Intracardiac Flow Patterns Research Articles

Transforming Heart Failure Management: The Power of Strain Imaging, 3D Imaging, and Vortex Analysis in Echocardiography.

Heart failure (HF) remains a critical global health challenge, necessitating advancements in diagnostic and therapeutic strategies. This review explores the evolution of imaging technologies and their impact on HF management, focusing on three-dimensional echocardiography (3DE), myocardial strain imaging, and vortex dynamics imaging. Three-dimensional echocardiography enhances traditional echocardiography by providing more accurate assessments of cardiac structures, while myocardial strain imaging offers the early detection of subclinical myocardial dysfunction, crucial in conditions such as chemotherapy-induced cardiotoxicity and ischemic heart disease. Vortex dynamics imaging, a novel technique, provides insights into intracardiac flow patterns, aiding in the evaluation of left ventricular function, valve diseases, and congenital heart anomalies. The integration of these advanced imaging modalities into clinical practice facilitates personalized treatment strategies, enabling the earlier diagnosis and more precise monitoring of disease progression. The ongoing refinement of these imaging techniques holds promise for improving patient outcomes and advancing the field of precision medicine in HF care.

Optimizing intracardiac flow assessment with high frequency ultrasound in a mouse model

Cardiomyopathy, a disorder affecting the heart muscle, is associated with severe symptoms, such as heart failure, arrhythmia, or cardiac arrest. Echocardiography is the primary clinical tool for myocardial assessment, which provides diagnostic and prognostic insights. However, current clinical parameters, such as myocardial strain, often detect the condition only after symptoms become pronounced, showing the need for early-stage assessment. Based on preliminary studies, intracardiac flow patterns have the potential to detect abnormal myocardial changes earlier than the current clinical parameters. Mouse models are commonly imaged with ultrasound in the cardiovascular disease research but their use for flow pattern evaluation has been hindered by spatial and temporal resolution limitations. Here, we address this limitation by conducting data acquisition using a Verasonics scanner with a range of high-frequency probes (16 to 42 MHz), transmit cycles, and transmit angles. A singular value decomposition (SVD) filter and frequency de-aliasing were also investigated to optimize flow quantification. Our findings show that a higher transmission frequency, while providing superior spatial resolution, may not yield the best flow quantification due to increased Doppler aliasing. Furthermore, SVD filtering and Doppler de-aliasing should be used with caution because improper implementation can adversely impact the quantification results.

Assessing Intracardiac Vortices with High Frame-Rate Echocardiography-Derived Blood Speckle Imaging in Newborns.

The left ventricle (LV) has a unique pattern of hemodynamic filling. During diastole, a rotational body or ring of fluid known as a vortex is formed due to the chiral geometry of the heart. A vortex is reported to have a role in conserving the kinetic energy of blood flow entering into the LV. Recent studies have shown that LV vortices may have prognostic value in describing diastolic function at rest in neonatal, pediatric, and adult populations, and may help with earlier subclinical intervention. However, the visualization and characterization of the vortex remain minimally explored. A number of imaging modalities have been utilized for visualizing and describing intracardiac blood flow patterns and vortex rings. In this article, a technique known as blood speckle imaging (BSI) is of particular interest. BSI is derived from high-frame rate color Doppler echocardiography and provides several advantages over other modalities. Namely, BSI is an inexpensive and noninvasive bedside tool that does not rely on contrast agents or extensive mathematical assumptions. This work presents a detailed step-by-step application of the BSI methodology used in our laboratory. The clinical utility of BSI is still in its early stages, but has shown promise within the pediatric and neonatal populations for describing diastolic function in volume-overloaded hearts. A secondary aim of this study is thus to discuss recent and future clinical work with this imaging technology.

Visualizable intracardiac flow pattern in fetuses with congenital heart defect: pilot study of blood speckle-tracking echocardiography.

