Intraventricular Flow Dynamics Research Articles

Intraventricular flow dynamics and thrombosis risk with a left ventricular assist device using accelerated thrombosis modeling and stress-blended eddy simulation

Intraventricular flow dynamics and thrombosis risk with a left ventricular assist device using accelerated thrombosis modeling and stress-blended eddy simulation

4D Flow Patterns and Relative Pressure Distribution in a Left Ventricle Model by Shake-the-Box and Proper Orthogonal Decomposition Analysis

PurposeIntraventricular blood flow dynamics are associated with cardiac function. Accurate, noninvasive, and easy assessments of hemodynamic quantities (such as velocity, vortex, and pressure) could be an important addition to the clinical diagnosis and treatment of heart diseases. However, the complex time-varying flow brings many challenges to the existing noninvasive image-based hemodynamic assessments. The development of reliable techniques and analysis tools is essential for the application of hemodynamic biomarkers in clinical practice.MethodsIn this study, a time-resolved particle tracking method, Shake-the-Box, was applied to reconstruct the flow in a realistic left ventricle (LV) silicone model with biological valves. Based on the obtained velocity, 4D pressure field was calculated using a Poisson equation-based pressure solver. Furthermore, flow analysis by proper orthogonal decomposition (POD) of the 4D velocity field has been performed.ResultsAs a result of the Shake-the-Box algorithm, we have extracted: (i) particle positions, (ii) particle tracks, and finally, (iii) 4D velocity fields. From the latter, the temporal evolution of the 3D pressure field during the full cardiac cycle was obtained. The obtained maximal pressure difference extracted along the base-to-apex was about 2.7 mmHg, which is in good agreement with those reported in vivo. The POD analysis results showed a clear picture of different scale of vortices in the pulsatile LV flow, together with their time-varying information and corresponding kinetic energy content. To reconstruct 95% of the kinetic energy of the LV flow, only the first six POD modes would be required, leading to significant data reduction.ConclusionsThis work demonstrated Shake-the-Box is a promising technique to accurately reconstruct the left ventricle flow field in vitro. The good spatial and temporal resolutions of the velocity measurements enabled a 4D reconstruction of the pressure field in the left ventricle. The application of POD analysis showed its potential in reducing the complexity of the high-resolution left ventricle flow measurements. For future work, image analysis, multi-modality flow assessments, and the development of new flow-derived biomarkers can benefit from fast and data-reducing POD analysis.

Non-Invasive Assessment of the Intraventricular Pressure Using Novel Color M-Mode Echocardiography in Animal Studies: Current Status and Future Perspectives in Veterinary Medicine.

The assessment of diastolic function has received great interest in order to comprehend its crucial role in the pathophysiology of heart failure and for the early identification of cardiac events. Silent changes in the intraventricular flow (IVF) dynamics occur before the deterioration of the cardiac wall, although they cannot be detected using conventional echocardiography. Collective information on left ventricular (LV) pressures throughout the cardiac cycle has great value when dealing with patients with altered hemodynamics. Accurate pressure measurement inside the ventricle can be obtained by invasive methods to determine the LV diastolic pressures, which reflect the myocardial relaxation and compliance. However, catheterization is only feasible in the laboratory setting and is not suitable for clinical use due to its disadvantages. In contrast, echocardiography is simple, safe, and accessible. Color M-mode echocardiography (CMME) is an advanced cardiac evaluation technique that can measure the intraventricular pressure differences (IVPDs) and intraventricular pressure gradients (IVPGs) based on the Doppler shift of the IVF. Recently, the assessment of IVPD and IVPG has gained growing interest in the cardiovascular literature in both animal and human studies as a non-invasive method for the early diagnosis of cardiac dysfunctions, especially diastolic ones. The usability of IVPD and IVPG has been reported in various surgically induced heart failure or pharmacologically altered cardiac functions in rats, dogs, cats, and goats. This report aims to give an overview of the current studies of CMME-derived IVPD and IVPG in animal studies and its feasibility for clinical application in veterinary practice and to provide the prospects of the technique's ability to improve our understanding.

