined with the cells to form one matrix. They maintained 3-D tubular structures well and their diameters were 4.1 mm (±0.1 mm). We compared the mechanical and biological properties of various vascular grafts with the electrospun PLCL sheets of different thickness. In these experiments, the vascular graft made with thin sheets showed a better cell proliferation and attachment than the grafts made with thick sheets because the thin layer allowed for more efficient mass transfer and better permeability than the thick layer. Culturing under physiological pulsatile flow condition was demonstrated in this work. These dynamic conditions provided the improved mass transport and aerobic cell metabolism. Therefore, the Cell Matrix Engineered vascular graft holds a great promise for clinical applications by overcoming the limitations associated with conventional scaffolds.

ANALYSIS OF WALL SHEAR PARAMETERS OF PHYSIOLOGICAL PULSATILE FLOW THROUGH MILD AND SEVERE ARTERIAL STENOSIS AND CORRELATION TO ATHEROSCLEROSIS

Numerical simulations of physiological pulsatile flow through mild and severe arterial stenosis are carried out to analyze wall shear stress parameters. The governing equations are solved by finite volume method. The study shows that the distribution patterns of time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI) and relative residence time (RRT) are same forboth mild stenosis and severe stenosis. The magnitude of peak TAWSS and low TAWSS and extent of negative TAWSS of severe stenosis is higher than those of mild stenosis. The OSI value of severe stenosis is higher at distal to throat of stenosis in comparison to mild stenosis. The size of recirculation zone of severe stenosis is lager than that of mild stenosis. The abnormally high peak value of RRT of severe stenosis is concentrated and located at far away from stenosis when it is compared with mild stenosis. Article DOI: https://dx.doi.org/10.20319/mijst.2016.23.4054 This work is licensed under the Creative Commons Attribution-Non-commercial 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc/4.0/ or send a letter to Creative Commons, PO Box 1866, Mountain View, CA 94042, USA.

Computational Modelling of Cardiovascular Stenosis

Stenosis is a narrowing of an artery. Atherosclerotic plaque deposits are a common abnormality found in major blood arteries that can potentially perturb the flow field. The work reported here describes the flow pattern in the various shape of stenosed artery for knowing the wall shear stress and pressure distribution. A fully developed pulsatile flow through stenotic tubes was considered. A finite volume CFD solver is developed for simulation of blood flow in 50-90% cross-section area reduction of stenosed artery. Carreau-Yasuda model is considered for modelling of blood viscosity. Inlet condition based on Womersley flow is applied at the inlet of the artery and time-varying spatial pressure boundary condition is imposed as the Dirichlet boundary condition at the outlet. The Neumann boundary conditions (zero gradient of velocity in the axial direction at the outlet) were applied for velocity at the outlet. The code was validated against the well-known problem and good agreement was found. Post-validation, the simulating physiological pulsatile flow was presented for the various shape of stenosis. The result shows that close to stenosis, the flow is transient developed and are responsible for developing high wall shear stress on the wall of arteries. The results show that 90% blockage in an artery can be extremely dangerous, causing the flow pattern distribute and become developing (i.e. velocity profile is not parabolic).

Where to Fenestrate in Aortic Dissection Type B? An Ex Vivo Study

Fenestration is a minimally invasive alternative for the treatment of acute symptomatic aortic dissections because it may quickly decrease the pressure gradient of the false lumen. It remains unclear where the optimal location of these fenestrations should be chosen. The purpose of this study was to study false lumen volume (FLV) after different fenestration strategies in porcine exvivo models of aortic type B dissection. An artificial dissection was created in exvivo porcine aortas. A total number of 6 aortic dissection models were made. The dissection flap was divided in 3 equal parts; proximal, mid, and distal sections. In 3 models, a fenestration was made in the center of the proximal section of the dissection flap. In the 3 others in the center of the distal part of the dissection flap. The aorta was positioned in a validated invitro circulatory system with physiological pulsatile flow. Volume measurements of true lumen volume and FLV were assessed with computed tomography. Performing a fenestration in the proximal part of the dissection flap resulted in FLV increase in 2 of the 3 models. Performing a fenestration in the distal part of the dissection flap resulted in FLV decrease in all 3 models. False lumen reduction was obtained significantly in the distally fenestrated models compared to the proximally fenestrated models (9.6±3.5% vs. 0.7±2.9%, P=0.03). In this exvivo study, we showed that distal fenestration of the false lumen in aortic dissection will result in the largest false lumen reduction.

Computational fluid dynamics simulation of the right subclavian artery cannulation

ObjectiveThe purpose of this study was to evaluate the efficacy of right subclavian artery cannulation using computational fluid dynamics. MethodsPatient-specific models of the aortic arch were made with 4 patterns (1: normal aorta, 2: ascending aorta aneurysm, 3: distal arch aneurysm, 4: bovine arch) based on the computed tomography images. Right subclavian artery and ascending aorta cannulation models were created to simulate the physiologic pulsatile flow. Perfusion flow through the arterial cannula was set to 2.50 L/min (50% flow), 3.75 L/min (75% flow), and 5.0 L/min (100%), respectively, and a 3-dimensional movie was made of 1 cardiac cycle to evaluate the blood flow. ResultsIn both 50% and 75% flow simulation with right subclavian artery cannulation, the blood streamline from the right subclavian artery produced retrograde flow of the brachiocephalic artery and antegrade flow of the right common carotid artery throughout the cardiac cycle in all cases. Right subclavian artery flow deflected ascending aorta flow to the descending aorta. Left-side supra-aortic branches were perfused by blood flow from both the right subclavian artery cannula and the aortic valve. The ascending aortic cannulation model showed that blood flow from the aortic valve reached all 3 supra-aortic vessels in systole. ConclusionsRight subclavian artery cannulation was cerebroprotective, especially on the right side.