Current clinical application of intracardiac flow analysis using echocardiography

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.

Fragmented Vortex in Heart Failure With Reduced Ejection Fraction: A Prospective Vector Flow Mapping Study

OBJECTIVE

Heart failure with reduced ejection fraction (HFrEF) is associated with structural and functional left ventricular changes. We compared intracardiac vortices between patients with HFrEF and normal participants using echocardiographic vector flow mapping, a novel intracardiac vortex analysis technology.

METHODS

Transthoracic echocardiography was performed on 20 patients with HFrEF (age: 61 ± 15 y, 15 men) and 20 normal participants (age: 59 ± 12 y, 12 men) age- and sex-balanced at the cohort level. Systolic and diastolic energy loss, area (indexed by left ventricular end-diastolic diameter), circulation (reflects vortex strength) and relative positions of the largest vortex during systole (S-vortex), early (E-vortex) and late (A-vortex) diastole and maximal number of vortices in a single frame (MNV) were assessed.

DISCUSSION

Patients with HFrEF had disproportionately sized vortices with smaller indexed vortex areas (p < 0.0001), and more fragmented vortices with higher MNV during both systole (p = 0.030) and diastole (p < 0.0001). These accompanied higher diastolic energy loss (p = 0.001). Additionally, the E-vortex (p = 0.002) and A-vortex (p < 0.0001) were more apically positioned, and the S-vortex was weaker (p = 0.033) in patients with HFrEF. More severe fragmentation (higher MNV) correlated with worse energy efficiency (higher energy loss).

CONCLUSION

Patients with HFrEF had more fragmented intracardiac vortices and lower energy efficiency predominantly during diastole.

Analysis of diastolic left ventricular wall shear stress in normal people of different age groups

Background

Diastolic wall shear stress (WSS), assessed by using vector flow mapping (VFM), is the result of the interaction between the blood flow and the ventricular wall. This study aimed to evaluate the trend of left ventricular (LV) WSS in normal subjects.

Methods and results

A total of 371 healthy volunteers were recruited and divided into four age groups (group I: 18–30 years; group II: 31–43 years; group III: 44–56 years; group IV: 57–70 years). LV WSS of different age groups was measured at each diastolic phase (P1: isovolumic diastolic period, P2: rapid filling period, P3: slow filling period, and P4:atrial contraction period) to evaluate the change trend of LV WSS. In each age group, LV WSS coincided with a trend of increasing-decreasing-increasing during P1–P4 (P < 0.05). Besides, among groups I, II, III, and IV, WSS of anterolateral, inferoseptal, and anteroseptal in P1 and WSS of inferolateral, inferoseptal, and anteroseptal in P4 all showed an increasing trend with age (P < 0.05). Regarding sex differences, women had greater diastolic WSS compared to men (P < 0.05).

Conclusion

LV WSS showed a regular variation and had specific age- and sex-related patterns in different diastolic phases.

Computational fluid dynamics modeling approaches to assess lower urinary tract hydraulic dynamics in posterior urethral valve before and after endoscopic valve ablation: a pilot study

PURPOSE

Computational fluid dynamics (CFD) has been used successfully in cardiovascular system research to analyze the physiological processes inside vessels. We evaluated the hydraulic information of urine through the lower urinary tract in a patient with posterior urethral valve (PUV) before and after valve ablation by CFD.

METHODS

A set of models of the lower urinary tract were developed based on geometrical data obtained by cystoscopy and voiding cystourethrography. Simulated assumptions and conditions were applied according to prior studies and urodynamic results. We used Fluent CFD 19.0 (Ansys Inc., USA) to compute the velocity and pressure of the fluid regions. The simplification of Bernoulli's formula was applied afterward to calculate the hydraulic energy of different positions.

RESULTS

The urine flow rates of the NORMALst, the PUVst, and the POSTst at 5000 Pa were 18.08 ml/s, 11.14 ml/s, and 12.16 ml/s, respectively. Precipitous pressure change was observed around the valve in the PUVst, and the abnormal change was concentrated in the dilated urethra in the POSTst. Major energy dissipations were generated around the valve and the dilated urethra in the PUVst. The energy loss that occurred in the dilated urethra did not improve after the operation.

CONCLUSIONS

Our findings are probably indicative of the hydrodynamics changes in the dilated urethra in PUV and need to be confirmed through more improved CFD models in the future. CFD may revolutionize pediatric urologists' perception in the management of urinary disease.

A Hybrid Approach for Cardiac Blood Flow Vortex Ring Identification Based on Optical Flow and Lagrangian Averaged Vorticity Deviation

Objective: The measurement of cardiac blood flow vortex characteristics can help to facilitate the analysis of blood flow dynamics that regulates heart function. However, the complexity of cardiac flow along with other physical limitations makes it difficult to adequately identify the dominant vortices in a heart chamber, which play a significant role in regulating the heart function. Although the existing vortex quantification methods can achieve this goal, there are still some shortcomings: such as low precision, and ignoring the center of the vortex without the description of vortex deformation processes. To address these problems, an optical flow Lagrangian averaged vorticity deviation (Optical flow-LAVD) method is proposed.

