Aortic Blood Flow Research Articles

(Endo)Anchors Aweigh

An 83 year old man had undergone endostapled endovascular aneurysm repair of an abdominal aortic aneurysm, with deployment of four Heli-FX EndoAnchors (Medtronic, Minneapolis, MN, USA), six years previously. Under regular surveillance, his most recent abdominal X-ray indicated that one EndoAnchor had dislodged, travelling down the right iliac limb (A). A computed tomography scan revealed it to be in a gluteal artery (B). It is likely that this event resulted from inadequate aortic wall penetration with continuing aortic neck dilatation and the shearing effect of aortic blood flow. The patient was asymptomatic and thus no further treatment was deemed necessary.Image 1

Automated Analysis of Doppler Echocardiographic Videos as a Screening Tool for Valvular Heart Diseases

ObjectivesThis study sought to develop a deep learning (DL) framework to automatically analyze echocardiographic videos for the presence of valvular heart diseases (VHDs). BackgroundAlthough advances in DL have been applied to the interpretation of echocardiograms, such techniques have not been reported for interpretation of color Doppler videos for diagnosing VHDs. MethodsThe authors developed a 3-stage DL framework for automatic screening of echocardiographic videos for mitral stenosis (MS), mitral regurgitation (MR), aortic stenosis (AS), and aortic regurgitation (AR) that classifies echocardiographic views, detects the presence of VHDs, and, when present, quantifies key metrics related to VHD severities. The algorithm was trained (n = 1,335), validated (n = 311), and tested (n = 434) using retrospectively selected studies from 5 hospitals. A prospectively collected set of 1,374 consecutive echocardiograms served as a real-world test data set. ResultsDisease classification accuracy was high, with areas under the curve of 0.99 (95% CI: 0.97-0.99) for MS; 0.88 (95% CI: 0.86-0.90) for MR; 0.97 (95% CI: 0.95-0.99) for AS; and 0.90 (95% CI: 0.88-0.92) for AR in the prospective test data set. The limits of agreement (LOA) between the DL algorithm and physician estimates of metrics of valve lesion severities compared to the LOAs between 2 experienced physicians spanned from −0.60 to 0.77 cm2 vs −0.48 to 0.44 cm2 for MV area; from −0.27 to 0.25 vs −0.23 to 0.08 for MR jet area/left atrial area; from −0.86 to 0.52 m/s vs −0.48 to 0.54 m/s for peak aortic valve blood flow velocity (Vmax); from −10.6 to 9.5 mm Hg vs −10.2 to 4.9 mm Hg for average peak aortic valve gradient; and from −0.39 to 0.32 vs −0.31 to 0.32 for AR jet width/left ventricular outflow tract diameter. ConclusionsThe proposed deep learning algorithm has the potential to automate and increase efficiency of the clinical workflow for screening echocardiographic images for the presence of VHDs and for quantifying metrics of disease severity.

Abstract 12867: Neuromodulation Of The Renal Nerves In Spontaneously Hypertensive Rats

Introduction: Hypertension is a global burden. Renal denervation has been touted as a possible therapeutic strategy for the treatment of hypertension. However, neuromodulation of the renal nerves’ traffic in hypertension has yet to receive a similar attention. Aim: This study investigated cardio-respiratory responses to renal nerve stimulation in a genetic model of hypertension, the spontaneously hypertensive rat (SHR). Methods: In pentobarbital-anesthetized male SHRs (n = 9), the left renal nerve was stimulated 5 times (5-6 minutes apart) at 5 Hz, 0.5 ms, 0.5 mA for 30s. Mean arterial pressure (MAP), heart rate (HR), left renal cortical blood flow (CBF) and cortical vascular resistance (CVR), hindquarter aortic blood flow (ABF) and vascular resistance (AVR), upper (UAP) and lower (LAP) airway pressure, airway flow (AF), airway resistance (AR), respiration rate (RR) and diaphragmatic EMG (dEMG) were measured and averaged. Results: Cardiovascular responses to renal nerve stimulation were characterized by reductions in MAP, HR, CBF and AVR, which were associated with increases in ABF and CVR. Respiratory responses to renal nerve stimulation, on the other hand, demonstrated increases in AF, RR and dEMG, decreases in AR and no change in UAP and LAP. Conclusions: Under hypertensive conditions, the renal nerves not only modulate cardiovascular function but also improve respiratory function. These studies suggest that neuromodulation of the renal nerves may offer a therapeutic alternative for hypertensive patients.

