Prognostic value of energy loss index in asymptomatic aortic stenosis

4D flow MRI-derived energy loss and RV workload in adults with tetralogy of Fallot

PURPOSE

To assess flow energy loss (EL) pattern inside the pulmonary circulation in adult patients with repaired tetralogy of Fallot (TOF), particularly in TOF with pulmonary stenosis (PS) and pulmonary regurgitation (PR), as a cardiac workload parameter and its relationship to symptoms and major adverse cardiovascular events (MACE).

METHODS

Prospectively, 51 consecutive TOF adults after intracardiac repair, who underwent four-dimensional flow magnetic resonance imaging, were enrolled. All of them had significant PR (PR regurgitant fraction >25 %). TOF patients who had already reached the conventional criteria were excluded. We defined MACE as the following: 1) fatal arrhythmias, 2) sudden cardiac death, 3) surgical pulmonary valvular repair (PVR), 4) right heart failure (HF) needing diuretics and/or hospitalization within 2 years.

RESULTS

A total of 15 patients had MACE; 1) 10 patients underwent PVR within 2 years, 2) 2 patients had ventricular tachycardia, and 3) 6 patients developed right HF (overlapped). Right ventricular (RV) end diastolic volume index (EDVI), RV end systolic volume index (ESVI), average EL/cardiac output (CO), and diastolic EL/CO in patients with MACE were greater than ones without MACE. On a multivariate logistic analysis, the diastolic EL/CO ratio and RVEDVI had the highest odds with MACE in all TOF (odds ratio, 40.7 and 1.15. 95%CI, 1.83-905 and 1.02-13.0; p-value, 0.02 and 0.03). In sub-analysis within 29 patients with moderate PS with PR, and 10 patients with MACE showed higher diastolic EL/CO. Average and diastolic EL/CO negatively correlated with RV ejection fraction (EF) in this sub-analysis.

CONCLUSIONS

High EL, particularly, high diastolic EL/CO, were the important factors for MACE in adult TOF. Higher diastolic EL/CO was also related to lower RV EF and deteriorated RV function in adult TOF with PS and PR. Right-sided EL can be a sensitive marker of excessive cardiac workload which integrates both afterload and preload in adult patients with TOF, beyond the RV size.

Energy Loss Index and Dimensionless Index Outperform Direct Valve Planimetry in Low-Gradient Aortic Stenosis

Background/Objectives: Among patients with suspected severe aortic stenosis (AS), discordance between effective orifice area (EOA) and transvalvular gradients is frequent and requires a multiparametric workup including flow assessment and calcium-scoring to confirm true severe AS. The aim of this study was to assess direct planimetry, energy loss index (Eli) and dimensionless index (DI) as stand-alone parameters to identify non-severe AS in discordant cases. Methods: In this prospective cohort study, we included consecutive AS patients > 70 years with EOA < 1.0 cm2 referred for valve replacement between 2014 and 2017. AS severity was retrospectively reassessed using the multiparametric work-up recommended in the 2021 ESC/EACTS guidelines. DI and ELi were calculated, and valve area was measured by direct planimetry on transesophageal echocardiography. Results: A total of 101 patients (mean age 82 y; 57% male) were included. Discordance between EOA and gradients was observed in 46% and non-severe AS found in 24% despite an EOA < 1 cm2. Valve planimetry performed poorly, with an area under the ROC curve (AUC) of 0.64. At a cut-off value of >0.82 cm2, sensitivity and specificity to identify non-severe AS were 67 and 66%, respectively. DI and ELi showed a higher diagnostic accuracy, with an AUC of 0.77 and 0.76, respectively. Cut-off values of >0.24 and >0.6 cm2/m2 identified non-severe AS, with a high specificity of 79% and 91%, respectively. Conclusions: Almost one in four patients with EOA < 1 cm2 had non-severe AS according to guideline-recommended multiparametric assessment. Direct valve planimetry revealed poor diagnostic accuracy and should be interpreted with caution. Usual prognostic cut-off values for DI > 0.24 and ELI > 0.6 cm2/m2 identified non-severe AS with high specificity and should therefore be included in the assessment of low-gradient AS.

Biomechanical Evaluation of Aortic Valve Stenosis by Means of a Virtual Stress Test: A Fluid-Structure Interaction Study

The impact of aortic valve stenosis (AS) extends beyond the vicinity of the narrowed leaflets into the left ventricle (LV) and into the systemic vasculature because of highly unpredictable valve behavior and complex blood flow in the ascending aorta that can be attributed to the strong interaction between the narrowed cusps and the ejected blood. These effects can become exacerbated during exercise and may have implications for disease progression, accurate diagnosis, and timing of intervention. In this 3-D patient-specific study, we employ strongly coupled fluid-structure interaction (FSI) modeling to perform a comprehensive biomechanical evaluation of systolic ejection dynamics in a stenosed aortic valve (AV) during increasing LV contraction. Our model predictions reveal that the heterogeneous ∆P vs. Q relationship that was observed in our previous clinical study can be attributed to a non-linear increase (by ~ 1.5-fold) in aortic valve area as LV heart rate increases from 70 to 115 bpm. Furthermore, our results show that even for a moderately stenotic valve, increased LV contraction during exercise can lead to high-velocity flow turbulence (Re = 11,700) in the aorta similar to that encountered with a severely stenotic valve (Re ~ 10,000), with concomitant greater viscous loss (~3-fold increase) and elevated wall stress in the ascending aorta. Our FSI predictions also reveal that individual valve cusps undergo distinct and highly non-linear increases (>100%) in stress during exercise, potentially contributing to progressive calcification. Such quantitative biomechanical evaluations from realistic FSI workflows provide insights into disease progression and can be integrated with current stress testing for AS patients to comprehensively predict hemodynamics and valve function under both baseline and exercise conditions.

Effect of race on pressure recovery adjustment for prevention of aortic stenosis grading discordance

OBJECTIVE

We sought to evaluate the potential impact of racial difference (Asians vs Caucasians) on the clinical usefulness of pressure recovery (PR) adjustment for preventing discordant aortic stenosis (AS) grading in patients with severe AS.

METHODS

Data from 1450 patients (mean age, 70.2±10.6 years; 290 (20%) Caucasians; aortic valve area (AVA), 0.77±0.26 cm2) were retrospectively analysed. PR-adjusted AVA was calculated using a validated equation. Discordant grading of severe AS was defined as AVA of <1.0 cm2 and mean gradient of <40 mm Hg. The frequency of discordant grading was assessed in the overall cohort and the propensity score-matched cohort.

RESULTS

Before PR adjustment, 1186 patients showed AVA values of <1.0 cm2; after PR adjustment, 170 (14.3%) were reclassified as having moderate AS. PR adjustment decreased the frequency of discordant grading from 31.4% to 14.1% in Caucasians and from 13.8% to 7.9% in Asians. Patients with reclassification to moderate AS after PR adjustment had a significantly lower risk of a composite of aortic valve replacement or all-cause death than did those with severe AS after PR adjustment (HR 0.38; 95% CI 0.31-0.46; p<0.001). In propensity score-matched cohorts (173 pairs), the frequency of discordant grading before PR adjustment was 42.2% and 43.9% in the Caucasian and Asian patients, respectively, which decreased to 21.4% and 20.2%, respectively, after PR adjustment.

CONCLUSIONS

Clinically relevant PR occurred, regardless of race in patients with moderate to severe AS. Routine PR adjustment may be useful for reconciling discordant AS grading.

