Assessment of left ventricular diastolic dysfunction based on the intraventricular velocity difference by vector flow mapping

A prediction model for major adverse cardiovascular events in patients with heart failure based on high-throughput echocardiographic data

Background

Heart failure (HF) is a serious end-stage condition of various heart diseases with increasing frequency. Few studies have combined clinical features with high-throughput echocardiographic data to assess the risk of major cardiovascular events (MACE) in patients with heart failure. In this study, we assessed the relationship between these factors and heart failure to develop a practical and accurate prognostic dynamic nomogram model to identify high-risk groups of heart failure and ultimately provide tailored treatment options.

Materials and methods

We conducted a prospective study of 468 patients with heart failure and established a clinical predictive model. Modeling to predict risk of MACE in heart failure patients within 6 months after discharge obtained 320 features including general clinical data, laboratory examination, 2-dimensional and Doppler measurements, left ventricular (LV) and left atrial (LA) speckle tracking echocardiography (STE), and left ventricular vector flow mapping (VFM) data, were obtained by building a model to predict the risk of MACE within 6 months of discharge for patients with heart failure. In addition, the addition of machine learning models also confirmed the necessity of increasing the STE and VFM parameters.

Results

Through regular follow-up 6 months after discharge, MACE occurred in 156 patients (33.3%). The prediction model showed good discrimination C-statistic value, 0.876 (p < 0.05), which indicated good identical calibration and clinical efficacy. In multiple datasets, through machine learning multi-model comparison, we found that the area under curve (AUC) of the model with VFM and STE parameters was higher, which was more significant with the XGboost model.

Conclusion

In this study, we developed a prediction model and nomogram to estimate the risk of MACE within 6 months of discharge among patients with heart failure. The results of this study can provide a reference for clinical physicians for detection of the risk of MACE in terms of clinical characteristics, cardiac structure and function, hemodynamics, and enable its prompt management, which is a convenient, practical and effective clinical decision-making tool for providing accurate prognosis.

Amount of dissipative energy loss when assessing left ventricular dysfunction in female patients with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is associated with an increased risk of cardiovascular disease. The purpose of the current study was to explore the amount of energy loss (EL) using vector flow mapping (VFM) in the detection of early stage left ventricular (LV) dysfunction among patients with SLE. Eighty-nine patients with SLE and fifty-six healthy controls were enrolled. SLE patients were further divided into inactive (SLEDAI ≤ 4, n = 43) and active (SLEDAI ≥ 5, n = 46) subgroups. A prosound F75 echocardiography machine was used for echocardiographic examination. Intra-cardiac flow images were analysed by a VFM workstation. Compared with the healthy group, the inactive SLE group had increased diastolic EL values (38.05 mW/m vs. 33.02 mW/m, p = 0.010). However, the systolic EL values were comparable between the inactive SLE group and the control group (26.07mW/m vs 23.15 mW/m, p = 0.105). The active SLE group exhibited significantly higher diastolic (104.13 mW/m vs 33.02 mW/m, p < 0.001) and systolic (48.83 mW/m vs 23.15 mW/m, p < 0.001) EL values than the control group. The most notable correlation was observed between the values of the diastolic EL and SLEDAI in the inactive SLE group (r = 0.633, p < 0.001) and in the active SLE group (r = 0.824, p < 0.001). LV-dissipative EL assessed by using VFM is useful and feasible for estimating lesions of LV systolic and diastolic function in active SLE patients with preserved left ventricular ejection fraction. Increased disease activity may lead to increased risk of LV dysfunction.

Evaluation of left ventricular function by vector flow mapping in females with systemic lupus erythematosus

OBJECTIVES

Compare the intraventricular hemodynamics of 60 females with systemic lupus erythematosus (SLE) and 61 healthy female controls, and determine cardiac function changes using vector flow mapping (VFM).