Abstract 9386: Marfan Syndrome Mouse Model MgΔ Lpn Presents Alterations in Glomerular Architecture and Increased Renal Vascular Resistance. Losartan Treatment Attenuates These Phenotypes

Introduction: Previously, we have shown that mgΔ lpn murine Marfan syndrome (MFS) model with a fibrillin-1 disruption presents increased Metalloproteinase-9 (MMP-9) expression in the cilliary body in eye. MMP-9 has been related to microfibrils degradation. In this study, we examined the fibrillin-1 and MMP-9 distribution in the kidney and their influence on hemodynamics. Hypothesis: The alteration of fibrillin-1 impacts the glomerular architecture and modify renal hemodynamics. Methods: Female mice at 4 months of age were used: MFS mgΔ lpn mice (n=5); mgΔ lpn treated with losartan for 3 months (n=5); and control wild type mice (n=5). The glomerular structure of the kidney was examined by histology. The distribution and quantification of fibrillin-1 and MMP-9 were analyzed by immunofluorescence assay. Blood flow in the aorta and renal artery was monitored with the probe 2SB-T206 of the Transonic Systems, and the cortical micro-hemodynamic of the kidney was examined by SDF video-microscopy (Sidestream Dark Field Imaging). Results: The mgΔ lpn mice showed reduction of fibrillin-1 deposition and an increase in MMP-9 in the entire kidney tissue, including the glomerular structures. In histologic aspects, the glomerulus showed a reduction of the glomerular area, urinary space, and vascular pole area. The reduced glomerulus dimension possibly squeezes the arteriolar system with a subsequent increase of their vascular resistance. In addition, the cortical microvessels showed a significant reduction in blood flow, and there was an increase in the distribution of microvessels with diameters 6 to 8 μm. Blood flow analysis in the mgΔ lpn showed decreased artery renal flow but did not reveal a difference in aorta blood flow when compared to WT animals. These results indicate vascular resistance in the renal artery. Losartan therapy increased fibrillin-1 and decreased MMP-9 quantifications, improved the glomerulus structures and significantly increased the velocity of the microcirculation blood flow. Conclusions: Alterations in fibrillin-1 modify the glomerular structures and impair kidney hemodynamics. Losartan therapy minimized the renal phenotypes.

Left ventricular epicardial pacing achieved hyper-responsiveness in young children with dilated cardiomyopathy with left bundle branch block.

AimsThe management of heart failure (HF) in young children is challenging. The present study aimed to clarify the effect of left univentricular epicardial pacing on dilated cardiomyopathy with left bundle branch block (LBBB) in children.Methods and resultsA total of five cases (30.86 ± 16.39 months, three female) of children weighing 5.8–15 kg with dilated cardiomyopathy and LBBB were included in this study. LBBB in one child occurred after device closure of peri‐membranous ventricular septal defects, and the remaining four were idiopathically discovered early after birth. Before implantation, all children suffered from refractory HF and cardiac dilatation; the left ventricular ejection fraction was 33.48 ± 5.84% with Ross Heart Failure Classification III–IV. Electrical and mechanical dyssynchrony were observed in all children with QRS duration >140 ms and prolonged septal‐to‐left posterior wall motion delay. Left univentricular epicardial pacing was successfully implanted via left axillary minithoracotomy in the five children. Sensed atrioventricular delays (83 ± 15 ms) were optimized by velocity time integral of aortic blood flow before discharge. During the follow‐up period (10.8 ± 2.68 months), the dilated failing heart was reversed significantly in terms of decreased left ventricular dimension (55.62 ± 3.46 vs. 38.94 ± 3.69 mm, P = 0.005), while the left ventricular ejection fraction improved to 60.18 ± 8.78% (P = 0.006).ConclusionsIn young children with low body weight, if HF is caused by or related to LBBB, left ventricular epicardial pacing still has an excellent effect.

