Relationship between cutoff values of peak aortic valve velocity and those of other Doppler echocardiographic parameters of severity in patients with aortic stenosis and normal flow

Improving accuracy in diagnosing aortic stenosis severity: An in-depth analysis of echocardiographic measurement error through literature review and simulation study

AIMS

The present guidelines advise replacing the aortic valve for individuals with severe aortic stenosis (AS) based on various echocardiographic parameters. Accurate measurements are essential to avoid misclassification and unnecessary interventions. The objective of this study was to evaluate the influence of measurement error on the echocardiographic evaluation of the severity of AS.

METHODS AND RESULTS

A systematic review was performed to examine whether measurement errors are reported in studies focusing on the prognostic value of peak aortic jet velocity (Vmax ), mean pressure gradient (MPG), and effective orifice area (EOA) in asymptomatic patients with AS. Out of the 37 studies reviewed, 17 (46%) acknowledged the existence of measurement errors, but none of them utilized methods to address them. Secondly, the magnitude of potential errors was collected from available literature for use in clinical simulations. Interobserver variability ranged between 0.9% and 8.3% for Vmax and MPG but was higher for EOA (range 7.7%-12.7%), indicating lower reliability. Assuming a circular left ventricular outflow tract area led to a median underestimation of EOA by 23% compared to planimetry by other modalities. A clinical simulation resulted in the reclassification of 42% of patients, shifting them from a diagnosis of severe AS to moderate AS.

CONCLUSIONS

Measurement errors are underreported in studies on echocardiographic assessment of AS severity. These errors can lead to misclassification and misdiagnosis. Clinicians and scientists should be aware of the implications for accurate clinical decision-making and assuring research validity.

Doppler and Pair-Wise Optical Flow Constrained 3D Motion Compensation for 3D Ultrasound Imaging

Volumetric (3D) ultrasound imaging using a 2D matrix array probe is increasingly developed for various clinical procedures. However, 3D ultrasound imaging suffers from motion artifacts due to tissue motions and a relatively low frame rate. Current Doppler-based motion compensation (MoCo) methods only allow 1D compensation in the in-range dimension. In this work, we propose a new 3D-MoCo framework that combines 3D velocity field estimation and a two-step compensation strategy for 3D diverging wave compounding imaging. Specifically, our framework explores two constraints of a round-trip scan sequence of 3D diverging waves, i.e., Doppler and pair-wise optical flow, to formulate the estimation of the 3D velocity fields as a global optimization problem, which is further regularized by the divergence-free and first-order smoothness. The two-step compensation strategy is to first compensate for the 1D displacements in the in-range dimension and then the 2D displacements in the two mutually orthogonal cross-range dimensions. Systematical in-silico experiments were conducted to validate the effectiveness of our proposed 3D-MoCo method. The results demonstrate that our 3D-MoCo method achieves higher image contrast, higher structural similarity, and better speckle patterns than the corresponding 1D-MoCo method. Particularly, the 2D cross-range compensation is effective for fully recovering image quality.

Valvulo-Arterial Impedance and Dimensionless Index for Risk Stratifying Patients With Severe Aortic Stenosis

The hemodynamic effects of aortic stenosis (AS) consist of increased left ventricular (LV) afterload, reduced myocardial compliance, and increased myocardial workload. The LV in AS patients faces a double load: valvular and arterial loads. As such, the presence of symptoms and occurrence of adverse events in AS should better correlate with calculating the global burden faced by the LV in addition to the transvalvular gradient and aortic valve area (AVA). The valvulo-arterial impedance (Zva) is a useful parameter providing an estimate of the global LV hemodynamic load that results from the summation of the valvular and vascular loads. In addition to calculating the global LV afterload, it is paramount to estimate the stenosis severity accurately. In clinical practice, the management of low-flow low-gradient (LF-LG) severe AS with preserved LV ejection fraction requires careful confirmation of stenosis severity. In addition to the Zva, the dimensionless index (DI) is a very useful parameter to express the size of the effective valvular area as a proportion of the cross-section area of the left ventricular outlet tract velocity-time integral (LVOT-VTI) to that of the aortic valve jet (dimensionless velocity ratio). The DI is calculated by a ratio of the sub-valvular velocity obtained by pulsed-wave Doppler (LVOT-VTI) divided by the maximum velocity obtained by continuous-wave Doppler across the aortic valve (AV-VTI). In contrast to AVA measurement, the DI does not require the calculation of LVOT cross-sectional area, a major cause of erroneous assessment and underestimation of AVA. Hence, among patients with LG severe AS and preserved LV ejection fraction, calculation of DI in routine echocardiographic practice may be useful to identify a subgroup of patients at higher risk of mortality who may derive benefit from aortic valve replacement. This article aims to elucidate the Zva and DI in different clinical situations, correlate with the standard indexes of AS severity, LV geometry, and function, and thus prove to improve risk stratification and clinical decision making in patients with severe AS.