Functional interaction of aortic valve and ascending aorta in patients after valve-sparing procedures

Pressure recovery (PR) is essential part of the post stenotic fluid mechanics and depends on the ratio of EOA/AA, the effective aortic valve orifice area (EOA) and aortic cross-sectional area (AA). In patients with advanced ascending aortic aneurysm and mildly diseased aortic valves, the effect of AA on pressure recovery and corresponding functional aortic valve opening area (ELCO) was evaluated before and after valve-sparing surgery (Dacron graft implantation). 66 Patients with ascending aortic aneurysm (mean aortic diameter 57 +/- 10 mm) and aortic valve-sparing surgery (32 reimplantation technique (David), 34 remodeling technique (Yacoub)) were routinely investigated by Doppler echocardiography. Dacron graft with a diameter between 26 and 34 mm were implanted. EOA was significantly declined after surgery (3.4 +/- 0.8 vs. 2.6 +/- 0.9cm2; p < 0.001). Insertion of Dacron prosthesis resulted in a significant reduction of AA (26.7 +/- 10.2 vs. 6.8 +/- 1.1cm2; p < 0.001) with increased ratio of EOA/AA (0.14 +/- 0.05 vs. 0.40 +/- 0.1; p < 0.001) and pressure recovery index (PRI; 0.24 +/- 0.08 vs. 0.44 +/- 0.06; p < 0.0001). Despite reduction of EOA, ELCO (= EOA corrected for PR) increased from 4.0 +/- 1.1 to 5.0 +/- 3.1cm2 (p < 0.01) with reduction in transvalvular LV stroke work (1005 +/- 814 to 351 +/- 407 mmHg × ml, p < 0.001) after surgery. These effects were significantly better in patients with Yacoub technique than with the David operation. The hemodynamic findings demonstrate a valve-vessel interaction almost entirely caused by a marked reduction in the ascending AA with significant PR gain. The greater hemodynamic benefit of the Yacoub technique due to higher EOA values compared to the David technique was evident and may be of clinical relevance.

Machine learning prediction of progressive subclinical myocardial dysfunction in moderate aortic stenosis

Background

Moderate severity aortic stenosis (AS) is poorly understood, is associated with subclinical myocardial dysfunction, and can lead to adverse outcome rates that are comparable to severe AS. Factors associated with progressive myocardial dysfunction in moderate AS are not well described. Artificial neural networks (ANNs) can identify patterns, inform clinical risk, and identify features of importance in clinical datasets.

Methods

We conducted ANN analyses on longitudinal echocardiographic data collected from 66 individuals with moderate AS who underwent serial echocardiography at our institution. Image phenotyping involved left ventricular global longitudinal strain (GLS) and valve stenosis severity (including energetics) analysis. ANNs were constructed using two multilayer perceptron models. The first model was developed to predict change in GLS from baseline echocardiography alone and the second to predict change in GLS using data from baseline and serial echocardiography. ANNs used a single hidden layer architecture and a 70%:30% training/testing split.

Results

Over a median follow-up interval of 1.3 years, change in GLS (≤ or >median change) could be predicted with accuracy rates of 95% in training and 93% in testing using ANN with inputs from baseline echocardiogram data alone (AUC: 0.997). The four most important predictive baseline features (reported as normalized % importance relative to most important feature) were peak gradient (100%), energy loss (93%), GLS (80%), and DI < 0.25 (50%). When a further model was run including inputs from both baseline and serial echocardiography (AUC 0.844), the top four features of importance were change in dimensionless index between index and follow-up studies (100%), baseline peak gradient (79%), baseline energy loss (72%), and baseline GLS (63%).

Conclusions

Artificial neural networks can predict progressive subclinical myocardial dysfunction with high accuracy in moderate AS and identify features of importance. Key features associated with classifying progression in subclinical myocardial dysfunction included peak gradient, dimensionless index, GLS, and hydraulic load (energy loss), suggesting that these features should be closely evaluated and monitored in AS.

Energy loss index as a predictor of all-cause mortality after transcatheter aortic valve replacement: A long-term follow-up

BACKGROUND

As transcatheter aortic valve replacement (TAVR) procedures become more widely available, there is a growing need to monitor and evaluate postoperative outcomes accurately. The energy loss index (ELI) of the ascending aorta has been commonly used to examine the agreement between the echocardiographic and Gorlin measurement of the aortic valve area.

OBJECTIVES

This project aims to demonstrate a link between ELI values and mortality following implanted TAVR valves and determine an ELI cutoff value associated with post-TAVR events.

METHOD

We retrospectively reviewed patients undergoing TAVR from 2012 to 2017. We calculated ELI values for patients immediately postoperative after a TAVR procedure. Using Receiver-Operator Characteristic and Cox Regression analyses, we identified a cutoff value to distinguish between "High ELI" (≥ 1.34) and "Low ELI" (< 1.34) patients.

RESULTS

This study showed low ELI (hazard ratio, 2.30; 95% confidence interval 1.57-3.36, p < .001) as representative of patients with a high risk of mortality post-TAVR. Additionally, post-TAVR, ejection fraction increased by 3.6% (p < .001), and the aortic valve effective orifice area increased by 1.41 cm squared (p < .001) while the mean transvalvular gradient decreased by 32.8 mmHg (p < .001) and the peak transvalvular gradient decreased by 49.0 mmHg (p < .001).

CONCLUSION

ELI is an additional prognostic factor that should be considered during risk assessment before TAVR. This study shows that patients with Low ELI had decreased cumulative survival post-TAVR. These patients almost had a fivefold increased risk of death following TAVR.

Evaluation of aortic stenosis: From Bernoulli and Doppler to Navier-Stokes

Uni-dimensional Doppler echocardiography data provide the mainstay of quantative assessment of aortic stenosis, with the transvalvular pressure drop a key indicator of haemodynamic burden. Sophisticated methods of obtaining velocity data, combined with improved computational analysis, are facilitating increasingly robust and reproducible measurement. Imaging modalities which permit acquisition of three-dimensional blood velocity vector fields enable angle-independent valve interrogation and calculation of enhanced measures of the transvalvular pressure drop. This manuscript clarifies the fundamental principles of physics that underpin the evaluation of aortic stenosis and explores modern techniques that may provide more accurate means to grade aortic stenosis and inform appropriate management.

Impact of pressure recovery on the assessment of pulmonary homograft function using Doppler ultrasound

Relevant pressure recovery (PR) has been shown to increase functional stenotic aortic valve orifice area and reduce left ventricular load. However, little is known about the relevance of PR in the pulmonary artery. The study examined the impact of PR using 2D-echocardiography in the pulmonary artery distal to the degenerated homograft in patients after Ross surgery. Ninety-two patients with pulmonary homograft were investigated by Doppler echocardiography (mean time interval after surgery 31 ± 26 months). PR was measured as a function of pulmonary artery diameter determined by computed tomography angiography. Homograft orifice area, valve resistance, and transvalvular stroke work were calculated with and without considering PR. PR decreased as the pulmonary artery diameter increased (r = -0.69, p < 0.001). Mean PR was 41.5 ± 7.1% of the Doppler-derived pressure gradient (Pmax ), which resulted in a markedly increased homograft orifice area (energy loss coefficient index [ELCOI] vs. effective orifice area index [EOAI], 1.3 ± 0.4 cm2 /m2 vs. 0.9 ± 0.4 cm2 /m2 , p < 0.001). PR significantly reduced homograft resistance and transvalvular stroke work (822 ± 433 vs. 349 ± 220 mmHg × ml, p < 0.0001). When PR was considered, the correlations of the parameters used were significantly better, and 11 of 18 patients (61%) in the group with severe homograft stenosis (EOAI <0.6 cm2 /m2 ) could be reclassified as moderate stenosis. Our results showed that the Doppler measurements overestimated the degree of homograft stenosis and thus the right ventricular load, when PR was neglected in the pulmonary artery. Therefore, Doppler measurements that ignore PR can misclassify homograft stenosis and may lead to premature surgery.