Methodology: We examined the flow within the right atrium (RA) of the participants’ hearts, by using a single set of scans pertaining to a slice at two-chamber short-axis orientation. Toward adequate extraction of the vortex ring characteristics, a novel approach driven by the Lagrangian averaged vorticity deviation (LAVD) was implemented and applied to characterize the trajectory integral associated with vorticity deviation and the spatial mean of rings, by using phase-contrast magnetic resonance imaging (PC-MRI) datasets as a case study. To interpolate the time frames between every larger discrete frame and minimize the error caused by constructing a continuous velocity field for the integral process of LAVD, we implemented the optical flow as an interpolator and introduced the backward warping as an intermediate frame synthesis basis, which is then used to generate higher quality continuous velocity fields.

Results: Our analytical study results showed that the proposed Optical flow-LAVD method can accurately identify vortex ring and continuous velocity fields, based on optical flow information, for yielding high reconstruction outcomes. Compared with the linear interpolation and phased-based frame interpolation methods, our proposed algorithm can generate more accurate synthesized PC-MRI.

Conclusion: This study has developed a novel Optical flow-LAVD model to accurately identify cardiac vortex rings, and minimize the associated errors caused by the construction of a continuous velocity field. Our paper presents a superior vortex characteristics detection method that may potentially aid the understanding of medical experts on the dynamics of blood flow within the heart.

Age-Related Changes in Left Ventricular Vortex Formation and Flow Energetics

Analysis of the cardiac vortex has been used for a deeper understanding of the pathophysiology in heart diseases. However, physiological changes of the cardiac vortex with normal aging are incompletely defined. Vector flow mapping (VFM) is a novel echocardiographic technique based on Doppler and speckle tracking for analysis of the cardiac vortex. Transthoracic echocardiography and VFM analysis were performed in 100 healthy adults (33 men; age = 18–67 years). The intracardiac flow was assessed throughout the cardiac cycle. The size (cross-sectional area) and circulation (equivalent to the integral of normal component of vorticity) of the largest vortices in systole (S-vortex), early diastole (E-vortex), and late diastole (A-vortex) were measured. Peak energy loss (EL) was calculated from information of the velocity vector of intracardiac flow in systole and diastole. With normal aging, the circulation (p = 0.049) of the E-vortex decreased, while that of the A-vortex increased (both p < 0.001). E-vortex circulation correlated directly to e’ (p = 0.003), A-vortex circulation correlated directly to A and a’ (both p < 0.001), and S-vortex circulation correlated directly to s’ (p = 0.032). Despite changes in vortex patterns, energy loss was not significantly different in older individuals. Normal aging is associated with altered intracardiac vortex patterns throughout the cardiac cycle, with the late-diastolic A-vortex becoming physiologically more dominant. Maintained energy efficiency accompanies changes in vortex patterns in aging hearts.

Blood Speckle-Tracking Based on High-Frame Rate Ultrasound Imaging in Pediatric Cardiology

BACKGROUND

Flow properties play an important role in cardiac function, remodeling, and morphogenesis but cannot be displayed in detail with today's echocardiographic techniques. The authors hypothesized that blood speckle-tracking (BST) could visualize and quantify flow patterns. The aim of this study was to determine the feasibility, accuracy, and potential clinical applications of BST in pediatric cardiology.

METHODS

BST is based on high-frame rate ultrasound, using a combination of plane-wave imaging and parallel receive beamforming. Pattern-matching techniques are used to quantify blood speckle motion. Accuracy of BST velocity measurements was validated using a rotating phantom and by comparing BST-derived inflow velocities with pulsed-wave Doppler obtained in the left ventricles of healthy control subjects. To test clinical feasibility, 102 subjects (21 weeks to 11.5 years of age) were prospectively enrolled, including healthy fetuses (n = 4), healthy control subjects (n = 51), and patients with different cardiac diseases (n = 47).

RESULTS

The phantom data showed a good correlation (r = 0.95, with a tracking quality threshold of 0.4) between estimated BST velocities and reference velocities down to a depth of 8 cm. There was a good correlation (r = 0.76) between left ventricular inflow velocity measured using BST and pulsed-wave Doppler. BST displayed lower velocities (mean ± SD, 0.59 ± 0.14 vs 0.82 ± 0.21 m/sec for pulsed-wave Doppler). However, the velocity amplitude in BST increases with reduced smoothing. The clinical feasibility of BST was high, as flow patterns in the area of interest could be visualized in all but one case (>99%).

