Effect of three-dimensional valve shape on the hemodynamics of aortic stenosis: three-dimensional echocardiographic stereolithography and patient studies

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.

Aortic Valvular Stenosis and Heart Failure: Advances in Diagnostic, Management, and Intervention

Up to 30% of patients with aortic stenosis (AS) present with heart failure (HF) symptoms with either reduced or preserved left ventricular ejection fraction. Many of these patients present with a low-flow state, reduced aortic-valve-area (≤1.0 cm²) with low aortic-mean-gradient and aortic-peak-velocity (<40 mm Hg and <4.0 m/s). Thus, determination of true severity is essential for correct management, and multi-imaging evaluation must be performed. Medical treatment of HF is imperative and should be optimized concurrently with the determination of AS-severity. Finally, AS should be treated according to guidelines, keeping in mind that HF and low-flow increase interventions risks.

Impact of Aortic Valve Regurgitation on Doppler Echocardiographic Parameters in Patients with Severe Aortic Valve Stenosis

BACKGROUND

Diagnosing severe aortic stenosis (AS) depends on flow and pressure conditions. It is suspected that concomitant aortic regurgitation (AR) has an impact on the assessment of AS severity. The aim of this study was to analyze the impact of concomitant AR on Doppler-derived guideline criteria. We hypothesized that both transvalvular flow velocity (maxV_AV) and the mean pressure gradient (mPG_AV) will be affected by AR, whereas the effective orifice area (EOA) and the ratio between maximum velocity of the left ventricular outflow tract and transvalvular flow velocity (maxV_LVOT/maxV_AV) will not. Furthermore, we hypothesized that EOA (by continuity equation), and the geometric orifice area (GOA) (by planimetry using 3D transesophageal echocardiography, TEE), will not be affected by AR.

METHODS AND RESULTS

In this retrospective study, 335 patients (mean age 75.9 ± 9.8 years, 44% male) with severe AS (defined by EOA < 1.0 cm²) who underwent a transthoracic and transesophageal echocardiography were analyzed. Patients with a reduced left ventricular ejection fraction (LVEF < 53%) were excluded (n = 97). The remaining 238 patients were divided into four subgroups depending on AR severity, and they were assessed using pressure half time (PHT) method: no, trace, mild (PHT 500-750 ms), and moderate AR (PHT 250-500 ms). maxV_AV, mPG_AV and maxV_LVOT/maxV_AV were assessed in all subgroups. Among the four subgroups (no (n = 101), trace (n = 49), mild (n = 61) and moderate AR (n = 27)), no differences were obtained for EOA (no AR: 0.75 cm² ± 0.15; trace AR: 0.74 cm² ± 0.14; mild AR: 0.75 cm² ± 0.14; moderate AR: 0.75 cm² ± 0.15, p = 0.998) and GOA (no AR: 0.78 cm² ± 0.20; trace AR: 0.79 cm² ± 0.15; mild AR: 0.82 cm² ± 0.19; moderate AR: 0.83 cm² ± 0.14, p = 0.424). In severe AS with moderate AR, compared with patients without AR, maxV_AV (p = 0.005) and mPG_AV (p = 0.022) were higher, whereas EOA (p = 0.998) and maxV_LVOT/maxV_AV (p = 0.243) did not differ. The EOA was smaller than the GOA in AS patients with trace (0.74 cm² ± 0.14 vs. 0.79 cm² ± 0.15, p = 0.024), mild (0.75 cm² ± 0.14 vs. 0.82 cm² ± 0.19, p = 0.021), and moderate AR (0.75 cm² ± 0.15 vs. 0.83 cm² ± 0.14, p = 0.024). In 40 (17%) patients with severe AS, according to an EOA < 1.0 cm², the GOA was ≥ 1.0 cm².

CONCLUSION

In severe AS with moderate AR, the maxV_AV and mPG_AV are significantly affected by AR, whereas the EOA and maxV_LVOT/maxV_AV are not. These results highlight the potential risk of overestimating AS severity in combined aortic valve disease by only assessing transvalvular flow velocity and the mean pressure gradient. Furthermore, in cases of borderline EOA, of approximately 1.0 cm², AS severity should be verified by determining the GOA.

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.

