Blood Flow Patterns In Aorta Research Articles

Restoration of flow in the aorta: a novel therapeutic target in aortic valve intervention.

Aortic blood flow patterns are closely linked to the morphology and function of the left ventricle, aortic valve and aorta. These flow patterns demonstrate the exceptional adaptability of the cardiovascular system to maintain blood circulation under a broad range of haemodynamic workloads and can be altered in various pathophysiological states. For instance, normal ascending aortic systolic flow is predominantly laminar, whereas abnormal aortic systolic flow is associated with increased eccentricity, vorticity and flow reversal. These flow abnormalities result in reduced aortic conduit function and increased energy loss in the cardiovascular system. Emerging evidence details the association of these flow patterns with loss of aortic compliance, which leads to adverse left ventricular remodelling, poor tissue perfusion, and an increased risk of morbidity and death. In this Perspective article, we review the evidence for the link between aortic flow-related abnormalities and cardiovascular disease and how these changes in aortic flow patterns are emerging as a therapeutic target for aortic valve intervention in first-in-human studies.

Non-intrusive data-driven ROM framework for hemodynamics problems

Reduced order modeling (ROM) techniques are numerical methods that approximate the solution of parametric partial differential equation (PED) by properly combining the high-fidelity solutions of the problem obtained for several configurations, i.e. for several properly chosen values of the physical/geometrical parameters characterizing the problem. By starting from a database of high-fidelity solutions related to a certain values of the parameters, we apply the proper orthogonal decomposition with interpolation (PODI) and then reconstruct the variables of interest for new values of the parameters, i.e. different values from the ones included in the database. Furthermore, we present a preliminary web application through which one can run the ROM with a very user-friendly approach, without the need of having expertise in the numerical analysis and scientific computing field. The case study we have chosen to test the efficiency of our algorithm is represented by the aortic blood flow pattern in presence of a left ventricular (LVAD) assist device when varying the pump flow rate.

Computational analyses of aortic blood flow under varying speed CF-LVAD support

Continuous Flow Left Ventricular Assist Devices (CF-LVADs) generally operate at a constant speed whilst supporting a failing heart. However, constant speed CF-LVAD support may cause complications and increase the morbidity rates in the patients. Therefore, different varying speed operating modes for CF-LVADs have been proposed to generate more physiological blood flow, which may reduce complication rates under constant speed CF-LVAD support. The proposed varying speed CF-LVAD algorithms simulate time-dependant dynamics and three dimensional blood flow patterns in aorta under varying speed CF-LVAD support remain unclear. The aim of this study is to evaluate three dimensional blood flow patterns in a patient-specific aorta model under co-pulsating and counter-pulsating CF-LVAD support modes driven by speed and flow rate control algorithms using numerical simulations. Aortic blood flow was evaluated for 10,000 rpm constant speed CF-LVAD support generating 4.71 L/min mean flow rate over a cardiac cycle. Co-pulsating and counter-pulsating CF-LVAD speed control operated the pump at the same average speed over a cardiac cycle and co-pulsating and counter-pulsating CF-LVAD flow rate control generated the same average flow rate over cardiac cycle as in the constant speed pump support. Simulation results show that the utilised counter-pulsating pump flow rate control may decrease the haemolysis to a third compared to the most commonly employed constant speed pump operating mode. Moreover, CF-LVAD support utilising counter-pulsating pump flow rate control generated the most favourable hemodynamic characteristics, i.e. low Dean number, least wall shear stress and least haemolysis values among the investigated cases.

Quantitative Study of Abdominal Blood Flow Patterns in Patients with Aortic Dissection by 4-Dimensional Flow MRI

The purpose of this study is to evaluate the hemodynamic characteristics of the true lumen (TL) and the false lumen (FL) in 16 patients with aortic dissection (AD) using 4D flow magnetic resonance imaging (MRI) and thoracic and abdominal computed tomography (CT) angiography. The quantitative parameters that were measured in the TL and FL included velocity and flow. The mean area and regurgitant fraction of the TL were significantly lesser at all four levels (p < 0.05); the average through-plane velocity, peak velocity magnitude, average net flow, peak flow, and net forward volume in the TL were considerably higher (p < 0.05). The intimal entry’s size was negatively correlated with the blood flow velocity and flow rate in the TL (p < 0.05) and positively correlated with the average through-plane velocity, average net flow, and peak flow in the FL (p < 0.05); the blood flow indices in the TL were enhanced with an increase in the intimal entry numbers (p < 0.05) and the peak flow in the FL was lowered (p = 0.025); if FL thrombosis existed, the average through-plane velocity and peak velocity magnitude in the TL were substantially higher (p < 0.05). 4D flow MRI facilitates qualitative and quantitative analysis of the alterations in the abdominal aortic blood flow patterns.