Dynamic variables predict fluid responsiveness in pre-school and school children undergoing neurosurgery: a prospective observational study.

BackgroundThe evidence that plethysmographic variability index (PVI), pulse pressure variation (PPV), FloTrac/Vigileo-derived stroke volume variation (SVV), and Eadyn (dynamic arterial elastance) predict fluid responsiveness in children is limited by conflicting results. We aim to evaluate their accuracy and reliability to predict fluid responsiveness after induction in children aged 4–9 years undergoing major neurosurgery.MethodsChildren aged 4–9 years undergoing intracranial epileptic foci excision were enrolled. After the induction of anesthesia, fluid loading with 10 mL/kg of Ringer’s solution over 10 min was administered before surgical incision. PVI, PPV, SVV, and Eadyn were measured before and within 5 min after fluid loading. Respiratory variation in aortic blood flow peak velocity (∆Vpeak) >15% at baseline, measured using transthoracic echocardiography, identified fluid “responders”. The abilities of dynamic variables to predict an increase in mean arterial pressure (MAP) of >10% following fluid loading were also assessed.ResultsFourteen (31.8%) of forty-four patients were responders defined by a baseline ∆Vpeak >15%. Before fluid loading, only the PVI value was significantly different between R and NR (P=0.017). Baseline PVI showed fair diagnostic accuracy for fluid responsiveness, with an area under the curve (AUROC) of 0.735 and the cutoff value of 13%. The R group showed a significantly greater absolute change in PPV and SVV after fluid loading from baseline compared with the NR group (P=0.021 and 0.040, respectively). The absolute change in the PPV and SVV values from baseline was greater in R than those in NR (P=0.021 and 0.040, respectively). Twenty (45.5%) showed a MAP increase of >10% following fluid loading and were defined as responders. Baseline ∆Vpeak and SVV showed fair predictive values for a MAP increase of >10% (AUROC =0.758 and 0.715, respectively).ConclusionsPVI at baseline showed fair reliability to predict fluid responsiveness after anesthesia induction in mechanically ventilated children aged 4–9 years undergoing neurosurgery. Baseline ∆Vpeak and SVV were fairly predictive for an increase in MAP following fluid loading.

Does the Intraluminal Thrombus Provoke the Rupture of the Abdominal Aortic Aneurysm Wall?

The role of intraluminal thrombus (ILT) in the rupture of abdominal aortic aneurysms (AAA) is controversial, and it is unclear whether it increases or decreases the risk of rupture. This research aims to find a clear answer to this question. Previous computer modelling suggests that an ILT lowers oxygen dissemination to the AAA wall, contributing to wall thinning. The methodology used in this study determines the amount of oxygen reaching the aneurysm wall after passing through the ILT by using the porous nature of the ILT to recreate the condition as closely as feasible. Using computed tomographic images, patient-specific three-dimensional (3D) AAA geometries were recreated. Modelling blood and oxygen flow in AAA was obtained using a computational fluid dynamics (CFD) approach. Our findings indicated that the oxygen volume percentage had completely reached the aneurysm wall. Only at the inlet and outflow did the greatest wall shear stress (WSS) occur, with a significant drop in the central region of the aneurysm wall. CFD was used to calculate the velocity, pressure, and WSS of aortic blood flow. ILT had no effect on oxygen flow to the aneurysm wall, disproving the theory that it produces local hypoxia.