P78: Risk Assessment of Thrombus Formation in the left Ventricle during VAD Support using computational Models. “How simple is too simple?”

Background: Thrombus formation is a major complication in LVAD treatment, and is influenced by intraventricular blood flow dynamics. Many numerical studies have investigated left ventricular (LV) blood flow patterns with LVAD support using various assumptions which are needed to simplify the highly complex physiological processes for a computational environment. Until now, these various assumptions have not been investigated systematically. This study aimed to assess the effect of modelling assumptions on the risk assessment of thrombus formation in the LV during VAD support. Methods: A patient-specific LV and left atrium (LA) was modelled from CT data of a VAD patient. The impact of the turbulence model (laminar vs turbulent), fluid model (Newtonian vs Carreau approach vs Multiphase approach), model geometry (cylindrical LA vs segmented LA, absent MV vs present MV) and boundary conditions (continuous inflow vs periodic inflow) were evaluated systematically, resulting in eleven simulation set ups in total (Figure 1). They were compared quantitatively over 5 s simulation time by the difference of averaged velocities, residence time, washout, turbulent kinetic energy and computing time for the various simulation models. Results: Geometrical LA changes resulted in the biggest quantitative impact, with a 30.7% lower residence time with a cylindrical LA compared to the segmented LA. The comparison of a laminar and a turbulent flow showed a 26.8 % lower residence time in the laminar flow model compared to a model with turbulent flow. The most significant difference in computational time was found when comparing a Newtonian fluid model and a multiphase approach: The simulation with a multiphase approach took 81 core hours longer than the model with a Newtonian fluid model. Conclusion: The recommended model for achieving a low computing time with minimized loss of accuracy compared to current numerical models assumes a turbulent viscous model with Newtonian-modelled blood, a segmented left atrium, a mitral valve geometry, and pulsatile inflow.Figure 1. Simplification study: Steps and result.

Ventricular Flow Dynamics With an Intra-Ventricular Balloon Pump: An In Vitro Analysis.

Due to the high treatment costs associated with durable ventricular assist devices, an intra-ventricular balloon pump (IVBP) was developed to provide low-cost, short-term support for patients suffering from severe heart failure. It is imperative that intraventricular flow dynamics are evaluated with an IVBP to ensure stagnation points, and potential regions for thrombus formation, are avoided. This study used particle image velocimetry to evaluate flow patterns within the left ventricle of a simulated severe heart failure patient with IVBP support to assess left ventricle pulsatility as an indicator of the likelihood of flow stasis. Two inflation timings were evaluated against the baseline severe heart failure condition: IVBP co-pulsation and IVBP counter-pulsation with respect to ventricular systole. IVBP co-pulsation was found to have a reduced velocity range compared to the severe heart failure condition (0.44 m/s compared to 0.54 m/s). IVBP co-pulsation demonstrated an increase in peak velocities (0.25 m/s directed toward the aortic valve during systole, as opposed to 0.2 m/s in severe heart failure), indicating constructive energy in systole and cardiac output (1.7 L/min increase with respect to severe heart failure baseline - 3.5 L/min) throughout the cardiac cycle. IVBP counter-pulsation, while exhibiting the greatest peak systolic velocity directed to the aortic valve (0.4 m/s) was found to counterasct the natural vortex flow pattern during ventricular filling, as well as inducing a secondary ventricular pulse during diastole and a 23% increase in left ventricle end-diastolic volume (indicative of dilation). Ideal IVBP actuation timing did not result in reduced intraventricular pulsatility, indicating promising blood washout.

Noninvasive Evaluation of Intraventricular Flow Dynamics by the HyperDoppler Technique: First Application to Normal Subjects, Athletes, and Patients with Heart Failure.

