Optimal vortex formation as an index of cardiac health

Left Ventricular Vortex Characteristics in Fetuses With Coarctation of the Aorta by Blood Speckle-Tracking Echocardiography

OBJECTIVES

The aims of this study were to assess the vortex characteristics of left ventricle (LV) in fetuses with coarctation of the aorta (CoA) using high-frame rate ultrasound with blood speckle-tracking (BST) and explore its relationships with cardiac function and morphology parameters.

METHODS

Thirty fetuses with CoA and 30 gestational-age matched normal fetuses were included in this cross-sectional study. The area, length, width, and position of the vortex in the LV were recorded and quantitatively analyzed by BST echocardiography. The associations of vortex properties with ventricular function and morphology were also determined.

RESULTS

Based on BST imaging, the LV vortex can be observed in 93% of the fetuses. The fetuses with CoA exhibited significantly larger and wider vortex than the controls (P < .05). Linear regression analysis indicated that vortex area was positively related to sphericity index of LV as well as isovolumic relaxation time (r = .52, P = .003 and r = .42, P = .021). There was a negative correlation between vortex area and mitral valve size (r = -.443, P = .014). No significant association was found between vortex area and myocardial performance index and aortic isthmus size.

CONCLUSIONS

It is feasible to quantitatively evaluate the left ventricular vortex in fetuses by BST. The fetuses with CoA exhibited greater vortex area and width, and the altered vortex property is associated with geometry of LV. This will facilitate our comprehension of the unique flow patterns and early cardiac remodeling in fetuses with CoA.

Vortex formation time in female athletes

Regular, vigorous physical activity can have a significant impact on cardiac function, leading to cardiac morphological alterations that may be challenging to distinguish from pathological changes. Therefore, new screening methods are needed to accurately differentiate between adaptive changes and pathological alterations in athletes. Vortex formation time (VFT) is an emerging method that shows potential in this regard, as it involves the formation of a rotating vortex ring in the left ventricle during the early filling phase of diastole. In this study, we investigated the difference in VFT between two groups of women: professional handball players and healthy middle-aged female athletes, along with their corresponding control groups. By using echocardiography-Doppler analysis of the heart, VFT was calculated based on the left ventricular ejection fraction, the ratio between the end-diastolic volume and the diameter of the mitral annulus, and the ratio of the atrial contraction volume to the total inflow via the mitral valve. The study reveals a significant increase in VFT in both professional handball players and middle-aged female athletes compared to their respective control groups. Moreover, statistically significant differences between handball players and middle-aged female athletes were observed, indicating that the level of physical activity may affect the VFT. These results suggest that VFT could be a promising screening tool for identifying cardiac adaptations due to long-term vigorous training, potentially enabling more accurate diagnoses of cardiac morphological alterations in athletes.

An Anatomically Shaped Mitral Valve for Hemodynamic Testing

In vitro modeling of the left heart relies on accurately replicating the physiological conditions of the native heart. The targeted physiological conditions include the complex fluid dynamics coming along with the opening and closing of the aortic and mitral valves. As the mitral valve possess a highly sophisticated apparatus, thence, accurately modeling it remained a missing piece in the perfect heart duplicator puzzle. In this study, we explore using a hydrogel-based mitral valve that offers a full representation of the mitral valve apparatus. The valve is tested using a custom-made mock circulatory loop to replicate the left heart. The flow analysis includes performing particle image velocimetry measurements in both left atrium and ventricle. The results showed the ability of the new mitral valve to replicate the real interventricular and atrial flow patterns during the whole cardiac cycle. Moreover, the investigated valve has a ventricular vortex formation time of 5.2, while the peak e- and a-wave ventricular velocities was 0.9 m/s and 0.4 m/s respectively.

Enhancement of intra-cardiac flow-field data using adaptive Kernel filtering

A method of determining the optimal kernel size for filtering noise in vortex dominated flow-fields, as found in the cardiac chambers is presented in this paper. Using synthetic flow fields generated using harmonic functions and perturbed using Gaussian noises of different amplitudes and spreads, the effect of kernel size on noise removal using the Median filter is tested systematically. It is shown that there exists an optimal kernel size at which the Median filter works best. The size of the optimal kernel is shown to be related to the vortex size. When applied to MRI generated cardiac flow-fields, the approach is seen to reveal underlying vortex patterns thereby aiding as an effective tool in the diagnosis and prognosis of cardiac diseases based on vortices as clinical biomarkers. The behavior of the restored cardiac flow fields which are filtered with the optimal kernel size and also with some values preceding and succeeding it are similar to that observed in studies with synthetic flow fields. This confirms that the optimal size of the kernel is related to the cardiac vortex size as is observed in the case of synthetic flow fields.

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

PURPOSE

Intraventricular 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.

METHODS

In 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.

RESULTS

As 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.

CONCLUSIONS

This 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.

Left ventricular vortex formation time: emerging clinical applications and limitations

Vortex formation during left ventricular diastolic filling may provide clinically useful insights into cardiac health. In recent years, there has been growing interest in the measurement of vortex formation time (VFT), especially because it is derived noninvasively. There are important applications of VFT in valvular heart disease, athletic physiology, heart failure and hypertrophic cardiomyopathy. The formation of the vortex as fluid propagates into the left ventricle from the left atrium is important for efficient fluid transport. Quantifying VFT may thus help in evaluating and understanding disease and pathophysiological processes.

Vector flow mapping analysis of left ventricular vortex performance in type 2 diabetic patients with early chronic kidney disease

BACKGROUND

Diabetes is the leading cause of chronic kidney disease (CKD) and contributes to an elevated incidence of diastolic dysfunction in the early stages of CKD. Intracardiac vortex is a novel hemodynamic index for perceiving cardiac status. Here, we visualized left ventricular (LV) vortex characteristics using vector flow mapping (VFM) in type 2 diabetic patients with early CKD.

METHODS

This cross-sectional study included 67 controls and 89 type 2 diabetic patients with stages 2-3a CKD. All subjects underwent transthoracic echocardiographic examination. LV anterior vortex during early diastole (E-vortex), atrial contraction (A-vortex) and systole (S-vortex) were assessed using VFM in the apical long-axis view. Its relation to glycemia or LV filling echocardiographic parameters were further analyzed using correlation analysis.