Diagnostic Work-Up of the Aortic Patient: An Integrated Approach toward the Best Therapeutic Option

Aortic stenosis (AS) is the most common valvular heart disease. In the last decade, transcatheter aortic valve implantation (TAVI) has become the standard of care for symptomatic patients at high surgical risk. Recently, indications to TAVI have also been extended to the low surgical risk and intermediate surgical risk populations. Consequently, in this setting, some aspects acquire greater relevance: surgical risk evaluation, clinical assessment, multimodality imaging of the valve, and management of coronary artery disease. Moreover, future issues such as coronary artery re-access and valve-in-valve interventions should be considered in the valve selection process. This review aims to summarize the principal aspects of a multidimensional (multidisciplinary) and comprehensive preprocedural work-up. The Heart Team is at the center of the decision-making process of the management of aortic valve disease and bears responsibility for offering each patient a tailored approach based on an individual evaluation of technical aspects together with the risks and benefits of each modality. Considering the progressive expansion in TAVI indication and technological progress, the role of a work-up and multidisciplinary Heart Team will be even more relevant.

Application of the proximal isovelocity surface area method for estimation of the effective orifice area in aortic stenosis

Although the echocardiographic effective orifice area (EOA) calculated using the continuity equation is widely used for the assessment of severity in aortic stenosis (AS), the existence of high flow velocity at the left ventricular outflow tract (LVOT) potentially causes its overestimation. The proximal isovelocity surface area (PISA) method could be an alternative tool for the estimation of EOA that limits the influence of upstream flow velocity. EOA was calculated using the continuity equation (EOA_Cont) and PISA method (EOA_PISA), respectively, in 114 patients with at least moderate AS. The geometric orifice area (GOA) was also measured using the planimetry method in 51 patients who also underwent three-dimensional transesophageal echocardiography. Patients were divided into two groups according to the median LVOT flow velocity. EOA_PISA could be obtained in 108 of the 114 patients (95%). Although there was a strong correlation between EOA_Cont and EOA_PISA (r = 0.78, P < 0.001), EOA_Cont was statistically significantly larger than EOA_PISA (0.86 ± 0.33 vs 0.75 ± 0.29 cm², P < 0.001). Both EOA_Cont and EOA_PISA similarly correlated with GOA (r = 0.70, P < 0.001 and r = 0.77, P < 0.001, respectively). However, a fixed bias, which is hydrodynamically supposed to exist between EOA and GOA, was not observed between EOA_Cont and GOA. In contrast, there was a negative fixed bias between EOA_PISA and GOA with smaller EOA_PISA than GOA. The difference between EOA_Cont and GOA was significantly greater with a larger EOA_Cont relative to GOA in patients with high LVOT flow velocity than in those without (0.16 ± 0.25 vs - 0.07 ± 0.10 cm², P < 0.001). In contrast, the difference between EOA_PISA and GOA was consistent regardless of the LVOT flow velocity (- 0.07 ± 0.12 vs - 0.07 ± 0.15 cm², P = 0.936). The PISA method was applied to estimate EOA in patients with AS. EOA_PISA could be an alternative parameter for AS severity grading in patients with high LVOT flow velocity in whom EOA_Cont would potentially overestimate the orifice area.

3D Printing in Modern Cardiology

BACKGROUND

3D printing represents an emerging technology in the field of cardiovascular medicine. 3D printing can help to perform a better analysis of complex anatomies to optimize intervention planning.

METHODS

A systematic review was performed to illustrate the 3D printing technology and to describe the workflow to obtain 3D printed models from patient-specific images. Examples from our laboratory of the benefit of 3D printing in planning interventions were also reported.

RESULTS

3D printing technique is reliable when applied to high-quality 3D image data (CTA, CMR, 3D echography), but it still needs the involvement of expert operators for image segmentation and mesh refinement. 3D printed models could be useful in interventional planning, although prospective studies with comprehensive and clinically meaningful endpoints are required to demonstrate the clinical utility.

CONCLUSION

3D printing can be used to improve anatomy understanding and surgical planning.

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.