Severe aortic stenosis echocardiographic thresholds revisited

BACKGROUND

In view of inconsistencies in threshold values of severe aortic stenosis (AS) hemodynamic indices, it is unclear what is the relative contribution of each variable in a binary classification of AS based on aortic valve replacement (AVR) indication. We aimed to assess relative discriminative value and optimal threshold of each constituent hemodynamic parameter for this classification and confirm additional prognostic value.

METHODS

Echocardiography studies of 168 patients with ≥ moderate AS were included. AS types were dichotomized into Group-A, comprising moderate and Normal-Flow Low-Gradient (NFLG), and Group-B, comprising High-Gradient(HG), Low Ejection Fraction Low-Flow Low-Gradient(Low EF-LFLG), and Paradoxical Low-Flow Low-Gradient(PLFLG) AS. Aortic valve area (AVA), Doppler velocity index (DVI), peak aortic velocity, mean gradient, stroke volume index and transaortic flow rate(TFR) were assessed for A/B Group discrimination value and optimal thresholds were determined. Dichotomized values were assessed for predictive value for AVR or death.

RESULTS

C-statistic values for binary AS classification was .74-.9 for the tested variables. AVA and DVI featured the highest score, and SVI the lowest one. AVA≤.81 cm² and DVI≤.249 had 87.6% and 86% respective sensitivity for Group B patients, and a similar specificity of 80.9%. During a mean follow-up of 9.1±10.1 months, each of the tested dichotomized variables except for SVI predicted AVR or death on multivariate analysis.

CONCLUSION

An AVA value ≤.81 cm² or a DVI ≤ .249 threshold carry the highest discriminative value for severe AS in patients with aortic stenosis, translating into an independent prognostic value, and can be helpful in making clinical decisions.

Prognostic Impact of Aortic Valve Area in Conservatively Managed Patients With Asymptomatic Severe Aortic Stenosis With Preserved Ejection Fraction

Background

Data are scarce on the role of aortic valve area (AVA) to identify those patients with asymptomatic severe aortic stenosis (AS) who are at high risk of adverse events. We sought to explore the prognostic impact of AVA in asymptomatic patients with severe AS in a large observational database.

Methods and Results

Among 3815 consecutive patients with severe AS enrolled in the CURRENT AS (Contemporary Outcomes After Surgery and Medical Treatment in Patients With Severe Aortic Stenosis) registry, the present study included 1309 conservatively managed asymptomatic patients with left ventricular ejection fraction ≥50%. The study patients were subdivided into 3 groups based on AVA (group 1: AVA >0.80 cm², N=645; group 2: 0.8 cm² ≥AVA >0.6 cm², N=465; and group 3: AVA ≤0.6 cm², N=199). The prevalence of very severe AS patients (peak aortic jet velocity ≥5 m/s or mean aortic pressure gradient ≥60 mm Hg) was 2.0%, 5.8%, and 26.1% in groups 1, 2, and 3, respectively. The cumulative 5‐year incidence of AVR was not different across the 3 groups (39.7%, 43.7%, and 39.9%; P=0.43). The cumulative 5‐year incidence of the primary outcome measure (a composite of aortic valve–related death or heart failure hospitalization) was incrementally higher with decreasing AVA (24.1%, 29.1%, and 48.1%; P<0.001). After adjusting for confounders, the excess risk of group 3 and group 2 relative to group 1 for the primary outcome measure remained significant (hazard ratio, 2.21, 95% CI, 1.56–3.11, P<0.001; and hazard ratio, 1.34, 95% CI, 1.01–1.78, P=0.04, respectively).

Conclusions

AVA ≤0.6 cm² would be a useful marker to identify those high‐risk patients with asymptomatic severe AS, who might benefit from early AVR.

Clinical Trial Registration

URL: www.umin.ac.jp. Unique identifier: UMIN000012140.