RESULTS

Type 2 diabetic patients with early CKD had a small area (439.94 ± 132.37 mm2 vs. 381.66 ± 136.85 mm2, P = 0.008) and weak circulation (0.0226 ± 0.0079 m2/s vs. 0.0195 ± 0.0070 m2/s, P = 0.013) of E-vortex, but a large area (281.52 ± 137.27 mm2 vs. 514.83 ± 160.33 mm2, P ˂ 0.001) and intense circulation (0.0149 ± 0.0069 m2/s vs. 0.0250 ± 0.0067 m2/s, P < 0.001) of A-vortex compared to controls. CKD patients with poorly controlled hyperglycemia had stronger A-vortex (area: 479.06 ± 146.78 mm2 vs. 559.96 ± 159.27 mm2, P = 0.015; circulation: 0.0221 ± 0.0058 m2/s vs. 0.0275 ± 0.0064 m2/s, P < 0.001) and S-vortex (area: 524.21 ± 165.52 mm2 vs. 607.87 ± 185.33 mm2, P = 0.029; circulation: 0.0174 ± 0.0072 m2/s vs. 0.0213 ± 0.0074 m2/s, P = 0.015), and a longer relative duration of S-vortex (0.7436 ± 0.0772 vs. 0.7845 ± 0.0752, P = 0.013) than those who had well-controlled hyperglycemia. Glycemia, and E/A (a LV filling parameter) were respectively found to had close correlation to the features of A-vortex and S-vortex (all P < 0.05).

CONCLUSIONS

Abnormal LV vortices were detected in type 2 diabetic patients with early CKD using VFM, especially in those who neglected hyperglycemic control. LV vortex might be a promising parameter to slow or halt the hyperglycemia-induced diastolic dysfunction in early CKD.

Vortex Formation Time is a Novel Measure for Early Detection of Diastolic Abnormalities in Adolescents with Hypertension

Pediatric hypertension (HTN) has demonstrated an upward trend in recent years. Adolescent HTN has been linked to adult HTN, cardiovascular disease, and other health conditions. Thus, it is essential that HTN and its associated cardiac abnormalities be diagnosed and treated early to minimize lifelong adverse effects. In this study, we evaluated whether vortex formation time (VFT), a validated echocardiogram measure of left ventricular diastolic dysfunction, correlated with ambulatory blood pressure monitoring (ABPM) and HTN in adolescents. Echocardiogram data including systolic and diastolic function indices and ABPM data from 2015 to 2022 in adolescents age 13-21 years were analyzed retrospectively. We found that VFT was significantly lower in adolescents with HTN compared to those without HTN (3.69 ± 1.39 vs. 4.50 ± 1.73, p = 0.02). Standard echocardiographic indices of systolic and diastolic function were similar between the two groups, except indexed left atrial volume. Higher overall systolic blood pressure (SBP) (β = - 0.01, CI - 0.02, - 2.2 × 10^-3, p = 0.02), mean wake SBP (β = - 0.01, CI - 0.02, - 9.4 × 10^-4, p = 0.03), and mean sleep SBP (β = - 0.01, CI - 0.02, - 1.2 × 10^-3, p = 0.03) were significantly associated with lower VFT. This study demonstrates that VFT correlates to ABPM data and can be used a novel diagnostic measure in adolescents with HTN.

Four-dimensional flow cardiac magnetic resonance assessment of left ventricular diastolic function

Left ventricular diastolic dysfunction is a major cause of heart failure and carries a poor prognosis. Assessment of left ventricular diastolic function however remains challenging for both echocardiography and conventional phase contrast cardiac magnetic resonance. Amongst other limitations, both are restricted to measuring velocity in a single direction or plane, thereby compromising their ability to capture complex diastolic hemodynamics in health and disease. Time-resolved three-dimensional phase contrast cardiac magnetic resonance imaging with three-directional velocity encoding known as '4D flow CMR' is an emerging technology which allows retrospective measurement of velocity and by extension flow at any point in the acquired 3D data volume. With 4D flow CMR, complex aspects of blood flow and ventricular function can be studied throughout the cardiac cycle. 4D flow CMR can facilitate the visualization of functional blood flow components and flow vortices as well as the quantification of novel hemodynamic and functional parameters such as kinetic energy, relative pressure, energy loss and vorticity. In this review, we examine key concepts and novel markers of diastolic function obtained by flow pattern analysis using 4D flow CMR. We consolidate the existing evidence base to highlight the strengths and limitations of 4D flow CMR techniques in the surveillance and diagnosis of left ventricular diastolic dysfunction.

Fluid Mechanics of Fetal Left Ventricle During Aortic Stenosis with Evolving Hypoplastic Left Heart Syndrome

In cases of fetal aortic stenosis and evolving Hypoplastic Left Heart Syndrome (feHLHS), aortic stenosis is associated with specific abnormalities such as retrograde or bidirectional systolic transverse arch flow. Many cases progressed to hypoplastic left heart syndrome (HLHS) malformation at birth, but fetal aortic valvuloplasty can prevent the progression in many cases. Since both disease and intervention involve drastic changes to the biomechanical environment, in-vivo biomechanics likely play a role in inducing and preventing disease progression. However, the fluid mechanics of feHLHS is not well-characterized. Here, we conduct patient-specific echocardiography-based flow simulations of normal and feHLHS left ventricles (LV), to understand the essential fluid dynamics distinction between the two cohorts. We found high variability across feHLHS cases, but also the following unifying features. Firstly, feHLHS diastole mitral inflow was in the form of a narrowed and fast jet that impinged onto the apical region, rather than a wide and gentle inflow in normal LVs. This was likely due to a malformed mitral valve with impaired opening dynamics. This altered inflow caused elevated vorticity dynamics and wall shear stresses (WSS) and reduced oscillatory shear index at the apical zone rather than mid-ventricle. Secondly, feHLHS LV also featured elevated systolic and diastolic energy losses, intraventricular pressure gradients, and vortex formation numbers, suggesting energy inefficiency of flow and additional burden on the LV. Thirdly, feHLHS LV had poor blood turnover, suggesting a hypoxic environment, which could be associated with endocardial fibroelastosis that is often observed in these patients.

Vortex formation time as an index of left ventricular filling efficiency: comparison between children volunteers and patients with tetralogy of Fallot

BACKGROUND

Vortex formation time (VFT) had been considered a useful marker for assessing diastolic performance. the VFT assessment of diastolic function using four-dimensional (4D) flow cardiovascular magnetic resonance (CMR) has not been used in repair of tetralogy of Fallot (rTOF) patient. The aims of this study were as follows: (I) establish reference ranges for VFT measurements in healthy children and adolescents using 4D flow CMR imaging; and (II) analyze VFT parameters to assess diastole dysfunction in rTOF patients group.

METHODS

We acquired the CMR data was of 62 healthy participants (aged 6-18 years; male: 40, female: 22) and 20 patients with rTOF (aged 10-13 years; male: 15, female: 5) using 4D flow and cine sequence in routine chamber view. The VFT was calculated based on comparison of different algorithms from cine measurements (VFT_volume) and 4D flow measurements (VFT_blood). Then, VFT measurements were compared to subject peak filling rate (PFR), age, and cardiac mass using simple linear regression and multiple regression analyses. Data were also categorized according to age for VFT and cardiac functional assessment comparisons between 3 age groups (Group 1: 6-9 years; Group 2: 10-13 years; Group 3: 14-18 years). The correlation of VFT and cardiac function parameters were analyzed in the rTOF group.