The study on hemodynamic effect of series type LVAD on aortic blood flow pattern: a primary numerical study.

BackgroundLeft ventricular assist device (LVAD) has become an alternative treatment for end-stage heart failure patients. Series type of LVAD, as a novel LVAD, has attracted more and more attention. The hemodynamic effects of series type LVAD on aortic blood pattern are considered as its important characteristics; however, the precise mechanism of it is still unclear.MethodsTo clarify the hemodynamic effects of series type LVAD on aortic blood flow pattern, a comparative study on the aortic blood flow pattern and hemodynamic states were carried out numerically for two cases, including series type LVAD support and normal condition. The steady-state computational fluid dynamic (CFD) approach was employed. The blood flow streamline, blood velocity vector and distribution of wall shear stress (WSS) were calculated to evaluate the differences of hemodynamic effects between both conditions.ResultsThe results demonstrated that the aortic flow pattern under series type LVAD showed significant different from that of normal condition. The strength of aortic swirling flow was significantly enhanced by the series type LVAD support. Meanwhile, the rotating direction of swirling flow under LVAD support was also dominated by the rotating direction of series type LVAD. Moreover, the blood velocity and WSS under LVAD support were also significantly enhanced, compared with that under normal condition.ConclusionThe hemodynamic states, including the aortic swirling flow characteristic, was significantly dominated by LVAD support. Present investigation could provide not only a useful information on the vascular complications caused by LVAD support, but also provide a useful guide for optimal the structure of the series type LVAD.

A numerical analysis of the aortic blood flow pattern during pulsed cardiopulmonary bypass

In the modern era, stroke remains a main cause of morbidity after cardiac surgery despite continuing improvements in the cardiopulmonary bypass (CPB) techniques. The aim of the current work was to numerically investigate the blood flow in aorta and epiaortic vessels during standard and pulsed CPB, obtained with the intra-aortic balloon pump (IABP). A multi-scale model, realized coupling a 3D computational fluid dynamics study with a 0D model, was developed and validated with in vivo data. The presence of IABP improved the flow pattern directed towards the epiaortic vessels with a mean flow increase of 6.3% and reduced flow vorticity.

108 4D-flow CMR demonstrates the regional distribution of aortic flow disturbance in Marfan syndrome

Background Marfan syndrome (MFS) commonly leads to progressive aortic dilation, aneurysm formation and aortic dissection, particularly at the aortic sinuses (∼60% of dissections), and descending thoracic aorta (∼30% of dissections). Abnormal aortic blood flow patterns may contribute to the enlargement and dissection of an inherently weak aorta, or to late complications after aortic dissection. Methods 18 patients with MFS (3 with a prior history of aortic dissection and aortic root surgery, 15 with no such history) and 18 healthy volunteers matched for age, sex and height underwent CMR at 3T, using a time-resolved 3-dimensional flow technique. The aorta was segmented into regions on the basis of anatomic features (Abstract 108 figure 1A). Each segment was visualised using streamlines (Abstract 108 figure 1B) and particle traces, and was rated as normal or abnormal, (defined as the presence of turbulent flow vortices) and, where abnormal, extent of abnormality was classified on a 4-point scale determined by the extent of radial involvement of the aortic lumen. Wall shear stress (WSS) quantification was undertaken at predefined aortic locations (Abstract 108 figure 1A). Results Significant vortical flow in any segment (defined as flow disturbance occupying more than one half of the aortic lumen) was present in all patients with MFS, but in only 7/18 controls (p 2 , compared to +0.54 N/m 2 in healthy controls). Aortic flow disturbance in MFS was of one of three types: Type A: flow disturbance confined to the sinuses of Valsalva, Type B: flow disturbance confined to the proximal descending aorta, Type C: flow disturbance in both the sinuses of Valsalva and the proximal descending aorta. Conclusion Patients with MFS commonly show aortic flow disturbance. The sinuses of Valsalva and proximal descending aorta are most frequently affected. Flow disturbance can be categorised into one of three categories, and we anticipate that flow abnormalities within a segment will predict progressive aortic dilation and dissection in an ongoing follow-up study.