Background: HyperDoppler is a new echocardiographic color Doppler-based technique that can assess intracardiac flow dynamics. The aim of this study was to verify the feasibility and reproducibility of this technique in unselected patients and its capability to differentiate measures of vortex flow within the left ventricle (LV) in normal sedentary subjects, athletes, and patients with heart failure. Methods: Two hundred unselected, consecutive patients presenting at the echocardiographic laboratory, 50 normal subjects, 30 athletes, and 50 patients with chronic heart failure and LV ejection fraction <50% were enrolled. Images were acquired using a MyLab X8 echo-scanner. Area, intensity, depth, length, and kinetic energy dissipation (KED) of vortex flow were measured. Results: The HyperDoppler technique feasibility was 94.5%. According to the intraclass correlation coefficient evaluations, repeatability and reproducibility of vortex flow measures were good for vortex area (0.82, 0.85), length (0.83, 0.82), and depth (0.87, 0.84) and excellent for intensity (0.92, 0.90) and KED (0.98, 0.98). Combining different vortex flow measures, the LV flow profile of healthy sedentary individuals, athletes, and heart failure patients could be differentiated. Conclusions: HyperDoppler is a feasible, reliable, and practical technique for the assessment of LV flow dynamics and may distinguish normal subjects and patients with heart failure.

Image-Based Computational Hemodynamics Analysis of Systolic Obstruction in Hypertrophic Cardiomyopathy.

Hypertrophic Cardiomyopathy (HCM) is a pathological condition characterized by an abnormal thickening of the myocardium. When affecting the medio-basal portion of the septum, it is named Hypertrophic Obstructive Cardiomyopathy (HOCM) because it induces a flow obstruction in the left ventricular outflow tract. In any type of HCM, the myocardial function can become compromised, possibly resulting in cardiac death. In this study, we investigated with computational analysis the hemodynamics of patients with different types of HCM. The aim was quantifying the effects of this pathology on the intraventricular blood flow and pressure gradients, and providing information potentially useful to guide the indication and the modality of the surgical treatment (septal myectomy). We employed an image-based computational approach, integrating fluid dynamics simulations with geometric and functional data, reconstructed from standard cardiac cine-MRI acquisitions. We showed that with our approach we can better understand the patho-physiological behavior of intraventricular blood flow dynamics due to the abnormal morphological and functional aspect of the left ventricle. The main results of our investigation are: (a) a detailed patient-specific analysis of the blood velocity, pressure and stress distribution associated to HCM; (b) a computation-based classification of patients affected by HCM that can complement the current clinical guidelines for the diagnosis and treatment of HOCM.

311 A new color Doppler-based echocardiographic technique for evaluation of intraventricular flow dynamics: first application to normal subjects, athletes, and patients

Abstract Aims A new echocardiographic, color Doppler-based technique, named HyperDoppler, has been recently introduced for non-invasive evaluation of intracardiac flow dynamics. The aim of this study was to verify the feasibility and reproducibility of this technique and its capability to differentiate geometrical and energy measures of vortex flow within the left ventricle (LV) in normal subjects, athletes and patients with heart failure. Methods and results Two Italian cardiology centres enrolled each one 100 unselected, consecutive patients presenting at the echocardiography laboratory for a clinical examination, regardless of the indication to echocardiography. In these patients, the feasibility, repeatability, reproducibility, and inter-centre reproducibility of the HyperDoppler technique were tested using the intraclass correlation coefficient (ICC) and Bland–Altman analysis. In addition, 50 normal subjects, 30 professional athletes, and 50 patients with stabilized chronic heart failure and LV ejection fraction &amp;lt;40% were enrolled. Images were acquired using a MyLab X8 echo-scanner and analysed to provide the following vortex flow measures: vortex area, normalized with the LV area; vortex intensity (i.e. the integral of the vorticity inside the vortex), normalized with the total vorticity; vortex depth (the distance of its centre from the LV base) and length along the base-apex direction, both normalized with the LV length; and the total kinetic energy dissipation (KED). Feasibility of HyperDoppler was very high (94.5%). According to the ICC values, at Centre 1 repeatability and reproducibility of vortex flow measures in unselected patients were good for vortex area (0.82, 0.85), length (0.83, 0.82) and depth (0.87, 0.84) and excellent for vortex intensity (0.92, 0.90) and KED (0.98, 0.98). Results of the Bland–Altman analysis showed no bias nor consistent under/overestimations of flow measures, with 95% of points always lying within the limits of agreement for each flow measure. Centre 2 provided similar repeatability and reproducibility evaluations for all the vortex measures, thus supporting a good-to-excellent inter-centre reproducibility. Athletes had greater vortex area, intensity, and KED compared to healthy subjects while they had smaller vortex length and depth and greater KED compared to patients with heart failure and reduced LV ejection fraction. In comparison with healthy subjects, heart failure patients showed greater vortex area, length, depth, and intensity but smaller KED. Combining vortex flow measures, the LV flow profile of healthy individuals, athletes, and heart failure patients could be differentiated. Conclusions HyperDoppler is a new ultrasound technique which is feasible, reliable, and practical for assessment of LV flow dynamics. It can quantitate several measures of the LV vortex and may distinguish normal subjects and patients. Future studies are needed to clarify how to implement this technique in cardiology clinical practice.