RESULTS

Normal mean value of VFT_volume and VFT_blood were 4.25±0.92 and 3.77±1.11 in healthy children participants. The VFT_volume was correlated with VFT_blood (r=0.61, P<0.001). There was a moderately significant correlation between VFT_volume and PFR (r=0.46, P<0.001) and between VFT_blood and PFR (r=0.47, P<0.001), age (r=0.41, P=0.002) and left ventricular (LV) mass (r=0.48, P<0.001). Multiple regression analyses demonstrated that VFT_volume was independently associated with PFR (T=2.239; P<0.05) and VFT_blood (T=4.361; P<0.001). There was a significant difference in VFT_volume between healthy controls and rTOF patients (5.44±1.93 vs. 4.27±0.88, P=0.018).

CONCLUSIONS

The VFT measurements showed that the LV that had appropriate space to form the optimal vortex ring in normal children and adolescents aged 6-18 years old. The VFT_volume could potentially be helpful in improving our understanding of LV diastolic dysfunction in rTOF patients.

Full-volume three-component intraventricular vector flow mapping by triplane color Doppler

Objective. Intraventricular vector flow mapping (iVFM) is a velocimetric technique for retrieving two-dimensional velocity vector fields of blood flow in the left ventricular cavity. This method is based on conventional color Doppler imaging, which makes iVFM compatible with the clinical setting. We have generalized the iVFM for a three-dimensional reconstruction (3D-iVFM). Approach. 3D-iVFM is able to recover three-component velocity vector fields in a full intraventricular volume by using a clinical echocardiographic triplane mode. The 3D-iVFM problem was written in the spherical (radial, polar, azimuthal) coordinate system associated to the six half-planes produced by the triplane mode. As with the 2D version, the method is based on the mass conservation, and free-slip boundary conditions on the endocardial wall. These mechanical constraints were imposed in a least-squares minimization problem that was solved through the method of Lagrange multipliers. We validated 3D-iVFM in silico in a patient-specific CFD (computational fluid dynamics) model of cardiac flow and tested its clinical feasibility in vivo in patients and in one volunteer. Main results. The radial and polar components of the velocity were recovered satisfactorily in the CFD setup (correlation coefficients, r  = 0.99 and 0.78). The azimuthal components were estimated with larger errors ( r  = 0.57) as only six samples were available in this direction. In both in silico and in vivo investigations, the dynamics of the intraventricular vortex that forms during diastole was deciphered by 3D-iVFM. In particular, the CFD results showed that the mean vorticity can be estimated accurately by 3D-iVFM. Significance. Our results tend to indicate that 3D-iVFM could provide full-volume echocardiographic information on left intraventricular hemodynamics from the clinical modality of triplane color Doppler.

Automated vortex identification based on Lagrangian averaged vorticity deviation in analysis of blood flow in the atrium from phase contrast MRI

OBJECTIVE

To present and validate a method for automated identification of the Lagrangian vortices and Eulerian vortices for analyzing flow within the right atrium (RA), from phase contrast magnetic resonance imaging (PC-MRI) data.

METHODOLOGY

Our proposed algorithm characterizes the trajectory integral associated with vorticity deviation and the spatial mean of vortex rings, for the Lagrangian averaged vorticity deviation (LAVD) based identification and tracking of vortex rings within the heart chamber. For this purpose, the optical flow concept was adopted to interpolate the time frames between larger discrete frames, to minimize the error caused by constructing a continuous velocity field for the integral process of LAVD. Then the Hough transform was used to automatically extract the vortex regions of interest. The computed flow data within the RA of the participants' hearts was then used to validate the performance of our proposed method.

RESULTS

In the paper, illustrations are provided for derived evolution of Euler vortices and Lagrangian vortices of a healthy subject. The visualization results have shown that our proposed method can accurately identify the Euler vortices and Lagrangian vortices, in the context of measuring the vorticity and vortex volume of the vortices within the RA chamber. Then the employment of Hough transform-based automated vortex extraction has improved the robustness and scalability of the LAVD in identifying cardiac vortices. The analytical results have demonstrated that the introduction of the Horn-Schunck optical flow can more accurately synthesize the intermediate PC-MRI to construct a continuous velocity field, compared with other interpolation methods.

CONCLUSION

A novel analytical framework has been developed to accurately identify the flow vortices in the RA chamber based on Horn-Schunck optical flow and Hough transform. From the obtained analytical study results, the development and changes of dominant vortices within this cardiac chamber during the cardiac cycle can be acquired. This can provide to cardiologists a deeper understanding of the hemodynamics within the heart chambers.

Intraventricular Flow Simulations in Singular Right Ventricles Reveal Deteriorated Washout and Low Vortex Formation

Purpose

Patients with a functionally univentricular heart represent one of the most common severe cardiac lesions with a prevalence of 3 per 10,000 live births. Hemodynamics of the singular ventricle is a major research topic in cardiology and there exists a relationship between fluid dynamical features and cardiac behavior in health and disease. The aim of the present work was to compare intraventricular flow in single right ventricle (SRV) patients and subjects with healthy left hearts (LV) through patient-specific CFD simulations.

Methods

Three-dimensional real-time echocardiographic images were obtained for five SRV patients and two healthy subjects and CFD simulations with a moving mesh methodology were performed. Intraventricular vortex formation and vortex formation time (VFT) as well as the turbulent kinetic energy (TKE) and ventricular washout were evaluated.

Results

The results show significantly lower values for the VFT and the TKE in SRV patients compared with healthy LV subjects. Furthermore, vortex formation does not progress to the apex in SRV patients. These findings were confirmed by a significantly lower washout in SRV patients.

Conclusions

The study pinpoints the intriguing role of intraventricular flows to characterize performance of SRVs that goes beyond standard clinical metrics such as ejection fraction.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13239-021-00598-9.

Ultrasonic biomechanics method for vortex and wall motion of left ventricle: a phantom and in vivo study

Background

The non-invasive quantitative evaluation of left ventricle (LV) function plays a critical role in clinical cardiology. This study proposes a novel ultrasonic biomechanics method by integrating both LV vortex and wall motion to fully assess and understand the LV structure and function. The purpose of this study was to validate the ultrasonic biomechanics method as a quantifiable approach to evaluate LV function.

Methods

Firstly, B-mode ultrasound images were acquired and processed, which were utilized to implement parameters for quantifying the LV vortex and wall motion respectively. Next, the parameters were compared in polyvinyl alcohol cryogen (PVA) phantoms with different degree of stiffness corresponding to different freezing and thawing cycles in vitro. Finally, the parameters were computed in vivo during one cardiac cycle to assess the LV function in normal and abnormal subjects in vivo.

Results

In vitro study, the velocity field of PVA phantom differed with stiffness (varied elasticity modulus). The peak of strain for wall motion decreases with the increase of elasticity modulus, and periodically changed values. Statistical analysis for parameters of vortex dynamics (energy dissipation index, DI; kinetic energy fluctuations, KEF; relative strength, RS; and vorticity, W) based on different elasticity (E) of phantom depicted the good viability of this algorithm. In vivo study, the results confirmed that subjects with LV dysfunction had lower vorticity and strain (S) compared to the normal group.