Blood-flow pattern is an essential factor in cardiovascular development. Recently, blood speckle-tracking echocardiography (BST) based on high-frame-rate ultrasound has emerged as a promising technique for the assessment of blood-flow patterns and properties. The objectives of this study were to determine the feasibility of BST in the fetus and to assess intracardiac blood-flow patterns of fetuses with a congenital heart defect (CHD) using this technique. This was a prospective study consisting of 35 normal fetuses, 35 fetuses with left-sided obstructive lesion (LSOL) and 35 fetuses with right-sided obstructive lesion (RSOL). BST images of fetal intracardiac regions of interest (ROIs), including the left ventricle (LV), right ventricle (RV), ascending aorta (AAo), aortic arch (AA), descending aorta (DAo) and pulmonary artery (PA), were obtained and analyzed. The feasibility of BST was assessed, and blood-flow pattern and number of vortices in the ROIs were recorded. The median gestational age of the fetuses was 24.7 weeks (range, 19.6-34.3 weeks). BST was feasible in 81.6% of cases, and the cut-off value of depth for an adequate BST image was ≤ 7.9 cm. There were no differences in the presence of vortex/turbulent blood flow in the LV or RV among the three groups. Vortex/turbulent blood flow in the AAo was detected in 0% (0/35), 14.3% (5/35) and 57.1% (20/35) of cases in the control, LSOL and RSOL groups, respectively. The respective values were 5.7% (2/35), 14.3% (5/35) and 51.4% (18/35) for the AA; 0% (0/35), 48.6% (17/35) and 0% (0/35) for the DAo; and 0% (0/35), 40.0% (14/35) and 51.4% (18/35) for the PA. With the exception of the DAo in the RSOL group, vortex/turbulent flow in the great artery ROIs was significantly more common in the LSOL and RSOL groups than in controls (P < 0.01). In the LSOL group, the number of vortices in the AAo, AA, DAo and PA was significantly greater compared with that in controls (P < 0.01). In the RSOL group, the number of vortices in the LV, AAo, AA and PA was significantly greater compared with that in controls (P < 0.01). Fetuses with CHD were more likely to exhibit vortex/turbulent blood flow and increased number of vortices in the great arteries compared with healthy controls. Further research is needed to determine the biomechanical effect of blood-flow patterns, especially vortex flow, on fetal cardiovascular structure and function. © 2023 International Society of Ultrasound in Obstetrics and Gynecology.

Flow dynamic assessment of native mitral valve, mitral valve repair and mitral valve replacement using vector flow mapping intracardiac flow dynamic in mitral valve regurgitation.

The present study aims to assess and describe the intracardiac blood flow dynamic in patients with mitral regurgitation (MR), repaired mitral valves (MV) and mitral valve prostheses using vector flow mapping (VFM). Patients with different MV pathologies and MV disease treatments were analysed. All patients underwent 2D transthoracic echocardiography, and images for flow visualization were acquired in VFM mode in an apical three-chamber view and four-chamber view. Vectors and vortices were qualitatively analyzed. thirty-two (32) patients underwent 2D transthoracic echocardiography (TTE) with VFM analysis. We evaluated intracardiac flow dynamics in 3 healthy subjects, 10 patients with MR (5 degenerative, 5 functional), 4 patients who underwent MV repair, 5 who underwent MV replacement (3 biological, 2 mechanical), 2 surgically implanted transcatheter heart valve (THV), 2 transcatheter edge-to-edge MV repair with MitraClip (TEER), 3 transcatheter MV replacement (TMVR) and 3 transapical off-pump MV repair with NeoChord implantation. Blood flow patterns are significantly altered in patients with MV disease and MV repair compared to control patients. MV repair is superior to replacement in restoring more physiologicalpatterns, while TMVR reproducesan intraventricular flowcloser to normal than surgical MVR and TEER. Intracardiac flow patterns can be clearly defined using VFM. Restoration of a physiological blood flow pattern inside the LV directly depends on the procedure used to address MV disease.

Highly Accelerated Compressed-Sensing 4D Flow for Intracardiac Flow Assessment.

