Systolic Peak Research Articles

Right Ventricular Dysfunction Predicts Outcome in Acute Heart Failure.

AimThe severity of cardiac impairment in acute heart failure (AHF) predicts outcome, but challenges remain to identify prognostically important non-invasive parameters of cardiac function. Left ventricular ejection fraction (LVEF) is relevant, but only in those with reduced LV systolic function. We aimed to assess the standard and advanced parameters of left and right ventricular (RV) function from echocardiography in predicting long-term outcomes in AHF.MethodsA total of 418 consecutive AHF patients presenting over 12 months were prospectively recruited and underwent bedside echocardiography within 24 h of recruitment. We retrospectively assessed 8 RV and 5 LV echo parameters of the cardiac systolic function to predict 2-year mortality, using both guideline-directed and study-specific cutoffs, based on the maximum Youden indices via ROC analysis. For the RV, these were the tricuspid annular plane systolic excursion, RV fractional area change, tissue Doppler imaging (TDI) peak tricuspid annular systolic wave velocity, both peak- and end-systolic RV free wall global longitudinal strain (RV GLS) and strain rate (mean RV GLSR), RV ejection fraction (RVEF) derived from a 2D ellipsoid model and the ratio of the TAPSE to systolic pulmonary artery pressure (SPAP). For the LV, these were the LVEF, mitral regurgitant ΔP/Δt (MR dP/dt), the lateral mitral annular TDI peak systolic wave velocity, LV GLS, and the LV GLSR.ResultsA total of 7/8 parameters of RV systolic function were predictive of 2-year outcome, with study cutoffs like international guidelines. A cutoff of < −1.8 s–1 mean RV GLSR was associated with worse outcome compared to > −1.8 s–1 [HR 2.13 95% CI 1.33–3.40 (p = 0.002)]. TAPSE:SPAP of > 0.027 cm/mmHg (vs. < 0.027 cm/mmHg) predicted worse outcome [HR 2.12 95% CI 1.53–2.92 (p < 0.001)]. A 3-way comparison of 2-year mortality by LVEF from the European Society of Cardiology (ESC) guideline criteria of LVEF > 50, 41–49, and < 40% was not prognostic [38.6% vs. 30.9 vs. 43.9% (p = 0.10)]. Of the 5 parameters of LV systolic function, only an MR dP/dt cutoff of < 570 mmHg was predictive of adverse outcome [HR 1.63 95% CI 1.01–2.62 (p = 0.047)].ConclusionWith cutoffs broadly like the ESC guidelines, we identified RV dysfunction to be associated with adverse prognosis, whereas LVEF could not identify patients at risk.

Cardiac magnetic resonance T1 mapping for evaluating myocardial fibrosis in patients with type 2 diabetes mellitus: correlation with left ventricular longitudinal diastolic dysfunction.

We aimed to evaluate myocardial fibrosis using cardiac magnetic resonance (CMR) T1 mapping in type 2 diabetes mellitus (T2DM) patients and investigate the association between left ventricular (LV) subclinical myocardial dysfunction and myocardial fibrosis. The study included 37 short-term (≤ 5 years) and 44 longer-term (> 5 years) T2DM patients and 41 healthy controls. The LV global strain parameters and T1 mapping parameters were compared between the abovementioned three groups. The association of T1 mapping parameters with diabetes duration, in addition to other risk factors, was determined using multivariate linear regression analysis. The correlation between LV strain parameters and T1 mapping parameters was evaluated using Pearson's correlation. The peak diastolic strain rates (PDSRs) were significantly lower in longer-term T2DM patients compared to those in healthy subjects and short-term T2DM patients (p < 0.05). The longitudinal peak systolic strain rate and peak strain were significantly lower in the longer-term T2DM compared with the short-term T2DM group (p < 0.05). The extracellular volumes (ECVs) were higher in both subgroups of T2DM patients compared with control subjects (all p < 0.05). Multivariate linear regression analysis showed that diabetes duration was independently associated with ECV (β = 0.413, p < 0.001) by taking covariates into account. Pearson's analysis showed that ECV was associated with longitudinal PDSR (r = - 0.441, p < 0.001). T1 mapping could detect abnormal myocardial fibrosis early in patients with T2DM, which can cause a decline in the LV diastolic function. • CMR T1 mapping could detect abnormal myocardial fibrosis early in patients with T2DM. • The diabetes duration was independently associated with ECV. • Myocardial fibrosis can cause a decline in the LV diastolic function in T2DM patients.

The Effects of Implantation Orientation of a Bileaflet Mechanical Heart Valve in an Anatomic Left Ventricle-Aorta Configuration.