Prognosis in asymptomatic patients with discordantly graded aortic valve stenosis based on pressure recovery adjusted valve area

OBJECTIVE

We hypothesised that patients with asymptomatic aortic stenosis (AS) who remain with discordantly graded aortic valve stenosis (DGAS) after adjustment for pressure recovery in the aortic root represents a subgroup of patients with increased cardiovascular risk.

METHODS

Data from 1353 patients with asymptomatic mild-moderate AS and preserved left ventricular ejection fraction enrolled in the Simvastatin and Ezetimibe in AS study was used. DGAS was identified as combined pressure adjusted valve area (energy loss) <1.0 cm² and mean aortic gradient<40 mm Hg (DGASEL). Outcome was assessed in Cox regression analysis and reported as HR and 95% CI.

RESULTS

DGASEL was found in 196 (14.5%) patients at baseline, and was associated with older age, female sex, smaller aortic annulus diameter, lower heart rate, more extensive valve calcification and low flow (all p<0.05). In Cox regression analysis, DGASEL was associated with higher rate of heart failure (HF) hospitalisation (HR 3.31 (95% CI 1.54 to 7.09)), cardiovascular death (HR 2.63 (95% CI 1.34 to 5.17)) and all-cause mortality (HR 1.73 (95% CI 1.04 to 2.87)) independent of confounders including low flow and aortic valve calcification (all p<0.05).

CONCLUSIONS

Patients with asymptomatic AS who remain with discordant grading after adjustment for pressure recovery have increased risk for HF and death.

TRIAL REGISTRATION NUMBER

NCT00092677.

Grading of Aortic Stenosis: Is it More Complicated in Women?

Aortic stenosis (AS) is the most common valvular heart disease and the main indication for valvular replacement in older women. Correct AS grading is mandatory for an adequate selection of patients for both surgical and transcatheter aortic valve replacement. Women and men have different AS severity grades at the same level of aortic valve calcification. Moreover, besides having smaller cardiac volumes, left ventricular outflow tract and aortic size, women have a specific pattern of left ventricular structural and functional remodelling in response to the AS-related chronic pressure overload. Here, the sex-specific cardiac changes in AS that make AS grading more challenging in women, with consequences for the management and outcome of this group of patients, are reviewed.

The role of 4-dimensional flow in the assessment of bicuspid aortic valve and its valvulo-aortopathies

Bicuspid aortic valve is the most common congenital cardiac malformation and the leading cause of aortopathy and aortic stenosis in younger patients. Aortic wall remodelling secondary to altered haemodynamic flow patterns, changes in peak velocity, and wall shear stress may be implicated in the development of aortopathy in the presence of bicuspid aortic valve and dysfunction. Assessment of these parameters as potential predictors of disease severity and progression is thus desirable. The anatomic and functional information acquired from 4D flow MRI can allow simultaneous visualisation and quantification of the pathological geometric and haemodynamic changes of the aorta. We review the current clinical utility of haemodynamic quantities including velocity, wall sheer stress and energy losses, as well as visual descriptors such as vorticity and helicity, and flow direction in assessing the aortic valve and associated aortopathies.

A soft robotic sleeve mimicking the haemodynamics and biomechanics of left ventricular pressure overload and aortic stenosis

Preclinical models of aortic stenosis can induce left ventricular pressure overload and coarsely control the severity of aortic constriction. However, they do not recapitulate the haemodynamics and flow patterns associated with the disease. Here we report the development of a customizable soft robotic aortic sleeve that can mimic the haemodynamics and biomechanics of aortic stenosis. By allowing for the adjustment of actuation patterns and blood-flow dynamics, the robotic sleeve recapitulates clinically relevant haemodynamics in a porcine model of aortic stenosis, as we show via in vivo echocardiography and catheterization studies, and a combination of in vitro and computational analyses. Using in vivo and in vitro magnetic resonance imaging, we also quantified the four-dimensional blood-flow velocity profiles associated with the disease and with bicommissural and unicommissural defects re-created by the robotic sleeve. The design of the sleeve, which can be adjusted on the basis of computed tomography data, allows for the design of patient-specific devices that may guide clinical decisions and improve the management and treatment of patients with aortic stenosis.

Prosthesis-patient mismatch after transcatheter aortic valve implantation

Prosthesis-patient mismatch (PPM), first described in 1978, occurs when a prosthetic valve functions normally, but has an effective orifice area that is too small relative to the patient's body surface area. It results in residual left ventricular afterload and higher transvalvular pressure gradient, which has been considered to impair prognosis. PPM following surgical aortic replacement is reportedly associated with worse clinical outcomes, such as high mortality. However, the impact of PPM on clinical outcomes after transcatheter aortic valve implantation (TAVI) remains unclear. There is conflicting evidence on the impact of PPM following TAVI due to differences across studies in terms of follow-up period, methods, patient populations, and type of bioprosthetic valve. The present review summarizes the most recent evidence on PPM after TAVI.

Aortic Viscous Energy Loss for Assessment of Valve-related Hemodynamics in Asymptomatic Severe Aortic Stenosis

Purpose

To investigate whether functional assessment of aberrant flow patterns by viscous energy loss (E′L ) using four-dimensional (4D) flow MRI could determine aortic stenosis (AS) severity in accordance with transvalvular energy loss and aid in surgical decision-making in asymptomatic patients with severe AS.

Materials and Methods

In this prospective, single-center study, E′L was measured in the thoracic aorta of 74 consecutive asymptomatic patients with severe AS and preserved left ventricular ejection fraction who presented between January 2015 and December 2017, and 23 healthy volunteers using 4D flow MRI. Transvalvular energy loss was assessed based on the energy loss index (ELI) measured using Doppler echocardiography. The association between E′L and AS-related events including aortic valve replacement was evaluated by receiver operating characteristic curve analysis, Kaplan-Meier analysis, and multivariable Cox regression analysis.

Results

Among 74 asymptomatic patients with severe AS (mean age, 60 years ± 9 [SD]; 43 men; 56 with bicuspid aortic valve), 33 experienced AS-related events during a median follow-up of 42 months (IQR, 30–53 months). Altered flow patterns in severe AS resulted in a sevenfold increase in peak systolic E′L in the ascending aorta compared with controls (13.9 mW ± 3.4 vs 1.80 mW ± 0.44; P < .001). Peak systolic E′L in the ascending aorta was independently associated with the ELI (standardized β, −0.52; P < .001) and showed better discrimination for AS-related events (area under the curve, 0.83; 95% CI: 0.74, 0.93; P < .001) than conventional echocardiographic parameters. After adjustment for confounding variables, peak systolic E′L in the ascending aorta was associated with a significant increase in AS-related events (P < .001 for adjusted hazard ratio).

Conclusion

Changes in AS-mediated poststenotic three-dimensional outflow patterns can be quantified by 4D flow MRI-derived energetic markers to aid in the risk stratification and clinical management of asymptomatic patients with severe AS.

Keywords: Aortic Stenosis, 4D Flow MRI, Flow Energetics, Vascular, Aorta, Aortic Valve, MR Angiography

Supplemental material is available for this article.