Model-based aortic power transfer: A potential measure for quantifying aortic stenosis severity based on measured data

Current aortic stenosis severity grading is based mainly on the local properties of the stenotic valve, such as pressure gradient or jet velocity. Success rates of valve replacement therapy are still suboptimal, so alternative grading of AS should be investigated. We suggest the efficiency of power transfer from the left ventricle to the aorta, as it takes into account heart, valve and circulatory system. Left ventricular and circulatory power were estimated using a 0D model, which was optimised to patient data: left ventricular and aortic pressure, aortic flow and diastolic left ventricular volume. Optimisation was performed using a data assimilation method. These data were available in rest as well as chemically induced exercise for twelve patients. Using this limited data set, we showed that aortic valve efficiency is highly heterogeneous between patients, but also often dependent on the haemodynamic load. This indicates that power transfer efficiency is a highly interesting metric for further research in 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.

In vitro correlation between the effective and geometric orifice area in aortic stenosis

BACKGROUND

Planimetry of aortic stenosis can be performed when Doppler measurements are unavailable. We sought to evaluate if, as advised in guidelines, the geometric orifice area (GOA) threshold value of 1 cm² was concordant with the threshold of 1 cm² of the effective orifice area (EOA), and the factors influencing the contraction coefficient (EOA/GOA ratio).

METHODS

In an in vitro mock circulatory system, we tested 6 degrees of AS severity (3 severe and 3 non-severe), and 3 levels of flow (<150 ml/s, 150-200 ml/s, >250 ml/s). The EOA was calculated by Doppler-echocardiography, and the GOA was measured with dedicated software after camera acquisition.

RESULTS

In all but the very low flow condition, an EOA of 1 cm² corresponded to a GOA of 1.2 cm². The contraction coefficient increased with both the flow and the stenosis severity. For very severe stenoses, the EOA and the GOA were interchangeable.

CONCLUSION

As observed in clinical studies, the GOA was larger than the EOA, and a GOA between 1 and 1.2 cm² should not discard the possibility of severe aortic stenosis.

Feasibility and accuracy of real-time three-dimensional echocardiography in evaluating the aortic valve in children

Background

Aortic valve assessment by 2D transthoracic echocardiography is a relatively complex task owing to the unique anatomical features of the left ventricular outflow tract and its dynamic nature. We aimed to evaluate the accuracy of 3D transthoracic echocardiography [3D TTE] in assessing the aortic valve in children.

Results

The first group included 11 males and six females, with a mean age of 5.76 ± 6.39 years. All of these patients had aortic valve disease with a bicuspid variant. The second group included seven males and seven females, with a mean age of 4.4 ± 4.05 years. All of these patients had normal aortic valve morphology and had another congenital cardiac anomaly. The aortic valve annulus was assessed using the three modalities; 2D, 3D echocardiography in the vertical and horizontal diameters, and angiography. The aortic valve area was measured by 2D and 3D echocardiography using multiplane reformatted mode. The results of the analysis were then compared. They revealed that 3D echocardiographic measurement of the aortic annulus (horizontal diameter) correlated better with angiography than 2D and 3D (vertical diameter) echocardiographic measurements. There was a significant difference between the aortic valve area measured by 2D echocardiography and that measured by 3D echocardiography among the two groups, 2D echocardiography seems to underestimate the true aortic valve area.

Conclusion

The study concluded that 3D TTE with multiplane reformatted mode allows a more accurate assessment of the aortic valve when compared to 2D echocardiography and this correlates better with the angiographic findings.

3D Bioprinting of cardiac tissue and cardiac stem cell therapy

Cardiovascular tissue engineering endeavors to repair or regenerate damaged or ineffective blood vessels, heart valves, and cardiac muscle. Current strategies that aim to accomplish such a feat include the differentiation of multipotent or pluripotent stem cells on appropriately designed biomaterial scaffolds that promote the development of mature and functional cardiac tissue. The advent of additive manufacturing 3D bioprinting technology further advances the field by allowing heterogenous cell types, biomaterials, and signaling factors to be deposited in precisely organized geometries similar to those found in their native counterparts. Bioprinting techniques to fabricate cardiac tissue in vitro include extrusion, inkjet, laser-assisted, and stereolithography with bioinks that are either synthetic or naturally-derived. The article further discusses the current practices for postfabrication conditioning of 3D engineered constructs for effective tissue development and stability, then concludes with prospective points of interest for engineering cardiac tissues in vitro. Cardiovascular three-dimensional bioprinting has the potential to be translated into the clinical setting and can further serve to model and understand biological principles that are at the root of cardiovascular disease in the laboratory.