CONCLUSIONS

BST is highly feasible in fetal and pediatric echocardiography and provides a novel approach for visualizing blood flow patterns. BST provides accurate velocity measurements down to 8 cm, but compared with pulsed-wave Doppler, BST displays lower velocities. Studying blood flow properties may provide novel insights into the pathophysiology of pediatric heart disease and could become an important diagnostic tool.

Validation of Echodynamography in Comparison with Particle-image Velocimetry

Echodynamography (EDG) is a computational method to estimate and visualize two-dimensional flow velocity vectors by applying dynamic flow theories to color Doppler echocardiography. The EDG method must be validated if applied to human cardiac flow function. However, a few studies of flow estimated have compared by EDG to the flow data were acquired by other methods. In this study, EDG was validated by comparing the analysis of estimating and visualizing flow velocity vectors obtained by original particle image velocimetry (PIV) based on a left ventricular (LV) phantom hydrogel (in vitro studies) and by EDG based on the virtual Doppler velocity. Velocity measured by PIV method and velocity estimated by EDG method in the perpendicular direction and the radial direction were compared. Regression analysis for the velocity estimated in the radial direction revealed an excellent correlation (R2=0.99, slope = 0.96) and moderate correlation in the perpendicular direction (R2=0.44, slope = 0.46). As revealed by the Bland-Altman plot, however, overestimations and higher relative error were observed in the perpendicular direction (0.51 ± 2.75 mm/s) and in the radial direction (-2.15 ± 21.13 mm/s). The percentage error of the norm-wise relative error of the velocity discrepancy is less than 10%, and velocity magnitude followed the same trends and are of comparable magnitude. These findings indicate that good estimates of velocity can be obtained by the EDG method. Therefore, the EDG method was appropriate for estimating and visualizing velocity vectors in clinical studies for higher measurement accuracy and reliability. The clinical in vivo application showed that the EDG method has the ability to visualize blood flow velocity vectors and differentiate the clinical information of vortex parameters both in normal and abnormal LV subjects. In conclusion, the EDG method has potentially greater clinical acceptance as a tool assessment of LV during the cardiac cycle.

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

OBJECTIVE

This study investigated the intraventricular flow dynamics in ischaemic heart disease patients.

PATIENTS AND METHODS

Fourteen patients with normal ejection fraction and 16 patients with reduced ejection fraction were compared with 20 healthy individuals. Phase-contrast MRI was used to assess intraventricular flow variables and speckle-tracking echocardiography to assess myocardial strain and left ventricular (LV) dyssynchrony. Infarct size was acquired using delayed-enhancement MRI.

RESULTS

The results obtained showed no significant differences in intraventricular flow variables between the healthy group and the patients with normal ejection fraction group, whereas considerable reductions in kinetic energy (KE) fluctuation index, E' (P<0.001) and vortex KE (P=0.003) were found in the patients with reduced ejection fraction group. In multivariate analysis, only vortex KE and infarct size were significantly related to LV ejection fraction (P<0.001); furthermore, vortex KE was correlated negatively with energy dissipation, energy dissipation index (r=-0.44, P=0.021).

CONCLUSION

This study highlights that flow energetic indices have limited applicability as early predictors of LV progressive dysfunction, whereas vortex KE could be an alternative to LV performance.

Impact of myocardial infarction on intraventricular vortex and flow energetics assessed using computational simulations

Flow energetics have been proposed as early indicators of progressive left ventricular (LV) functional impairment in patients with myocardial infarction (MI), but its correlation with individual MI parameters has not been fully explored. Using electro-fluid-structure interaction LV models, this study investigated the correlation between four MI parameters: infarct size, infarct multiplicity, regional enhancement of contractility at the viable myocardium area (RECVM), and LV mechanical dyssynchrony (LVMD) with intraventricular vortex and flow energetics. In LV with small infarcts, our results showed that infarct appearance amplified the energy dissipation index (DI), where substantial viscous energy loss was observed in areas with high flow velocity and near the infarct-vortex interface. The LV with small multiple infarcts and RECVM showed remarkable DI increment during systole and diastole. In correlation analysis, the systolic kinetic energy fluctuation index (E') was positively related to ejection fraction (EF) (R²  = 0.982) but negatively correlated with diastolic E' (R²  = 0.970). Diastolic E' was inversely correlated with vortex kinetic energy (R²  = 0.960) and vortex depth (R²  = 0.876). We showed an excessive systolic DI could differentiate infarcted LV with normal EF from healthy LV. Strong flow acceleration, LVMD, and vortex-infarct interactions were predominant factors that induced excessive DI in infarcted LVs. Instead of causing undesired flow turbulence, high systolic E' suggested the existence of energetic flow acceleration, while high diastolic E' implied an inefficient diastolic filling. Thus, systolic E' is not a suitable early indicator for progressive LV dysfunction in MI patients, while diastolic E' may be a useful index to indicate diastolic impairment in these patients.