© RSNA, 2022

Component quantification of aortic blood flow energy loss using computational fluid-structure interaction hemodynamics

BACKGROUND AND OBJECTIVES

The aorta serves as the main tube of the human blood circulation system. Energy loss (EL) occurs when blood flows through the aorta and there may be a potential correlation between EL and aortic diseases. However, the components of blood flow EL are still not fully understood. This study aims to quantitatively reveal the EL components in healthy and diseased aortas.

METHODS

We construct an idealized healthy aorta and three idealized representative diseased aortas: aortic aneurysm, coarctation of the aorta, and aortic dissection. Computational hemodynamic studies are carried out by using the fluid-structure interaction simulation framework.

RESULTS

Four kinds of EL components: viscous friction, turbulence dissipation, wall deformation, and local lesion are firstly acquired in healthy and diseased aortas based on the high-resolution blood flow information. Viscous friction contributes most to the EL (45.69%-57.22%). EL caused by the deformation of the aortic wall ranks second (15.18%-33.12%). The proportions of turbulence dissipation and local lesion depend on individual geometric characteristics. Besides, the buffering efficiency of the healthy and diseased aorta is about 80%.

CONCLUSIONS

This study quantitatively reports the components of blood flow EL in healthy and diseased aortas, the finding may provide novel insights into the pathogenesis of aortic diseases.

New Evidence About Aortic Valve Stenosis and Cardiovascular Hemodynamics

Aortic stenosis (AS) is the most common degenerative valvular disease in western word. In patients with severe AS, small changes in aortic valve area can lead to large changes in hemodynamics. The correct understanding of cardiac hemodynamics and its interaction with vascular function is of paramount importance for correct identification of severe AS and to plan effective strategies for its treatment. In the current review with highlight the importance of pressure recovery phenomenon and valvular arterial impedance as novel tools in the evaluation of patients with aortic stenosis.

Predicting outcomes in patients with aortic stenosis using machine learning: the Aortic Stenosis Risk (ASteRisk) score

OBJECTIVE

To use echocardiographic and clinical features to develop an explainable clinical risk prediction model in patients with aortic stenosis (AS), including those with low-gradient AS (LGAS), using machine learning (ML).

METHODS

In 1130 patients with moderate or severe AS, we used bootstrap lasso regression (BLR), an ML method, to identify echocardiographic and clinical features important for predicting the combined outcome of all-cause mortality or aortic valve replacement (AVR) within 5 years after the initial echocardiogram. A separate hold out set, from a different centre (n=540), was used to test the generality of the model. We also evaluated model performance with respect to each outcome separately and in different subgroups, including patients with LGAS.

RESULTS

Out of 69 available variables, 26 features were identified as predictive by BLR and expert knowledge was used to further reduce this set to 9 easily available and input features without loss of efficacy. A ridge logistic regression model constructed using these features had an area under the receiver operating characteristic curve (AUC) of 0.74 for the combined outcome of mortality/AVR. The model reliably identified patients at high risk of death in years 2-5 (HRs ≥2.0, upper vs other quartiles, for years 2-5, p<0.05, p=not significant in year 1) and was also predictive in the cohort with LGAS (n=383, HRs≥3.3, p<0.05). The model performed similarly well in the independent hold out set (AUC 0.78, HR ≥2.5 in years 1-5, p<0.05).

CONCLUSION

In two separate longitudinal databases, ML identified prognostic features and produced an algorithm that predicts outcome for up to 5 years of follow-up in patients with AS, including patients with LGAS. Our algorithm, the Aortic Stenosis Risk (ASteRisk) score, is available online for public use.

Technical Background for 4D Flow MR Imaging

Recently, the hemodynamic assessments with 3D cine phase-contrast (PC) MRI (4D flow MRI) have attracted considerable attention from clinicians. Unlike 2D cine PC MRI, the technique allows for cardiac phase-resolved data acquisitions of flow velocity vectors within the entire FOV during a clinically viable period. Thus, the method has enabled retrospective flowmetry in the spatial and temporal axes, which are essential to derive hemodynamic parameters related to vascular homeostasis and those to the progression of the pathologies. Accelerations in imaging are critical for this technology to be clinically viable; however, a high SNR or velocity-to-noise ratio (VNR) is also vital for accurate flow measurements. In this chapter, the technologies enabling this difficult balance are discussed.

Hemodynamic Parameters for Cardiovascular System in 4D Flow MRI: Mathematical Definition and Clinical Applications

Blood flow imaging becomes an emerging trend in cardiology with the recent progress in computer technology. It not only visualizes colorful flow velocity streamlines but also quantifies the mechanical stress on cardiovascular structures; thus, it can provide the detailed inspections of the pathophysiology of diseases and predict the prognosis of cardiovascular functions. Clinical applications include the comprehensive assessment of hemodynamics and cardiac functions in echocardiography vector flow mapping (VFM), 4D flow MRI, and surgical planning as a simulation medicine in computational fluid dynamics (CFD).For evaluation of the hemodynamics, novel mathematically derived parameters obtained using measured velocity distributions are essential. Among them, the traditional and typical parameters are wall shear stress (WSS) and its related parameters. These parameters indicate the mechanical damages to endothelial cells, resulting in degenerative intimal change in vascular diseases. Apart from WSS, there are abundant parameters that describe the strength of the vortical and/or helical flow patterns. For instance, vorticity, enstrophy, and circulation indicate the rotating flow strength or power of 2D vortical flows. In addition, helicity, which is defined as the cross-linking number of the vortex filaments, indicates the 3D helical flow strength and adequately describes the turbulent flow in the aortic root in cases with complicated anatomies. For the description of turbulence caused by the diseased flow, there exist two types of parameters based on completely different concepts, namely: energy loss (EL) and turbulent kinetic energy (TKE). EL is the dissipated energy with blood viscosity and evaluates the cardiac workload related to the prognosis of heart failure. TKE describes the fluctuation in kinetic energy during turbulence, which describes the severity of the diseases that cause jet flow. These parameters are based on intuitive and clear physiological concepts, and are suitable for in vivo flow measurements using inner velocity profiles.

Impact of calcific aortic valve disease on valve mechanics

The aortic valve is a highly dynamic structure characterized by a transvalvular flow that is unsteady, pulsatile, and characterized by episodes of forward and reverse flow patterns. Calcific aortic valve disease (CAVD) resulting in compromised valve function and increased pressure overload on the ventricle potentially leading to heart failure if untreated, is the most predominant valve disease. CAVD is a multi-factorial disease involving molecular, tissue and mechanical interactions. In this review, we aim at recapitulating the biomechanical loads on the aortic valve, summarizing the current and most recent research in the field in vitro, in-silico, and in vivo, and offering a clinical perspective on current strategies adopted to mitigate or approach CAVD.

Low myocardial energetic efficiency is associated with increased mortality in aortic stenosis

Objectives

In hypertension, low myocardial energetic efficiency (MEEi) has been documented as an integrated marker of metabolic and left ventricular (LV) myocardial dysfunction. We tested the predictive performance of MEEi in initially asymptomatic aortic stenosis (AS) patients free from diabetes and known cardiovascular disease.

Methods

Data from 1703 patients with mostly moderate AS enrolled in the Simvastatin and Ezetimibe in Aortic Stenosis study followed for 4.3 years was used. MEE was calculated from Doppler stroke volume/([heart rate/60]) and indexed to LV mass (MEEi). The threshold value for MEEi associated with increased mortality was identified in generalised additive model with smoothing splines. Covariables of MEEi were identified in logistic regression analysis. Outcome was assessed in Cox regression analysis and reported as HR and 95% CI.