Three-dimensional printing and virtual surgery for congenital heart procedural planning

Complex unrepaired congenital heart disease requires extensive planning to determine the optimal procedural approach. Conventional noninvasive diagnostic imaging initially provides only two-dimensional (2D) representations of the complex, three-dimensional cardiovascular anatomy. With the expansion of 3D visualization techniques in imaging, a paradigm shift has occurred in complex congenital heart disease surgical planning using digital and 3D printed heart models. There has been early success in demonstrating the benefit of these models in interdisciplinary communication and education. The future goal of this work is to demonstrate a clinical outcome benefit using digital and 3D printed models to plan both surgical and catheterization-based interventional procedures. Ultimately, the hope is that advanced procedural planning with virtual surgery and 3D printing will enhance decision-making in complex congenital heart disease cases resulting in improved perioperative performance by reducing operative times, complications, and reoperations.

Innovative interventional catheterization techniques for congenital heart disease

Since 1929, when the first cardiac catheterization was safely performed in a human by Dr. Werner Forssmann (on himself), there has been a rapid progression of cardiac catheterization techniques and technologies. Today, these advances allow us to treat a wide variety of patients with congenital heart disease using minimally invasive techniques; from fetus to infants to adults, and from simple to complex congenital cardiac lesions. In this article, we will explore some of the exciting advances in cardiac catheterization for the treatment of congenital heart disease, including transcatheter valve implantation, hybrid procedures, biodegradable technologies, and magnetic resonance imaging (MRI)-guided catheterization. Additionally, we will discuss innovations in imaging in the catheterization laboratory, including 3D rotational angiography (3DRA), fusion imaging, and 3D printing, which help to make innovative interventional approaches possible.

Normal reference ranges for cardiac valve cross-sectional areas in preterm infants

Objective:

To establish normal reference ranges for cardiac valve crosssectional areas (CSAs) in preterm infants and their correlation with gestational age, body weight, and chronological age.

Materials and Methods:

In a prospective study, 268 preterm babies fulfilling the criteria for inclusion were examined. Echocardiograms were performed to measure aortic, pulmonary, mitral, and tricuspid valve CSAs on 0–6 day (s) of life and at weekly intervals until they reached 36 weeks. Gestational age was divided into three groups, 24–27, 28–31, and 32–35 weeks, and body weight was divided into five groups, ≤999, 1000–1499, 1500–1999, 2000–2499, and ≥2500 g. Overall group differences were compared for each period of life: 0–6 days and 1–2, 3–4, and ≥5 weeks.

Results:

The mean gestational age was 29.8 (±2.38 standard deviation [SD]) weeks, ranging between 24 and 35 weeks, and the mean body weight was 1479 (±413 SD) g, ranging between 588 and 3380 g. All cardiac valve CSAs correlated well with body weight. A significant gradual increase was observed in all valve CSAs with body weight during each period of life. Overall, a progressive and significant increase in all valve CSAs was observed during the first 9 weeks of life.

Conclusions:

Cardiac valve CSAs were found to be significantly correlated with body weight. The study also provides reference data, which can be used as a normal reference tool for valve CSAs in preterm infants against gestational age, body weight, and chronological age.

Recommendations on the echocardiographic assessment of aortic valve stenosis: a focused update from the European Association of Cardiovascular Imaging and the American Society of Echocardiography

Echocardiography is the key tool for the diagnosis and evaluation of aortic stenosis. Because clinical decision-making is based on the echocardiographic assessment of its severity, it is essential that standards are adopted to maintain accuracy and consistency across echocardiographic laboratories. Detailed recommendations for the echocardiographic assessment of valve stenosis were published by the European Association of Echocardiography and the American Society of Echocardiography in 2009. In the meantime, numerous new studies on aortic stenosis have been published with particular new insights into the difficult subgroup of low gradient aortic stenosis making an update of recommendations necessary. The document focuses in particular on the optimization of left ventricular outflow tract assessment, low flow, low gradient aortic stenosis with preserved ejection fraction, a new classification of aortic stenosis by gradient, flow and ejection fraction, and a grading algorithm for an integrated and stepwise approach of artic stenosis assessment in clinical practice.