Four-dimensional (4D) flow MRI allows for the quantification of complex flow patterns; however, its clinical use is limited by its inherently long acquisition time. Compressed sensing (CS) is an acceleration technique that provides substantial reduction in acquisition time. To compare intracardiac flow measurements between conventional and CS-based highly accelerated 4D flow acquisitions. Prospective. Fifty healthy volunteers (28.0 ± 7.1 years, 24 males). Whole heart time-resolved 3D gradient echo with three-directional velocity encoding (4D flow) with conventional parallel imaging (factor 3) as well as CS (factor 7.7) acceleration at 3T. 4D flow MRI data were postprocessed by applying a valve tracking algorithm. Acquisition times, flow volumes (mL/cycle) and diastolic function parameters (ratio of early to late diastolic left ventricular peak velocities [E/A] and ratio of early mitral inflow velocity to mitral annular early diastolic velocity [E/e']) were quantified by two readers. Paired-samples t-test and Wilcoxon rank sum test to compare measurements. Pearson correlation coefficient (r), Bland-Altman-analysis (BA) and intraclass correlation coefficient (ICC) to evaluate agreement between techniques and readers. A P value < 0.05 was considered statistically significant. A significant improvement in acquisition time was observed using CS vs. conventional accelerated acquisition (6.7 ± 1.3 vs. 12.0 ± 1.3min). Net forward flow measurements for all valves showed good correlation (r > 0.81) and agreement (ICCs > 0.89) between conventional and CS acceleration, with 3.3%-8.3% underestimation by the CS technique. Evaluation of diastolic function showed 3.2%-17.6% error: E/A 2.2 [1.9-2.4] (conventional) vs. 2.3 [2.0-2.6] (CS), BA bias 0.08 [-0.81-0.96], ICC 0.82; and E/e' 4.6 [3.9-5.4] (conventional) vs. 3.8 [3.4-4.3] (CS), BA bias -0.90 [-2.31-0.50], ICC 0.89. Analysis of intracardiac flow patterns and evaluation of diastolic function using a highly accelerated 4D flow sequence prototype is feasible, but it shows underestimation of flow measurements by approximately 10%. 2 TECHNICAL EFFICACY: Stage 1.

746 Assessment of intracardiac fluid-dynamics of patients with aortic stenosis

Abstract Aims Recent technological developments enabled visualization of intracardiac flow patterns. This study aims to evaluate intracardiac flow dynamics of patients with aortic stenosis (AS). Methods and results Sixty-one patients with severe AS and 38 healthy sex- and BSA-matched controls (CTRL) were prospectively included. Standard echocardiographic assessment was performed in all patients. Fluid dynamics were evaluated using the HyperDoppler software to measure vortex area (VA), vortex length (VL), and vortex depth (VD). The assessment of VA, VL, and VD was feasible and reliable, as the inter-rater variability (ICCs) were very good for VA (0.878, P = 0.033), VL (0.960, P = 0.004), and VD (0.905, P = 0.021). Mean VA, VL, and VD (P = 0.033, P = 0.026, and P &amp;gt; 0.001, respectively) were significantly larger in AS patients compared with CTRL. A significant difference in the delta values of VA and VL, reflecting their change from before to after TAVI, was observed in patients with and without significant paravalvular leak. Conclusions The newly developed quantitative indices of flow dynamics, namely VA, VL, and VD, were significantly increased in the LV of patients with severe AS compared to controls and their measurement was feasible and reliable in a clinical setting.

Impact of prosthetic mitral valve orientation on the ventricular flow field: Comparison using patient-specific computational fluid dynamics

Significant mitral valve regurgitation creates progressive adverse remodeling of the left ventricle (LV). Replacement of the failing valve with a prosthesis generally improves patient outcomes but leaves the patient with non-physiological intracardiac flow patterns that might contribute to their future risk of thrombus formation and embolism.It has been suggested that the angular orientation of the implanted valve might modify the postoperative distortion of the intraventricular flow field. In this study, we investigated the effect of prosthetic valve orientation on LV flow patterns by using heart geometry from a patient with LV dysfunction and a competent native mitral valve to calculate intracardiac flow fields with computational fluid dynamics (CFD). Results were validated using in vivo 4D Flow MRI. The computed flow fields were compared to calculations following virtual implantation of a mechanical heart valve oriented in four different angles to assess the effect of leaflet position. Flow patterns were visualized in long- and short-axes and quantified with flow component analysis. In comparison to a native valve, valve implantation increased the proportion of the mitral inflow remaining in the basal region and further increased the residual volume in the apical area. Only slight changes due to valve orientation were observed.Using our numerical framework, we demonstrated quantitative changes in left ventricular blood flow due to prosthetic mitral replacement. This framework may be used to improve design of prosthetic heart valves and implantation procedures to minimize the potential for apical flow stasis, and potentially assist personalized treatment planning.