Intraventricular Flow: More than Pretty Pictures

Patients with heart failure show myocardial, valvular, and electrical dysfunction, which results in enlarged cardiac chambers and increased intracardiac volume and pressure. Intracardiac flow analysis can provide information regarding the shape and wall properties, chamber dimensions, and flow efficiency throughout the cardiac cycle. There is increasing interest in vortex flow analysis for patients with heart failure to overcome limitations of conventional parameters. In conjunction with the conventional structural and functional parameters, vortex flow analysis-guided treatment in heart failure might be a novel option for cardiac physicians.

Relationship between left ventricular vortex and preejectional flow velocity during isovolumic contraction studied by using vector flow mapping

OBJECTIVES

The purpose of this study was to investigate the relationship between the vortex in left ventricle (LV) during the isovolumic contraction (IVC) period and the preejectional flow velocity in LV outflow tract (V_LVOT ).

METHODS

Color Doppler loops were acquired for vector flow mapping in apical long-axis view in 76 patients with dilated cardiomyopathy, 61 patients with coronary artery disease and 36 healthy controls.

RESULTS

All normals exhibited an IVC vortex reaching the LV base. V_LVOT was significantly related to IVC vortex area flux, transmitral A velocity, mitral annular a' velocity and E/e' ratio, respectively. Transmitral A velocity was the only independent predictor of V_LVOT (R²  = 0.292, P = 0.001). In patients the IVC vortex could reach the LV base, middle, or apex. V_LVOT was significantly related to range, area and area flux of the IVC vortex, LV size, LVEF, mitral annular velocities, E/e' ratio, transmitral A velocity, and IVC time, respectively. Range and corrected area flux of the IVC vortex, LV end-systolic short diameter, and IVC time were independent predictors of V_LVOT (R²  = 0.608, P < 0.001).

CONCLUSIONS

In normals, the transmitral A velocity (momentum) is efficiently transferred from mitral orifice to LV outflow tract by a normally formed IVC vortex, and transmitral A velocity is the only independent predictor of V_LVOT . However, in patients with a wide range of LV enlargement and dysfunction, the momentum transfer is associated with not only the LV dimension and function, but also the range and volume of the IVC vortex.

Advanced Age Attenuates Left Ventricular Filling Efficiency Quantified Using Vortex Formation Time: A Study of Octogenarians With Normal Left Ventricular Systolic Function Undergoing Coronary Artery Surgery

OBJECTIVE

Blood flow across the mitral valve during early left ventricular (LV) filling produces a 3-dimensional rotational fluid body, known as a vortex ring, that enhances LV filling efficiency. Diastolic dysfunction is common in elderly patients, but the influence of advanced age on vortex formation is unknown. The authors tested the hypothesis that advanced age is associated with a reduction in LV filling efficiency quantified using vortex formation time (VFT) in octogenarians undergoing coronary artery bypass graft (CABG) surgery.

DESIGN

Observational study.

SETTING

Veterans Affairs medical center.

PARTICIPANTS

After institutional review board approval, octogenarians (n = 7; 82 ± 2 year [mean ± standard deviation]; ejection fraction 56% ± 7%) without valve disease or atrial arrhythmias undergoing CABG were compared with a younger cohort (n = 7; 55 ± 6 year; ejection fraction 57% ± 7%) who were undergoing coronary revascularization.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

All patients were monitored using radial and pulmonary arterial catheters and transesophageal echocardiography. Peak early LV filling (E) and atrial systole (A) blood flow velocities and their corresponding velocity-time integrals were obtained using pulse-wave Doppler echocardiography to determine E/A, atrial filling fraction (β), and E wave deceleration time. Pulse-wave Doppler also was used to measure pulmonary venous blood flow during systole and diastole. Mitral valve diameter (D) was calculated as the average of major and minor axis lengths obtained in the midesophageal LV bicommissural and long-axis transesophageal echocardiography imaging planes, respectively. VFT was calculated as 4 × (1 - β) × SV/(πD³), where SV is the stroke volume measured using thermodilution. Systemic and pulmonary hemodynamics, LV diastolic function, and VFT were determined during steady-state conditions 30 minutes before cardiopulmonary bypass. A delayed relaxation pattern of LV filling (E/A 0.81 ± 0.16 v 1.29 ± 0.19, p = 0.00015; β 0.44 ± 0.05 v 0.35 ± 0.03, p = 0.0008; E wave deceleration time 294 ± 58 v 166 ± 28 ms, p < 0.0001; ratio of peak pulmonary venous systolic and diastolic blood flow velocity 1.42 ± 0.23 v 1.14 ± 0.20, p = 0.0255) was observed in octogenarians compared with younger patients. Mitral valve diameter was similar between groups (2.7 ± 0.2 and 2.6 ± 0.2 cm, respectively, in octogenarians v younger patients, p = 0.299). VFT was reduced in octogenarians compared with younger patients (3.0 ± 0.9 v 4.5 ± 1.2; p = 0.0171). An inverse correlation between age and VFT was shown using linear regression analysis (VFT = -0.0627 × age + 8.24; r² = 0.408; p = 0.0139).