Innovations in Preoperative Planning: Insights into Another Dimension Using 3D Printing for Cardiac Disease

Two-dimensional visualization of complex congenital heart disease has limitations in that there is variation in the interpretation by different individuals. Three-dimensional printing technology has been in use for decades but is currently becoming more commonly used in the medical field. Congenital heart disease serves as an ideal pathology to employ this technology because of the variation of anatomy between patients. In this review, the authors aim to discuss basics of applicability of three-dimensional printing, the process involved in creating a model, as well as challenges with establishing utility and quality.

Evolving new concepts in the assessment of aortic stenosis

Echocardiography has been pivotal in evaluating aortic stenosis (AS) over the past several decades. Recent experience has shown a wide spectrum in the clinical presentation of AS. A better understanding of the underlying hemodynamic principles has resulted in emergence of new subtypes of AS. New treatment modalities have also been introduced, requiring precise evaluation of aortic valve (AV) pathology for implementation of these therapies. This review will discuss new concepts and indices in the use of echocardiography in patients with AS. Specifically, we will address the hemodynamic characteristics, clinical presentation, and management of normal-flow, high-gradient; paradoxical low-flow, low-gradient; and classical low-flow, low-gradient aortic stenoses.

3D printing in medicine of congenital heart diseases

Congenital heart diseases causing significant hemodynamic and functional consequences require surgical repair. Understanding of the precise surgical anatomy is often challenging and can be inadequate or wrong. Modern high resolution imaging techniques and 3D printing technology allow 3D printing of the replicas of the patient’s heart for precise understanding of the complex anatomy, hands-on simulation of surgical and interventional procedures, and morphology teaching of the medical professionals and patients. CT or MR images obtained with ECG-gating and breath-holding or respiration navigation are best suited for 3D printing. 3D echocardiograms are not ideal but can be used for printing limited areas of interest such as cardiac valves and ventricular septum. Although the print materials still require optimization for representation of cardiovascular tissues and valves, the surgeons find the models suitable for practicing closure of the septal defects, application of the baffles within the ventricles, reconstructing the aortic arch, and arterial switch procedure. Hands-on surgical training (HOST) on models may soon become a mandatory component of congenital heart disease surgery program. 3D printing will expand its utilization with further improvement of the use of echocardiographic data and image fusion algorithm across multiple imaging modalities and development of new printing materials. Bioprinting of implants such as stents, patches and artificial valves and tissue engineering of a part of or whole heart using the patient’s own cells will open the door to a new era of personalized medicine.

Replicating Patient-Specific Severe Aortic Valve Stenosis With Functional 3D Modeling

BACKGROUND

3D stereolithographic printing can be used to convert high-resolution computed tomography images into life-size physical models. We sought to apply 3D printing technologies to develop patient-specific models of the anatomic and functional characteristics of severe aortic valve stenosis.

METHODS AND RESULTS

Eight patient-specific models of severe aortic stenosis (6 tricuspid and 2 bicuspid) were created using dual-material fused 3D printing. Tissue types were identified and segmented from clinical computed tomography image data. A rigid material was used for printing calcific regions, and a rubber-like material was used for soft tissue structures of the outflow tract, aortic root, and noncalcified valve cusps. Each model was evaluated for its geometric valve orifice area, echocardiographic image quality, and aortic stenosis severity by Doppler and Gorlin methods under 7 different in vitro stroke volume conditions. Fused multimaterial 3D printed models replicated the focal calcific structures of aortic stenosis. Doppler-derived measures of peak and mean transvalvular gradient correlated well with reference standard pressure catheters across a range of flow conditions (r=0.988 and r=0.978 respectively, P<0.001). Aortic valve orifice area by Gorlin and Doppler methods correlated well (r=0.985, P<0.001). Calculated aortic valve area increased a small amount for both methods with increasing flow (P=0.002).

CONCLUSIONS

By combing the technologies of high-spatial resolution computed tomography, computer-aided design software, and fused dual-material 3D printing, we demonstrate that patient-specific models can replicate both the anatomic and functional properties of severe degenerative aortic valve stenosis.

