Pulsatile Distention of the Nondiseased and Stenotic Aortic Valve Annulus: Analysis With Electrocardiogram-Gated Computed Tomography

Misidentification of the True Aortic Annulus With 2-dimensional Echocardiography: A Critical Appraisal Using 3-Dimensional Imaging

OBJECTIVES

This study aimed to evaluate the accuracy of identifying the true aortic valve (AV) annulus using 2-dimensional (2D) echocardiography, with the goal of highlighting potential misidentification issues in clinical practice.

DESIGN

An observational study employing 3-dimensional (3D) datasets to generate 2D images of the AV annulus for analysis.

SETTING

The study was conducted in an academic medical center.

PARTICIPANTS

Three-dimensional transesophageal echocardiography datasets were obtained from 11 patients with normal AV and aortic root anatomies undergoing coronary artery bypass surgery. Attending anesthesiologists certified by the National Board of Echocardiography (NBE) were approached subsequently to participate in this study.

INTERVENTIONS

Two images per patient were generated from 3D datasets, reflecting the mid-esophageal long-axis view of the AV, a true AV annulus image, and an off-axis image. A survey was distributed to NBE-certified perioperative echocardiographers across 12 academic institutions to identify the true AV annulus from these images.

MEASUREMENTS AND MAIN RESULTS

The survey, completed by 45 qualified respondents, revealed a significant misidentification rate of the true AV annulus, with only 36.8% of responses correctly identifying it. The rate of correct identification varied across image sets, with 44.4% of participants unable to correctly identify any true AV annulus image.

CONCLUSIONS

The study highlighted the limitations of 2D echocardiography in accurately identifying the true AV annulus in complex 3D structures like the aortic root. The findings suggest a need for greater reliance on advanced imaging modalities, such as 3D echocardiography, to improve accuracy in clinical practice.

The myth of aortic valve annulus changes in aortic valve disease

Background

The characteristics of aortic annulus changes in aortic regurgitation (AR) patients are poorly understood, and predictive factors among aortic valve disease are yet to be established.

Objective

This study seeks to elucidate the pattern of annular size fluctuations across different cardiac phases in AR patients and to identify predictors for annular enlargement during either systole or diastole in aortic valve diseases.

Methods

A retrospective analysis was conducted on 55 patients with severe aortic valve diseases, including 26 patients with aortic stenosis (AS) and 29 with AR, to discern the two groups' contrasting and analogous patterns of annular changes. The patient sample was expanded to 107 to investigate the factors influencing the size of the annulus during different cardiac phases. Based on our findings, patients were then divided into two groups: those with an annulus that is larger during systole (83 patients) and those where the annulus is larger during diastole (24 patients).

Results

Typically, AR patients exhibit a dynamic annulus, with both perimeter and area being largest during mid-systole. These dimensions diminish progressively and then increase again in early diastole, a pattern consistent with observations in AS patients. Among 107 patients, 21% had diastolic enlargement. Systolic measurements would lead to prosthesis undersizing in 17% of these. Male gender and lower systolic annulus minimum relative to body surface area (AnMin index) were predictors of diastolic enlargement, with ROC curve areas of 0.70 and 0.87 for AR and AS, respectively.

Conclusions

Systolic measurements are recommended for AR patients. Gender and the AnMin index are significant predictors, particularly potent in AS patients.

Imaging Modalities Employed in the TAVR Procedure With a Focus on CTA: What the Radiologist Needs to Know

RATIONALE AND OBJECTIVES

Aortic stenosis (AS) is one of the most common valvular heart disease. Symptomatic AS is associated with a high mortality rate which prompts fast intervention. The introduction of transcatheter aortic valve replacement (TAVR) has drastically improved the outcome of high surgical risk for mortality patients with severe AS. However, this procedure requires the employment of multimodality imaging in the pre-procedural planning, intra-procedural optimization, and post-procedural follow-up stages. This also requires an accurate understanding of the indications, measurements, strength, and limitations of each imaging modality during the different TAVR stages.

CONCLUSION

In this review, we aim to outline to radiologists the evidence-based approach and indications of different imaging modalities through the pre, peri, and post TAVR stages.

Assessment of thoracic aorta in different cardiac phases in patients with non-aorta diseases using cardiac CT