Right ventricle in hypoplastic left heart syndrome exhibits altered hemodynamics in the human fetus

Hypoplastic left heart syndrome (HLHS) represents approximately 9% of all congenital heart defects and is one of the most complex, with the left side of the heart being generally underdeveloped. Numerous studies demonstrate that intracardiac fluid flow patterns in the embryonic and fetal circulation can impact cardiac structural formation and remodeling. This highlights the importance of quantifying the altered hemodynamic environment in congenital heart defects, like HLHS, relative to a normal heart as it relates to cardiac development. Therefore, to study human cardiovascular fetal flow, computational fluid dynamic simulations were performed using 4D patient-specific ultrasound scans in normal and HLHS hearts. In these simulations, we find that the HLHS right ventricle exhibits a greater cardiac output than normal; yet, hemodynamics are relatively similar between normal and HLHS right ventricles. Overall, this study provides detailed quantitative flow patterns for HLHS, which has the potential to guide future prevention and therapeutic interventions, while more immediately providing additional functional detail to cardiologists to aid in decision making.

P1449 CMR-driven computational modeling of right ventricular flow dynamics

Abstract Introduction The analysis of intracardiac blood flow patterns can significantly contribute to improve the understanding and treatment of cardiovascular disease. In contrast to the substantial literature on the left side of the heart, there is currently a significant lack of knowledge about the fluid mechanics of the right heart – pulmonary circulation unit (RH-PCU), both in healthy and diseased conditions. Purpose It is conjectured that computational modeling can be a key element to enhance current imaging techniques and provide quantitative insights into the unique RH-PCU biomechanics. Here we present a novel methodology that allows personalized numerical simulations of right heart flows, through a proper combination of cardiac magnetic resonance (CMR) with computational fluid dynamics (CFD). Methods and results We developed a patient-specific pipeline from medical images to computational models, as depicted in the figure. First, the RV geometry is reconstructed from time-resolved CMR cine images, comprising short-axis and longitudinal slices of the heart, where feature-tracking techniques are used to extract the motion of the RV endocardium contours. A time-continuous description of the moving geometry is obtained through an image-registration algorithm based on diffeomorphic mappings. The moving model of the RV, including the outflow tract and proximal pulmonary arteries, is finally fed to a dedicated CFD solver. The tool is able to provide a detailed description of the velocity and pressure fields inside the right ventricle and proximal pulmonary arteries during all phases of the cardiac cycle. From these fields, global hemodynamic quantities such as vortex properties, kinetic energy, pressure gradients and hemodynamic forces can be computed. Conclusions CMR-driven computational modeling of intra-ventricular flow enables a promising approach for understanding and evaluating the biomechanical environment of the right heart. This high-fidelity framework can be applied to investigate the RV response and adaptation to abnormal pressure and/or volume load conditions. It can also be used to reproduce the virtual flow that would realize in hypothetical conditions, and therefore adds predictive capabilities to modern flow imaging. The analysis may allow to determine an association between blood flow patterns and disease progression, and ultimately lead to derive and validate imaging biomarkers of clinical significance. Abstract P1449 Figure. Pipeline for patient-specific modeling

Reactivation of Notch signaling is required for cardiac valve regeneration

Cardiac Valve Disease is one of the most common heart disorders with an emerging epidemic of cardiac valve degeneration due to aging. Zebrafish can regenerate most of their organs, including their heart. We aimed to explore the regenerative potential of cardiac valves and the underlying molecular mechanisms involved. We used an inducible, tissue-specific system of chemogenetic ablation and showed that zebrafish can also regenerate their cardiac valves. Upon valvular damage at larval stages, the intracardiac flow pattern becomes reminiscent of the early embryonic stages, exhibiting an increase in the retrograde flow fraction through the atrioventricular canal. As a result of the altered hemodynamics, notch1b and klf2a expression are ectopically upregulated, adopting the expression pattern of earlier developmental stages. We find that Notch signaling is re-activated upon valvular damage both at larval and adult stages and that it is required during the initial regeneration phase of cardiac valves. Our results introduce an animal model of cardiac valve specific ablation and regeneration.