We have performed three-dimensional high-resolution numerical simulations of a bi-leaflet mechanical heart valve implanted at different orientations in an anatomic left ventricle-aorta obtained from magnetic resonance imaging of a volunteer. The thoroughly validated overset curvilinear-immersed boundary fluid-structure interaction flow solver is used in which the aorta and left ventricle (LV) are discretized with boundary-conforming and nonconforming curvilinear grids, respectively. The motion of the left ventricle wall is prescribed based on a lumped parameter model while the motion of the leaflets is calculated using a strongly coupled fluid-structure interaction algorithm enhanced with Aitken convergence technique. We carried out simulations for three valve orientations, which differ from each other by 45 deg, and compared the leaflet motion and flow field for multiple cycles. Our results show reproducible and relatively symmetrical opening for all valve orientations. The presence of small-scale vortical structures after peak systole causes significant cycle-to-cycle variations in valve kinematics during the closing phase for all valve orientations. Furthermore, our results show that valve orientation does not have a significant effect on the distribution of viscous shear stress in the ascending aorta. Additionally, two different mathematical activation models including linear level of activation and Soares model are used to quantify the platelet activation in the ascending aorta. The results show that the valve orientation does not significantly affect (less than 8%) the total platelet activation in the ascending aorta.

Efficacy of Dialectical Comprehensive Treatment of Traditional Chinese Medicine in Patients with Chronic Stable Heart Failure: A Randomized Controlled Trial.

The treatment of chronic stable heart failure (CSHF) with integrated traditional Chinese and Western medicine has been of wide concern. We mainly discuss the clinical efficacy of TCM decoction combined with acupuncture and moxibustion (A&M) in CSHF treatment on the basis of syndrome differentiation and treatment (SDT). The control group was given conventional cardiac rehabilitation (CCR), and the treatment group was given TCM decoction combined with A&M treatment based on SDT on the basis of conventional cardiac rehabilitation. The clinical efficacy and cardiopulmonary exercise testing (CPET) indicators were evaluated. Left ventricular ejection fraction (LVEF), NT-proBNP, myocardial ischemia threshold (MIT), and 6-minute walking distance (6MWD) were measured by ultrasound, ELISA, electrocardiogram, and 6MWD test. After treatment, the clinical efficacy, LVEF, and 6MWD of the treatment group were better than in the control group. The NT-proBNP plasma level and MIT in the treatment group were lower than in the control group. The treatment group had enhanced AT, VO2 Peak, VO2 Peak/HR, and Peak power and decreased resting systolic pressure and peak systolic pressure, and the difference was statistically significant. Dialectical comprehensive treatment of TCM could effectively improve cardiac function and clinical treatment effect, which was worthy of clinical application.

Left Ventricular Systolic‐Diastolic Coupling: Insight from Magnetic Resonance Dobutamine Stress

Left ventricular systolic and diastolic function are intrinsically linked, such that diastolic relaxation is influenced by the preceding systolic contraction – similar to how a springs recoil to its original shape is influenced by the degree of compression. Several clinical investigations have proposed quantifying the ratio between diastolic and systolic function to assess the coupling efficiency between the two, however, these cross‐sectional comparisons may be influenced by additional confounding factors, such as differences in tissue characteristics. Therefore, to extend our understanding, and directly examine the relationship between left ventricular systolic and diastolic coupling, we performed cardiac magnetic resonance imaging in six healthy volunteers (4F/2M, 22 ± 3 years, 24.4 ± 3.0 kg/m2) at rest and during low‐dose intravenous dobutamine infusion (2 µg/kg/min) to increase cardiac inotropy without affecting other, potentially confounding, regulators of diastolic function. Systolic and diastolic function was measured using gold‐standard tissue tagging, from three evenly spaced short axis images spanning the left ventricle from base to apex. As expected, dobutamine infusion increased peak circumferential strain (‐19.8 ± 1.6 % vs ‐21.3 ± 2.0 %, p = 0.002), systolic circumferential strain rate (CSRs: ‐96 ± 2 %/s vs ‐117 ± 7 %/s, p = 0.001), peak twist (8.2 ± 0.9 ° vs 10.7 ± 1.1 °, p = 0.002) and peak rate of systolic twist (TR: 40 ± 7 °/s vs 58 ± 8 °/s, p = 0.004). Independent of any changes in heart rate (59 ± 9 bpm vs 58 ± 9 bpm, p = 0.303) or end‐diastolic volume (171 ± 26 mL vs 170 ± 24 mL, p = 0.882), early diastolic circumferential strain rate (CSRd: 141 ± 15 %/s vs 163 ± 9 %/s, p = 0.019) and peak untwisting rate (UTR: ‐67 ± 24 °/s vs ‐88 ± 16 °/s, p = 0.018) subsequently increased. As a result, the ratio between diastolic and systolic measurements remained unchanged (CSRd/CSRs: 1.47 ± 0.14 vs 1.40 ± 0.15, p = 0.266; UTR/TR: 1.69 ± 0.54 vs 1.57 ± 0.37, p = 0.190). Taken together, these data support a growing body of evidence linking left ventricular systolic function with subsequent early diastolic relaxation and suggest that future investigations examining diastolic function should consider the influence of preceding systolic contractions.