METHODS

To determine the effect of pulmonary artery pressure changes on left ventricular function, SLE patients were divided into a normal pulmonary artery pressure group (S1, n=24) and an elevated pulmonary artery pressure group (S2, n=36). The energy loss (EL) at each segment of the left ventricular chamber (total, basal, middle, and apical segments) during each period of the cardiac cycle (isovolumic contraction, rapid ejection, rapid filling, reduced filling, atrial contraction) was determined.

RESULTS

The S1 group had significantly more vortices than the control group during the rapid ejection, rapid filling, and atrial contraction periods (p<0.01), and the maximum vortex areas in the S1 and S2 groups were smaller than in the control group during rapid filling and atrial contraction periods (p<0.05). Compared with the control group, the S2 group had greater EL during the systole and diastole periods (p<0.01). EL in the S1 group was significantly greater than in the control group during systole (p<0.01). During the rapid filling period, the EL was positively correlated with septal E' (r=0.784, p<0.01), and during the atrial contraction period, EL was positively correlated with septal E/e' (r=0.812, p<0.01) and A (r=0.715, p<0.01).

CONCLUSION

VFM of patients with SLE can comprehensively, rapidly, and efficiently evaluate changes of myocardial mechanics and intracardiac hemodynamics and provide quantitative analysis of complex intracardiac blood flow. Key points • Vector flow mapping (VFM) is a new non-invasive ultrasound technique that evaluates changes of myocardial mechanics and intracardiac hemodynamics, and provides quantitative analysis of complex intracardiac blood flow. • This study showed that vortex and energy loss may provide more sensitive detection of cardiac dysfunction than conventional echocardiographic indexes in patients with systemic lupus erythematosus.

Assessment of left ventricular energy loss using vector flow mapping in patients with stages 1-3 chronic kidney disease

BACKGROUND

Patients with chronic kidney disease (CKD) experience abnormality of intracardiac blood flow status during early-stages of disease. Left ventricular energy loss (EL) derived from vector flow mapping (VFM) represents fluid energy lost as heat in left ventricle and had been used to detect intracardiac blood flow efficiency. We aimed to evaluate the left ventricular EL in stage 1-3 CKD patients, and explored whether hypertension, a main cardiovascular risk, deteriorate the abnormality of intracardiac blood flow status.

METHODS

Transthoracic echocardiography was performed in 41 controls and 48 patients with stages 1-3 CKD. CKD patients consisted a subgroup with no hypertension, a subgroup with well-controlled hypertension and a subgroup with poorly controlled hypertension. The EL were calculated in the left ventricle using VFM analysis from the apical 3-chamber view. Furthermore, the correlation and stepwise multiple regression analysis were used to explore the potential independent predictors of left ventricular EL.

RESULTS

Compared with controls, stage 1-3 CKD patients showed increased left ventricular EL during total diastole, late diastole, total systole, isovolumic contraction and ejection. CKD patients with poorly controlled hypertension had higher left ventricular EL compared to the other CKD subgroups. Additionally, the ratio of mitral early filling wave peak velocity and early mitral annular peak velocity on septal side, mitral early filling wave peak velocity, and left ventricular mass index were independent predictors of the diastolic EL; whereas systolic blood pressure and left ventricular mass index were independent predictors of the systolic EL.

CONCLUSIONS

Left ventricular EL was a useful echocardiographic parameter to evaluate the impaired intracardiac blood flow efficiency in patients with stages 1-3 CKD. Hypertension was a crucial contributor for intracardiac blood flow abnormality. This study might provide valuable clinical data to discern cardiac dysfunction and reduce the cardiovascular risk in early-stage CKD.

A Network-Based "Phenomics" Approach for Discovering Patient Subtypes From High-Throughput Cardiac Imaging Data

OBJECTIVES

The authors present a method that focuses on cohort matching algorithms for performing patient-to-patient comparisons along multiple echocardiographic parameters for predicting meaningful patient subgroups.

BACKGROUND

Recent efforts in collecting multiomics data open numerous opportunities for comprehensive integration of highly heterogenous data to classify a patient's cardiovascular state, eventually leading to tailored therapies.