Accelerated time-resolved three-dimensional MR velocity mapping of blood flow patterns in the aorta using SENSE and k-t BLAST

Purpose To assess the feasibility and potential limitations of the acceleration techniques SENSE and k-t BLAST for time-resolved three-dimensional (3D) velocity mapping of aortic blood flow. Furthermore, to quantify differences in peak velocity versus heart phase curves. Materials and methods Time-resolved 3D blood flow patterns were investigated in eleven volunteers and two patients suffering from aortic diseases with accelerated PC-MR sequences either in combination with SENSE ( R = 2) or k-t BLAST (6-fold). Both sequences showed similar data acquisition times and hence acceleration efficiency. Flow-field streamlines were calculated and visualized using the GTFlow software tool in order to reconstruct 3D aortic blood flow patterns. Differences between the peak velocities from single-slice PC-MRI experiments using SENSE 2 and k-t BLAST 6 were calculated for the whole cardiac cycle and averaged for all volunteers. Results Reconstruction of 3D flow patterns in volunteers revealed attenuations in blood flow dynamics for k-t BLAST 6 compared to SENSE 2 in terms of 3D streamlines showing fewer and less distinct vortices and reduction in peak velocity, which is caused by temporal blurring. Solely by time-resolved 3D MR velocity mapping in combination with SENSE detected pathologic blood flow patterns in patients with aortic diseases. For volunteers, we found a broadening and flattering of the peak velocity versus heart phase diagram between the two acceleration techniques, which is an evidence for the temporal blurring of the k-t BLAST approach. Conclusion We demonstrated the feasibility of SENSE and detected potential limitations of k-t BLAST when used for time-resolved 3D velocity mapping. The effects of higher k-t BLAST acceleration factors have to be considered for application in 3D velocity mapping.

In Vivo Quantification of Helical Blood Flow in Human Aorta by Time-Resolved Three-Dimensional Cine Phase Contrast Magnetic Resonance Imaging

The mechanics of blood flow in arteries plays a key role in the health of individuals. In this framework, the role played by the presence of helical flow in the human aorta is still not clear in its relation to physiology and pathology. We report here a method for quantifying helical flow in vivo employing time-resolved cine phase contrast magnetic resonance imaging to obtain the complete spatio-temporal description of the three-dimensional pulsatile blood flow patterns in aorta. The method is applied to data of one healthy volunteer. Particle traces were calculated from velocity data: to them we applied a Lagrangian-based method for helical flow quantification, the Helical Flow Index, which has been developed and evaluated in silico in order to reveal global organization of blood flow. Our results: (i) put in evidence that the systolic hemodynamics in aorta is characterized by an evolving helical flow (we quantified a 24% difference in terms of the content of helicity in the streaming blood, between mid and early systole); (ii) indicate that in the first part of the systole helicity is ascrivable mainly to the asymmetry of blood flow in the left ventricle, joined with the laterality of the aorta. In conclusion, this study shows that the quantification of helical blood flow in vivo is feasible, and it might allow detection of anomalies in the expected physiological development of helical flow in aorta and accordingly, could be used in a diagnostic/prognostic index for clinical practice.

IN VIVO QUANTITATIVE ANALYSIS OF HELICAL FLOW IN AORTA USING 3D PHASE CONTRAST MRI

The mechanics of blood flow in arteries represents a central issue of the biological research [Liepsch, 1986]. The asymmetry of the blood flow in the left ventricle, assumed to facilitate the ejection of blood in the primary circulation, joined with the righthanded twist of the great arteries, produce a flow field characterized by complicated helical motions in the aortic arch [Kilner, 1993]. The role played by the presence of helical flow in the human aorta has not been fully clarified, and several aspects are still not clear in their relation to physiology. The challenge in this field is represented by the search for a quantitative description from the in vivo available information. We report here the first attempt of quantifying helical flow in vivo employing time-resolved CINE PC MRI to obtain complete spatio-temporal coverage of the 3D pulsatile blood flow patterns in aorta. To do this, we applied a quantitative method [Grigioni, 2005; Morbiducci., 2007], which has been found useful to reveal global organization of the flow.