Circumferential wall shear stress predicts co-localized progressive dilation in bicuspid aortic valve patients

Abstract Background Bicuspid aortic valve (BAV), a congenital heart defect, is associated with ascending aorta (AAo) dilation. Whether the high prevalence of dilation in BAV patients is related to alteration of aortic blood flow and thus in wall shear stress (WSS) [1,2], which have been associated with aortic wall degeneration [3], or intrinsic abnormalities of the aortic wall, such as altered aortic stiffness [4], has not been established. Recently, a technique for the semi-automatic quantification of progressive aortic dilation maps via image registration has been introduced [5]. Purpose To test whether ascending aorta WSS predicts co-localized progressive dilation in BAV patients. Methods Forty BAV patients free from moderate and severe aortic valve regurgitation (regurgitant fraction <16%) and stenosis (maximum velocity at the aortic valve <3m/s), with no previous aortic or aortic valve surgery or replacement and included in a double-blind clinical trial (BICATOR, NCT02679261) were enrolled. All patients underwent a baseline 4D flow CMR study to assess aortic hemodynamics, followed by two contrast-enhanced computed tomography angiographies to quantify progressive dilation. WSS was computed at 64 pre-specified standardized ascending aortic regions, automatically obtained dividing the ascending aorta into 8 equidistant longitudinal sections which were further divided along the circumference into 8 equal regions (I = inner, L = left, O = outer and R = right) [2]. WSS was also projected into axial and circumferential directions, as previously described [1,2]. Progressive dilation was assessed in terms of growth rate (GR), i.e. increase in diameter divided by follow-up duration [mm/year], following a previously described methodology [5], at the same 64 pre-specified ascending aortic locations. A two-tailed p-value <0.05 was considered statistically significant. Results Demographic and clinical characteristics of the patients are shown in Table 1. WSS and growth rate maps are shown in Figure 1. Follow-up duration was 44.8±2.6 months. Growth rate (Figure 1A) was heterogeneously distributed, being highest (up to 0.26 mm/year) in the outer region of the mid AAo and in the inner region of the proximal-mid AAo. Circumferential WSS showed highest values in the outer region of the mid AAo (Figure 1C) while WSS (magnitude) and its axial component (Figure 1B and D) presented maximum values in the right region of the mid AAo. Maps of statistically significant association between GR and WSS values showed circumferential WSS to be correlated with GR in regions where progressive dilation was fastest, while WSS magnitude and its axial component resulted in limited associations with GR maps. Conclusions Circumferential wall shear stress predicts location-matched progressive dilation in bicuspid aortic valve patients. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): This study has received funding from the Instituto de Salud Carlos III (PI17/00381). Guala A. has received funding from Spanish Ministry of Science, Innovation and Universities (IJC2018-037349-I). Table 1. DemographicsFigure 1. GR and WSS maps and correlations

Peripheral chemoreflex activation and cardiac function during hypoxemia in near-term fetal sheep without placental compromise.

A drop in arterial oxygen content activates fetal chemoreflex including an increase in sympathetic activity leading to peripheral vasoconstriction and redistribution of blood flow to protect the brain, myocardium, and adrenal glands. By using a chronically instrumented fetal sheep model with intact placental circulation at near-term gestation, we investigated the relationship between peripheral chemoreflex activation induced by hypoxemia and central hemodynamics. A total of 17 Åland landrace sheep fetuses at 115-128/145 gestational days were instrumented. Carotid artery was catheterized in 10 fetuses and descending aorta in 7 fetuses. After a 4-day recovery, baseline measurements of fetal arterial blood pressures, blood gas values, and fetal cardiovascular hemodynamics by pulsed Doppler ultrasonography were obtained under isoflurane anesthesia. Comparable data to baseline were collected 10 min (acute hypoxemia) and 60 min (prolonged hypoxemia) after maternal hypo-oxygenation to saturation level of 70%-80% was achieved. During prolonged hypoxemia, pH and base excess (BE) were lower and lactate levels were higher in the descending aorta than in the carotid artery. During hypoxemia mean arterial blood pressure (MAP) in the descending aorta increased, whereas in the carotid artery, MAP decreased. In addition, right pulmonary artery pulsatility index values increased, and the diastolic component in the aortic isthmus blood flow velocity waveform became more retrograde, thus decreasing the aortic isthmus antegrade/retrograde blood flow (AoI Net Flow) ratio. Both fetal ventricular cardiac outputs were maintained even during prolonged hypoxemia when significant fetal metabolic acidemia developed. Fetal chemoreflex activation induced by hypoxemia decreased the perfusion pressure in the cerebral circulation. Fetal weight-indexed left ventricular cardiac output (LVCO) or AoI Net Flow ratio did not correlate with a drop in carotid artery blood pressure.NEW & NOTEWORTHY During fetal hypoxemia with intact placental circulation, peripheral chemoreflex was activated, as demonstrated by an increase in the descending aorta blood pressure, pulmonary vasoconstriction, and an increase in retrograde diastolic AoI blood flow, while both ventricular cardiac outputs remained stable. However, perfusion pressure in the cerebral circulation decreased. These changes were seen even during prolonged hypoxemia when significant metabolic acidosis developed. Weight-indexed LVCO or AoI Net Flow ratio did not correlate with a drop in carotid artery blood pressure.