The aim was to evaluate the thoracic aorta in different cardiac phases to obtain the correct cardiac phase for measuring the maximum diameter required to predict aortic disease. Cardiac CT was performed on 97 patients for suspected coronary artery disease. The average diameter of ascending (AAD) and descending aorta (DAD) in the plane of pulmonary bifurcation, in the plane of the sinus junction (AAD [STJ] and DAD [STJ]), descending aorta in the plane of the diaphragm (DAD [Dia]), the diameter of the main pulmonary artery (MPAD), distance from the sternum to the spine (S-SD), and distance from the sternum to the ascending aorta (S-AAD) were assessed at 20 different time points in the cardiac cycle. Differences in aortic diameter in different cardiac phases and the correlation between aortic diameter and traditional risk factors were analyzed by the general linear mixed model. The diameter of the thoracic aorta reached the minimum at the phase of 95–0%, and reached the maximum at 30–35%. The maximum values of AAD, AAD (STJ), DAD, DAD (STJ), and DAD (Dia) were 32.51 ± 3.35 mm, 28.86 ± 3.01 mm, 23.46 ± 2.88 mm, 21.85 ± 2.58 mm, and 21.09 ± 2.66 mm, respectively. The maximum values of MPAD/AAD and DAD/AAD (STJ) were 0.8140 ± 0.1029, 0.7623 ± 0.0799, respectively. The diameter of the thoracic aorta varies with the cardiac phase. Analyzing the changes in aortic diameter, which can be done using cardiac CT, could provide a more accurate clinical measurement for predicting aortic disease.

Bicuspid aortic valve annulus: assessment of geometry and size changes during the cardiac cycle as measured with a standardized method to define the annular plane

Purpose

Bicuspid aortic valve (BAV) is a complex malformation affecting not merely the aortic valve. However, little is known regarding the dynamic physiology of the aortic annulus in these patients and whether it is similar to tricuspid aortic valves (TAV). Determining the BAV annular plane is more challenging than for TAV. Our aim was to present a standardized methodology to determine BAV annulus and investigate its changes in shape and dimensions during the cardiac cycle.

Methods

BAV patients were prospectively included and underwent an ECG-gated cardiac CTA. The annulus plane was manually identified on reconstructions at 5% intervals of the cardiac cycle with a new standardized method for different BAV types. Based on semi-automatically defined contours, maximum and minimum diameter, area, area-derived diameter, perimeter, asymmetry ratio (AR), and relative area were calculated. Differences of dynamic annular parameters were assessed also per BAV type.

Results

Of the 55 patients included (38.4 ± 13.3 years; 58% males), 38 had BAV Sievers type 1, 10 type 0, and 7 type 2. The minimum diameter, perimeter, area, and area-derived diameter were significantly higher in systole than in diastole with a relative change of 13.7%, 4.8%, 13.7%, and 7.2% respectively (all p < 0.001). The AR was ≥ 1.1 in all phases, indicating an elliptic shape, with more pronounced flattening in diastole (p < 0.001). Different BAV types showed comparable dynamic changes.

Conclusions

BAV annulus undergo significant changes in shape during the cardiac cycle with a wider area in systole and a more elliptic conformation in diastole regardless of valve type.

Key Points

• A refined method for the identification of the annulus plane on CT scans of patients with bicuspid aortic valves, tailored for the specific anatomy of each valve type, is proposed.

• The annulus of patients with bicuspid aortic valves undergoes significant changes during the cardiac cycle with a wider area and more circular shape in systole regardless of valve type.

• As compared to previously published data, the bicuspid aortic valve annulus has physiological dynamics similar to that encountered in tricuspid valves but with overall larger dimensions.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00330-021-07916-8.

Multidetector computed tomography in transcatheter aortic valve replacement: an update on technological developments and clinical applications

INTRODUCTION

Transcatheter aortic valve replacement (TAVR) has revolutionized the treatment of patients with underlying sever aortic valve stenosis across all spectrum of the disease. CT imaging is so crucial to the pre procedural planning, to incorporate the information from the CT imaging in the decision making intraprocedurally and to predict and identity the post procedural complications.Areas covered: In this article, we review available studies on CT role in TAVR procedure and provide update on the technological developments and clinical applications.Expert opinion: CT imaging, with its high resolution, and in particular its utilization in aortic annular measurements, bicuspid aortic valve assessment, hypoattenuated leaflet thickening and valve in valve therapy proved to be the ideal approach to study the mechanisms of aortic stenosis, detection of high-risk anatomy, more accurate risk stratification and thus to allow a personalized catheter based intervention of the affected patients.

Surgically implanted aortic valve bioprostheses deform after implantation: insights from computed tomography

OBJECTIVE

Little is known about the prevalence and degree of deformation of surgically implanted aortic biological valve prostheses (bio-sAVRs). We assessed bio-sAVR deformation using multidetector-row computed tomography (MDCT).

METHODS

Three imaging databases were searched for patients with MDCT performed after bio-sAVR implantation. Minimal and maximal valve ring diameters were obtained in systole and/or diastole, depending on the acquired cardiac phase(s). The eccentricity index (EI) was calculated as a measure of deformation as (1 - (minimal diameter/maximal diameter)) × 100%. EI of < 5% was considered none or trivial deformation, 5-10% mild deformation, and > 10% non-circular. Indications for MDCT and implanted valve type were retrieved.