Effects of continuous flow left ventricular assist device support on skin tissue microcirculation and aortic hemodynamics.

Continuous flow ventricular assist devices (CFVADs) are thought to be the next generation of circulatory assist devices. With many now in various stages of development or clinical trial, it is important that the physiologic aspects of these pumps be critically analyzed. In this study, 15 calves were divided into two groups. One group received a CFVAD, and the other a sham implant. Two additional animals were used in an acute study to examine aortic blood flow patterns from a CFVAD. Tissue perfusion was measured on all animals before surgery and then weekly thereafter. Before surgery, there was no difference in hemodynamics or tissue perfusion between studied animals. Postoperatively, CFVAD animals had statistically significant increased diastolic pressure. Significantly decreased pulse pressure, pulse index, and tissue perfusion were also observed in CFVAD animals. Results from the flow pattern studies suggested that at moderate levels of pump support (40-75%), the amount of blood flow distal to the outflow graft anastomosis decreased approximately 25% because of increased regurgitant blood flow in the aorta. These results suggest that the diminished tissue perfusion is likely due to changes in aortic hemodynamics and provide some insight into the distribution of flow from CFVADs.

The physiologic basis for and nursing considerations in the use of subatmospheric concentrations of oxygen in HLHS.

Subatmospheric concentrations of oxygen are used in the preoperative and postoperative care of infants with hypoplastic left heart syndrome (HLHS). This technique increases the pulmonary vascular resistance (PVR) and thereby improves systemic blood flow. There have been no controlled studies of this therapy in humans. Changes in aortic blood flow patterns, suggesting improved systemic circulation after administration of nitrogen, have been shown by Doppler ultrasound. Video segments are included in the electronic version of this article to demonstrate the immediate circulatory effects of therapy. No significant long-term effects on PVR have been found. A clear understanding of the anatomy, physiology, and therapeutic maneuvers used to balance pulmonary blood flow and systemic blood flow is essential for caregivers of infants with HLHS. Infants receiving subatmospheric concentrations of oxygen require meticulous nursing care to detect early changes in the relative vascular resistance and to monitor for the hemodynamic effects of medical and nursing interventions.

Effective dose and cardiovascular effects of cilazapril in children with heart failure

A enzyme (ACE) inhibitors are effective for the treatment of heart failure, but their pharmacology and precise hemodynamic effects have not yet been well defined in pediatric patients. The purpose of the present study, therefore, was to clarify acute pharmacologic characteristics and to determine the effective dose of cilazapril, an ACE inhibitor, along with its cardiovascular effects. We chose cilazapril because our preliminary experience in children and data in adults has shown that this ACE inhibitor may have a less renotoxic effect. The present study consisted of 2 steps: the first step was to determine the effective dose of cilazapril and the second step was to show its cardiovascular effects by using the stress-velocity index and aortic blood flow pattern. • • • The first step study included 20 patients, age range from 3 months to 13 years (4.5 3.5 years), who were hospitalized for either diagnostic or interventional cardiac catheterization; none had cyanosis. The 20 patients were divided randomly into 3 groups according to cilazapril dose; group 1 included 7 patients who were given 0.01 mg/kg; group 2 included 8 patients who were given 0.02 mg/kg; and group 3 included 5 patients who received 0.04 mg/kg. Age and body weight were not statistically different in these 3 groups. We determined plasma concentration of cilazaprilat, which is a diacid body and active metabolite of cilazapril, and ACE activity by prevalidated radioenzymatic assays, at 2, 6, 12, and 24 hours after a single oral dose of the medicine. The second step study consisted of 13 patients with congestive heart failure. Heart failure was clinically defined as the use of anticongestive medicine, such as diuretics and/or digoxin, because of persistent cardiomegaly, hepatomegaly, or reduced physical activity. Accordingly, all patients were on diuretics, 4 were on digoxin, and 5 were on isosorbide dinitrate. During the present study, doses of these medications were not changed. Twelve patients took part in the study 1 to 2 months after open heart surgery, and the remaining patient had dilated cardiomyopathy (Table 1). They were in stable heart failure with conventional therapy. Their age averaged 5.0 3.6 years. Cilazapril was administered orally twice a day. The dose was initially 0.01 mg/kg/day to avoid unexpected hypotension, which is often seen after the first dose, and it was gradually increased until apparent cardiovascular effects were confirmed or the dose reached 0.04 mg/kg/day. The 0.04 mg/kg/day dose was determined to be effective by the first step study. After 5 days on the final dose, plasma concentration of cilazaprilat, plasma ACE activity, and plasma renin activity were measured 2 hours after oral ingestion of the drug. By Bor M-mode echocardiography, we measured left ventricular (LV) diastolic and systolic dimensions, end-systolic LV posterior wall thickness, and LV preejection and ejection time according to standard methods. The RR interval was also measured on an electrocardiogram that was recorded simultaneously with echocardiogrpahic recordings. Fractional shortening (FS) and systolic time interval were also calculated as