METHODS

A total of 42 echocardiography features, including 2-dimensional and Doppler measurements, left ventricular (LV) and atrial speckle-tracking, and vector flow mapping data, were obtained in 297 patients. A similarity network was developed to delineate distinct patient phenotypes, and then neural network models were trained for discriminating the phenotypic presentations.

RESULTS

The patient similarity model identified 4 clusters (I to IV), with patients in each cluster showed distinctive clinical presentations based on American College of Cardiology/American Heart Association heart failure stage and the occurrence of short-term major adverse cardiac and cerebrovascular events. Compared with other clusters, cluster IV had a higher prevalence of stage C or D heart failure (78%; p < 0.001), New York Heart Association functional classes III or IV (61%; p < 0.001), and a higher incidence of major adverse cardiac and cerebrovascular events (p < 0.001). The neural network model showed robust prediction of patient clusters, with area under the receiver-operating characteristic curve ranging from 0.82 to 0.99 for the independent hold-out validation set.

CONCLUSIONS

Automated computational methods for phenotyping can be an effective strategy to fuse multidimensional parameters of LV structure and function. It can identify distinct cardiac phenogroups in terms of clinical characteristics, cardiac structure and function, hemodynamics, and outcomes.

Relationship between left ventricular isovolumic relaxation flow patterns and mitral inflow patterns studied by using vector flow mapping

The purpose of this study was to investigate the relationship between isovolumic relaxation flow (IRF) patterns in left ventricle (LV) and mitral inflow patterns. Color Doppler loops were acquired for vector flow mapping in apical long-axis view in 57 patients with coronary artery disease, 31 patients with dilated cardiomyopathy, and 58 healthy controls. IRF patterns were classified into three categories: pattern A, apically directed flow; pattern B, bidirectional flow with small scattered vortices; and pattern C, a large vortex. All normals and patients with normal LV filling (n = 10) showed pattern A. Patients with impaired relaxation consisted of 31 (66%) patients having pattern A, 11 (23%) having pattern B, and 5 (11%) having pattern C. Patients with pseudonormal filling included 4 (31%) patients having pattern A, 7 (54%) having pattern B, and 2 (15%) having pattern C. In patients with restrictive filling, 14 (78%) showed pattern C, 4 (22%) showed pattern B, and no patient showed pattern A. IRF patterns were associated with LV filling patterns (χ² = 52.026, p < 0.001). There are significant relationships between LV filling and IRF patterns. IRF patterns may provide an index for evaluation of LV diastolic function.

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.

Left ventricular energy loss and wall shear stress assessed by vector flow mapping in patients with hypertrophic cardiomyopathy

The aim of this study was to assess left ventricular (LV) summation of energy loss (EL-SUM), average energy loss (EL-AVE) and wall shear stress (WSS) using vector flow mapping (VFM) in patients with hypertrophic cardiomyopathy (HCM). Forty HCM patients, and 40 controls were evaluated by transthoracic echocardiography. Conventional echocardiographic parameters, summation and average of energy loss (EL-total, EL-base, EL-mid and EL-apex), and WSS in each segment were calculated at different phases. Compared with controls, conventional diastolic measurements were impaired in HCM patients. HCM patients also showed increased EL-SUM-total and EL-AVE-total at the peak of LV rapid ejection period as well as decreased EL-SUM-total and EL-AVE-total at the end of early diastole. In controls, EL-SUM and EL-AVE showed a gradual decrease from the basal segment to the apex, this regularity was not observed in HCM patients. Compared with controls, HCM patients showed increased WSS at the peak of the LV rapid ejection period and the atrial contraction period as well as decreased WSS at the end of early diastole (all p < 0.05). WSS was increased slightly at the peak of the LV rapid filling period in HCM patients (p = 0.055). EL and WSS values derived from VFM are novel flow dynamic parameters that can effectively evaluate systolic and diastolic hemodynamic function in HCM patients.