An isolated beating pig heart platform for a comprehensive evaluation of intracardiac blood flow with 4D flow MRI: a feasibility study

BackgroundCardiac magnetic resonance imaging (MRI) in large animals is cumbersome for various reasons, including ethical considerations, costs of housing and maintenance, and need for anaesthesia. Our primary purpose was to show the feasibility of an isolated beating pig heart model for four-dimensional (4D) flow MRI for investigating intracardiac blood flow patterns and flow parameters using slaughterhouse side products. In addition, the feasibility of evaluating transcatheter aortic valve replacement (TAVR) in the model was investigated.MethodsSeven slaughterhouse pig hearts were installed in the MRI-compatible isolated beating pig heart platform. First, Langendorff perfusion mode was established; then, the system switched to working mode, in which blood was actively pumped by the left ventricle. A pacemaker ensured a stable HR during 3-T MRI scanning. All hearts were submitted to human physiological conditions of cardiac output and stayed vital for several hours. Aortic flow was measured from which stroke volume, cardiac output, and regurgitation fraction were calculated.Results4D flow MRI acquisitions were successfully conducted in all hearts. Stroke volume was 31 ± 6 mL (mean ± standard deviation), cardiac output 3.3 ± 0.9 L/min, and regurgitation fraction 16% ± 9%. With 4D flow, intracardiac and coronary flow patterns could be visualised in all hearts. In addition, we could study valve function and regurgitation in two hearts after TAVR.ConclusionsThe feasibility of 4D flow MRI in an isolated beating pig heart loaded to physiological conditions was demonstrated. The platform is promising for preclinical assessment of cardiac blood flow and function.

Left ventricular blood flow patterns at rest and under dobutamine stress in healthy pigs.

Intracardiac blood flow patterns are affected by the morphology of cardiac structures and are set up to support the heart's pump function. Exercise affects contractility and chamber size as well as pre- and afterload. The aim of this study was to test the feasibility of four-dimensional phase contrast cardiovascular MRI under pharmacological stress and to study left ventricular blood flow under stress. 4D flow data were successfully acquired and analysed in 12 animals. During dobutamine infusion, heart rate and ejection fraction increased (82±5bpm versus 124±3bpm/46±9% versus 65±7%; both p<0.05). A decrease in left ventricular end-diastolic volume (72±14mL versus 55±8mL; p<0.05) and end-systolic volume (40±15mL versus 19±6mL; p<0.05) but no change in stroke volume were observed. Trans-mitral diastolic inflow velocity increased under dobutamine and the trajectory of inflowing blood was directed towards the anterior septum with increased inflow angle (26±5°) when compared with controls (15±2°). In 5/6 animals undergoing stress diastolic vortices developed later, and in 3/6 animals vortices collapsed earlier with significantly smaller cross-sectional area during diastole. The vorticity index was not affected. Under the stress condition direct flow (% ejection within the next heart beat) increased from 43±6% to 53±8%. 4D MRI blood flow acquisition and analysis are feasible in pig hearts under dobutamine-induced stress. Flow patterns characterized by high blood velocity and antero-septally oriented diastolic inflow as well as decreased ventricular volumes are unfavourable conditions for diastolic vortex development under pharmacological stress, and cardiac output is increased by a rise in heart rate and directly ejected left ventricular blood volume.

Abstract 19155: Quantification of Progressive Pulmonary Valvular Insufficiency Using 4-Dimensional Flow Magnetic Resonance Imaging in an Ovine Model

Introduction: Chronic postoperative pulmonary insufficiency (PPI) is the major cause of long-term morbidity and mortality in patients (pts) with tetralogy of Fallot (TOF). Pulmonary valve replacement (PVR) can mitigate the risk, but optimal timing for PVR remains controversial. Time-resolved 3D phase-contrast MRI (4DF) provides insight into complex intracardiac flow patterns. 4DF may help inform management decisions regarding timing of PVR. We describe the first quantitative serial 4DF analysis in an ovine model of PPI. Methods: A baseline cardiac MRI (CMRI) was performed on four Dorsett sheep (36-39kg) on a 3-Tesla Siemens scanner. Following baseline MRI, animals underwent pulmonary valvectomy and transannular patch (TAP) placement yielding PPI. Follow-up CMRI were obtained at 5mo and 7mo post-valvectomy (PoVa). Pathlines were emitted from a circular region of interest (ROI) representing the pulmonary valve annulus. Velocities, flow rate, and stresses were obtained throughout a complete cardiac cycle and compared across time. Results: Systolic max velocity, average velocity, and flow rate normal to the ROI plane decreased over time. Diastolic velocities increased at 5mo before decreasing at 7mo PoVa. Regurgitant flow was observed in diastole PoVa , and regurgitant flow rate increased with time. The max and average component of shear stress (viscosity = 3 cP) along the pulmonary artery wall decreased over time in systole. In diastole, shear stress increased at 5mo and decreased at 7mo. Parameters plotted in Figure 1. Conclusion: 4DF provides a new method for visualization and quantification of alterations in blood flow patterns in the right side of the heart in an ovine model of PPI. Alterations in above parameters may indicate myocardial and pulmonary vascular deterioration precedent to morphological changes. Characterization of altered flow patterns in human pts with TOF may help to ultimately inform decisions regarding timing of PVR.