CONCLUSION

The results indicate that LV filling efficiency quantified using VFT is reduced in octogenarians compared with younger patients undergoing coronary artery bypass grafting.

Development and Validation of a Phase-Filtered Moving Ensemble Correlation for Echocardiographic Particle Image Velocimetry

A new processing method for echocardiographic particle image velocimetry (EchoPIV) using moving ensemble (ME) correlation with dynamic phase correlation filtering was developed to improve velocity measurement accuracy for routine clinical evaluation of cardiac function. The proposed method was tested using computationally generated echocardiogram images. Error analysis indicated that ME EchoPIV yields a twofold improvement in bias and random error over the current standard correlation method (β_Pairwise = -0.15 vs. β_ME = -0.06; σ_Pairwise = 1.00 vs. σ_ME = 0.49). Subsequently a cohort of eight patients with impaired diastolic filling underwent similar evaluation. Comparison of patient EchoPIV velocity time series with corresponding color M-mode velocity time series revealed better agreement for ME EchoPIV compared with standard PIV processing (R_ME = 0.90 vs. R_Pairwise = 0.70). Further time series analysis was performed to measure filling propagation velocity and 1-D intraventricular pressure gradients. Comparison against CMM values indicated that both measurements are completely decorrelated for pairwise processing (R²_Vp = 0.15, R²_IVPD = 0.07), whereas ME processing correlates decently (R²_Vp = 0.69, R²_IVPD = 0.69). This new approach enables more robust processing of routine clinical scans and can increase the utility of EchoPIV for the assessment of left ventricular function.

Patient-specific modeling of left ventricular electromechanics as a driver for haemodynamic analysis

Aims

Models of blood flow in the left ventricle (LV) and aorta are an important tool for analysing the interplay between LV deformation and flow patterns. Typically, image-based kinematic models describing endocardial motion are used as an input to blood flow simulations. While such models are suitable for analysing the hemodynamic status quo, they are limited in predicting the response to interventions that alter afterload conditions. Mechano-fluidic models using biophysically detailed electromechanical (EM) models have the potential to overcome this limitation, but are more costly to build and compute. We report our recent advancements in developing an automated workflow for the creation of such CFD ready kinematic models to serve as drivers of blood flow simulations.

Methods and results

EM models of the LV and aortic root were created for four pediatric patients treated for either aortic coarctation or aortic valve disease. Using MRI, ECG and invasive pressure recordings, anatomy as well as electrophysiological, mechanical and circulatory model components were personalized.

Results

The implemented modeling pipeline was highly automated and allowed model construction and execution of simulations of a patient’s heartbeat within 1 day. All models reproduced clinical data with acceptable accuracy.

Conclusion

Using the developed modeling workflow, the use of EM LV models as driver of fluid flow simulations is becoming feasible. While EM models are costly to construct, they constitute an important and nontrivial step towards fully coupled electro-mechano-fluidic (EMF) models and show promise as a tool for predicting the response to interventions which affect afterload conditions.

Relationship between the abnormal diastolic vortex structure and impaired left ventricle filling in patients with hyperthyroidism

Intraventricular hydrodynamics plays an important role in evaluating cardiac function. Relationship between diastolic vortex and left ventricular (LV) filling is still rarely elucidated. The aim of this study was to evaluate the evolution of vortex during diastole in hyperthyroidism (HT) and explore the alteration of hydromechanics characteristics with sensitive indexes.Forty-three patients diagnosed with HT were classified into 2 groups according to whether myocardial damage existed: simple hyperthyroid group (HT1, n = 21) and thyrotoxic cardiomyopathy (HT2, n = 22). Twenty-seven age- and gender-matched healthy volunteers were enrolled as the control group. Offline vector flow mapping (VFM model) was used to analyze the LV diastolic blood flow patterns and fluid dynamics. Hemodynamic parameters, vortex area (A), circulation (C), and intraventricular pressure gradient (ΔP), in different diastolic phases (early, mid, and late) were calculated and analyzed.HT2, with a lower E/A ratio and left ventricular ejection fraction (LVEF), had a larger left atrium diameter (LAD) compared with those of the control group and HT1 (P < .05). Compared with the control group, the vortex size and strength, intraventricular pressure gradient during early and mid-diastole were higher in HT1 and lower in HT2 (P < .05). And in late diastole, the vortex size and strength, intraventricular pressure gradient of HT2 became higher than those of the control group (P < .05). Good correlation could be found between CE and E/A (P < .05), CM and ΔPM (P < .01), CL and FT3 (P < .05).VFM is proven practical for detecting the relationship between the changes of left ventricular diastolic vortex and the abnormal left ventricular filling.