Novel Transcatheter Mitral Prosthesis Designed to Preserve Physiological Ventricular Flow Dynamics

BackgroundCurrent mitral bioprostheses are akin to the aortic valve and therefore abolish the left ventricular (LV) physiological vortex. We evaluated the hemodynamic performance and the effects on intraventricular flow dynamics (IFD) of a novel mitral bioprosthesis that presents an innovative design mimicking the native valve. MethodsA D-shaped self-expandable stent-bovine pericardium monoleaflet valve was designed to provide physiological asymmetric intraventricular flow. Transapical implantation was consecutively performed in 12 juvenile sheep. Postimplant studies using Doppler echocardiography and IFD using echo particle imaging velocimetry were obtained immediately after the implantation and at 3 months to assess the hemodynamic performance of the prostheses. ResultsThere were 3 deaths during follow-up, 1 due to valve misplacement because of poor imaging visualization and 2 not valve related. The mean transvalvular gradient and effective orifice area were 2.2 ± 1.2 mm Hg and 4.0 ± 1.1 cm2 after implantation and 3.3 ± 1.5 mm Hg and 3.5 ± 0.5 cm2 at 3 months, respectively. LV vortex dimension, orientation, and physiological anticlockwise rotation were preserved compared with preoperative normal LV flow pattern. One animal showed a moderate paravalvular leak, others mild or none. LV outflow tract obstruction, valve thrombosis, and hemolysis were not observed. ConclusionsOur preclinical in vivo results confirm the good hemodynamic performance of this new transcatheter bioprosthesis with preservation of the physiological IFD. Clinical studies are needed to document whether these characteristics will foster LV recovery and improve the clinical outcome of patients with mitral regurgitation.

Assessment of ventricular flow dynamics by 4D-flow MRI in patients following surgical repair of d-transposition of the great arteries

ObjectivesTo use 4D-flow MRI to describe systemic and non-systemic ventricular flow organisation and energy loss in patients with repaired d-transposition of the great arteries (d-TGA) and normal subjects.MethodsPathline tracking of ventricular volumes was performed using 4D-flow MRI data from a 1.5-T GE Discovery MR450 scanner. D-TGA patients following arterial switch (n = 17, mean age 14 ± 5 years) and atrial switch (n = 15, 35 ± 6 years) procedures were examined and compared with subjects with normal cardiac anatomy and ventricular function (n = 12, 12 ± 3 years). Pathlines were classified by their passage through the ventricles as direct flow, retained inflow, delayed ejection flow, and residual volume and visually and quantitatively assessed. Additionally, viscous energy losses (ELv) were calculated.ResultsIn normal subjects, the ventricular flow paths were well ordered following similar trajectories through the ventricles with very little mixing of flow components. The flow paths in all atrial and some arterial switch patients were more irregular with high mixing. Direct flow and delayed ejection flow were decreased in atrial switch patients’ systemic ventricles with a corresponding increase in residual volume compared with normal subjects (p = 0.003 and p < 0.001 respectively) and arterial switch patients (p < 0.0001 and p < 0.001 respectively). In non-systemic ventricles, arterial switch patients had increased direct flow and decreased delayed ejection fractions compared to normal (p = 0.007 and p < 0.001 respectively) and atrial switch patients (p = 0.01 and p < 0.001 respectively). Regions of high levels of mixing of ventricular flow components showed elevated ELv.Conclusions4D-flow MRI pathline tracking reveals disordered ventricular flow patterns and associated ELv in d-TGA patients.Key Points• 4D-flow MRI can be used to assess intraventricular flow dynamics in d-TGA patients.• d-TGA arterial switch patients mostly show intraventricular flow dynamics representative of normal subjects, while atrial switch patients show increased flow disorder and different proportions of intraventricular flow volumes.• Flow disruption and disorder increase viscous energy losses.