7-Tesla Functional Cardiovascular MR Using Vectorcardiographic Triggering-Overcoming the Magnetohydrodynamic Effect.

Objective: Ultra-high-field B0 ≥ 7 tesla (7T) cardiovascular magnetic resonance (CMR) offers increased resolution. However, electrocardiogram (ECG) gating is impacted by the magneto-hydrodynamic effect distorting the ECG trace. We explored the technical feasibility of a 7T magnetic resonance scanner using an ECG trigger learning algorithm to quantitatively assess cardiac volumes and vascular flow. Methods: 7T scans were performed on 10 healthy volunteers on a whole-body research MRI MR scanner (Siemens Healthineers, Erlangen, Germany) with 8 channel Tx/32 channels Rx cardiac coils (MRI Tools GmbH, Berlin, Germany). Vectorcardiogram ECG was performed using a learning phase outside of the magnetic field, with a trigger algorithm overcoming severe ECG signal distortions. Vectorcardiograms were quantitatively analyzed for false negative and false positive events. Cine CMR was performed after 3rd-order B0 shimming using a high-resolution breath-held ECG-retro-gated segmented spoiled gradient echo, and 2D phase contrast flow imaging. Artefacts were assessed using a semi-quantitative scale. Results: 7T CMR scans were acquired in all patients (100%) using the vectorcardiogram learning method. 3,142 R-waves were quantitatively analyzed, yielding sensitivity of 97.6% and specificity of 98.7%. Mean image quality score was 0.9, sufficient to quantitate both cardiac volumes, ejection fraction, and aortic and pulmonary blood flow. Mean left ventricular ejection fraction was 56.4%, right ventricular ejection fraction was 51.4%. Conclusion: Reliable cardiac ECG triggering is feasible in healthy volunteers at 7T utilizing a state-of-the-art three-lead trigger device despite signal distortion from the magnetohydrodynamic effect. This provides sufficient image quality for quantitative analysis. Other ultra-high-field imaging applications such as human brain functional MRI with physiologic noise correction may benefit from this method of ECG triggering.

Competition between Conflicting Aortic Blood Flows

A 58-year-old man suffered a cardiopulmonary arrest requiring urgent venoarterial extracorporeal membrane oxygenation, which was promptly performed through his left common femoral artery and vein at a flow rate of 5 L/min at 5,000 rpm. Subsequently, computed tomography angiography of the chest was performed 20 seconds after the injection of 90-mL of contrast medium (Xenetix 350, Iobitridol; Guerbet, Villepinte, France) via a peripheral vein, which showed an apparent type B aortic dissection in addition to bilateral pulmonary emboli (Figs 1–3).