A two-dimensional speckle-tracking echocardiography for the diagnosis of early myocardial disease in beta-thalassemia major patients.

Although magnetic resonance imaging T2* is considered the gold standard to assess myocardial iron overload in β-thalassemia patients, its routine use is limited by the high cost and limited availability. Recent data demonstrated that strain imaging by speckle tracking is a sensitive tool for early assessment of the left ventricular myocardial dysfunction. This study aims to evaluate the clinical utility of two-dimensional (2D) speckle-tracking echocardiography (STE) for the detection of early myocardial disease in beta-thalassemia major (β-TM) patients. 2D STE, magnetic resonance imaging (MRI) heart T2* and MRI liver iron content were done for 30 β-TM patients with no clinical heart disease, compared to 2D STE in 30 healthy age- and sex-matched controls. There was a significant reduction in the longitudinal systolic strain values by STE among β-TM patients compared to controls (P = 0.05). A longitudinal peak systolic strain cutoff values of ≤-19 was able to detect β-TM patients having subclinical cardiac iron overload by MRI T2* (sensitivity = 90%-93.3%, specificity = 83%-100%). Mean serum ferritin in the past 2 years correlated negatively to longitudinal systolic strain values global longitudinal peak systolic strain average (P = 0.05).

Aortic Leaflet Stresses Are Substantially Lower Using Pulmonary Visceral Pleura Than Pericardial Tissue.

Background: Porcine heart and bovine pericardium valves, which are collagen-based with relatively little elastin, have been broadly utilized to construct bioprosthetic heart valves (BHVs). With a larger proportion of elastin, the pulmonary visceral pleura (PVP) has greater elasticity and could potentially serve as an advantageous biomaterial for the construction/repair of BHVs. The question of how the aortic valve’s performance is affected by its bending rigidity has not been well studied. Methods: Based on the stress–strain relationships of the pericardium and PVP determined by planar uni-axial tests, a three-dimensional (3D) computational fluid–structure interaction (FSI) framework is employed to numerically investigate the aortic valve’s performance by considering three different cases with Young’s modulus as follows: , , and kPa, respectively. Results: The stroke volumes are 112, 99.6, and 91.4 ml as Young’s modulus increases from 375 to 750 and 1500 kPa, respectively. Peak geometric opening area (GOA) values are 2.3, 2.2, and 2.0 cm2 for , 750, and 1500 kPa, respectively. The maximum value of the aortic leaflet stress is about 271 kPa for kPa, and it increases to about 383 and 540 kPa for and 1500 kPa in the belly region at the peak systole, while it reduces from 550 kPa to 450 and 400 kPa for , 750, and 1500 kPa, respectively, at the instant of peak “water-hammer”. Conclusion: A more compliant PVP aortic leaflet valve with a smaller Young’s modulus, , has a higher cardiac output, larger GOA, and lower hemodynamic resistance. Most importantly, the aortic leaflet stresses are substantially lower in the belly region within the higher compliance PVP aortic valve tissue during the systole phase, even though some stress increase is also found during the fast-closing phase due to the “water-hammer” effect similar to that in the pericardial tissue. Future clinical studies will be conducted to test the hypothesis that the PVP-based valve leaflets with higher compliance will have lower fatigue or calcification rates due to the overall lower stress.

Evaluation of Endocrine and Metabolic Changes in Polycystic Ovary Syndrome by Ultrasonic Imaging Features under an Intelligent Algorithm.