Vector flow mapping analysis of left ventricular energetic performance in healthy adult volunteers

BACKGROUND

Vector flow mapping, a novel flow visualization echocardiographic technology, is increasing in popularity. Energy loss reference values for children have been established using vector flow mapping, but those for adults have not yet been provided. We aimed to establish reference values in healthy adults for energy loss, kinetic energy in the left ventricular outflow tract, and the energetic performance index (defined as the ratio of kinetic energy to energy loss over one cardiac cycle).

METHODS

Transthoracic echocardiography was performed in fifty healthy volunteers, and the stored images were analyzed to calculate energy loss, kinetic energy, and energetic performance index and obtain ranges of reference values for these.

RESULTS

Mean energy loss over one cardiac cycle ranged from 10.1 to 59.1 mW/m (mean ± SD, 27.53 ± 13.46 mW/m), with a reference range of 10.32 ~ 58.63 mW/m. Mean systolic energy loss ranged from 8.5 to 80.1 (23.52 ± 14.53) mW/m, with a reference range of 8.86 ~ 77.30 mW/m. Mean diastolic energy loss ranged from 7.9 to 86 (30.41 ± 16.93) mW/m, with a reference range of 8.31 ~ 80.36 mW/m. Mean kinetic energy in the left ventricular outflow tract over one cardiac cycle ranged from 200 to 851.6 (449.74 ± 177.51) mW/m with a reference range of 203.16 ~ 833.15 mW/m. The energetic performance index ranged from 5.3 to 37.6 (18.48 ± 7.74), with a reference range of 5.80 ~ 36.67.

CONCLUSIONS

Energy loss, kinetic energy, and energetic performance index reference values were defined using vector flow mapping. These reference values enable the assessment of various cardiac conditions in any clinical situation.

Assessing the Performance of Ultrafast Vector Flow Imaging in the Neonatal Heart via Multiphysics Modeling and In Vitro Experiments

Ultrafast vector flow imaging would benefit newborn patients with congenital heart disorders, but still requires thorough validation before translation to clinical practice. This paper investigates 2-D speckle tracking (ST) of intraventricular blood flow in neonates when transmitting diverging waves at ultrafast frame rate. Computational and in vitro studies enabled us to quantify the performance and identify artifacts related to the flow and the imaging sequence. First, synthetic ultrasound images of a neonate's left ventricular flow pattern were obtained with the ultrasound simulator Field II by propagating point scatterers according to 3-D intraventricular flow fields obtained with computational fluid dynamics (CFD). Noncompounded diverging waves (opening angle of 60°) were transmitted at a pulse repetition frequency of 9 kHz. ST of the B-mode data provided 2-D flow estimates at 180 Hz, which were compared with the CFD flow field. We demonstrated that the diastolic inflow jet showed a strong bias in the lateral velocity estimates at the edges of the jet, as confirmed by additional in vitro tests on a jet flow phantom. Furthermore, ST performance was highly dependent on the cardiac phase with low flows (<5 cm/s), high spatial flow gradients, and out-of-plane flow as deteriorating factors. Despite the observed artifacts, a good overall performance of 2-D ST was obtained with a median magnitude underestimation and angular deviation of, respectively, 28% and 13.5° during systole and 16% and 10.5° during diastole.

Moderate Aortic Valvular Insufficiency Invalidates Vortex Formation Time as an Index of Left Ventricular Filling Efficiency in Patients With Severe Degenerative Calcific Aortic Stenosis Undergoing Aortic Valve Replacement

OBJECTIVE

Transmitral blood flow produces a vortex ring (quantified using vortex formation time [VFT]) that enhances the efficiency of left ventricular (LV) filling. VFT is attenuated in LV hypertrophy resulting from aortic valve stenosis (AS) versus normal LV geometry. Many patients with AS also have aortic insufficiency (AI). The authors tested the hypothesis that moderate AI falsely elevates VFT by partially inhibiting mitral leaflet opening in patients with AS.

DESIGN

Observational study.

SETTING

Veterans Affairs medical center.

PARTICIPANTS

Patients with AS in the presence or absence of moderate AI (n = 8 per group) undergoing aortic valve replacement (AVR) were studied after institutional review board approval.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Under general anesthesia, peak early LV filling (E) and atrial systole (A) blood flow velocities and their corresponding velocity-time integrals were obtained using pulse-wave Doppler transesophageal echocardiography (TEE) to determine E/A and atrial filling fraction (beta). Mitral valve diameter (D) was calculated as the average of major and minor axis lengths obtained in the midesophageal bicommissural (transcommissural anterior-lateral-posterior medial) and LV long-axis (anterior-posterior) TEE imaging planes, respectively. VFT was calculated as 4·(1-beta)·SV/πD(3), where SV = stroke volume measured using thermodilution. Hemodynamics, diastolic function, and VFT were determined during steady-state conditions before cardiopulmonary bypass. The severity of AS (mean and peak pressure gradients, peak transvalvular jet velocity, aortic valve area) and diastolic function (E/A, beta) were similar between groups. Moderate centrally directed AI was present in 8 patients with AS (ratio of regurgitant jet width to LV outflow tract diameter of 36±6%). Pulse pressure and mean pulmonary artery pressure were elevated in patients with versus without AI, but no other differences in hemodynamics were observed. Mitral valve minor and major axis lengths, diameter, and area were reduced in the presence versus the absence of AI. VFT was increased significantly (5.7±1.7 v 3.2±0.6; p = 0.00108) in patients with AS and AI compared with AS alone.