Conclusion

Ultrasonic biomechanics method can obtain the vortex and wall motion of left ventricle. The method may have potential clinical value in evaluation of LV dysfunction.

Alterations in Intracardiac Flow Patterns Affect Mitral Leaflets Dynamics in a Model of Ischemic Mitral Regurgitation

PURPOSE

This study was to evaluate the effects of ischemic mitral regurgitation (IMR) on vortex formation and leaflet dynamics using an established porcine infarct model of IMR.

METHODS

Using direct coronary ligation, five animals were subjected to a posterolateral myocardial infarction (MI) followed by an MRI at 12-weeks post MI. MR imaging consisted of 4D time-resolved left ventricular (LV) flow, full coverage 2D LV cine, and high resolution 2D cine of mitral valve dynamics. Five additional naïve animals underwent identical imaging protocols to serve as controls. Image analysis was performed to obtain mitral transvalvular flows as well as LV volumes throughout the cardiac cycle. In addition, anterior to posterior mid-leaflet tip distances were measured throughout the cardiac cycle for determination of temporal leaflet dynamics.

RESULTS

It was found IMR caused asymmetric vortex ring formation with the anterior vortex having a lower vorticity relative to its posterior counterpart. In contrast, normal ventricles create symmetric and tightly curled vortices in the basal chamber just underneath the mitral leaflets which conserve kinetic energy and aid in effective ejection. IMR animals were also evaluated for leaflet separation and were found to have a greater leaflet opening and achieved peak vorticity and peak leaflet opening later than control animals.

CONCLUSION

In conclusion, this study shows the effects that altered vortex formation, due to IMR, can have on ventricular filling and leaflet dynamics. These findings have important implications for understanding blood flow through the dilated heart and how ring annuloplasty and volume reduction interventions may influence mitral valve dynamics.

Lagrangian-averaged vorticity deviation of spiraling blood flow in the heart during isovolumic contraction and ejection phases

The formation of vortex rings in the left ventricular (LV) blood flow is a mechanism for optimized blood transport from the mitral valve inlet to aortic valve outlet, and the vorticity is an important measure of a well-functioning LV. However, due to lack of quantitative methods, the process of defining the boundary of a vortex in the LV and identifying the dominant vortex components has not been studied previously. The Lagrangian-averaged vorticity deviation (LAVD) can enable us to compute the trajectory integral of the normed difference of the vorticity from its spatial mean. Therefore, in this work, we have employed LAVD to identify the Lagrangian vortices and Eulerian vortices for measuring the vortex volume and vorticity in the LV blood flow. We found that during the LV ejection period, the positive (counterclockwise) and negative (clockwise) vorticity of patients are consistently stronger than those of the healthy groups, and the counterclockwise vortex volume of healthy groups (0.84+0.26 ml) is greater than that of patients (0.55+0.28 ml) during the pre-ejection period. Then, during the middle ejection phase, the counterclockwise vortex ring volume of patients (1.89+0.36 ml) exceeds that of healthy groups (1.38+0.43 ml). Finally, during the end-ejection period, the counterclockwise vortex ring volume of healthy subjects (0.61+0.17 ml) is the same as that of patients (0.60+0.19 ml). The results presented in this paper can provide new insights into the blood flow patterns within the LV. It can accurately indicate the role of vortices and vorticity values in intra-LV flow, and portray how cardiomyopathy (and its distorted contractile mechanism) can affect intra-LV flow patterns and mitigate adequate LV outflow.

Personalized intervention cardiology with transcatheter aortic valve replacement made possible with a non-invasive monitoring and diagnostic framework

One of the most common acute and chronic cardiovascular disease conditions is aortic stenosis, a disease in which the aortic valve is damaged and can no longer function properly. Moreover, aortic stenosis commonly exists in combination with other conditions causing so many patients suffer from the most general and fundamentally challenging condition: complex valvular, ventricular and vascular disease (C3VD). Transcatheter aortic valve replacement (TAVR) is a new less invasive intervention and is a growing alternative for patients with aortic stenosis. Although blood flow quantification is critical for accurate and early diagnosis of C3VD in both pre and post-TAVR, proper diagnostic methods are still lacking because the fluid-dynamics methods that can be used as engines of new diagnostic tools are not well developed yet. Despite remarkable advances in medical imaging, imaging on its own is not enough to quantify the blood flow effectively. Moreover, understanding of C3VD in both pre and post-TAVR and its progression has been hindered by the absence of a proper non-invasive tool for the assessment of the cardiovascular function. To enable the development of new non-invasive diagnostic methods, we developed an innovative image-based patient-specific computational fluid dynamics framework for patients with C3VD who undergo TAVR to quantify metrics of: (1) global circulatory function; (2) global cardiac function as well as (3) local cardiac fluid dynamics. This framework is based on an innovative non-invasive Doppler-based patient-specific lumped-parameter algorithm and a 3-D strongly-coupled fluid-solid interaction. We validated the framework against clinical cardiac catheterization and Doppler echocardiographic measurements and demonstrated its diagnostic utility by providing novel analyses and interpretations of clinical data in eleven C3VD patients in pre and post-TAVR status. Our findings position this framework as a promising new non-invasive diagnostic tool that can provide blood flow metrics while posing no risk to the patient. The diagnostic information, that the framework can provide, is vitally needed to improve clinical outcomes, to assess patient risk and to plan treatment.

Four-dimensional flow cardiovascular magnetic resonance in tetralogy of Fallot: a systematic review

BACKGROUND

Patients with repaired Tetralogy of Fallot (rTOF) often develop cardiovascular dysfunction and require regular imaging to evaluate deterioration and time interventions such as pulmonary valve replacement. Four-dimensional flow cardiovascular magnetic resonance (4D flow CMR) enables detailed assessment of flow characteristics in all chambers and great vessels. We performed a systematic review of intra-cardiac 4D flow applications in rTOF patients, to examine clinical utility and highlight optimal methods for evaluating rTOF patients.

METHODS

A comprehensive literature search was undertaken in March 2020 on Google Scholar and Scopus. A modified version of the Critical Appraisal Skills Programme (CASP) tool was used to assess and score the applicability of each study. Important clinical outcomes were assessed including similarities and differences.

RESULTS

Of the 635 articles identified, 26 studies met eligibility for systematic review. None of these were below 59% applicability on the modified CASP score. Studies could be broadly classified into four groups: (i) pilot studies, (ii) development of new acquisition methods, (iii) validation and (vi) identification of novel flow features. Quantitative comparison with other modalities included 2D phase contrast CMR (13 studies) and echocardiography (4 studies). The 4D flow study applications included stroke volume (18/26;69%), regurgitant fraction (16/26;62%), relative branch pulmonary artery flow(4/26;15%), systolic peak velocity (9/26;35%), systemic/pulmonary total flow ratio (6/26;23%), end diastolic and end systolic volume (5/26;19%), kinetic energy (5/26;19%) and vorticity (2/26;8%).