Evaluation of patients with a HeartMate 3 left ventricular assist device using echocardiographic particle image velocimetry

PurposePoor left ventricular (LV) function may affect the physiological intraventricular blood flow and physiological vortex formation. The aim of this study was to investigate the pattern of intraventricular blood flow dynamics in patients with LV assist devices (LVADs) using echocardiographic particle image velocimetry.Materials and methodsThis prospective study included 17 patients (mean age 57 ± 11 years, 82% male) who had received an LVAD (HeartMate 3, Abbott Laboratories, Chicago, Illinois, USA) because of end-stage heart failure and poor LV function. Eleven (64%) patients had ischemic cardiomyopathy, and six patients (36%) had nonischemic cardiomyopathy. All patients underwent echocardiography, including intravenous administration of an ultrasound-enhancing agent (SonoVue, Bracco, Milan, Italy). Echocardiographic particle image velocimetry was used to quantify LV blood flow dynamics, including vortex formation (Hyperflow software, Tomtec imaging systems Gmbh, Unterschleissheim, Germany).ResultsContrast-enhanced ultrasound was well tolerated in all patients and was performed without adverse reactions or side effects. The LVAD function parameters did not change during or after the ultrasound examination. The LVAD flow was on average 4.3 ± 0.3 L/min, and the speed was 5247 ± 109 rotations/min. The quantification of LV intraventricular flow demonstrated substantial impairment of vortex parameters. The energy dissipation, vorticity, and kinetic energy fluctuation indices were severely impaired.ConclusionsEcho particle velocimetry is safe and feasible for the quantitative assessment of intraventricular flow in patients with an LVAD. The intraventricular LV flow and vortex parameters are severely impaired in these patients.

Injectable Shear-Thinning Hydrogels Prevent Ischemic Mitral Regurgitation and Normalize Ventricular Flow Dynamics

Injectable hydrogels are known to attenuate left-ventricular (LV) remodeling following myocardial infarction (MI), dependent on material mechanical properties. The effect of hydrogel injection on ischemic mitral regurgitation (IMR) resultant from LV remodeling remains relatively unexplored. This study uses multiple imaging methods to evaluate the efficacy of injectable hydrogels with tunable modulus to prevent post-MI development of IMR. Posterolateral MI was induced in 20 sheep with subsequent epicardial injection of saline (control (MI); n = 7), soft hydrogel (guest-host crosslinking, modulus <1 kPa, n = 7), or stiff hydrogel (dual-crosslinking, modulus = 41.4 ± 4.3 kPa, n = 6) within the infarct region and 8-week follow-up. IMR and valve geometry were assessed by echocardiography. LV geometry (long-axis dimension, posterior chordae length) and ventricular flow dynamics were assessed by magnetic resonance imaging. IMR developed in MI controls at 8 weeks and was attenuated with hydrogel treatment (IMR grade for MI: 1.86 ± 0.69; guest-host crosslinking: 1.29 ± 1.11; dual-crosslinking: 0.50 ± 0.55, P = 0.02 vs MI). Tethering of the posterior leaflet increased in MI controls, but not with stiff hydrogel treatment. Across cohorts, IMR was correlated with changes in the long-axis dimension (Spearman R = 0.77) and posterior chordae length (Spearman R = 0.64). Intraventricular flow dynamics were highly disturbed in MI controls, but stiff hydrogel treatment normalized flow patterns and reduced the prevalence of large (≥2+ MR, >5 mL) regurgitant volumes. Injectable hydrogels attenuated subvalvular remodeling and leaflet tethering, preventing IMR development and normalizing LV flow dynamics. Hydrogels with a supraphysiological modulus yielded best outcomes.