To explore the application of intelligent algorithm-based ultrasound in the evaluation of polycystic ovary syndrome (PCOS) and the endocrine and metabolic changes of PCOS, 44 patients diagnosed with PCOS were recruited and rolled into three groups regarding detection methods. Backpropagation algorithm-based ultrasonic detection was adopted for the patients in the experimental group. The patients in the control group were tested by conventional ultrasound. In addition, 18 healthy volunteers were selected as the normal group. The results showed that the images processed by the backpropagation algorithm were substantially better than the traditional ultrasound images (P < 0.05), and the image display was clearer. S, A, and S/A ratios measured by two different detection methods were 7.8 mm2, 3.5 mm2, and 0.449 in the experimental group, respectively, which were significantly different from 6.3 mm2, 2.6 mm2, and 0.413 in the control group (P < 0.05). The PI and RI values of the interstitial ovarian artery in the experimental group were lower than those in the control group, and the systolic peak velocity (PSV) and end diastolic velocity (EDV) values were higher than those in the control group (P < 0.05). Compared with the control group, the ovarian volume, interstitial vascularization-flow index (VFI), and flow index (FI) in the experimental group were substantially increased, and the total number of detected follicles was more (P < 0.05). The level of follicle-stimulating hormone (FSH) in PCOS patients was substantially lower than that in normal controls (P < 0.05). The LH, E2, P, and T of PCOS patients were substantially higher than those of normal controls (P < 0.05). Ultrasound on account of the backpropagation algorithm can directly display the three-dimensional structure of the ovary and follicle and accurately measure the ovarian volume and follicle number. Endocrine and metabolic indicators can provide objective information for the clinical diagnosis of PCOS and can be used as a way of clinical evaluation of PCOS.

Regional Fat Distributions Are Associated With Subclinical Right Ventricular Dysfunction in Adults With Uncomplicated Obesity.

ObjectiveObesity is a prominent public health problem that has increased cardiovascular mortality risks. However, the specific effects of obesity, independent of comorbidities, on cardiac structure and function have not been well clarified, especially those effects on the right ventricle (RV). Cardiovascular magnetic resonance (CMR) tissue tracking can assess detailed RV mechanical features. This study aimed to evaluate RV strain using CMR in uncomplicated obese adults and assess its association with fat distributions.MethodsA total of 49 obese patients and 30 healthy controls were included. The RV global systolic function and strain parameters based on CMR were assessed. Body fat distributions were measured with dual X-ray absorptiometry. RV function indices of obese patients were compared with those of healthy controls. Correlations among related body fat distribution parameters and RV function indices were conducted with multivariable linear regression.ResultsCompared with healthy controls, the obese group had impaired RV strain with lower global longitudinal peak strain (PS), longitudinal peak systolic strain rate (PSSR), circumferential and longitudinal peak diastolic strain rates (PDSR) (all P < 0.05), while LV and RV ejection fractions were not significantly different between the two groups (P > 0.05). Multivariable linear regression analysis demonstrated that android fat% was independently associated with longitudinal PS (β = −0.468, model R2 = 0.219), longitudinal PDSR (β = −0.487, model R2 = 0.237), and circumferential PSSR (β = −0.293, model R2 = 0.086). Trunk fat% was independently associated with longitudinal PSSR (β = −0.457, model R2 = 0.209). In addition, the strongest correlations of circumferential PDSR were BMI and gynoid fat% (β = −0.278, β = 0.369, model R2 = 0.324).ConclusionsExtensive subclinical RV dysfunction is found in uncomplicated obese adults. BMI, as an index of overall obesity, is independently associated with subclinical RV dysfunction. In addition, central obesity (android fat and trunk fat distributions) has a negative effect on subclinical RV function, while peripheral obesity (gynoid fat distribution) may have a positive effect on it.Clinical Trials RegistrationEffect of lifestyle intervention on metabolism of obese patients based on smart phone software (ChiCTR1900026476).

Comparison of performance of self-expanding and balloon-expandable transcatheter aortic valves

ObjectiveTo evaluate the flow dynamics of self-expanding and balloon-expandable transcatheter aortic valves pertaining to turbulence and pressure recovery. Transcatheter aortic valves are characterized by different designs that have different valve performance and outcomes. MethodsAssessment of transcatheter aortic valves was performed using self-expanding devices (26-mm Evolut [Medtronic], 23-mm Allegra [New Valve Technologies], and small Acurate neo [Boston Scientific]) and a balloon-expandable device (23-mm Sapien 3 [Edwards Lifesciences]). Particle image velocimetry assessed the flow downstream. A Millar catheter was used for pressure recovery calculation. Velocity, Reynolds shear stresses, viscous shear stress, and pressure gradients were calculated. ResultsThe maximal velocity at peak systole obtained with the Evolut R, Sapien 3, Acurate neo, and Allegra was 2.12 ± 0.19 m/sec, 2.41 ± 0.06 m/sec, 2.99 ± 0.10 m/sec, and 2.45 ± 0.08 m/sec, respectively (P < .001). Leaflet oscillations with the flow were clear with the Evolut R and Acurate neo. The Allegra shows the minimal range of Reynolds shear stress magnitudes (up to 320 Pa), and Sapien 3 the maximal (up to 650 Pa). The Evolut had the smallest viscous shear stress magnitude range (up to 3.5 Pa), and the Sapien 3 the largest (up to 6.2 Pa). The largest pressure drop at the vena contracta occurred with the Acurate neo transcatheter aortic valve with a pressure gradient of 13.96 ± 1.35 mm Hg. In the recovery zone, the smallest pressure gradient was obtained with the Allegra (3.32 ± 0.94 mm Hg). ConclusionsFlow dynamics downstream of different transcatheter aortic valves vary significantly depending on the valve type, despite not having a general trend depending on whether or not valves are self-expanding or balloon-expandable. Deployment design did not have an influence on flow dynamics.