CONCLUSIONS

4D flow CMR shows potential in rTOF assessment, particularly in retrospective valve tracking for flow evaluation, velocity profiling, intra-cardiac kinetic energy quantification, and vortex visualization. Protocols should be targeted to pathology. Prospective, randomized, multi-centered studies are required to validate these new characteristics and establish their clinical use.

Left Ventricular Deformation and Vortex Analysis in Heart Failure: From Ultrasound Technique to Current Clinical Application

Heart failure (HF) is a leading cause of cardiovascular morbidity and mortality. However, its symptoms and signs are not specific or can be absent. In this context, transthoracic echocardiography plays a key role in diagnosing the various forms of HF, guiding therapeutic decision making and monitoring response to therapy. Over the last few decades, new ultrasound modalities have been introduced in the field of echocardiography, aiming at better understanding the morpho-functional abnormalities occurring in cardiovascular diseases. However, they are still struggling to enter daily and routine use. In our review article, we turn the spotlight on some of the newest ultrasound technologies; in particular, analysis of myocardial deformation by speckle tracking echocardiography, and intracardiac flow dynamics by color Doppler flow mapping, highlighting their promising applications to HF diagnosis and management. We also focus on the importance of these imaging modalities in the selection of responses to cardiac resynchronization therapy.

Wall Shear Stress Topological Skeleton Analysis in Cardiovascular Flows: Methods and Applications

A marked interest has recently emerged regarding the analysis of the wall shear stress (WSS) vector field topological skeleton in cardiovascular flows. Based on dynamical system theory, the WSS topological skeleton is composed of fixed points, i.e., focal points where WSS locally vanishes, and unstable/stable manifolds, consisting of contraction/expansion regions linking fixed points. Such an interest arises from its ability to reflect the presence of near-wall hemodynamic features associated with the onset and progression of vascular diseases. Over the years, Lagrangian-based and Eulerian-based post-processing techniques have been proposed aiming at identifying the topological skeleton features of the WSS. Here, the theoretical and methodological bases supporting the Lagrangian- and Eulerian-based methods currently used in the literature are reported and discussed, highlighting their application to cardiovascular flows. The final aim is to promote the use of WSS topological skeleton analysis in hemodynamic applications and to encourage its application in future mechanobiology studies in order to increase the chance of elucidating the mechanistic links between blood flow disturbances, vascular disease, and clinical observations.

Characterization of Vortex Flow in a Mouse Model of Ventricular Dyssynchrony by Plane-Wave Ultrasound Using Hexplex Processing

The rodent heart is frequently used to study human cardiovascular disease (CVD). Although advanced cardiovascular ultrasound imaging methods are available for human clinical practice, application of these techniques to small animals remains limited due to the temporal and spatial-resolution demands. Here, an ultrasound vector-flow workflow is demonstrated that enables visualization and quantification of the complex hemodynamics within the mouse heart. Wild type (WT) and fibroblast growth factor homologous factor 2 (FHF2)-deficient mice (Fhf2 ^KO/Y ), which present with hyperthermia-induced ECG abnormalities highly reminiscent of Brugada syndrome, were used as a mouse model of human CVD. An 18-MHz linear array was used to acquire high-speed (30 kHz), plane-wave data of the left ventricle (LV) while increasing core body temperature up to 41.5 °C. Hexplex (i.e., six output) processing of the raw data sets produced the output of vector-flow estimates (magnitude and phase); B-mode and color-Doppler images; Doppler spectrograms; and local time histories of vorticity and pericardium motion. Fhf2 ^WT/Y mice had repeatable beat-to-beat cardiac function, including vortex formation during diastole, at all temperatures. In contrast, Fhf2 ^KO/Y mice displayed dyssynchronous contractile motion that disrupted normal inflow vortex formation and impaired LV filling as temperature rose. The hexplex processing approach demonstrates the ability to visualize and quantify the interplay between hemodynamic and mechanical function in a mouse model of human CVD.

The hemodynamic power of the heart differentiates normal from diseased right ventricles

Cardiac mechanics is primarily described by the pressure-volume relationship. The ventricular pressure-volume loop displays the instantaneous relationship between intraventricular pressure and volume throughout the cardiac cycle; however, it does not consider the shape of the ventricles, their spatiotemporal deformation patterns, and how these balance with the flowing blood. Our study demonstrates that the pressure-volume relationship represents a first level of approximation for the mechanical power of the ventricles, while, at a further level of approximation, the importance of hemodynamic power emerges through the balance between deformation patterns and fluid dynamics. The analysis is preliminarily tested in a healthy subject's right ventricle and two patients. Moreover, patients' geometry was then rescaled to present a normal volumetric profile to verify whether results were affected by volume size or by the spatiotemporal pattern of how that volume profile was achieved. Results show that alterations of hemodynamic power were found in the abnormal ventricles and that they were not directly caused by the ventricular size but by changes in the ability of intraventricular pressure gradient to generate blood flow. Therefore, hemodynamic power represents a physics-based measure that takes into account the dynamics of the space-time shape changes in combination with blood flow. Hemodynamic power is assessed non-invasively using cardiac imaging techniques and can be an early indicator of cardiac dysfunction before changes occur in volumetric measurements. These preliminary results provide a physical ground to evaluate its diagnostic or prognostic significance in future clinical studies.

Optimal vortex formation time index in mitral valve stenosis

Left ventricular vortex formation time (VFT) is a novel dimensionless index of flow propagation during left ventricular diastole, which has been demonstrated to be useful in heart failure and cardiomyopathy. In mitral stenosis (MS), flow propagation in the LV may be suboptimal. We studied VFT in varying degrees of MS. Echocardiography was performed on 20 healthy controls and 50 cases of rheumatic MS. Patients with atrial fibrillation, LV ejection fraction < 50% and other valvular heart diseases were excluded. VFT was obtained using the length-to-diameter ratio (L/D), where L is the continuous-wave Doppler velocity time integral stroke distance, divided by D, the mitral leaflet separation index. This was correlated against varying degrees of MS severity, left atrial (LA) volume and function. In controls, VFT was 3.92 ± 2.00 (optimal range) and was higher (suboptimal) with increasing severity of mitral stenosis (4.98 ± 2.43 in mild MS; 7.22 ± 2.98 in moderate MS; 11.55 ± 2.67 in severe MS, p < 0.001). VFT negatively correlated with mitral valve area (R² = 0.463, p < 0.001) and total LA emptying fraction (R² = 0.348, p < 0.001), and positively correlated with LA volume index (R² = 0.440, p < 0.001) and mean transmitral pressure gradient (R² = 0.336, p < 0.001). More severe MS correlated with suboptimal (higher) VFT. The restricted mitral valve opening may disrupt vortex formation and optimal fluid propagation in the LV. Despite the compensatory increase in LA size with increasingly severe MS, reduced LA function also contributed to the suboptimal LV vortex formation.