P2477Assessment of intraventricular flow dynamics in acute heart failure studied by Vector Flow Mapping

Abstract Background Although left ventricular (LV) flow dynamics should be closely related to LV morphology and function, little is known about how heart failure (HF) changes it. Pathline Analysis (PA), a recently developed software based on Vector Flow Mapping (VFM, Hitachi), enables us to trace the virtual blood particles entering to the LV in diastole and being ejected in systole. We investigated the change of flow dynamics in HF induced in dogs using PA. Methods In 15 open-chest dogs, HF was induced by intracoronary injection of microspheres. Color Doppler images of apical long-axis view were acquired using Prosound F75 (Hitachi) before and after HF and were analyzed by PA. We calculated the ratio of the numbers of entering particles in diastole and ejected particles in systole (ejection rate) and the distance reached by the particles in diastole corrected by the LV long-axis diameter (propagation distance). Apical and basal short axis images were acquired using GE Vivid E9 and were analyzed for peak rotation and peak twist. Results After inducing HF, LV end-diastolic pressure increased from 6±2 to 15±5 mmHg (p&lt;0.001) and ejection fraction (EF), apical peak rotation and peak twist decreased significantly (EF; 58±5 to 36±8%, apical peak rotation; 14±5 to 3±2 degree, peak twist; 19±5 to 6±3 degree, p&lt;0.05, respectively). PA showed most of the entering particles to the LV were ejected in the following systole at the control stage, but in HF, a significant part of the entering particles were not ejected and remained in the LV (Figure). Ejection rate decreased from 50±11 to 26±11% (p&lt;0.001) and the propagation distance decreased from 85±9 to 66±13% (p&lt;0.001) after inducing HF. There were significant relationships between indices obtained by PA and EF and peak twist (Table). Conclusion A significant part of inflow is not ejected directly to the outflow in the next systole and remains in the LV in HF, suggesting inefficient flow dynamics.

Evaluation of left ventricular diastolic function based on flow energetic parameters in chronic kidney disease with diastolic dysfunction

Intra-ventricular blood flow dynamics is considered as an important component of left ventricular (LV) function assessment. The purpose of this study was to evaluate the LV diastolic function in chronic kidney disease (CKD) with different degrees of LV diastolic dysfunction (LVDD) by using flow energetic parameters. In this study, a total of 96 cases were recruited, including 58 CKD patients and 38 healthy controls. CKD patients were divided into 2 groups according to LVDD severity, named as DD1 and DD2. Vector flow-mapping (VFM) analysis was executed to calculate left ventricle average energy loss (EL) during early filling phase (E-EL_ave), atrial filling phase (A-EL_ave), diastole phase (D-EL_ave), and ejection phase (S-EL_ave). Moreover, the average vortex circulation during early filling phase (E-cir_ave) and atrial filling phase (A-cir_ave) was also assessed in the apical three-chamber view. The rate of average EL during early filling and atrial filling was expressed as E/A-EL. Compared to the control group, A-EL_ave, S-EL_ave, and A-cir_ave in the DD1 group were higher (P<0.05), and all parameters were obviously higher in the DD2 group (P<0.05). In the control group and the DD2 subgroup, the E-EL_ave value was significantly higher than A-EL_ave value, which was opposite to the DD1 group. As diastolic dysfunction worsened, E-EL_ave and D-EL_ave risen gradually (P<0.05), and A-EL_ave and S-EL_ave were slightly elevated with no significance. There were significant correlations between LV diastolic function and flow energetic parameters. Stepwise multiple regression analysis revealed that various LV function parameters could be regarded as independent predictors of average diastolic EL (all P<0.01). For CKD patient with LVDD and LVEF>50%, effective LV filling and systolic ejection with optimized energy consumption have been impaired. As a new flow-derived index, EL can quantitatively evaluate LV diastolic function in terms of blood fluid dynamics in CKD with various LVDD.

The Influence of Rotary Blood Pump Speed Modulation on the Risk of Intraventricular Thrombosis.