Abstract 13435: Deranged Intra-Cardiac Blood Flow Components and Kinetic Energy in Dilated Cardiomyopathy Are an Additional Marker of Disease Severity and Correlate With Established Markers of Prognosis

Introduction: Heart failure (HF) due to dilated cardiomyopathy (DCM) is a complex syndrome in which numerous cellular, mechanical and flow processes/interactions become deranged. Insights into derangement of left ventricular intra-cardiac flow patterns and kinetic energy (KE) are now afforded by the use of 4D flow CMR. Previous studies have found derangements of intra-ventricular flow components and KE within DCM patients compared to healthy volunteers. Hypothesis: We hypothesised that increasing derangement in 4D flow measures would relate to: 1) decreased mechanical cardiac function, as assessed by myocardial strain, 2) increased levels of biochemical remodelling markers and 3) worsening patient symptoms and functional capacity. Methods: 26 idiopathic DCM patients (69% male, mean age 55±2 yr, LVEF 35±2%) and 10 controls (70% male, mean age 57±4yr, LVEF 68±1.2%) were assessed with 3T CMR. Results: The LV volume was divided into 4 functional components; direct flow (DF), delayed ejection flow (DEF), retained inflow (RI) and residual volume (RV). Compared to controls DCM’s had significantly decreased DF (11±1% vs 38±2%) and increased RV (51±2% vs 31±1%) (fig a). The KE at end diastole differed significantly for all flow components between groups (fig b). Circumferential strain was significantly impaired in DCM’s vs controls (-9.9±0.8% vs -19.7±0.5%, p&lt;0.0001). DF KE correlated positively to the 6 minute walk test (6MWT) and strain, and negatively to the Minnesota HF questionnaire and BNP (fig c). Conclusions: DCM patients demonstrated less efficient blood flow patterns and deranged KE profiles. The greater the derangement of flow parameters from normal, the worse the myocardial strain, BNP, 6MWT and patient symptoms. This study suggests that flow parameter derangements are novel biomarkers of disease severity in DCM, correlating with established markers of prognosis such as BNP and 6MWT and may become useful in monitoring novel therapies and predicting prognosis.

Intracardiac flow dynamics regulate atrioventricular valve morphogenesis.

Valvular heart disease is responsible for considerable morbidity and mortality. Cardiac valves develop as the heart contracts, and they function throughout the lifetime of the organism to prevent retrograde blood flow. Their precise morphogenesis is crucial for cardiac function. Zebrafish is an ideal model to investigate cardiac valve development as it allows these studies to be carried out in vivo through non-invasive imaging. Accumulating evidence suggests a role for contractility and intracardiac flow dynamics in cardiac valve development. However, these two factors have proved difficult to uncouple, especially since altering myocardial function affects the intracardiac flow pattern. Here, we describe novel zebrafish models of developmental valve defects. We identified two mutant alleles of myosin heavy chain 6 that can be raised to adulthood despite having only one functional chamber-the ventricle. The adult mutant ventricle undergoes remodelling, and the atrioventricular (AV) valves fail to form four cuspids. In parallel, we characterized a novel mutant allele of southpaw, a nodal-related gene involved in the establishment of left-right asymmetry, which exhibits randomized heart and endoderm positioning. We first observed that in southpaw mutants the relative position of the two cardiac chambers is altered, affecting the geometry of the heart, while myocardial function appears unaffected. Mutant hearts that loop properly or exhibit situs inversus develop normally, whereas midline, unlooped hearts exhibit defects in their transvalvular flow pattern during AV valve development as well as defects in valve morphogenesis. Our data indicate that intracardiac flow dynamics regulate valve morphogenesis independently of myocardial contractility.

Left atrial ligation alters intracardiac flow patterns and the biomechanical landscape in the chick embryo.