Numerical simulations of flow patterns in the human left ventricle model with a novel dynamic mesh morphing approach based on radial basis function

We present a new numerical simulation framework for prediction of flow patterns in the human left ventricle model. In this study, a radial basis function (RBF) mesh morphing method is developed and applied within the finite-volume computational fluid dynamics (CFD) approach. The numerical simulations are designed to closely mimic details of recent tomographic particle image velocimetry (TomoPIV) experiments. The numerically simulated dynamic motions of the left ventricle and tri-leaflet biological mitral valve are emulated through the RBF morphing method. The arbitrary Lagrangian-Eulerian (ALE) based CFD is performed with the RBF-defined deforming wall boundaries. The results obtained show a good agreement with experiments, confirming the reliability and accuracy of the developed simulation framework.

Automating Model Generation for Image-Based Cardiac Flow Simulation

Computational fluid dynamics (CFD) modeling of left ventricle (LV) flow combined with patient medical imaging data has shown great potential in obtaining patient-specific hemodynamics information for functional assessment of the heart. A typical model construction pipeline usually starts with segmentation of the LV by manual delineation followed by mesh generation and registration techniques using separate software tools. However, such approaches usually require significant time and human efforts in the model generation process, limiting large-scale analysis. In this study, we propose an approach toward fully automating the model generation process for CFD simulation of LV flow to significantly reduce LV CFD model generation time. Our modeling framework leverages a novel combination of techniques including deep-learning based segmentation, geometry processing, and image registration to reliably reconstruct CFD-suitable LV models with little-to-no user intervention.1 We utilized an ensemble of two-dimensional (2D) convolutional neural networks (CNNs) for automatic segmentation of cardiac structures from three-dimensional (3D) patient images and our segmentation approach outperformed recent state-of-the-art segmentation techniques when evaluated on benchmark data containing both magnetic resonance (MR) and computed tomography(CT) cardiac scans. We demonstrate that through a combination of segmentation and geometry processing, we were able to robustly create CFD-suitable LV meshes from segmentations for 78 out of 80 test cases. Although the focus on this study is on image-to-mesh generation, we demonstrate the feasibility of this framework in supporting LV hemodynamics modeling by performing CFD simulations from two representative time-resolved patient-specific image datasets.

Diastolic Vortex Alterations With Reducing Left Ventricular Volume: An In Vitro Study

Despite the large number of studies of intraventricular filling dynamics for potential clinical applications, little is known as to how the diastolic vortex ring properties are altered with reduction in internal volume of the cardiac left ventricle (LV). The latter is of particular importance in LV diastolic dysfunction (LVDD) and in congenital diseases such as hypertrophic cardiomyopathy (HCM), where LV hypertrophy (LVH) can reduce LV internal volume. We hypothesized that peak circulation and the rate of decay of circulation of the diastolic vortex would be altered with reducing end diastolic volume (EDV) due to increasing confinement. We tested this hypothesis on physical models of normal LV and HCM geometries, under identical prescribed inflow profiles and for multiple EDVs, using time-resolved particle image velocimetry (TR-PIV) measurements on a left heart simulator. Formation and pinch-off of the vortex ring were nearly unaffected with changes to geometry and EDV. Pinch-off occurred before the end of early filling (E-wave) in all test conditions. Peak circulation of the vortex core near the LV outflow tract (LVOT) increased with lowering EDV and was lowest for the HCM model. The rate of decay of normalized circulation in dimensionless formation time (T*) increased with decreasing EDV. When using a modified version of T* that included average LV cross-sectional area and EDV, normalized circulation of all tested EDVs collapsed closely in the normal LV model (10% maximum difference between EDVs). Collectively, our results show that LV shape and internal volume play a critical role in diastolic vortex ring dynamics.

A hybrid echocardiography-CFD framework for ventricular flow simulations

Image-based CFD is a powerful tool to study cardiovascular flows while 2D echocardiography (echo) is the most widely used noninvasive imaging modality for the diagnosis of heart disease. Here, echo is combined with CFD, that is, an echo-CFD framework, to study ventricular flows. To achieve this, the previous 3D reconstruction from multiple 2D echo at standard cross sections is extended by: (a) reconstructing aortic and mitral valves from 2D echo and closing the left-ventricle (LV) geometry by approximating a superior wall; (b) incorporating the physiological assumption of the fixed apex as a reference (fixed) point in the 3D reconstruction; and (c) incorporating several smoothing algorithms to remove the nonphysical oscillations (ringing) near the basal section. The method is applied to echo from a baseline LV and one after inducing acute myocardial ischemia (AMI). The 3D reconstruction is validated by comparing it against a reference reconstruction from many echo sections while flow simulations are validated against the Doppler ultrasound velocity measurements. The sensitivity study shows that the choice of the smoothing algorithm does not change the flow pattern inside the LV. However, the presence of the mitral valve can significantly change the flow pattern during the diastole phase. In addition, the abnormal shape of a LV with AMI can drastically change the flow during diastole. Furthermore, the hemodynamic energy loss, as an indicator of the LV pumping performance, for different test cases is calculated, which shows a larger energy loss for a LV with AMI compared to the baseline one.

Three-Dimensional Vortex-Induced Reaction Hot Spots at Flow Intersections

We show the emergence of reaction hot spots induced by three-dimensional (3D) vortices with a simple A+B→C reaction. We conduct microfluidics experiments to visualize the spatial map of the reaction rate with a chemiluminescence reaction and cross validate the results with direct numerical simulations. 3D vortices form at spiral-saddle-type stagnation points, and the 3D vortex flow topology is essential for initiating reaction hot spots. The effect of vortices on mixing and reaction becomes more vigorous for rough-walled channels, and our findings are valid over wide ranges of channel dimensions and Damköhler numbers.

Mixed Valvular Disease Following Transcatheter Aortic Valve Replacement: Quantification and Systematic Differentiation Using Clinical Measurements and Image-Based Patient-Specific In Silico Modeling

Background

Mixed valvular disease (MVD), mitral regurgitation (MR) from pre‐existing disease in conjunction with paravalvular leak (PVL) following transcatheter aortic valve replacement (TAVR), is one of the most important stimuli for left ventricle (LV) dysfunction, associated with cardiac mortality. Despite the prevalence of MVD, the quantitative understanding of the interplay between pre‐existing MVD, PVL, LV, and post‐TAVR recovery is meager.

Methods and Results

We quantified the effects of MVD on valvular‐ventricular hemodynamics using an image‐based patient‐specific computational framework in 72 MVD patients. Doppler pressure was reduced by TAVR (mean, 77%; N=72; P<0.05), but it was not always accompanied by improvements in LV workload. TAVR had no effect on LV workload in 22 patients, and LV workload post‐TAVR significantly rose in 32 other patients. TAVR reduced LV workload in only 18 patients (25%). PVL significantly alters LV flow and increases shear stress on transcatheter aortic valve leaflets. It interacts with mitral inflow and elevates shear stresses on mitral valve and is one of the main contributors in worsening of MR post‐TAVR. MR worsened in 32 patients post‐TAVR and did not improve in 18 other patients.