Blood Flow Acoustics in Carotid Artery

This paper aims to identify and study the blood flow and acoustics characteristics of different degrees of stenosis in the carotid artery. Blood flow will produce acoustics, but the presence of different levels of stenosis are expected to produce different acoustic characteristics. The blood flow and acoustic characteristics are simulated by using computational fluid dynamics software (CFD). Several three-dimensional models of carotid arteries that have different degrees of stenosis are used together with a normal/healthy carotid artery - i.e., 30% and 70% degrees of blockage. The geometry of 30% and 70% stenosed model are computationally generated from a normal carotid artery geometry. In addition, the blood viscosity level was also increased in this study to a value of 0.005 kgms-1 (from the normal viscosity of 0.004 kgms-1) to compare the effect of hyperglycaemia (i.e., diabetes mellitus) that may bring additional complications to blood flow. Pulsatile simulations are used for all cases in order to mimic the exact blood flow condition in which the inlet velocity and outlet pressure change with time. The present study shows that as the degree of stenosis increases at the common carotid artery (CCA), the velocity at the internal carotid artery (ICA) and external carotid artery (ECA) outlet increases. The maximum velocity changes for ICA at the systolic peak from normal to 70% degree of stenosis for carotid artery shows an increase by 8%, while an opposite trend is observed for the maximum velocity changes of ECA at the systolic peak, where a reduction by 3% occurs from normal to 70% degree of stenosis for carotid artery. In terms of viscosity, as the viscosity of the blood increases, the velocity of the blood flow decreases in all geometry carotid arteries and may potentially provide further complications on clinical problems. The acoustic simulation showed that the acoustic power increases by 5% and 20% for carotid artery geometry that has 30% and 70% degree of stenosis, respectively. The present study indicates potential for further developing non-invasive acoustic means to diagnose and measure stenosis in carotid arteries.

Pulsatile Flow Interaction between Aorta and Pulmonary Artery

Introduction: Hypoplastic left heart patients have significant blood flow unbalance in the cardiovascular system; excess blood flows from the right ventricles to the lung. Patent Ductus Arteriosus (PDA) stenting prevents excess blood flow and shunts the blood flow to the aorta through PDA without conventional heart surgeries. On the other hand, past clinical researches report that PDA stenting can bring on thrombosis around ductus arteriosus. This study elucidated the hemodynamics of the aorta-pulmonary artery system by using three patient-specific morphological data, experimentally and numerically. Methods: This study carried out Particle Image Velocimetry (PIV) measurement and Computational Fluid Dynamics (CFD) analysis for three patient-specific models. Results: The experimental and numerical analysis clarified transient hemodynamics in the aorta-pulmonary artery system; pulmonary blood flow was shunt to the aorta at the peak systole and diastole. Q-criterion, which indicates both the second-order invariant of turbulence flow and the structure’s characteristics, was generated in the PDA at the same period. Conclusion: This study found the influence of PDA morphology on transient hemodynamics; the highest Q-criterion in the PDA is 600 [s-2]; on the contrary, the lowest case is around 200 [s-2]. These flow characteristics are essential factors in thrombus formation in PDA.

Blunted coronary flow velocity reserve is associated with impairment in systolic function and functional capacity in hypertrophic cardiomyopathy