Rotary left ventricular assist devices (LVADs) are commonly operated at a constant speed, attenuating blood flow pulsatility. Speed modulation of rotary LVADs has been demonstrated to improve vascular pulsatility and pump washout. The effect of LVAD speed modulation on intraventricular flow dynamics is not well understood, which may have an influence on thromboembolic events. This study aimed to numerically evaluate intraventricular flow characteristics with a speed modulated LVAD. A severely dilated anatomical left ventricle was supported by a HeartWare HVAD in a three-dimensional multiscale computational fluid dynamics model. Three LVAD operating scenarios were evaluated: constant speed and sinusoidal co- and counter-pulsation. In all operating scenarios, the mean pump speed was set to restore the cardiac output to 5.0L/min. Co- and counter-pulsation was speed modulated with an amplitude of 750rpm. The risk of thrombosis was evaluated based on blood residence time, ventricular washout, kinetic energy densities, and a pulsatility index map. Blood residence time for co-pulsation was on average 1.8 and 3.7% lower than constant speed and counter-pulsation mode, respectively. After introducing fresh blood to displace preexisting blood for 10 cardiac cycles, co-pulsation had 1.5% less old blood in comparison to counter-pulsation. Apical energy densities were 84 and 27% higher for co-pulsation in comparison to counter-pulsation and constant speed mode, respectively. Co-pulsation had an increased pulsatility index around the left ventricular outflow tract and mid-ventricle. Improved flow dynamics with co-pulsation was caused by increased E-wave velocities which minimized blood stasis. In the studied scenario and from the perspective of intraventricular flow dynamics, co-pulsation of rotary LVADs could minimize the risk of intraventricular thrombosis.

Quantitative analysis of intraventricular flow-energetics and vortex in ischaemic hearts.

This study investigated the intraventricular flow dynamics in ischaemic heart disease patients. Fourteen patients with normal ejection fraction and 16 patients with reduced ejection fraction were compared with 20 healthy individuals. Phase-contrast MRI was used to assess intraventricular flow variables and speckle-tracking echocardiography to assess myocardial strain and left ventricular (LV) dyssynchrony. Infarct size was acquired using delayed-enhancement MRI. The results obtained showed no significant differences in intraventricular flow variables between the healthy group and the patients with normal ejection fraction group, whereas considerable reductions in kinetic energy (KE) fluctuation index, E' (P<0.001) and vortex KE (P=0.003) were found in the patients with reduced ejection fraction group. In multivariate analysis, only vortex KE and infarct size were significantly related to LV ejection fraction (P<0.001); furthermore, vortex KE was correlated negatively with energy dissipation, energy dissipation index (r=-0.44, P=0.021). This study highlights that flow energetic indices have limited applicability as early predictors of LV progressive dysfunction, whereas vortex KE could be an alternative to LV performance.

Patient-specific CFD models for intraventricular flow analysis from 3D ultrasound imaging: Comparison of three clinical cases

BackgroundAs the intracardiac flow field is affected by changes in shape and motility of the heart, intraventricular flow features can provide diagnostic indications. Ventricular flow patterns differ depending on the cardiac condition and the exploration of different clinical cases can provide insights into how flow fields alter in different pathologies. MethodsIn this study, we applied a patient-specific computational fluid dynamics model of the left ventricle and mitral valve, with prescribed moving boundaries based on transesophageal ultrasound images for three cardiac pathologies, to verify the abnormal flow patterns in impaired hearts. One case (P1) had normal ejection fraction but low stroke volume and cardiac output, P2 showed low stroke volume and reduced ejection fraction, P3 had a dilated ventricle and reduced ejection fraction. ResultsThe shape of the ventricle and mitral valve, together with the pathology influence the flow field in the left ventricle, leading to distinct flow features. Of particular interest is the pattern of the vortex formation and evolution, influenced by the valvular orifice and the ventricular shape. The base-to-apex pressure difference of maximum 2mmHg is consistent with reported data. ConclusionWe used a CFD model with prescribed boundary motion to describe the intraventricular flow field in three patients with impaired diastolic function. The calculated intraventricular flow dynamics are consistent with the diagnostic patient records and highlight the differences between the different cases. The integration of clinical images and computational techniques, therefore, allows for a deeper investigation intraventricular hemodynamics in patho-physiology.