Results

MEEi <0.34 mL/s per gram was associated with increased cardiovascular mortality (n=80) (HR 2.53 (95% CI 1.50 to 4.28)) and all-cause mortality (n=155) (HR 1.74 (95% CI 1.20 to 2.52)) (both p<0.01). The association was independent of confounders of low MEEI (<0.34 mL/s per gram) identified in multivariable logistic regression analysis, including more severe AS, higher body mass index, lower LV midwall shortening and ejection fraction and presence of hypertension. Comparison of the Cox models with and without MEEi among the covariables demonstrated that MEEi significantly improved the prognostic yield (both p<0.01).

Conclusions

In patients with initially asymptomatic AS, low MEEi was associated with clustering of cardiometabolic risk factors, lower LV myocardial function and subsequent increased mortality during 4.3 years follow-up, independent of known prognosticators.

Trial registration number

NCT00092677.

Blood flow dynamics with four-dimensional flow cardiovascular magnetic resonance in patients with aortic stenosis before and after transcatheter aortic valve replacement

BACKGROUND

Pre- and post-procedural hemodynamic changes which could affect adverse outcomes in aortic stenosis (AS) patients who undergo transcatheter aortic valve replacement (TAVR) have not been well investigated. Four-dimensional (4D) flow cardiovascular magnetic resonance (CMR) enables accurate analysis of blood flow dynamics such as flow velocity, flow pattern, wall shear stress (WSS), and energy loss (EL). We sought to examine the changes in blood flow dynamics of patients with severe AS who underwent TAVR.

METHODS

We examined 32 consecutive severe AS patients who underwent TAVR between May 2018 and June 2019 (17 men, 82 ± 5 years, median left ventricular ejection fraction 61%, 6 self-expanding valve), after excluding those without CMR because of a contraindication or inadequate imaging from the analyses. We analyzed blood flow patterns, WSS and EL in the ascending aorta (AAo), and those changes before and after TAVR using 4D flow CMR.

RESULTS

After TAVR, semi-quantified helical flow in the AAo was significantly decreased (1.4 ± 0.6 vs. 1.9 ± 0.8, P = 0.002), whereas vortical flow and eccentricity showed no significant changes. WSS along the ascending aortic circumference was significantly decreased in the left (P = 0.038) and left anterior (P = 0.033) wall at the basal level, right posterior (P = 0.011) and left (P = 0.010) wall at the middle level, and right (P = 0.012), left posterior (P = 0.019) and left anterior (P = 0.028) wall at the upper level. EL in the AAo was significantly decreased (15.6 [10.8-25.1 vs. 25.8 [18.6-36.2]] mW, P = 0.012). Furthermore, a significant negative correlation was observed between EL and effective orifice area index after TAVR (r = - 0.38, P = 0.034).

CONCLUSIONS

In severe AS patients undergoing TAVR, 4D flow CMR demonstrates that TAVR improves blood flow dynamics, especially when a larger effective orifice area index is obtained.

Cardiac hypertrophic risk markers of left ventricle and left atrium in chronic heart failure due to aortic and mitral valve disease

BACKGROUND

Chronic valvular heart disease leads to systolic dysfunction and left atrial enlargement that ultimately results in heart failure.

PURPOSE

To investigate prognostic importance of Echocardiography and plasma natriuretic peptide levels that increase as a compensatory response and can be used as predictive markers for cardiac hypertrophy.

MATERIAL AND METHODS

The patients were divided into three groups: 51 with left ventricle hypertrophy due to aortic valve disease; 126 with left atrial enlargement due to mitral valve dysfunction; and 76 with both conditions. Atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) plasma levels were measured in all three respective groups showing dilated cardiomyopathy.

RESULTS

The mean left ventricular end-diastolic dimension at 64.3 ± 1.6 mm (P < 0.00) and left atrial dimension at 58.3 ± 3.7 mm (P < 0.00) were significantly high. However, patients with both conditions showed significantly high values for left ventricular end-diastolic dimension (63.3 ± 3 mm, P < 0.00) and left atrial dimension (54.9 ± 4 mm, P < 0.00) when compared with controls. A significant positive correlation was found between plasma natriuretic peptides levels and dilated cardiomyopathy. The mean values of ANP were 173 ± 46.6 pg/mL (P < 0.00), 140.4 ± 42.4 pg/mL (P < 0.00), and 295.1 ± 67.5 pg/mL (P < 0.00), significantly high in all three respective disease groups. The levels of BNP were also significantly high at 189 ± 44.5 pg/mL (P < 0.00), 166.6 ± 36.6 pg/mL (P < 0.00), and 323 ± 69.1 pg/mL (P < 0.00) in the disease groups with left ventricular hypertrophy, left atrial enlargement, and the disease group showing both characteristics, respectively.

CONCLUSION

Significant positive associations were found between left ventricle hypertrophy and left atrial enlargement with ANP and BNP.

Echocardiographic assessment of aortic stenosis: a practical guideline from the British Society of Echocardiography

The guideline provides a practical step-by-step guide in order to facilitate high-quality echocardiographic studies of patients with aortic stenosis. In addition, it addresses commonly encountered yet challenging clinical scenarios and covers the use of advanced echocardiographic techniques, including TOE and Dobutamine stress echocardiography in the assessment of aortic stenosis.

Multimodality Imaging for Discordant Low-Gradient Aortic Stenosis: Assessing the Valve and the Myocardium

Aortic stenosis (AS) is a disease of the valve and the myocardium. A correct assessment of the valve disease severity is key to define the need for aortic valve replacement (AVR), but a better understanding of the myocardial consequences of the increased afterload is paramount to optimize the timing of the intervention. Transthoracic echocardiography remains the cornerstone of AS assessment, as it is universally available, and it allows a comprehensive structural and hemodynamic evaluation of both the aortic valve and the rest of the heart. However, it may not be sufficient as a significant proportion of patients with severe AS presents with discordant grading (i.e., an AVA ≤ 1 cm² and a mean gradient <40 mmHg) which raises uncertainty about the true severity of AS and the need for AVR. Several imaging modalities (transesophageal or stress echocardiography, computed tomography, cardiovascular magnetic resonance, positron emission tomography) exist that allow a detailed assessment of the stenotic aortic valve and the myocardial remodeling response. This review aims to provide an updated overview of these multimodality imaging techniques and seeks to highlight a practical approach to help clinical decision making in the challenging group of patients with discordant low-gradient AS.

Non-invasive determination of pressure recovery by cardiac MRI and echocardiography in patients with severe aortic stenosis: short and long-term outcome prediction

OBJECTIVE

To assess the influence of pressure recovery (PR)-corrected haemodynamic parameters on outcome in patients with aortic stenosis.

METHODS

Aortic stenosis severity parameters were corrected for PR (increase in static pressure due to decreasing dynamic pressure), assessed using transthoracic echocardiography (TTE) or cardiac magnetic resonance imaging (CMR), in patients with aortic stenosis. PR, indexed PR (iPR) and energy loss index (ELI) were determined. Factors that predicted all-cause mortality, and 9-month or 10-year New York Heart Association classification ≥2 were assessed using Cox proportional hazards regression.

RESULTS

A total of 25 patients, aged 68 ± 10 years, were included. PR was 17 ± 6 mmHg using CMR, and CMR correlated with TTE measurements. PR correction using CMR data reduced the AS-severity classification in 12-20% of patients, and correction using TTE data reduced the AS-severity classification in 16% of patients. Age (Wald 4.774) was a statistically significant predictor of all-cause mortality; effective orifice area (Wald 3.753) and ELI (Wald 3.772) almost reached significance.