Bicuspid aortic valve fusion length correlates with maximum aortic diameter and heamodynamic abnormalities: a 4D flow CMR study

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Guala A. received funding from the Spanish Ministry of Science, Innovation and Universities. Background Bicuspid aortic valve (BAV), a congenital heart defect, is associated with ascending aorta dilation, possibly via alteration of aortic blood flow [1]. In BAV abnormal flow condition have been associated with aortic extracellular matrix dysregulation and elastic fiber degeneration [2]. Current morphological classification of BAV patients with aortic valve with a single fusion between two adjacent leaflets does not allow for risk stratification. Purpose This research work tested whether the extent of fusion between leaflets is related to AAo diameter and flow alterations. Methods Ninety BAV patients free from moderate and severe aortic valve disease and with no previous aortic or aortic valve surgery or replacement were prospectively enrolled. A comprehensive magnetic resonance protocol comprised a stack of double-oblique 2D balanced steady-state free-precession (bSSFP) cine CMR of the aortic valve, which was used to measure the length of the fusion between leaflets, a cine CMR at the level of the pulmonary bifurcation to assess aortic diameter and 4D flow MRI sequence to assess flow characteristics and regional stiffness [3]. Jet angle and flow radial displacement, quantifying the extent of flow eccentricity, and systolic flow reversal ratio (SFRR), assessing the relative amount of backward flow during systole, were computed at 8 equidistant planes in the ascending aorta and 4 equidistant planes in the aortic arch [4]. A two-tailed p-value < 0.05 was considered statistically significant. Results The length of leaflet fusion varied widely (median 7.7 mm, inter-quartile range [5.5; 10.2]), Table 1). In bivariate analysis, fusion length was also associated to ascending aortic diameter (R = 0.391, p < 0.001), age (R = 0.313, p = 0.005) and body surface area (R = 0.396, p < 0.001). It was also positively related to flow abnormalities: like displacement in the proximal and distal ascending aorta, jet angle in the mid ascending aorta, and SFRR in the ascending aorta and the aortic arch (see Figure 1). The association between fusion length and ascending aorta diameter persisted in multivariate analysis after correction for age (p = 0.006). Conclusions Bicuspid aortic valve fusion extent varies greatly and it is associated with aortic diameter, possibly through flow alterations. Prospective longitudinal studies are needed to establish whether fusion length may allow for risk stratification in bicuspid aortic valve patients.

End-organ saturations correlate with aortic blood flow estimates by echocardiography in the extremely premature newborn \u2013 an observational cohort study

BackgroundNear-infrared spectroscopy (NIRS) measures of cerebral saturation (Csat) and renal saturation (Rsat) in extreme premature newborns may be affected by systemic blood flow fluctuations. Despite increasing clinical use of NIRS to monitor tissue saturation in the premature infant, validation of NIRS measures as a correlate of blood flow is still needed. We compared echocardiography (ECHO) derived markers of ascending aorta (AscAo) and descending aorta (DesAo) blood flow with NIRS measurements obtained during the ECHO.MethodsNewborns < 29 weeks’ gestation (2013–2017) underwent routine NIRS monitoring. Csat, Rsat and systemic saturation at the time of ECHO were retrospectively analyzed and compared with Doppler markers of aortic flow. Renal and cerebral fractional tissue oxygen extraction (rFTOE and cFTOE, respectively) were calculated. Mixed effects models evaluated the association between NIRS and Doppler markers.ResultsForty-nine neonates with 75 Csat-ECHO and 62 Rsat-ECHO observations were studied. Mean post-menstrual age was 28.3 ± 3.8 weeks during the ECHO. Preductal measures including AscAo velocity time integral (VTI) and AscAo output were correlated with Csat or cFTOE, while postductal measures including DesAo VTI, DesAo peak systolic velocity, and estimated DesAo output were more closely correlated with Rsat or rFTOE.ConclusionsNIRS measures are associated with aortic blood flow measurements by ECHO in the extremely premature population. NIRS is a tool to consider when following end organ perfusion in the preterm infant.