Visual Estimation of the Severity of Aortic Stenosis and the Calcium Burden by 2-Dimensional Echocardiography: Is It Reliable?

OBJECTIVES

Guidelines have recommended aortic valve surgery in asymptomatic patients with severe aortic stenosis and a large aortic valve calcium burden. The purpose of this study was to determine whether visual assessment of aortic valve calcium and stenosis severity are reliable based on 2-dimensional echocardiography alone.

METHODS

We prospectively enrolled 68 patients with aortic stenosis and compared them with 30 control participants without aortic stenosis. All had aortic valve calcium score assessment by computed tomography. In a random order, 2-dimensional images without hemodynamic data were independently reviewed by 2 level 3-trained echocardiographers, who then classified these patients into categories based on aortic valve calcium and stenosis severity.

RESULTS

The 68 patients (mean age ± SD, 74 ± 10 years) were classified as having mild (n = 28), moderate (n = 22), and severe (n = 18) aortic stenosis. When the observers were asked to grade the degree of valve calcification, the agreement between them was poor (κ = 0.33-0.39). The visual ability to determine stenosis severity compared with Doppler echocardiography had high specificity (81% and 88% for observers 1 and 2). However, sensitivity was unacceptably low (56%-67%), and the positive predictive value was poor (44%-50%). Agreement was fair (κ= 0.58-0.69) between the observers for determining severe stenosis.

CONCLUSIONS

Our results suggest that visual assessment of aortic valve calcium has high interobserver variability; the visual ability to determine severe aortic stenosis has low sensitivity but high specificity. Our results may have important implications for treatment of patients with aortic stenosis and guiding the use of handheld echocardiography. Further research with larger cohorts is needed to validate the variability, sensitivity, and specificity reported in our study.

Aortic stenosis and perioperative risk with noncardiac surgery

Aortic stenosis (AS) is characterized as a high-risk index for cardiac complications during noncardiac surgery. The American College of Cardiology/American Heart Association guidelines define severe AS as aortic valve area ≤1 cm(2), mean gradient of ≥40 mm Hg, and peak velocity of ≥4 m/s. As per current clinical practice, any of these characteristic features label a patient as at high risk for noncardiac surgery. However, these parameters appear inconsistent, particularly with respect to the aortic valve area cutoff value. The perioperative risk associated with AS during noncardiac surgery depends upon its severity (moderate vs. severe), clinical status, and the complexity of the surgical procedure (low to intermediate risk vs. high risk). A critical analysis of old and new data from published studies indicates that the significance of the presence of AS in patients undergoing noncardiac surgery is overemphasized in studies that predate the more recent advances in echocardiography and cardiac catheterization in assessment of aortic stenosis, anesthetic and surgical techniques, as well as post-operative patient care.

Aortic stenosis severity assessment: how to match non-invasive to invasive metrics

This article underscores the importance of the haemodynamic principles of the methods of measurement, as well as inherited limitations of each method, to adequately manage differing data between invasive and non-invasive tests.

2014 AHA/ACC guideline for the management of patients with valvular heart disease: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines

Aortic stenosis is the most frequent valvular heart disease. In aortic stenosis, therapeutic decision essentially depends on symptomatic status, stenosis severity, and status of left ventricular systolic function. Surgical aortic valve replacement or transcatheter aortic valve implantation is the sole effective therapy in symptomatic patients with severe aortic stenosis, whereas the management of asymptomatic patients remains controversial and is mainly based on individual risk stratification. Imaging is fundamental for the initial diagnostic work-up, follow-up, and selection of the optimal timing and type of intervention. The present review provides specific recommendations for utilization of multimodality imaging to optimize risk stratification and therapeutic decision-making processes in aortic stenosis.

The complex nature of discordant severe calcified aortic valve disease grading: new insights from combined Doppler echocardiographic and computed tomographic study

OBJECTIVES

With concomitant Doppler echocardiography and multidetector computed tomography (MDCT) measuring aortic valve calcification (AVC) load, this study aimed at defining: 1) independent physiologic/structural determinants of aortic valve area (AVA)/mean gradient (MG) relationship; 2) AVC thresholds best associated with severe aortic stenosis (AS); and 3) whether, in AS with discordant MG, severe calcified aortic valve disease is generally detected.