CONCLUSION

Moderate AI falsely elevates VFT in patients with severe AS undergoing AVR by partially inhibiting mitral valve opening. VFT may be an unreliable index of LV filling efficiency with competitive diastolic flow into the LV.

Changes in electrical activation modify the orientation of left ventricular flow momentum: novel observations using echocardiographic particle image velocimetry

AIMS

Changes in electrical activation sequence are known to affect the timing of cardiac mechanical events. We aim to demonstrate that these also modify global properties of the intraventricular blood flow pattern. We also explore whether such global changes present a relationship with clinical outcome.

METHODS AND RESULTS

We investigated 30 heart failure patients followed up after cardiac resynchronization therapy (CRT). All subjects underwent echocardiography before implant and at follow-up after 6+ months. Left ventricular mechanics was investigated at follow-up during active CRT and was repeated after a temporary interruption <5 min later. Strain analysis, performed by speckle tracking, was used to assess the entity of contraction (global longitudinal strain) and its synchronicity (standard deviation of time to peak of radial strain). Intraventricular fluid dynamics, by echographic particle image velocimetry, was used to evaluate the directional distribution of global momentum associated with blood motion. The discontinuation of CRT pacing reflects into a reduction of deformation synchrony and into the deviation of blood flow momentum from the base-apex orientation with the development of transversal flow-mediated haemodynamic forces. The deviation of flow momentum presents a significant correlation with the degree of volumetric reduction after CRT.

CONCLUSION

Changes in electrical activation alter the orientation of blood flow momentum. The long-term CRT outcome correlates with the degree of re-alignment of haemodynamic forces. These preliminary results suggest that flow orientation could be used for optimizing the biventricular pacing setting. However, larger prospective studies are needed to confirm this hypothesis.

Differences in aortic vortex flow pattern between normal and patients with stroke: qualitative and quantitative assessment using transesophageal contrast echocardiography

The flow in the aorta forms a vortex, which is a critical determinant of the flow dynamics in the aorta. Arteriosclerosis can alter the blood flow pattern of the aorta and cause characteristic alterations of the vortex. However, this change in aortic vortex has not yet been studied. This study aimed to characterize aortic vortex flow pattern using transesophageal contrast echocardiography in normal and stroke patients. A total of 85 patients who diagnosed with ischemic stroke and 16 normal controls were recruited for this study. The 16 normal control subjects were designated as the control group, and the 85 ischemic stroke patients were designated as the stroke group. All subjects underwent contrast transesophageal echocardiography (TEE), and particle image velocimetry was used to assess aortic vortex flow. Qualitative and quantitative analyses of vortex flow morphology, location, phasic variation, and pulsatility were undertaken and compared between the groups. In the control group, multiple irregularly-shaped vortices were observed in a peripheral location in the descending thoracic aorta. In contrast, the stroke group had a single, round, merged, and more centrally located aortic vortex flow. In the quantitative analysis of vortex, vortex depth, which represents the location of the major vortex in the aorta, was significantly higher in the control group than in the stroke group (0.599 ± 0.159 vs. 0.522 ± 0.101, respectively, P = 0.013). Vortex relative strength, which is the pulsatility parameter of the vortex itself, was significantly higher in the stroke group than in the control group (0.367 ± 0.148 vs. 0.304 ± 0.087, respectively, P = 0.025). It was feasible to visualize and quantify the characteristic morphology and pulsatility of the aortic vortex flow using contrast TEE, and aortic vortex pattern significantly differed between normal and stroke patients.

Left ventricular systolic intraventricular flow field assessment in hyperthyroidism patients using vector flow mapping