Flow dynamics and energy efficiency of flow in the left ventricle during myocardial infarction

Cardiovascular disease is a leading cause of death worldwide, where myocardial infarction (MI) is a major category. After infarction, the heart has difficulty providing sufficient energy for circulation, and thus, understanding the heart's energy efficiency is important. We induced MI in a porcine animal model via circumflex ligation and acquired multiple-slice cine magnetic resonance (MR) images in a longitudinal manner-before infarction, and 1 week (acute) and 4 weeks (chronic) after infarction. Computational fluid dynamic simulations were performed based on MR images to obtain detailed fluid dynamics and energy dynamics of the left ventricles. Results showed that energy efficiency flow through the heart decreased at the acute time point. Since the heart was observed to experience changes in heart rate, stroke volume and chamber size over the two post-infarction time points, simulations were performed to test the effect of each of the three parameters. Increasing heart rate and stroke volume were found to significantly decrease flow energy efficiency, but the effect of chamber size was inconsistent. Strong complex interplay was observed between the three parameters, necessitating the use of non-dimensional parameterization to characterize flow energy efficiency. The ratio of Reynolds to Strouhal number, which is a form of Womersley number, was found to be the most effective non-dimensional parameter to represent energy efficiency of flow in the heart. We believe that this non-dimensional number can be computed for clinical cases via ultrasound and hypothesize that it can serve as a biomarker for clinical evaluations.

Dissipative energy loss within the left ventricle detected by vector flow mapping in diabetic patients with controlled and uncontrolled blood glucose levels

Diabetes mellitus (DM) is related to increased risks of cardiovascular diseases, such as myocardial infarction, diabetic cardiomyopathy and secondary hypertension. Dissipative energy loss (EL) derived from vector flow mapping (VFM) is thought to reflect the efficiency of blood flow and has been deemed to be an index for the evaluation of left ventricular function. Our study aimed to investigate the value of dissipative EL in diabetic patients with controlled and uncontrolled blood glucose by VFM. Eighty-eight patients with DM and 58 age-matched healthy controls were recruited. All of the patients received echocardiography examinations. VFM analyses were executed to calculate the EL values according to the apical four-chamber examinations from the left ventricle (LV) view. Our results showed that diastolic EL was compromised in the controlled-blood glucose (59.19 mV/m vs. 32.68 mV/m, p = 0.039) patients and was more dramatically increased in the uncontrolled blood glucose group (88.84 mV/m vs. 32.68 mV/m, p < 0.001) compared with the healthy controls. The impairment of systolic EL was observed only in the uncontrolled blood glucose patients (39.65 mV/m vs. 20.29 mV/m, p < 0.001) and not in the controlled blood glucose patients (29.25 mV/m vs. 20.29 mV/m, p = 0.072). Multivariate backward stepwise linear regression analysis revealed that the HbA1c level was independently related to the diastolic EL (β = 0.233, p = 0.026) and systolic EL (β = 0.237, p = 0.023). VFM is feasible and reproducible for assessing LV dissipative EL in DM patients with normal LVEF values in whom diastolic EL may be a more vulnerable indicator of early LV cardiac dysfunction in patients with DM. However, LV systolic EL may be a sensitive indicator of preclinical LV dysfunction for patients with DM with uncontrolled blood glucose levels. Uncontrolled blood glucose, which is independently correlated with subclinical LV dysfunction, may lead to increases in systolic EL and diastolic EL in LV.

Effect of Electrical Stimulation on Blood Flow Velocity and Vessel Size

Interferential current electrical stimulation alters blood flow velocity and vessel size. We aimed to investigate the changes in the autonomic nervous system depending on electrical stimulation parameters. Forty-five healthy adult male and female subjects were studied. Bipolar adhesive pad electrodes were used to stimulate the autonomic nervous system at the thoracic vertebrae 1-4 levels for 20 min. Using Doppler ultrasonography, blood flow was measured to determine velocity and vessel size before, immediately after, and 30 min after electrical stimulation. Changes in blood flow velocity were significantly different immediately and 30 min after stimulation. The interaction between intervention periods and groups was significantly different between the exercise and pain stimulation groups immediately after stimulation (p<0.05). The vessel size was significantly different before and 30 min after stimulation (p<0.05). Imbalances in the sympathetic nervous system, which regulates balance throughout the body, may present with various symptoms. Therefore, in the clinical practice, the parameters of electrical stimulation should be selectively applied in accordance with various conditions and changes in form.