Hypoplastic left heart syndrome (HLHS) is a major human congenital heart defect that results in single ventricle physiology and high mortality. Clinical data indicate that intracardiac blood flow patterns during cardiac morphogenesis are a significant etiology. We used the left atrial ligation (LAL) model in the chick embryo to test the hypothesis that LAL immediately alters intracardiac flow streams and the biomechanical environment, preceding morphologic and structural defects observed in HLHS. Using fluorescent dye injections, we found that intracardiac flow patterns from the right common cardinal vein, right vitelline vein, and left vitelline vein were altered immediately following LAL. Furthermore, we quantified a significant ventral shift of the right common cardinal and right vitelline vein flow streams. We developed an in silico model of LAL, which revealed that wall shear stress was reduced at the left atrioventricular canal and left side of the common ventricle. Our results demonstrate that intracardiac flow patterns change immediately following LAL, supporting the role of hemodynamics in the progression of HLHS. Sites of reduced WSS revealed by computational modeling are commonly affected in HLHS, suggesting that changes in the biomechanical environment may lead to abnormal growth and remodeling of left heart structures.

Objective method for assessment of reliability of particle tracing visualization in 4D FLOW MRI

Background Three-dimensional (3D) velocity-encoded MRI (4DFLOW) of the heart may be used for the assessment of systolic and diastolic function. Particle tracing is frequently used as a technique for visualization of 3D intra-cardiac flow patterns. As the obtained velocity data may suffer from imperfections in the acquisition technique, it is important to have a means for image quality control. Consistency of the 4D FLOW data with other CMR measurements is a means for internal data consistency and may serve as surrogate validation. The purpose of the study was to apply particle tracing in 4DFLOW MRI of the heart and to compare aortic flow measurements derived from particle tracing with an alternative validated MR analysis technique. Methods

Time‐resolved spin‐labeled balanced steady‐state free precession cineangiography for visualizing intracardiac shunt: technical considerations and clinical feasibility

A time-resolved spin-labeled cineangiographic MRI technique for visualizing blood flow in the heart and defects of the atrial septum is described. The method utilizes a spin labeling preparation and a time-resolved balanced steady-state free precession imaging readout that enhances blood in the left atrium or right atrium and suppresses background signal through inversion recovery. Four volunteer studies and 10 patient studies were performed at 1.5 T to characterize the signal properties and to test the clinical feasibility of depicting atrial septal defects. In volunteers, the spin-labeled cineangiographic method depicted intracardiac blood flow patterns and demarcated the intact atrial septum. Peak target to adjacent atrial chamber contrast-to-noise ratios of 84 and 94 were obtained 758 and 689 ms postlabeling; 50% of peak contrast-to-noise ratio was maintained for 803 and 599 ms in the left atrium and right atrium, respectively. In all patients with an atrial septal defect, the spin-labeled cineangiographic method demonstrated left-to-right flow and maintained good morphological assessment of surrounding cardiac structures. Right-to-left flow was seen in three patients. In conclusion, the spin-labeled cineangiographic method displayed favorable signal properties in volunteers and demonstrated shunting in patients with atrial septal defects. The technique is expected to be a viable alternative to the few techniques available for visualizing blood flow in the heart.

Disruption of intracardiac flow patterns in the newborn infant.

Consistent patterns of rotational intracardiac flow have been demonstrated in the healthy adult human heart. Intracardiac rotational flow patterns are hypothesized to assist in the maintenance of kinetic energy of inflowing blood, augmenting cardiac function. Newborn cardiac function is known to be suboptimal secondary to decreased receptor number and sympathetic innervation, increased afterload, and increased reliance on atrial contraction to support ventricular filling. Patterns of intracardiac flow in the newborn have not previously been examined. Whereas 5 of the 13 infants studied showed significant evidence of rotational flow within the right atrium, 8 infants showed little or no rotational flow. Presence or absence of rotational flow was not related to gestational age, birth weight, postnatal age, atrial size, or image quality. Despite absence of intra-atrial rotational flow, atrioventricular valve flow into the left and right ventricles later in the cardiac cycle could be seen, suggesting that visualization techniques were adequate. While further study is required to assess its exact consequences on cardiac mechanics and energetics, disruption to intracardiac flow patterns could be another contributor to the multifactorial sequence that produces newborn circulatory failure. We studied 13 newborn infants, using three-dimensional (3D) cardiac magnetic resonance phase-contrast imaging (spatial resolution 0.84 mm, temporal resolution 22.6 ms) performed without sedation/anesthesia.