BACKGROUND

Aortic stenosis with discordant markers of severity, AVA in severe range but low MG, is a conundrum, unresolved by outcome studies.

METHODS

Patients (n = 646) with normal left ventricular ejection fraction AS underwent Doppler echocardiography and AVC measurement by MDCT. On the basis of AVA-indexed-to-body surface area (AVAi) and MG, patients were categorized as concordant severity grading (CG) with moderate AS (AVAi >0.6 cm²/m², MG <40 mm Hg), severe AS (AVAi ≤0.6 cm²/m², MG ≥ 40 mm Hg), discordant-severity-grading (DG) with low-MG (AVAi ≤0.6 cm(2)/m(2), MG <40 mm Hg), or high-MG (AVAi >0.6 cm(2)/m(2), MG ≥40 mm Hg).

RESULTS

The MG (discordant in 29%) was strongly determined by AVA and flow but also independently and strongly influenced by AVC-load (p < 0.0001) and systemic arterial compliance (p < 0.0001). The AVC-load (median [interquartile range]) was similar within patients with DG (low-MG: 1,619 [965 to 2,528] arbitrary units [AU]; high-MG: 1,736 [1,209 to 2,894] AU; p = 0.49), higher than CG-moderate-AS (861 [427 to 1,519] AU; p < 0.0001) but lower than CG-severe-AS (2,931 [1,924 to 4,292] AU; p < 0.0001). The AVC-load thresholds separating severe/moderate AS were defined in CG-AS with normal flow (stroke-volume-index >35 ml/m(2)). The AVC-load, absolute or indexed, identified severe AS accurately (area under the curve ≥0.89, sensitivity ≥86%, specificity ≥79%) in men and women. Upon application of these criteria to DG-low MG, at least one-half of the patients were identified as severe calcified aortic valve disease, irrespective of flow.

CONCLUSIONS

Among patients with AS, MG is often discordant from AVA and is determined by multiple factors, valvular (AVC) and non-valvular (arterial compliance) independently of flow. The AVC-load by MDCT, strongly associated with AS severity, allows diagnosis of severe calcified aortic valve disease. At least one-half of the patients with discordant low gradient present with heavy AVC-load reflective of severe calcified aortic valve disease, emphasizing the clinical yield of AVC quantification by MDCT to diagnose and manage these complex patients.

Severe aortic valve stenosis with low-gradient and preserved ejection fraction: a misclassification issue?

INTRODUCTION AND OBJECTIVES

Low-gradient severe aortic stenosis with preserved ejection fraction is a controversial entity. Misclassification of valvulopathy severity could explain the inconsistencies reported in the prognosis of these patients. Planimetry of the aortic area using three-dimensional transesophageal echocardiography could clear up these doubts. The objectives were to assess the agreement between measurements of the valvular aortic area by continuity equation in transthoracic echocardiography and that obtained through planimetry with three-dimensional transesophageal echocardiography in low-gradient severe aortic stenosis patients.

METHODS

Cross-sectional descriptive study of consecutive patients referred due to severe aortic stenosis. Patients underwent transthoracic echocardiography and three-dimensional transesophageal echocardiography. Paradoxical low-gradient severe aortic stenosis was defined by the presence in the transthoracic echocardiography of aortic valve area<1 cm(2), mean ventricular gradient<40 mmHg, and ejection fraction ≥ 50%. Concordance between the two techniques was evaluated.

RESULTS

Of 212 consecutive severe aortic stenosis patients evaluated, 63 cases (29.7%) fulfilled the paradoxical low-gradient inclusion criteria. We obtained three-dimensional aortic valve planimetry in 61 (96.8%) of those patients. In 52 patients (85.2%), aortic valve area by transesophageal echocardiography was <1 cm(2). The intraclass correlation coefficient between the two methods was 0.505 (95% confidence interval, 0.290-0.671; P<.001).

CONCLUSIONS

Paradoxical low-gradient severe aortic stenosis is an actual entity, confirmed in 85% of cases evaluated by three-dimensional transesophageal echocardiography.