CONCLUSIONS

PR determination may result in significant reclassification of aortic stenosis severity and may hold value in predicting all-cause mortality.

Evaluation of the Left Ventricular Hemodynamic Status of Double-Root Translocation Patients Through Vector Flow Mapping

The double-root translocation (DRT) procedure is considered as a new choice for surgical management of complex congenital heart disease. Our study aims to investigate the left ventricular hemodynamic status after DRT by energy loss (EL), involving 42 patients who underwent DRT as well as 42 healthy volunteers as controls. The EL of left ventricle (LV) during different periods (rapid filling-RF, atrial contraction-AC, isovolumic contraction-IVC, rapid ejection-RE) of the same cardiac cycle were obtained and analyzed. Compared to the controls, global LV and apical three chamber-EL at AC and IVC periods in DRT group were higher (p < 0.05), and EL at RE period of DRT group was moderately lower. In the correlation analysis, the global EL at the RF was correlated with E wave (r = 0.47, p = 0.03), E/e' (r = 0.50, p = 0.02), BSA (r = - 0.54, p = 0.01), and age (r = - 0.67, p < 0.001). AC and RE- global EL were significantly correlated with E/e' (r = 0.49, r = 0.59, p < 0.05). There was a strong positive correlation between E/e' and global EL at the IVC (r = 0.62, p = 0.003) and a moderate negative correlation with age (r = - 0.44, p = 0.04). The present study confirms that EL is a feasible and reproducible indicator for quantitatively evaluating LV hemodynamic status in patients who underwent DRT and reveals that DRT can lead to approximatively normal long-term hemodynamic performance of LV.

4D flow imaging of the thoracic aorta: is there an added clinical value?

Four-dimensional (4D) flow MRI has emerged as a powerful non-invasive technique in cardiovascular imaging, enabling to analyse in vivo complex flow dynamics models by quantifying flow parameters and derived features. Deep knowledge of aortic flow dynamics is fundamental to better understand how abnormal flow patterns may promote or worsen vascular diseases. In the perspective of an increasingly personalized and preventive medicine, growing interest is focused on identifying those quantitative functional features which are early predictive markers of pathological evolution. The thoracic aorta and its spectrum of diseases, as the first area of application and development of 4D flow MRI and supported by an extensive experimental validation, represents the ideal model to introduce this technique into daily clinical practice. The purpose of this review is to describe the impact of 4D flow MRI in the assessment of the thoracic aorta and its most common affecting diseases, providing an overview of the actual clinical applications and describing the potential role of derived advanced hemodynamic measures in tailoring follow-up and treatment.

The change in the mitral-septal angle after surgery for atrial functional mitral regurgitation

OBJECTIVE

The optimal surgical strategy for atrial functional mitral regurgitation remains uncertain. Preoperative mitral-septal angle ≤ 70° has been reported as a risk factor for an abnormal vortex pattern in mitral valve repair. This study aimed to elucidate the change in the mitral-septal angle after surgery for atrial functional mitral regurgitation and its effect on the mid-term outcomes.

METHODS

Forty patients underwent mitral valve repair for atrial functional mitral regurgitation. The mitral-septal angle was defined as the angle between the mitral annulus and the anteroseptal wall of the left ventricular mid-portion in the parasternal long-axis view on transthoracic echocardiography. All patients underwent mitral ring annuloplasty. Left atrial plication was performed in nine patients. The mean clinical follow-up period was 42 ± 24 months.

RESULTS

The ratio of left atrial volume to left ventricular end-systolic volume was negatively correlated with the preoperative mitral-septal angle. The postoperative mitral-septal angles were significantly smaller than the preoperative ones. The mitral-septal angle decreased with a decrease in the mitral annuloplasty ring size. Patients who underwent left atrial plication tended to show an increase in the mitral-septal angle postoperatively. There were no significant differences in mid-term morbidities, including heart failure, requiring re-hospitalization and mortalities between patients with postoperative MSA > 70° and those with postoperative MSA ≤ 70°.

CONCLUSIONS

Mitral ring annuloplasty negatively changed the mitral-septal angle, while left atrial plication may induce a positive change to the mitral-septal angle. An association between the mitral-septal angle and mid-term outcomes was not revealed in this study.

Multimodality imaging derived energy loss index and outcome after transcatheter aortic valve replacement

Aims 

To assess whether the combination of transthoracic echocardiography (TTE) and multidetector computed tomography (MDCT) data affects the grading of aortic stenosis (AS) severity under consideration of the energy loss index (ELI) in patients undergoing transcatheter aortic valve replacement (TAVR).

Methods and results 

Multimodality imaging was performed in 197 patients with symptomatic severe AS undergoing TAVR at the University Hospital Zurich, Switzerland. Fusion aortic valve area index (fusion AVAi) assessed by integrating MDCT derived planimetric left ventricular outflow tract area into the continuity equation was significantly larger as compared to conventional AVAi (0.41 ± 0.1 vs. 0.51 ± 0.1 cm2/m2; P &lt; 0.01). A total of 62 patients (31.4%) were reclassified from severe to moderate AS with fusion AVAi being &gt;0.6 cm2/m2. ELI was obtained for conventional AVAi and fusion AVAi based on sinotubular junction area determined by TTE (ELILTL 0.47 ± 0.1 cm2/m2; fusion ELILTL 0.60 ± 0.1 cm2/m2) and MDCT (ELIMDCT 0.48 ± 0.1 cm2/m2; fusion ELIMDCT 0.61 ± 0.05 cm2/m2). When ELI was calculated with fusion AVAi the effective orifice area was &gt;0.6 cm2/m2 in 85 patients (43.1%). Survival rate 3 years after TAVR was higher in patients reclassified to moderate AS according to multimodality imaging derived ELI (78.8% vs. 67%; P = 0.01).

Conclusion 

Multimodality imaging derived ELI reclassifies AS severity in 43% undergoing TAVR and predicts mid-term outcome.

Personalized Perioperative Multi-scale, Multi-physics Heart Simulation of Double Outlet Right Ventricle

For treatment of complex congenital heart disease, computer simulation using a three-dimensional heart model may help to improve outcomes by enabling detailed preoperative evaluations. However, no highly integrated model that accurately reproduces a patient's pathophysiology, which is required for this simulation has been reported. We modelled a case of complex congenital heart disease, double outlet right ventricle with ventricular septal defect and atrial septal defect. From preoperative computed tomography images, finite element meshes of the heart and torso were created, and cell model of cardiac electrophysiology and sarcomere dynamics was implemented. The parameter values of the heart model were adjusted to reproduce the patient's electrocardiogram and haemodynamics recorded preoperatively. Two options of in silico surgery were performed using this heart model, and the resulting changes in performance were examined. Preoperative and postoperative simulations showed good agreement with clinical records including haemodynamics and measured oxyhaemoglobin saturations. The use of a detailed sarcomere model also enabled comparison of energetic efficiency between the two surgical options. A novel in silico model of congenital heart disease that integrates molecular models of cardiac function successfully reproduces the observed pathophysiology. The simulation of postoperative state by in silico surgeries can help guide clinical decision-making.

Clinical significance of energy loss index in patients with low-gradient severe aortic stenosis and preserved ejection fraction

Aims 

We hypothesized that among patients with low-gradient severe aortic stenosis (AS) and preserved left ventricular ejection fraction (LVEF), reclassification of AS severity as moderate by pressure recovery adjusted indexed aortic valve area (AVAi) = energy loss index (ELI), may identify a subgroup of patients with a better outcome.