BackgroundCoronary microvascular dysfunction constitutes an important pathophysiological feature in hypertrophic cardiomyopathy (HCM).We aimed to assess the association between impaired coronary flow velocity reserve (CFVR) and ventricular systolic function and functional capacity. MethodsEighty-three patients with HCM were enrolled in this prospective cohort study. Patients underwent echocardiogram to evaluate ventricular performance and CFVR in the left anterior descending artery (LAD) and posterior descending artery (PD). Diastolic coronary flow velocity was measured in basal conditions and in hyperemia. CFVR was calculated as the ratio of hyperemic and basal peak diastolic flow velocities. Functional capacity was evaluated by cardiopulmonary exercise testing (CPET). The link between CFVR and biventricular systolic function and peak VO2 was studied. ResultsAge was 55.0(14.4)years, 50 patients (60%) were male; 59 patients (71%) had nonobstructive HCM. Mean CFVR LAD was 1.81(0.49) and CFVR PD was 1.73(0.55). Lower CFVR PD was associated with impaired global longitudinal strain (GLS) 2D (β-estimate:-3.240,95%CI:-4.634;-1.846, p < 0.001), GLS 3D (β-estimate:-2.559,95%CI:-3.932;-1.186, p < 0.001) and area strain (β-estimate:-3.044,95%CI:-5.373;-0.716, p = 0.011). Lower values of CFVR PD related to worse global work index (β-estimate:267.824,95%CI:75.964;459.683, p = 0.007), global constructive work (β-estimate:217.300,95%CI:38.750;395.850, p = 0.018) and global work efficiency (β-estimate:5.656,95%CI:2.229;9.084, p = 0.002). Impaired CFVR LAD (β-estimate:2.826, 95%CI:0.913;4.739, p = 0.004) and CFVR PD (β-estimate:2.801,95%CI:0.657;4.945, p = 0.011) were associated with lower TAPSE. Lower values of CFVR LAD (β-estimate:2.580, 95%CI:0.169;4.991, p = 0.036) and CFVR PD (β-estimate:3.163, 95%CI: 0.721;5.606, p = 0.012) were associated with worse peak VO2. ConclusionLower CFVR was associated with impairment in biventricular systolic function parameters and functional capacity assessed by pVO2.

A computational analysis of potential aortic dilation induced by the hemodynamic effects of bicuspid aortic valve phenotypes

Background and objectivesThe bicuspid aortic valve (BAV) is a major risk factor for the progression of aortic dilation (AD) because of the induced abnormal blood flow environment in aorta. The differences in the development of AD induced by BAV phenotypes remains unclear. Therefore, the objective of this study was to assess the potential locations of AD induced by different phenotypes of BAV. The different effects of opening orifice area and leaflet orientation on ascending aortic hemodynamics in Type-1 BAV was investigated by means of numerical simulation. MethodsFinite element dynamic analysis was performed on tricuspid aortic valve (TAV) and BAV models to simulate the motion of the leaflets and obtain the geometrical characteristics of AV at peak systole as a reference, which were used for aortic models. Then, four sets of aortic fluid models were designed according to the leaflet fusion types [TAV; BAV (left-right-coronary cusp fusion, LR; right-non-coronary cusp fusion, RN; left-non-coronary cusp fusion, LN)], and the computational fluid dynamics method was applied to compare the hemodynamic differences within the aorta at peak systole. ResultsThe maximum opening area of BAV was significantly reduced, resulting in alterations in aortic hemodynamics compared with TAV. The velocity streamlines were essentially parallel to the aortic wall in TAV. The average pressure and wall shear stress in aorta tend to be stable. In contrary, the eccentricity of BAV orifice jet resulted in high-velocity flow directed toward the ascending aorta (AA) wall and aortic arch for LR and LN; RN features an asymmetrical velocity distribution toward the outer bend of the middle AA, and eccentric flow tends to impact the distal AA. As the flow angle is associated with distinct flow impingement locations, different degrees of WSS and pressure concentration occur along the aortic wall from the AA to the aortic arch in three BAV types. ConclusionsThe BAV morphotype affects the aortic hemodynamics, and the abnormal blood flow associated with BAV may play a role in AD. The different BAV phenotypes determine the direction of blood flow jet and change the expression of dilation. LR is likely to cause dilation of the tubular AA; RN results in dilation of the middle AA to proximal aortic arch; and LN causes an increased incidence of the tubular AA and the proximal aortic arch.

Pulsatile CFD Numerical Simulation to investigate the effect of various degree and position of stenosis on carotid artery hemodynamics

This study is intended to investigate the effect of various degree and position (pre-bifurcation and post-bifurcation) of stenosis on carotid artery hemodynamics trough realistic CFD numerical simulations with appropriate turbulence model. The blood rheological properties were assumed as incompressible and Newtonian fluid. A 3 dimensional model of a non-stenotic carotid artery model was used this investigation. Several turbulence model were tested. The non-stenotic artery geometry was altered as 30% and 70%pre-bifurcation stenosis model, 30% and 70% post-bifurcation stenosis model. Pulsatile simulations were conducted for the non-stenotic and each stenotic artery models. The SST k-ω with Low-Reynolds number was found to be more appropriate for the simulation. As the degree of pre-bifurcation stenosis increases from 30% to 70%, the ICA maximum velocity increases from 12% to 65%. Also, the ECA maximum velocity increases from 5% to 45%. Besides, the ICA velocity ratio decreases by 22% but the ECA velocity ratioincreases by 101%. As the degree of post-bifurcation stenosis increases, the ICA maximum velocity takes a longer time to decrease after the peak systole velocity and the ECA maximum velocity becomes higher than a non-stenotic artery throughout the cardiac cycle. A mild stenosis at post-bifurcation does not show much effect on the carotid artery hemodynamics. However, even a mild stenosis at pre-bifurcation resulted in fluctuating maximum velocity at both ICA and ECA, especially during the diastole of the cardiac cycle

Using a reduced-order model to investigate the effect of the heart rate on the aortic dissection.