See Editorial by Tribouilloy et al

Impact of Mean Transaortic Pressure Gradient on Long-Term Outcome in Patients With Severe Aortic Stenosis and Preserved Left Ventricular Ejection Fraction

Background

Mean transaortic pressure gradient (MTPG) has never been validated as a predictor of mortality in patients with severe aortic stenosis. We sought to determine the value of MTPG to predict mortality in a large prospective cohort of severe aortic stenosis patients with preserved left ventricular ejection fraction and to investigate the cutoff of 60 mm Hg, proposed in American guidelines.

Methods and Results

A total of 1143 patients with severe aortic stenosis defined by aortic valve area ≤1 cm² and MTPG ≥40 mm Hg were included. The population was divided into 3 groups according to MTPG: between 40 and 49 mm Hg, between 50 and 59 mm Hg, and ≥60 mm Hg. The end point was all‐cause mortality. MTPG was ≥60 mm Hg in 392 patients. Patients with MTPG ≥60 mm Hg had a significantly increase risk of mortality compared with patients with MTPG <60 mm Hg (hazard ratio [HR]=1.62 [1.27–2.05] P<0.001), even for the subgroup of asymptomatic or minimally symptomatic patients (HR=1.56 [1.04–2.34] P=0.032). After adjustment for established outcome predictors, patients with MTPG ≥60 mm Hg had a significantly higher risk of mortality than patients with MTPG <60 mm Hg (HR=1.71 [1.33–2.20] P<0.001), even after adjusting for surgery as a time‐dependent variable (HR=1.71 [1.43–2.11] P<0.001). Similar results were observed for the subgroup of asymptomatic or minimally symptomatic patients (HR=1.70 [1.10–2.32] P=0.018 and HR=1.68 [1.20–2.36] P=0.003, respectively).

Conclusions

This study shows the negative prognostic impact of high MTPG (≥60 mm Hg), on long‐term outcome of patients with severe aortic stenosis with preserved left ventricular ejection fraction, irrespective of symptoms.

Prognostic Value of Aortic Valve Area by Doppler Echocardiography in Patients With Severe Asymptomatic Aortic Stenosis

Background

The aim of this study was to evaluate the relationship between aortic valve area (AVA) obtained by Doppler echocardiography and outcome in patients with severe asymptomatic aortic stenosis and to define a specific threshold of AVA for identifying asymptomatic patients at very high risk based on their clinical outcome.

Methods and Results

We included 199 patients with asymptomatic severe aortic stenosis (AVA ≤1.0 cm²). The risk of events (death or need for aortic valve replacement) increased linearly on the scale of log hazard with decreased AVA (adjusted hazard ratio 1.17; 95% CI 1.06–1.29 per 0.1 cm²AVA decrement; P=0.002). Event‐free survival at 12, 24, and 48 months was 63±6%, 51±6%, and 34±6%, respectively, for AVA 0.8 to 1 cm²; 49±6%, 36±6%, and 26±6%, respectively, for AVA 0.6 to 0.8 cm²; and 33±8%, 20±7%, and 11±5%, respectively, for AVA ≤0.6 cm² (P_trend=0.002). Patients with AVA ≤0.6 cm² had a significantly increased risk of events compared with patients with AVA 0.8 to 1 cm² (adjusted hazard ratio 2.22; 95% CI 1.41–3.52; P=0.001), whereas patients with AVA 0.6 to 0.8 cm² had an increased risk of events compared with those with AVA 0.8 to 1 cm², but the difference was not statistically significant (adjusted hazard ratio 1.38; 95% CI 0.93–2.05; P=0.11). After adjustment for covariates and aortic valve replacement as a time‐dependent variable, patients with AVA ≤0.6 cm² had a significantly greater risk of all‐cause mortality than patients with AVA >0.6 cm² (hazard ratio 3.39; 95% CI 1.80–6.40; P<0.0001).

Conclusions

Patients with severe asymptomatic aortic stenosis and AVA ≤0.6 cm² displayed an important increase in the risk of adverse events during short‐term follow‐up. Further studies are needed to determine whether elective aortic valve replacement improves outcome in this high‐risk subgroup of patients.

Viewpoint: the ENIGMAS trial - when should we treat patients with moderate aortic stenosis?

Aortic stenosis (AS) is the most frequent valvular heart disease encountered in our daily practice. Although there are clear guidelines for severe AS management, cardiologists often have few treatment options for patients with moderate AS; however, there is higher mortality in this patient subgroup versus an age-matched population. The authors reviewed all of the studies on moderate AS, summarized the factors that increase disease progression and discussed an ideal trial design to prospectively evaluate AS progression factors using modern cardiology tools such as strain and magnetic resonance imaging.