Comparison of left ventricular outflow geometry and aortic valve area in patients with aortic stenosis by 2-dimensional versus 3-dimensional echocardiography

The present study sought to elucidate the geometry of the left ventricular outflow tract (LVOT) in patients with aortic stenosis and its effect on the accuracy of the continuity equation-based aortic valve area (AVA) estimation. Real-time 3-dimensional transesophageal echocardiography (RT3D-TEE) provides high-resolution images of LVOT in patients with aortic stenosis. Thus, AVA is derived reliably with the continuity equation. Forty patients with aortic stenosis who underwent 2-dimensional transthoracic echocardiography (2D-TTE), 2-dimensional transesophageal echocardiography (2D-TEE), and RT3D-TEE were studied. In 2D-TTE and 2D-TEE, the LVOT areas were calculated as π × (LVOT dimension/2)(2). In RT3D-TEE, the LVOT areas and ellipticity ([diameter of the anteroposterior axis]/[diameter of the medial-lateral axis]) were evaluated by planimetry. The AVA is then determined using planimetry and the continuity equation method. LVOT shape was found to be elliptical (ellipticity of 0.80 ± 0.08). Accordingly, the LVOT areas measured by 2D-TTE (median 3.7 cm(2), interquartile range 3.1 to 4.1) and 2D-TEE (median 3.7 cm(2), interquartile range 3.1 to 4.0) were smaller than those by 3D-TEE (median 4.6 cm(2), interquartile range 3.9 to 5.3; p <0.05 vs both 2D-TTE and 2D-TEE). RT3D-TEE yielded a larger continuity equation-based AVA (median 1.0 cm(2), interquartile range 0.79 to 1.3, p <0.05 vs both 2D-TTE and 2D-TEE) than 2D-TTE (median 0.77 cm(2), interquartile range 0.64 to 0.94) and 2D-TEE (median 0.76 cm(2), interquartile range 0.62 to 0.95). Additionally, the continuity equation-based AVA by RT3D-TEE was consistent with the planimetry method. In conclusion, RT3D-TEE might allow more accurate evaluation of the elliptical LVOT geometry and continuity equation-based AVA in patients with aortic stenosis than 2D-TTE and 2D-TEE.

Comparison between cardiovascular magnetic resonance and transthoracic Doppler echocardiography for the estimation of effective orifice area in aortic stenosis

BACKGROUND

The effective orifice area (EOA) estimated by transthoracic Doppler echocardiography (TTE) via the continuity equation is commonly used to determine the severity of aortic stenosis (AS). However, there are often discrepancies between TTE-derived EOA and invasive indices of stenosis, thus raising uncertainty about actual definite severity. Cardiovascular magnetic resonance (CMR) has emerged as an alternative method for non-invasive estimation of valve EOA. The objective of this study was to assess the concordance between TTE and CMR for the estimation of valve EOA.

METHODS AND RESULTS

31 patients with mild to severe AS (EOA range: 0.72 to 1.73 cm2) and seven (7) healthy control subjects with normal transvalvular flow rate underwent TTE and velocity-encoded CMR. Valve EOA was calculated by the continuity equation. CMR revealed that the left ventricular outflow tract (LVOT) cross-section is typically oval and not circular. As a consequence, TTE underestimated the LVOT cross-sectional area (ALVOT, 3.84 ± 0.80 cm2) compared to CMR (4.78 ± 1.05 cm2). On the other hand, TTE overestimated the LVOT velocity-time integral (VTILVOT: 21 ± 4 vs. 15 ± 4 cm). Good concordance was observed between TTE and CMR for estimation of aortic jet VTI (61 ± 22 vs. 57 ± 20 cm). Overall, there was a good correlation and concordance between TTE-derived and CMR-derived EOAs (1.53 ± 0.67 vs. 1.59 ± 0.73 cm2, r = 0.92, bias = 0.06 ± 0.29 cm2). The intra- and inter- observer variability of TTE-derived EOA was 5 ± 5% and 9 ± 5%, respectively, compared to 2 ± 1% and 7 ± 5% for CMR-derived EOA.

CONCLUSION

Underestimation of ALVOT by TTE is compensated by overestimation of VTILVOT, thereby resulting in a good concordance between TTE and CMR for estimation of aortic valve EOA. CMR was associated with less intra- and inter- observer measurement variability compared to TTE. CMR provides a non-invasive and reliable alternative to Doppler-echocardiography for the quantification of AS severity.