Sequential numerical simulation of vascular remodeling and thrombosis in unconventional hybrid repair of ruptured middle aortic syndrome

Unconventional surgical procedures may be utilized in treating complicated middle aortic syndrome (MAS), the outcome and prognosis of which remain largely undetermined due to limited numbers and significant heterogeneity of this population. Using computational fluid dynamics (CFD) analysis, this study aimed to assess the dynamic changes of postoperative aortic flow in seeking to unveil the relationship between hemodynamics and vascular remodeling and thrombotic events. One patient with middle aortic syndrome complicated with aortic rupture was treated with hybrid repair of extra-anatomic bypass and fenestrated endovascular aortic repair. The patient was followed-up for 8 months by computational tomography angiography and Doppler ultrasound. Thoracoabdominal aortic blood flow and locations with ongoing thrombosis at 1, 3, and 6 months postoperatively were simulated and analyzed. Remodeling processes, including low wall shear-mediated constrictive remodeling of non-stented aorta, neointimal hyperplasia at suture lines, and minimal thrombosis at various locations, were evident. Meanwhile, abdominal blood flow was tri-phasic at 1 month after surgery, and was reversed and stabilized at 6 months. The distribution of newly formed thrombus vary at different follow-up stages, which were in line with the numerical simulation of thrombosis from different postoperative time points. CFD-based sequential monitoring is of promising value in capturing dynamic changes of vascular outcome.

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.

Assessing the methodology used to study the ascending aorta haemodynamics in bicuspid aortic valve.

Modern imaging techniques provide evermore-detailed anatomical and physiological information for use in computational fluid dynamics to predict the behaviour of physiological phenomena. Computer modelling can help plan suitable interventions. Our group used magnetic resonance imaging and computational fluid dynamics to study the haemodynamic variables in the ascending aorta in patients with bicuspid aortic valve before and after isolated tissue aortic valve replacement. Computer modelling requires turning a physiological model into a mathematical one, solvable by equations that undergo multiple iterations in four dimensions. Creating these models involves several steps with manual inputs, making the process prone to errors and limiting its inter- and intra-operator reproducibility. Despite these challenges, we created computational models for each patient to study ascending aorta blood flow before and after surgery. Magnetic resonance imaging provided the anatomical and velocity data required for the blood flow simulation. Patient-specific in- and outflow boundary conditions were used for the computational fluid dynamics analysis. Haemodynamic variables pertaining to blood flow pattern and derived from the magnetic resonance imaging data were calculated. However, we encountered problems in our multi-step methodology, most notably processing the flow data. This meant that other variables requiring computation with computational fluid dynamics could not be calculated. Creating a model for computational fluid dynamics analysis is as complex as the physiology under scrutiny. We discuss some of the difficulties associated with creating such models, along with suggestions for improvements in order to yield reliable and beneficial results.

Numerical study of hemodynamics after stent implantation during the cardiac cycle

The descending aortic aneurysm is one of the most catastrophic cardiovascular emergencies resulting in high mortality worldwide. Clinical observations have pointed out that stent implantation in the sick aorta should probably allow stabilization of the hemodynamic state of the patient's aorta. To better understand the hemodynamic impact of a stent-treated aneurysm, numerical simulations are used to evaluate hemodynamic parameters. These latter including flow profile, velocity distribution, aortic wall pressure and shear stress, which are difficult to measure in vivo. It should be noted that the numerical modeling assists in medical planning by providing patterns of blood circulation, in particular, the distribution of pressures and shear stresses in the wall. In this context, the pulsatile blood flow in the aneurysmal aorta with stent is studied by CFD (Computational Fluid Dynamics) simulations. Realistic boundary conditions time dependent are prescribed at the level of the different arteries of the complete aorta models. The hemodynamic profile of the aneurysmal aorta with stent was analyzed by contour planes of velocity vectors, pressures and shear stresses at different times during the cardiac cycle. The obtained results made it possible to show the effect of the stent on the improvement of the blood flow by solving the problems of hemodynamic disturbances in the aorta. The methodology used in this work has revealed detailed and necessary information for the cases studied and shows the interest of the numerical tool for diagnosis and surgery.