Conclusions

PVL limits the benefit of TAVR by increasing LV load and worsening of MR and heart failure. Post‐TAVR, most MVD patients (75% of N=72; P<0.05) showed no improvements or even worsening of LV workload, whereas the majority of patients with PVL, but without that pre‐existing MR condition (60% of N=48; P<0.05), showed improvements in LV workload. MR and its exacerbation by PVL may hinder the success of TAVR.

Impact of Aortoseptal Angle Abnormalities and Discrete Subaortic Stenosis on Left-Ventricular Outflow Tract Hemodynamics: Preliminary Computational Assessment

Discrete subaortic stenosis (DSS) is an obstruction of the left ventricular outflow tract (LVOT) due to the formation of a fibromuscular membrane upstream of the aortic valve. DSS is a major risk factor for aortic regurgitation (AR), which often persists after surgical resection of the membrane. While the etiology of DSS and secondary AR is largely unknown, the frequent association between DSS and aortoseptal angle (AoSA) abnormalities has supported the emergence of a mechanobiological pathway by which hemodynamic stress alterations on the septal wall could trigger a biological cascade leading to fibrosis and membrane formation. The resulting LVOT flow disturbances could activate the valve endothelium and contribute to AR. In an effort to assess this hypothetical mechano-etiology, this study aimed at isolating computationally the effects of AoSA abnormalities on septal wall shear stress (WSS), and the impact of DSS on LVOT hemodynamics. Two-dimensional computational fluid dynamics models featuring a normal AoSA (N-LV), a steep AoSA (S-LV), and a steep AoSA with a DSS lesion (DSS-LV) were designed to compute the flow in patient-specific left ventricles (LVs). Boundary conditions consisted of transient velocity profiles at the mitral inlet and LVOT outlet, and patient-specific LV wall motion. The deformation of the DSS lesion was computed using a two-way fluid-structure interaction modeling strategy. Turbulence was accounted for via implementation of the k-ω turbulence model. While the N-LV and S-LV models generated similar LVOT flow characteristics, the DSS-LV model resulted in an asymmetric LVOT jet-like structure, subaortic stenotic conditions (up to 2.4-fold increase in peak velocity, 45% reduction in effective jet diameter vs. N-LV/S-LV), increased vorticity (2.8-fold increase) and turbulence (5- and 3-order-of-magnitude increase in turbulent kinetic energy and Reynolds shear stress, respectively). The steep AoSA subjected the septal wall to a 23% and 69% overload in temporal shear magnitude and gradient, respectively, without any substantial change in oscillatory shear index. This study reveals the existence of WSS overloads on septal wall regions prone to DSS lesion formation in steep LVOTs, and the development of highly turbulent, stenotic and asymmetric flow in DSS LVOTs, which support a possible mechano etiology for DSS and secondary AR.

Quantitative Analysis of Left Ventricular Flow Dynamics in Latent Obstructive Hypertrophic Cardiomyopathy Using Vector Flow Mapping

OBJECTIVES

This study aimed to assess left ventricular (LV) energy loss (EL), circulation and vortex area using vector flow mapping (VFM) in patients with latent obstructive hyper-trophic cardiomyopathy (LOHCM) and nonobstructive hypertrophic cardiomyopathy (NOHCM).

METHODS

Fourteen LOHCM patients, 10 NOHCM patients, and 11 healthy individuals were evaluated by transthoracic echocardiography. An offline VFM workstation was used to analyze the LV blood flow patterns and fluid dynamics. The hemodynamic parameters, EL, circulation, and vortex area in 7 cardiac phases were calculated and analyzed.

RESULTS

Compared with controls and NOHCM patients, EL was significantly higher in -LOHCM patients during the rapid ejection phase, slow ejection (SE) phase, and isovolumetric relaxation phase (p < 0.05). LOHCM patients also showed increased circulation during SE compared to the other two groups (p < 0.05). The ability to discriminate between NOHCM and LOHCM was assessed by the area under the receiver-operating characteristic curve (AUC), and EL during SE was found to have the largest AUC (0.964); the best cutoff value was 6.34 J/m3/s, with a sensitivity of 100% and specificity of 80%.

CONCLUSIONS

The VFM technique can detect abnormal changes of LV EL and vortex characteristics in hypertrophic cardiomyopathy patients. Compared with controls and NOHCM patients, the LOHCM patients have worse systolic and diastolic functions.

Automated Quantitative Extraction and Analysis of 4D flow Patterns in the Ascending Aorta: An intraindividual comparison at 1.5 T and 3 T

4D flow MRI enables quantitative assessment of helical flow. Current methods are susceptible to noise. To evaluate helical flow patterns in healthy volunteers and patients with bicuspid aortic valves (BAV) at 1.5 T and 3 T using pressure-based helix-extraction in 4D flow MRI. Two intraindividual 4D flow MRI examinations were performed at 1.5 T and 3 T in ten healthy volunteers (5 females, 32 ± 3 years) and 2 patients with BAV using different acceleration techniques (kt-GRAPPA and centra). Several new quantitative parameters for the evaluation of volumes [ml], lengths [mm] as well as temporal parameters [ms] of helical flow were introduced and analyzed using the software tool Bloodline. We found good correlations between measurements in volunteers at 1.5 T and 3 T regarding helical flow volumes (R = 0.98) and temporal existence (R = 0.99) of helices in the ascending aorta. Furthermore, we found significantly larger (11.7 vs. 77.6 ml) and longer lasting (317 vs. 769 ms) helices in patients with BAV than in volunteers. The assessed parameters do not depend on the magnetic field strength used for the acquisition. The technique of pressure-based extraction of 4D flow MRI pattern is suitable for differentiation of normal and pathological flow.

Ventricular Flow Field Visualization During Mechanical Circulatory Support in the Assisted Isolated Beating Heart

Investigations of ventricular flow patterns during mechanical circulatory support are limited to in vitro flow models or in silico simulations, which cannot fully replicate the complex anatomy and contraction of the heart. Therefore, the feasibility of using echocardiographic particle image velocimetry (Echo-PIV) was evaluated in an isolated working heart setup. Porcine hearts were connected to an isolated, working heart setup and a left ventricular assist device (LVAD) was implanted. During different levels of LVAD support (unsupported, partial support, full support), microbubbles were injected and echocardiographic images were acquired. Iterative PIV algorithms were applied to calculate flow fields. The isolated heart setup allowed different hemodynamic situations. In the unsupported heart, diastolic intra-ventricular blood flow was redirected at the heart’s apex towards the left ventricular outflow tract (LVOT). With increasing pump speed, large vortex formation was suppressed, and blood flow from the mitral valve directly entered the pump cannula. The maximum velocities in the LVOT were significantly reduced with increasing support. For the first time, cardiac blood flow patterns during LVAD support were visualized and quantified in an ex vivo model using Echo-PIV. The results reveal potential regions of stagnation in the LVOT and, in future the methods might be also used in clinical routine to evaluate intraventricular flow fields during LVAD support.