The computational cost of a three-dimensional (3D) fluid-structure interaction (FSI) simulation of a dissected aorta has prevented researchers from investigating the effect of a wide range of the heart rate on the hemodynamic quantities in the disease. We have presented a systematic procedure to develop a zero-dimensional (0D) model for a dissected aorta. A series of numerical experiments were used to calculate the values for the resistance, inertance, and compliance of each lumen with irregular geometries. Having validated the results from the 0D model against those from the 3D model for one heart rate, we used the 0D model to investigate the effect of the heart rate of 50-150 bpm on the flow rates and the pressures in an idealized geometry of an aortic dissection. The 0D model showed acceptable accuracy when compared with the 3D FSI simulation. For instance, at peak systole, 7.18% relative error in the flow rate in the true lumen was observed for 0D and 3D simulations. The flow rate in the true lumen showed a stronger dependency on the heart rate, that is, 300% for the true lumen and 1.5% for the false lumen. The pressure difference between the lumina increased non-monotonically as the heart beats faster. Because of its efficiency, the reported procedure can be used for uncertainty and sensitivity analysis of the hemodynamic quantities in a diseased aorta with complex geometries such as that of the aortic dissection.

In-vitro and In-silico Haemodynamic Analyses of a Novel Embedded Iliac Branch Device.

BackgroundIliac branch devices (IBDs) are valid tools for internal iliac artery preservation during endovascular abdominal aortic aneurysm and iliac aneurysm repair. The purpose of this study was to evaluate the effectiveness of a novel IBD with an embedded branch configuration.MethodA typical iliac artery model was reconstructed, and two models were manufactured using three-dimensional printing technology. The novel IBD was deployed into one iliac artery model by an experienced vascular surgeon. A mock circulation loop (MCL) and a computational fluid dynamics (CFD) simulation were used to investigate the haemodynamic parameters of the iliac models without (Model A) and with (Model B) the IBD. A morphological analysis was conducted using computed tomography angiography and medical endoscopy. The flow distribution rate (FDR) and energy loss (EL) were used to quantify IBD performance.ResultsThe FDR of the right internal iliac artery in the MCL of Model A and Model B was 18.88 ± 0.12% and 16.26 ± 0.09%, respectively (P = 0.0013). The FDR of the right internal iliac artery in the CFD simulation of Model A and Model B was 17.52 and 14.49%, respectively. The EL of Model A was greater than Model B in both the MCL and the CFD simulation. Compared with Model A, Model B had a larger region (8.46 vs. 3.64%) with a relative residence time of >20 Pa−1 at peak systole. Meanwhile, the area where the oscillatory flow index was >0.4 was significantly smaller in Model B than in Model A (0.46 vs. 0.043%). The region with an average wall shear stress of >4 Pa was greater in Model B than in Model A (0 vs. 0.22%).ConclusionThe MCL and CFD simulation showed that the novel IBD had little impact on the FDR and EL of the iliac artery models. However, the IBD might be an effective tool for the treatment of abdominal aortic/iliac aneurysms that extend into branches. Further investigations are warranted to confirm whether this IBD could be useful in the clinic.

Unique Findings of Myocardial Improvement with Lower Left Ventricular Assist Device Pump Speed