Intraventricular hydrodynamics is considered an important component of cardiac function assessment. Vector flow mapping (VFM) is a novel flow visualization method to describe cardiac pathophysiological condition. This study examined use of new VFM and flow field for assessment of left ventricular (LV) systolic hemodynamics in patients with simple hyperthyroidism (HT). Thirty-seven simple HT patients were enrolled as HT group, and 38 gender- and age-matched healthy volunteers as control group. VFM model was used to analyze LV flow field at LV apical long-axis view. The following flow parameters were measured, including peak systolic velocity (Vs), peak systolic flow (Fs), total systolic negative flow (SQ) in LV basal, middle and apical level, velocity gradient from the apex to the aortic valve (ΔV), and velocity according to half distance (V1/2). The velocity vector in the LV cavity, stream line and vortex distribution in the two groups were observed. The results showed that there were no significant differences in the conventional parameters such as left ventricular ejection fraction (LVEF), left ventricular end-diastolic diameter (LVEDD) and left atrium diameter (LAD) between HT group and control group (P>0.05). Compared with the control group, a brighter flow and more vortexes were detected in HT group. Non-uniform distribution occurred in the LV flow field, and the stream lines were discontinuous in HT group. The values of Vs and Fs in three levels, SQ in middle and basal levels, ΔV and V1/2 were higher in HT group than in control group (P<0.01). ΔV was positively correlated with serum free thyroxin (FT4) (r=0.48, P<0.01). Stepwise multiple regression analysis showed that LVEDD, FT4, and body surface area (BSA) were the influence factors of ΔV. The unstable left ventricular systolic hydrodynamics increased in a compensatory manner in simple HT patients. The present study indicated that VFM may be used for early detection of abnormal ventricle contraction in clinical settings.

Clinical impact of quantitative left atrial vortex flow analysis in patients with atrial fibrillation: a comparison with invasive left atrial voltage mapping

Recently, left atrial (LA) vortex flow analysis using contrast transesophageal echocardiography (TEE) has been shown to be feasible and has demonstrated significant differences in vortex flow morphology and pulsatility between normal subjects and patients with atrial fibrillation (AF). However, the relationship between LA vortex flow and electrophysiological properties and the clinical significance of LA vortex flow are unknown. The aims of this study were (1) to compare LA vortex flow parameters with LA voltage and (2) to assess the predictive value of LA vortex flow parameters for the recurrence of AF after radiofrequency catheter ablation (RFCA). Thirty-nine patients with symptomatic non-valvular AF underwent contrast TEE before undergoing RFCA for AF. Quantitative LA vortex flow parameters were analyzed by Omega flow (Siemens Medical Solution, Mountain View, CA, USA). The morphology and pulsatility of LA vortex flow were compared with electrophysiologic parameters that were measured invasively. Hemodynamic, electrophysiological, and vortex flow parameters were compared between patients with and without early recurrence of AF after RFCA. Morphologic parameters, including LA vortex depth, length, width, and sphericity index were not associated with LA voltage or hemodynamic parameters. The relative strength (RS), which represents the pulsatility power of LA, was positively correlated with LA voltage (R = 0.53, p = 0.01) and LA appendage flow velocity (R = 0.73, p < 0.001) and negatively correlated with LA volume index (R = -0.56, p < 0.001). Patients with recurrent AF after RFCA showed significantly lower RS (1.7 ± 0.2 vs 1.9 ± 0.4, p = 0.048) and LA voltage (0.9 ± 0.7 vs 1.7 ± 0.8, p = 0.004) than patients without AF recurrence. In the relatively small LA dimension group (LA volume index ≤ 33 ml/m(2)), RS was significantly lower (2.1 ± 0.3 vs 1.7 ± 0.1, p = 0.029) in patients with the recurrent AF. Quantitative LA vortex flow analysis, especially RS, correlated well with LA voltage. Decreased pulsatility strength in the LA was associated with recurrent AF. LA vortex may have incremental value in predicting the recurrence of AF.

Mechanotransduction mechanisms for intraventricular diastolic vortex forces and myocardial deformations: part 1

Epigenetic mechanisms are fundamental in cardiac adaptations, remodeling, reverse remodeling, and disease. This two-article series proposes that variable forces associated with diastolic RV/LV rotatory intraventricular flows can exert physiologically and clinically important, albeit still unappreciated, epigenetic actions influencing functional and morphological cardiac adaptations and/or maladaptations. Taken in toto, the two-part survey formulates a new paradigm in which intraventricular diastolic filling vortex-associated forces play a fundamental epigenetic role, and examines how heart cells react to these forces. The objectives are to provide a perspective on vortical epigenetic effects, to introduce emerging ideas, and to suggest directions of multidisciplinary translational research. The main goal is to make pertinent biophysics and cytomechanical dynamic systems concepts accessible to interested translational and clinical cardiologists. I recognize that the diversity of the epigenetic problems can give rise to a diversity of approaches and multifaceted specialized research undertakings. Specificity may dominate the picture. However, I take a contrasting approach. Are there concepts that are central enough that they should be developed in some detail? Broadness competes with specificity. Would, however, this viewpoint allow for a more encompassing view that may otherwise be lost by generation of fragmented results? Part 1 serves as a general introduction, focusing on background concepts, on intracardiac vortex imaging methods, and on diastolic filling vortex-associated forces acting epigenetically on RV/LV endocardium and myocardium. Part 2 will describe pertinent available pluridisciplinary knowledge/research relating to mechanotransduction mechanisms for intraventricular diastolic vortex forces and myocardial deformations and to their epigenetic actions on myocardial and ventricular function and adaptations.