Methods and results 

Three hundred and seventy-nine patients with low-gradient AS (defined by AVAi ≤ 0.6 cm2/m2 and mean aortic pressure gradient &lt; 40 mmHg) and preserved LVEF ≥50% were studied. Reclassification as moderate AS by ELI was defined as AVAi ≤0.6 cm2/m2 but with an ELI &gt;0.6 cm2/m2. Cardiac events [cardiac mortality and/or need for aortic valve replacement (AVR)] during follow-up were studied. One hundred and forty-eight patients (39%) were reclassified as moderate AS by ELI. Reclassification as moderate AS was independently associated with decreased body surface area, normal flow status, decreased left ventricular mass index, and left atrial volume index (all P &lt; 0.05). After adjustment for variables of prognostic interest, reclassification as moderate AS by ELI was associated with a considerable reduction of risk of cardiac events {adjusted hazard ratio (HR) 0.49 [95% confidence interval (CI) 0.33–0.72]; P &lt; 0.001}, need for AVR [adjusted HR 0.52 (95% CI 0.34–0.81); P = 0.004], and cardiac mortality [adjusted HR 0.46 (95% CI 0.22–0.98); P = 0.044].

Conclusion 

In patients with low-gradient severe AS and preserved LVEF, calculation of ELI permits to reclassify almost 40% of patients as having moderate AS. These reclassified patients have a considerable reduction of the risk of cardiac events during follow-up. Calculation of ELI is useful for decision-making in patients with low-gradient severe AS and preserved ejection fraction.

Differences in Pressure Recovery Between Balloon Expandable and Self-expandable Transcatheter Aortic Valves

Pressure recovery downstream of the aortic valve constitutes an important factor affecting the calculation of pressure gradient (PG) across the valve and therefore the accuracy of the calculated aortic valve area. Some clinical studies hypothesized that stent and valve cusps design contribute to flow acceleration and Doppler-measured valve gradients across the balloon-expandable transcatheter aortic valve. This study aims at elucidating the physical mechanisms behind pressure recovery variations between Edwards SAPIEN 3 and Medtronic Evolut TAVs through the measurements of sensitive and precise axial pressure profiles. A 23 mm Edwards SAPIEN3 and a 26 mm Medtronic Evolut were deployed in a pulse duplicator. A Millar catheter was used to record 50 cycles of pressure data along the centerline of the valve chamber upstream and downstream of the valve. The peak PG obtained with SAPIEN at vena contracta (VC) is 18.83 ± 0.75 mmHg and after recovery, 9.56 ± 0.78 mmHg. For Evolut at VC, peak PG is 18.25 ± 0.63 mmHg and after recovery, 10.3 ± 0.57 mmHg. The differences in peak PG at VC and at the recovery were statistically significant (p < 0.001). With SAPIEN 3 at VC, the mean PG obtained is 10.11 ± 0.63 mmHg and after recovery 7.06 ± 0.46 mmHg. For Evolut, mean PG at VC is 10.45 ± 0.67 mmHg and after recovery 7.99 ± 0.61 mmHg. The differences between the mean PG between the two valves was not statistically significant at VC (p = 0.71) but significant post-recovery (p < 0.00001). While gradients at the VC are higher with the SAPIEN 3, the net gradient after pressure recovery is significantly lower compared to Evolut TAV. Efficiency of pressure recovery significantly depends on valve type due to stent interference with the recovering blood flow.

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.

Energetic performance index improvement after Glenn and Damus-Kaye-Stansel procedure using vector flow mapping analysis: a case report

Background

Echocardiography vector flow mapping can assess dynamic flow to treat congenital heart diseases. We evaluated intracardiac flow, energy loss, left ventricular output kinetic energy, and energetic performance index using vector flow mapping during Glenn and Damus-Kaye-Stansel procedures in order to assess the efficacy of the surgery.

Case presentation

A 9-month-old boy underwent Glenn and Damus-Kaye-Stansel procedures. The energy loss depends on the left ventricular preload; therefore, energy loss decreased after the Glenn procedure. After the Damus-Kaye-Stansel procedure, the kinetic energy would increase owing to the integrated systemic outflow; however, in our case, kinetic energy decreased, which was potentially explained by the fact that kinetic energy also depends on the left ventricular preload. After the Glenn and Damus-Kaye-Stansel procedures, we detected an improvement in energetic performance index, indicating that the cardiac workload improved as well.

Conclusion

We revealed the efficiency of the Glenn and Damus-Kaye-Stansel procedures using vector flow mapping.

Medical Image-Based Hemodynamic Analyses in a Study of the Pulmonary Artery in Children With Pulmonary Hypertension Related to Congenital Heart Disease

Objective: Pulmonary hypertension related to congenital heart disease (PH-CHD) is a devastating disease caused by hemodynamic disorders. Previous hemodynamic research in PH-CHD mainly focused on wall shear stress (WSS). However, energy loss (EL) is a vital parameter in evaluation of hemodynamic status. We investigated if EL of the pulmonary artery (PA) is a potential biomechanical marker for comprehensive assessment of PH-CHD. Materials and Methods: Ten PH-CHD patients and 10 age-matched controls were enrolled. Subject-specific 3-D PA models were reconstructed based on computed tomography. Transient flow, WSS, and EL in the PA were calculated using non-invasive computational fluid dynamics. The relationship between body surface area (BSA)-normalized EL ( E . ) and PA morphology and PA flow were analyzed. Results: Morphologic analysis indicated that the BSA-normalized main PA (MPA) diameter (D_MPAnorm), MPA/aorta diameter ratio (D_MPA/D_AO), and MPA/(left PA + right PA) [D_MPA/D_(LPA+RPA)] diameter ratio were significantly larger in PH-CHD patients. Hemodynamic results showed that the velocity of the PA branches was higher in PH-CHD patients, in whom PA flow rate usually increased. WSS in the MPA was lower and E . was higher in PH-CHD patients. E . was positively correlated with D_MPAnorm, D_MPA/D_AO, and D_MPA/D_(LPA+RPA) ratios and the flow rate in the PA. E . was a sensitive index for the diagnosis of PH-CHD. Conclusion: E . is a potential biomechanical marker for PH-CHD assessment. This hemodynamic parameter may lead to new directions for revealing the potential pathophysiologic mechanism of PH-CHD.

Higher left ventricular mass-wall stress-heart rate product and outcome in aortic valve stenosis

OBJECTIVE

Whether increased myocardial oxygen demand could help explain the association of left ventricular (LV) hypertrophy with higher adverse event rate in patients with aortic valve stenosis (AS) is unknown.

METHODS

Data from 1522 patients with asymptomatic mostly moderate AS participating in the Simvastatin-Ezetimibe in AS study followed for a median of 4.3 years was used. High LV mass-wall stress-heart rate product was identified as >upper 95% CI limit in normal subjects. The association of higher LV mass-wall stress-heart rate product with major cardiovascular (CV) events, combined CV death and hospitalised heart failure and all-cause mortality was tested in Cox regression analyses, and reported as HR and 95% CI.

RESULTS

High LV mass-wall stress-heart rate product was found in 19% at baseline, and associated with male sex, higher body mass index, hypertension, LV hypertrophy, more severe AS and lower LV ejection fraction (all p<0.01). Adjusting for these confounders in time-varying Cox regression analysis, 1 SD higher LV mass-wall stress-heart rate product was associated with higher HR of major CV events (HR 1.16(95% CI 1.06 to 1.29)), combined CV death and hospitalised heart failure (HR 1.29(95% CI 1.09 to 1.54)) and all-cause mortality (HR 1.34(95% CI 1.13 to 1.58), all p<0.01).