Ventricular vortex loss analysis due to various tricuspid valve repair techniques: an ex vivo study

The deteriorating nature of severe functional tricuspid regurgitation (FTR) has led to the heightened interest in this pathology. However, therapies are heterogeneous and an ideal technique is uncertain. The hemodynamic impact on the cardiac chamber following therapeutic repairs has not been well studied, while its analysis could be used to predict the treatment success. In this study, the hemodynamics of the right ventricle (RV) after 1) clover edge-to-edge tricuspid repair, and 2) double orifice tricuspid repair was evaluated in three right heart models using an ex vivo pulsatile platform emulating severe FTR with the aid of stereoscopic particle image velocimetry. Although all repairs substantially reduced tricuspid regurgitant area, they resulted in a more than 50% reduction in diastolic tricuspid valve (TV) opening area. Splitting the TV orifice into multiple smaller orifices by both repairs eliminated the ring-shaped vortical structure inside the RV observed in FTR cases. Postrepair RV domain was mostly occupied with irregular vortical features and isolated vortex residuals. Moreover, vortical features varied among repair samples, indicating enhanced sensitivity of RV flow to postrepair TV morphology. Compared with clover repair, double orifice subjected the RV to enhanced swirling motions and exposed more regions to vortical motions, potentially indicating better rinsing and lower risk of mural thrombus formation. Double orifice repair increased the levels of RV mean kinetic energy and viscous energy loss than those observed in clover repair, although the impact of these on the cardiac efficiency remains unclear. These preliminary insights could be used to improve future treatment design and planning.NEW & NOTEWORTHY While clover and double orifice tricuspid repairs markedly improved leaflet coaptation, they substantially reduced diastolic tricuspid opening area. Postrepair right ventricle (RV) exhibited specific hemodynamic traits, including the loss of ring-shaped vortical structure and the enhanced sensitivity of RV flow to postrepair tricuspid valve morphology. Compared with clover technique, double orifice repair led to higher swirling motions in the RV domain, which could indicate lower risk of mural thrombus formation.

Investigation of left heart flow using a numerical correlation to model heart wall motion

A three-dimensional computational fluid dynamics (CFD) method has been developed to model the flow in the left heart including atrium and ventricle. Since time resolution of the medical scans does not fit the requirements of the CFD calculations, the main challenge in a numerical simulation of heart chambers is wall motion modeling. This study employs a novel three-dimensional approximation scheme to correlate the wall boundary and grid movement in systole and diastole. It uses a geometry extracted from medical images in the literature and deformed based on the reported flow rates. The opening and closing of the mitral (MV) and the aortic valve (AV) considered as simultaneous events. Unstructured tetragonal grids were used for the meshing of the domain. The calculation was performed by a Navier-Stokes solver using the arbitrary Lagrange-Euler (ALE) formulation. Results show that the proposed correlation for the wall motion could predict the main features of heart flows.

Left ventricular vortex formation time in elite athletes: novel predictor of myocardial performance

Background

Efficient transportation of blood through the left ventricle (LV) during diastole depends on vortex formation. Vortex formation time (VFT) can be measured by echocardiography as a dimensionless index. As elite athletes have supranormal diastolic LV function, we aim to assess resting and post-exercise VFT in these athletes and hypothesised that VFT may predict myocardial performance immediately post-exercise.

Method

Subjects were world class speedskaters training for the Winter Olympic Games. Echocardiographic measurements were obtained before and immediately after 3000 m of racing. VFT was computed as 4×(1-β)/π×α³×left ventricle ejection fraction where β is the fraction of diastolic stroke volume contributed by atrial contraction, α is the biplane end diastolic volume (EDV)^1/3 divided by mitral annular diameter during early diastole.

Results

Baseline VFT was 2.6±0.7 (n=24, age 22±3 years, 67% males). Post-exercise, heart rates increased (64±10 vs 89±12 beats/min, p<0.01); however, VFT was unchanged (2.9±1.0, p>0.05). VFT at rest correlated modestly with post-exertion early diastolic mitral in-flow velocity (E; r=0.59, p=0.01), tissue Doppler-derived early mitral annular velocity (E'; septal and lateral, both r=0.59, p=0.01) and systolic annular velocity (S'; septal: r=0.46, p=0.02 and lateral: r=0.48, p=0.02) but not late diastolic mitral in-flow velocity (A; r=0.06, p>0.05) or annular velocity (A'; septal: r=0.34, p=NS and lateral: r=0.35, p>0.05).

Conclusion

There was no significant difference between VFT at rest and immediately post-exercise. However, VFT at rest correlated with immediate post-exercise augmented systolic and early diastolic tissue Doppler indicators of myocardial performance in elite athletes.

Evaluation of hemodynamics in patients with hypertrophic cardiomyopathy by vector flow mapping: Comparison with healthy subjects

The present study investigated the role of energy loss assessed by vector flow mapping (VFM) in patients with hypertrophic cardiomyopathy (HCM). VFM analysis was performed in 42 patients with HCM and in 40 control subjects, which were matched for age, sex and left ventricular (LV) ejection fraction. The intra-LV and left atrial blood flow were obtained from the apical 3-chamber view, and the energy loss (EL) during the systolic and diastolic phases was calculated. The measurements were averaged over three cardiac cycles and indexed to body surface area. Compared with the controls, the left ventricular energy loss (LVEL)-total value was significantly decreased in patients with HCM during the diastolic phase (P1, P2 and P3; all P<0.05). A tendency for increased systolic LVEL-total values was observed in the patients with HCM compared with the controls (P>0.05). LVEL-base values were decreased in the patients with HCM during P1 and P2 (slow filling time). Compared with the controls, patients with HCM had lower LVEL-mid values during the diastolic phases (P0, P1, P2 and P3; all P<0.05). However, the LVEL-mid value of patients with HCM was higher compared with that of the controls during systolic P5 (P<0.05). LVEL-apex was decreased in patients with HCM during P0, P2 and P3. Compared with the controls, the left atrial energy loss (LAEL) of all three phases in patients with HCM were lower (each P<0.01). The diastolic LVEL values were significantly lower in patients with HCM compared with the controls; however, the systolic LVEL levels tended to be higher in HCM. The LAEL of the reservoir phase, conduit phase and atrial systolic phase were decreased in HCM compared with controls. The present study demonstrated that measurement of EL by VFM is a sensitive method of determining subclinical LV dysfunction in patients with HCM. The value of EL has been considered to be a quantitative parameter for the estimation of the efficiency of intraventricular blood flow.