Pediatric Sized REBOA Catheter Testing in a Pulsatile Aortic Flow Model

Background – Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) in the management of pediatric abdomino-pelvic hemorrhage from trauma or iatrogenic injury is limited by a lack of appropriately sized balloon catheters that can be delivered through less than a 7 French sheath.&#x0D; Methods – We bench tested the occlusion capability of eight commercially available balloon catheters deliverable through 4Fr, 5Fr and 6Fr sheaths in an anatomic pulsatile flow model of the pediatric aorta with variable luminal diameters (5mm, 6mm, 7mm, 8mm, 9mm, 10mm, and 12mm). Inflated balloon migration and the deflated balloon’s effect on aortic flow were recorded. The flow chamber was calibrated to approximate size-appropriate physiologic aortic blood flow.&#x0D; Results – Seven of eight devices were able to occlude the test lumen diameter corresponding to their manufacture specifications. Deflated luminal flow restriction in the smallest test lumen was lowest in the Fogarty devices (0-3%) followed by Cordis (8-10%) and Numed (14-26%) devices. The Fogarty devices demonstrated the most distal migration (10-15mm) followed by Numed (1-5mm). Device migration was undetectable in the Cordis devices. &#x0D; Conclusion – There are commercially available balloon catheters, deliverable through smaller than 7Fr sheaths which can occlude pediatric sized aortic test lumens in the setting of physiologic pulsatile flow. These results will help inform future research, device development and practice in the field of pediatric REBOA.

The physiological effects of cardiac resynchronization therapy on aortic and pulmonary flow and dynamic and static components of systemic impedance.

BackgroundPatients who improve following cardiac resynchronization therapy (CRT) have left ventricular (LV) remodeling and improved cardiac output (CO). Effects on the systemic circulation are unknown.ObjectiveTo explore the effects of CRT on aortic and pulmonary blood flow and systemic afterload.MethodsAt CRT implant patients underwent a noninvasive assessment of central hemodynamics, including wave intensity analysis (n = 28). This was repeated at 6 months after CRT. A subsample (n = 11) underwent an invasive electrophysiological and hemodynamic assessment immediately following CRT. CRT response was defined as reduction in LV end-systolic volume ≥15% at 6 months.ResultsIn CRT responders (75% of those in the noninvasive arm), there was a significant increase in CO (from 3 ± 2 L/min to 4 ± 2 L/min, P = .002) and LV dP/dtmax (from 846 ± 162 mm Hg/s to 958 ± 194 mm Hg/s, P = .001), immediately after CRT in those in the invasive arm. They demonstrated a significant increase in aortic forward compression wave (FCW) both acutely and at follow-up. The relative change in LV dP/dtmax strongly correlated with changes in the aortic FCW (Rs 0.733, P = .025). CRT responders displayed a significant reduction in afterload, and a decrease in systemic vascular resistance and pulse wave velocity acutely; there was a significant decrease in acute pulmonary afterload measured by the pulmonary FCW and forward expansion wave.ConclusionImproved cardiac function following CRT is attributable to a combination of changes in the cardiac and cardiovascular system. The relative importance of these 2 mechanisms may then be important for optimizing CRT.

Targeted Regional Optimization: Increasing the Therapeutic Window for Endovascular Aortic Occlusion In Traumatic Hemorrhage.

Resuscitative endovascular balloon occlusion of the aorta (REBOA) allows for effective temporization of exsanguination from non-compressible hemorrhage (NCTH) below the diaphragm. However, the therapeutic window for aortic occlusion is time-limited given the ischemia-reperfusion injury generated. Significant effort has been put into translational research to develop new strategies to alleviate the ischemia-reperfusion injury and extend the application of endoaortic occlusion. Targeted regional optimization (TRO) is a partial REBOA strategy to augment proximal aortic and cerebral blood flow while targeting minimal threshold of distal perfusion beyond the zone of partial aortic occlusion. The objective of TRO is to reduce the degree of ischemia caused by complete aortic occlusion while providing control of distal hemorrhage. This review provides a synopsis of the concept of TRO, pre-clinical, translational experiences with TRO and early clinical outcomes. Early results from TRO strategies are promising; however, further studies are needed prior to large-scale implementation into clinical practice.