<h3>Purpose</h3> Currently, optimizing hemodynamics and unloading in patients with left ventricular assist device (LVAD) relies on echocardiography and right heart catherization guidance for pump speed adjustments. However, the ideal unloading strategy to maximize reverse remodelling is uncertain - whether to provide maximal pump support to unload the heart (‘rest'), or maximize ventricular work with partial pump support (‘work'). Using non-invasively derived PV loops, we sought to characterize the longitudinal changes in chamber contractile parameters stroke work (SW), peak systolic pressure (LVP_max) and peak LV elastance (E_es) at different pump speeds [2400 vs 2500 vs 2600 revolutions/min (rpm)]. <h3>Methods</h3> 32 Medtronic HVAD patients (mean 55.9±12.3 yrs, 81.3% male) were included in the study. Single-cycle pressure and volume estimations were performed using a validated algorithm with the following bedside measurements: echo parameters, HVAD controller-derived data and oscillometric brachial pressure waveform (SphygmoCor Xcel). In total, 77 PV loops were prospectively collected at 3 intervals: 1, 3 and 6 months post-implant (n=26, 29, 22). Corresponding ventricular contractile parameters SW, LVP_max and E_es were calculated. Pump speed was included as a fixed effect to determine its impact on the longitudinal changes in PV parameters. <h3>Results</h3> There were no significant differences in demographics and clinical data between pump speed groups. Linear mixed-effects model was performed to estimate trends in PV parameters. Patients with pump speed of 2400rpm demonstrated significant monthly increase in SW, LVP_max and E_es at 0.05mmHg/L (95%CI 0.02-0.08, p<0.001), 5.64mmHg (95%CI 1.08-10.2, p=0.016) and 0.071mmHg/mL (95%CI 0.002-0.141, p=0.041) per month respectively. The trajectories were significantly different to the patients with higher speeds of 2500rpm and 2600rpm, in whom the PV parameters were largely unchanged across the first 6 months. These findings were consistent after adjusting for baseline cardiovascular risk factors in a covariate-adjusted model. <h3>Conclusion</h3> Our results provide compelling evidence of the impact pump speed has on the longitudinal changes in cardiac chamber function post-LVAD. Randomized studies are required to evaluate the impacts of lowering pump speed as a strategy, to enhance reverse remodelling in suitable patients.

Analysis of Hemodynamic on Different Stent Strut Configurations in Femoral Popliteal Artery

Peripheral arterial disease is a narrowing of the peripheral arteries that might result in blockage if not immediately treated. Normally, an invasive technique called stenting is used at the stenosed arterial region to restore normal blood flow. Furthermore, the impact of physiological stresses on the stented arterial wall may worsen the condition and divert blood away from the main direction of flow. This phenomenon may promote the formation of thrombosis in the stented artery due to the presenting flow recirculation. This study aims to investigate the effect of physiological loads with different hemodynamic factors on the strut configuration in Peripheral arterial. The computational fluid dynamics (CFD) method is governed by continuity and Navier-Stokes equations were implemented. Three-dimensional geometries of the different strut configurations inserted into the peripheral artery are modelled. Each of the struts has different characteristics in terms of strut angle and the number of strut configurations. Due to hemodynamic differences, the pulsatile waveform of the velocity and pressure at the peak systole time were investigated. Hemodynamic factors analysed in this study consist of wall shear stress (WSS), velocity, and pressure. From the result, the prediction of thrombosis formation is around 30% higher for the largest number of strut design. The lowest formation of thrombosis was seen with the fewer strut configurations and the reduction of the strut angle with an overall percentage of 15%.

Second systolic peak in fetal middle cerebral artery Doppler after intrauterine transfusion

ObjectiveTo evaluate functional relationship between fetal circulatory response to intrauterine transfusion (IUT) as a circulatory challenge and appearance of second systolic peak (P2) in middle cerebral artery (MCA) based on hemodynamic principles.MethodsAccording to the concept of pulse wave (PW) propagation and reflection in adults, PWs arrive twice at cerebral circulation, as primary wave caused by left ventricle ejection and secondary after reflection in peripheral arteries. Thus adults show a biphasic contour of systolic blood flow in cerebral arteries. Similar waveforms may appear in fetal MCA-Doppler, as a response to IUT as a circulatory challenge. This is a proof-of-principle study, applying classical hemodynamic principles to fetal circulation. Accordingly, appearance of MCA-P2 may indicate vasoconstriction with increased PW reflection and timing of P2(Δt) should agree with the additional PW travel time down to reflection and return (Tr). To test this agreement, we searched our database for IUTs performed for severe fetal anemia, and compared Δt, obtained by Doppler, with Tr, obtained by hemodynamic calculation using human fetal data. Level of agreement was assessed using Bland–Altman-Plots.ResultsWe identified 21 fetuses with adequate Doppler quality for Δt evaluation. In four cases (19%) MCA-P2 was observed before the intervention, and in 17 interventions (81%) thereafter; a highly significant association between IUT and P2 appearance (p < 0.001). In these 17 interventions good agreement of P2 timing was found between Doppler assessment: Δt = 80 ± 8 ms, and hemodynamic calculation: Tr = 76 ± 4 ms.ConclusionP2 appearance in fetal MCA-Doppler seems to indicate PW reflection due to increased vasoconstriction after IUT. Thus hemodynamic considerations might enable Doppler monitoring of fetal vasoconstriction.