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.

Assessment of Left Ventricular Dissipative Energy Loss by Vector Flow Mapping in Patients With End-Stage Renal Disease

OBJECTIVES

Dissipative energy loss derived from vector flow mapping represents the viscous dissipation of turbulent blood flow. We aimed to determine the left ventricular (LV) energy loss in patients with end-stage renal disease (ESRD).

METHODS

Patients with ESRD and a preserved LV ejection fraction, who consisted of a group receiving peritoneal dialysis, a group receiving hemodialysis, and a group receiving preparation for dialysis initiation, were examined by echocardiography; a group of healthy control participants were examined as well. Vector flow mapping analysis was then performed from the apical 4-chamber view to calculate the energy loss during diastole and systole in the left ventricle.

RESULTS

Conventional transthoracic echocardiography and LV energy loss calculations were successfully performed in 63 cases and 50 controls. The patients with ESRD had significantly higher diastolic energy loss [median (interquartile range), 71.73 (46.08-106.75) versus 23.32 (17.17-29.26) mW/m; P < .001] and higher systolic energy loss [25.28 (19.03-33.93) versus 12.52 (9.35-16.47) mW/m; P < .001]. A significant difference in diastolic energy loss between the peritoneal dialysis and preparation groups was found [54.92 (39.28-89.94) versus 84.82 (62.58-171.4) mW/m; P = .04]. In patients with ESRD, the log-transformed diastolic energy loss had a significant association with the peak early diastolic transmitral flow velocity (P = .011), peak early diastolic transmitral flow velocity-to-peak early diastolic mitral annular flow velocity ratio (P = .001), LV mass index (P = .017), and heart rate (P = .003).

CONCLUSIONS

Impaired blood flow efficiency was detected in patients with ESRD by using dissipative energy loss derived from vector flow mapping. The energy loss value could be a novel parameter for evaluating the ventricular workload of uremic hearts in terms of fluid mechanics.

Intervendor Variabilities of Left and Right Ventricular Myocardial Velocities among Three Tissue Doppler Echocardiography Systems

BACKGROUND

Whether an intervendor discordance of myocardial velocities determined by tissue Doppler echocardiography (TDE) can be generalized remains unclear. We compared intervendor variabilities of left ventricular (LV) and right ventricular (RV) myocardial velocities among three TDE systems.

METHODS

Examinations with TDE were performed in 41 healthy subjects and 11 patients with cardiovascular risk factors (CVR) using α-7 (V1, Hitachi Aloka Medical), Artida (V2, Toshiba Medical Systems), and Vivid E9 (V3, GE Healthcare) on the same day. Peak systolic (s'), early diastolic (e'), and late diastolic (a') myocardial velocities at medial and lateral sites of the mitral annulus and lateral site of the tricuspid annulus were measured using both pulsed-wave TDE and color TDE. Intra-observer and inter-observer variabilities were determined in 10 subjects and test-retest variability in 14 subjects.

RESULTS

As for test-retest variability, reproducibilities of LV and RV myocardial velocities determined by pulsed-wave TDE and color TDE were relatively low but comparable between V1, V2, and V3. Myocardial velocities in healthy subjects determined by both pulsed-wave TDE and color TDE were significantly different among the three TDE systems. Myocardial velocities by pulsed-wave TDE in V3 were 2-12% lower (P < 0.05) than those by V2 and 5-14% lower (P < 0.05) than those by V1. Similar differences in myocardial velocities determined by both pulsed-wave TDE and color TDE were found in patients with CVR.

CONCLUSIONS

LV and RV myocardial velocities determined by both pulsed-wave TDE and color TDE are vendor dependent, and reproducibility of the myocardial velocities determined by both TDE systems is relatively low.