CONCLUSION

In patients with initially mild-moderate AS, higher LV mass-wall stress-heart rate product was associated with higher mortality and heart failure hospitalisation. Our results suggest that higher myocardial oxygen demand is contributing to the higher adverse event rate reported in AS patients with LV hypertrophy.

TRIAL REGISTRATION NUMBER

NCT000092677;Post-results.

Contemporary Imaging of Aortic Stenosis

Degenerative or fibrocalcific aortic stenosis (AS) is now the most common native valvular heart disease assessed and managed by cardiologists in developed countries. Transthoracic echocardiography remains the quintessential imaging modality for the non-invasive characterisation of AS due to its widespread availability, superior assessment of flow haemodynamics, and a wealth of prognostic data accumulated over decades of clinical utility and research applications. With expanding technologies and increasing availability of treatment options such as transcatheter aortic valve replacements, in addition to conventional surgical approaches, accurate and precise assessment of AS severity is critical to guide decisions for and timing of interventions. Despite clear guideline echocardiographic parameters demarcating severe AS, discrepancies between transvalvular velocities, gradients, and calculated valve areas are commonly encountered in clinical practice. This often results in diagnostically challenging cases with significant implications. Greater emphasis must be placed on the quality of performance of basic two dimensional (2D) and Doppler measurements (attention to detail ensuring accuracy and precision), incorporating ancillary haemodynamic surrogates, understanding study- or patient-specific confounders, and recognising the role and limitations of stress echocardiography in the subgroups of low-flow low-gradient AS. A multiparametric approach, along with the incorporation of multimodality imaging (cardiac computed tomography or magnetic resonance imaging) in certain scenarios, is now mandatory to avoid incorrect misclassification of severe AS. This is essential to ensure appropriate selection of patients who would most benefit from interventions on the aortic valve to relieve the afterload mismatch resulting from truly severe valvular stenosis.

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.

Low systemic arterial compliance is associated with increased cardiovascular morbidity and mortality in aortic valve stenosis

Objective

Lower systemic arterial compliance (SAC) is associated with increased cardiovascular morbidity and mortality in hypertension, but this has not been assessed in a prospective study in aortic valve stenosis (AS).

Methods

Data from 1641 patients (38% women) with initially asymptomatic mild-moderate AS enrolled in the Simvastatin and Ezetimibe in Aortic Stenosis study was used. Median follow-up was 4.3 years. SAC was assessed from Doppler stroke volume index to central pulse pressure ratio and considered low if ≤0.64 mL/m², corresponding to the lower tertile in the population. The association of SAC with outcome was assessed in Cox regression analysis and reported as HR and 95% CI.

Results

Low SAC at baseline was characterised by older age, female sex, hypertension, obesity, presence of a small aortic root, lower mean aortic gradient and more severe AS by effective aortic valve area (all p<0.01). In Cox regression analysis adjusting for factors, low SAC was associated with higher HRs for cardiovascular death (HR 2.13(95% CI 1.34 to 3.40) and all-cause mortality (HR 1.71(95% CI 1.23 to 2.38)), both p=0.001). The results did not change when systolic or diastolic blood pressure, other measures of AS severity or presence of discordantly graded AS were included in subsequent models. Presence of low SAC did not improve mortality prediction in reclassification analysis.

Conclusions

In patients with AS without diabetes and known cardiovascular disease, but a high prevalence of hypertension, low SAC was associated with higher cardiovascular and all-cause mortality independent of well-known prognosticators.

Trial registration number

NCT00092677; Post-results.

Evaluation using a four-dimensional imaging tool before and after pulmonary valve replacement in a patient with tetralogy of Fallot: a case report

BACKGROUND

Pulmonary regurgitation is a common complication after tetralogy of Fallot repair, resulting in right ventricular dysfunction, arrhythmia, and sudden death. However, the indications and optimal timing for pulmonary valve replacement are not fully known. We describe a case in which a four-dimensional imaging tool was useful in the decision to re-operate, thus resulting in decreased energy loss and improved right ventricular function after the re-operation for tetralogy of Fallot.

CASE PRESENTATION

A 54-year-old Japanese woman visited our hospital due to palpitations and wide QRS tachycardia with persistent tiredness for several months. She underwent repair of tetralogy of Fallot when she was 2-years old. An electrocardiogram showed prolonged QRS duration (199 msec) with a complete right bundle branch block and an echocardiograph demonstrated that her right ventricle was highly enlarged and had poor contraction, and severe pulmonary valve regurgitation with one leaflet flail. Four-dimensional flow magnetic resonance imaging demonstrated that regurgitant volumes and regurgitant fractions of pulmonary regurgitation were calculated as 63.12 ml and 54.0%, respectively. Right ventricular end-diastolic/end-systolic volume index was 169.54/99.76 mL/m², and the cardiac index was 1.78 L/minute per m². Flow energy loss was 2.93 mW, which is estimated to be three times higher than normal controls. An electrophysiological study showed an intact anterior internodal pathway and a slow pathway just through the outside of the right atriotomy line scar, which is supposed to cause a re-entry circuit. We decided to perform a pulmonary valve replacement and a right maze procedure. A 27 mm bioprosthetic valve was implanted in the native pulmonary annulus with a supra-annular position. Concomitantly, the right maze procedure was performed. A four-dimensional flow magnetic resonance imaging done 3 months later showed that right ventricular end-diastolic/end-systolic volume index had significantly reduced to 85.24/55.41 mL/m² and the cardiac index had increased from 1.78 to 2.58 L/minute per m². Energy loss had greatly improved from 2.93 to 1.48 mW.

CONCLUSIONS

A four-dimensional imaging tool was useful in the decision to re-operate, thus resulting in decreased energy loss and improved right ventricular function after the re-operation for tetralogy of Fallot.

Right Ventricular Dissipative Energy Loss Detected by Vector Flow Mapping in Children: Characteristics of Normal Values

OBJECTIVES

The feasible application of vector flow mapping (VFM)-derived right ventricular (RV) energy loss (EL) is lacking. This study was designed to determine reference values of VFM-derived EL within the right ventricle and evaluate potential correlated variables.

METHODS

A total of 90 healthy children were enrolled. Velocity vector fields of the intra-RV outflow tract and pulmonary trunk (OP) and RV blood flow were obtained from the parasternal short-axis view and RV focused apical 4-chamber view, respectively. RV-EL and OP-EL values during diastole and systole were calculated using VFM analysis. The potential relationships between demographic and echocardiographic parameters and the dissipative EL were also identified.

RESULTS

Mean subject age was 8.99 ± 5.35 years. The median (interquartile range) values were 8.82 (5.47-14.30) W/m for RV diastolic EL, 3.17 (2.11-5.54) W/m for RV systolic EL, 18.82 (13.93-24.92) W/m for OP diastolic EL, and 29.88 (20.62-40.78) W/m for OP systolic EL, respectively. The dissipative EL values were negatively correlated with age and RV global strain, and positively correlated with heart rate and RV Tei index. Multivariate analysis showed that age was the primary independent predictor of these 4 types of EL, while heart rate and strain were contributors of the RV diastolic EL and OP systolic EL.

CONCLUSIONS

The present study initially validated the application of vector flow mapping-derived EL analysis in right ventricle and established reference values for the future assessment of children with cardiopulmonary disease. Age, heart rate, and strain were independent variables correlated with the dissipative EL.