Patient-specific CFD simulation of intraventricular haemodynamics based on 3D ultrasound imaging.

BackgroundThe goal of this paper is to present a computational fluid dynamic (CFD) model with moving boundaries to study the intraventricular flows in a patient-specific framework. Starting from the segmentation of real-time transesophageal echocardiographic images, a CFD model including the complete left ventricle and the moving 3D mitral valve was realized. Their motion, known as a function of time from the segmented ultrasound images, was imposed as a boundary condition in an Arbitrary Lagrangian–Eulerian framework.ResultsThe model allowed for a realistic description of the displacement of the structures of interest and for an effective analysis of the intraventricular flows throughout the cardiac cycle. The model provides detailed intraventricular flow features, and highlights the importance of the 3D valve apparatus for the vortex dynamics and apical flow.ConclusionsThe proposed method could describe the haemodynamics of the left ventricle during the cardiac cycle. The methodology might therefore be of particular importance in patient treatment planning to assess the impact of mitral valve treatment on intraventricular flow dynamics.Electronic supplementary materialThe online version of this article (doi:10.1186/s12938-016-0231-9) contains supplementary material, which is available to authorized users.

Quantitative analysis of intraventricular blood flow dynamics by echocardiographic particle image velocimetry in patients with acute myocardial infarction at different stages of left ventricular dysfunction.

Left ventricular (LV) diastolic filling is characterized by the formation of a vortex that supports an efficient transit into systolic ejection. Aim of this study was to assess the intraventricular (IV) blood flow dynamics among patients with ST elevated myocardial infarction (STEMI) at different degrees of LV dysfunction, in the attempt to find novel indicators of LV pump efficiency. Sixty-four subjects, 34 consecutive STEMI patients and 30 healthy controls, underwent before hospital discharge 2D speckle tracking echocardiography to assess global longitudinal strain (GLS), and echo-particle image velocimetry analysis to assess flow energetic parameters. Left ventricular volumes ejection fraction (LVEF) and global wall motion score index (GWMSI) were evaluated by 3D echocardiography. ST elevated myocardial infarction patients were subdivided into three groups according to LVEF. Energy dissipation, vorticity fluctuation, and kinetic energy fluctuation indexes, which characterize the degree of disturbance in the flow, exhibit a biphasic behaviour in STEMI patients when compared with controls, with the highest values in patients with still preserved LV function and progressive lower values with LV function worsening. Significant linear correlations were found between energy dissipation index and both LVEF and GLS (r = 0.57, P < 0.001 and r = -0.61, P = 0.001, respectively). Kinetic energy fluctuation index significantly correlates with both LVEF (r = 0.75, P < 0.001) and GLS (-0.58, P = 0.002). Finally, a significant correlation was observed between GWMSI and energy dissipation index (-0.56, P = 0.008). The present study describes, for the first time, the progression of IV flow energetic properties in patients with acute myocardial infarction at different stages of LV dysfunction when compared with healthy controls. Further data are needed to assess the role of these parameters in the development and maintenance of LV dysfunction.

Evaluation of right and left ventricular diastolic filling.

A conceptual fluid-dynamics framework for diastolic filling is developed. The convective deceleration load (CDL) is identified as an important determinant of ventricular inflow during the E wave (A wave) upstroke. Convective deceleration occurs as blood moves from the inflow anulus through larger-area cross-sections toward the expanding walls. Chamber dilatation underlies previously unrecognized alterations in intraventricular flow dynamics. The larger the chamber, the larger becomes the endocardial surface and the CDL. CDL magnitude affects strongly the attainable E wave (A wave) peak. This underlies the concept of diastolic ventriculoannular disproportion. Large vortices, whose strength decreases with chamber dilatation, ensue after the E wave peak and impound inflow kinetic energy, averting an inflow-impeding, convective Bernoulli pressure rise. This reduces the CDL by a variable extent depending on vortical intensity. Accordingly, the filling vortex facilitates filling to varying degrees, depending on chamber volume. The new framework provides stimulus for functional genomics research, aimed at new insights into ventricular remodeling.