Magnetic resonance velocity vector mapping of blood flow in thoracic aortic aneurysms and grafts

Magnetic resonance imaging with multidirectional cine velocity mapping was used to study relationships between aortic blood flow patterns and the geometry of thoracic aortic aneurysms and grafts. Ten patients with 13 thoracic aortic aneurysms, single or multiple, or grafts (4) participated in the study. The causes of disease were atherosclerosis (4), Marfan's syndrome (2), trauma (1), and unknown (1), and there were two dissections. Spin-echo imaging and cine velocity mapping in 10 mm thick slices with vertical and horizontal velocity encoding were done. Maps of the two velocity components were processed into multiple computer-generated streaks whose orientation and length corresponded to velocity vectors in the chosen plane. The dynamic arrow maps were compared with previously reported aortic arrow maps from normal subjects. The forward flow occupied the entire lumen in the normal aorta in systole and small vortices were only present in the sinuses of Valsalva. Atherosclerotic aneurysms in the ascending aorta were located at the anterior right and had oblique, eccentric jet flows that created a large secondary vortex in the aneurysm. Patients with Marfan's syndrome had a central jet and two large vortices, one on each side. All other aneurysms, dissections, and grafts had irregular flows and vortices not seen in normal subjects. Magnetic resonance imaging with multidirectional velocity mapping is a powerful noninvasive tool to assess morphologic features and disturbed blood flow in aortic aneurysms and grafts. Recognizably altered flow patterns were found to be associated with altered vessel geometry. The significance of this requires further investigation. (J T HORAC C ARDIOVASC S URG 1995;110: 704-14)

95 GATED PULSED DOPPLER ASSESSMENT OE SIMPLE COARCTATION IN OF THE AORTA IN PEDIATRIC PATIENTS

Pulsatile flow dynamics are altered distal to an area of obstruction. To investigate the effects of simple coarctation of the aorta (CAo) on descending aortic blood flow patterns, doppler interrogation of the thoracoabdominal aorta was performed in 12 infants with CAo less than 18 months of age, and 15 age matched controls. All patients with CAo demonstrated continuation of high forward flow throughout the cardiac cycle with prolongation of both acceleration and deceleration phases. Indexing the ratio of acceleration and deceleration phases of flow with acceleration time, measured as the time from onset of flow to peak frequency corrected for cycle length, separated CAo patients from normal subjects. In contrast, doppler frequency distributions from the ascending aorta did not distinguish CAo from controls. In conclusion, gated pulsed doppler examination of the thoracoabdominal aorta displayed a frequency distribution specific for coarctation of the aorta. The discrepancy between ascending and descending frequency distributions represents systolic loading and diastolic decompression of the obstructed proximal thoracic aorta. This method can provide a useful adjunct to serial follow-up of coarctation patients and early detection of recoarctation.

Organ blood flow during pulsatile cardiopulmonary bypass.

Organ blood flow during pulsatile cardiopulmonary bypass.