RESULTS

One hundred fifty-two scans of bio-sAVRs were included. One hundred seventeen measurements were performed in systole and 35 in diastole. None or trivial deformation (EI < 5%) was seen in 67/152 (44%) of patients. Mild deformation (EI 5-10%) was seen in 59/152 (39%) and non-circularity was found in 26/152 (17%) of cases. Overall, median EI was 5.5% (IQR 3.4-7.8). In 77 patients, both systolic and diastolic measurements were performed from the same scan. For these scans, the median EI was 6.5% (IQR 3.4-10.2) in systole and 5.1% (IQR3.1-7.6) in diastole, with a significant difference between both groups (p = 0.006).

CONCLUSIONS

Surgically implanted aortic biological valve prostheses show mild deformation in 39% of cases and were considered non-circular in 17% of studied valves.

KEY POINTS

• Deformation of surgically implanted aortic valve bioprostheses (bio-sAVRs) can be adequately assessed using MDCT. • Bio-sAVRs show at least mild deformation (eccentricity index > 5%) in 56% of studied cases and were considered non-circular (eccentricity index > 10%) in 17% of studied valves. • The higher deformity rate found in bio-sAVRs with (suspected) valve pathology could suggest that geometric deformity may play a role in leaflet malformation and thrombus formation similar to that of transcatheter heart valves.

CT in planning transcatheter aortic valve implantation procedures and risk assessment

For surgical aortic valve replacement, the Society of Thoracic Surgeons score (STSS) is the reference standard for the prediction of operative risk. In transcatheter aortic valve implantation (TAVI) though, where the procedure itself is minimally invasive, the traditional risk assessment is supplemented by CTA. Through a consistent approach to the acquisition of high-quality images and the standardised reporting of annular measurements and adverse root and vascular features, patients at risk of complications can be identified. In turn, this may allow for a personalised procedural approach and treatment strategies devised to potentially reduce or mitigate this risk. This article provides a systematic and standardised approach to pre-procedural work-up with computed tomography angiography (CTA) and explores the current state of evidence and future areas of development in this rapidly developing field.

Population-specific material properties of the implantation site for transcatheter aortic valve replacement finite element simulations

Patient-specific computational models are an established tool to support device development and test under clinically relevant boundary conditions. Potentially, such models could be used to aid the clinical decision-making process for percutaneous valve selection; however, their adoption in clinical practice is still limited to individual cases. To be fully informative, they should include patient-specific data on both anatomy and mechanics of the implantation site. In this work, fourteen patient-specific computational models for transcatheter aortic valve replacement (TAVR) with balloon-expandable Sapien XT devices were retrospectively developed to tune the material parameters of the implantation site mechanical model for the average TAVR population. Pre-procedural computed tomography (CT) images were post-processed to create the 3D patient-specific anatomy of the implantation site. Balloon valvuloplasty and device deployment were simulated with finite element (FE) analysis. Valve leaflets and aortic root were modelled as linear elastic materials, while calcification as elastoplastic. Material properties were initially selected from literature; then, a statistical analysis was designed to investigate the effect of each implantation site material parameter on the implanted stent diameter and thus identify the combination of material parameters for TAVR patients. These numerical models were validated against clinical data. The comparison between stent diameters measured from post-procedural fluoroscopy images and final computational results showed a mean difference of 2.5 ± 3.9%. Moreover, the numerical model detected the presence of paravalvular leakage (PVL) in 79% of cases, as assessed by post-TAVR echocardiographic examination. The final aim was to increase accuracy and reliability of such computational tools for prospective clinical applications.

Rotational angiography with motion compensation: first-in-man use for the 3D evaluation of transcatheter valve prostheses

AIMS

We evaluated a novel motion-compensating 3D reconstruction technique applied to rotational angiography (R-angio) which produces MSCT-like images for evaluation of implanted TAVI prostheses without requiring rapid pacing.

METHODS AND RESULTS

Fifty-one consecutive patients were retrospectively identified who were evaluated with rotational angiography (R-angio) using the Siemens Artis zee angiographic C-arm system after TAVI with a Medtronic CoreValve prosthesis. A novel 3D image reconstruction technique was applied which corrects for cardiac motion. CoreValve frame geometry was evaluated according to the same protocol for MSCT and R-angio at the level of: 1) the inflow, 2) the nadirs, 3) central coaptation, and 4) the commissures. The native aortic annulus dimensions were measured at the nadirs of the three leaflets. Sizing ratio, prosthesis expansion and frame ellipticity were assessed. Good quality 3D reconstructions were obtained in 43 patients (84%) and failure was predictable prior to reconstruction in six of the other seven patients (superposition of radiographically dense object n=4, obesity n=2). Prosthesis inflow ellipticity and expansion were correlated with implantation depth (respectively r=-0.46, p<0.01, and r=0.61, p<0.001). Aortic regurgitation grade ≥2 was associated with greater prosthesis ellipticity at the level of central coaptation (median [25th-75th percentile]: 1.15 [1.10-1.20] vs. 1.08 [1.06-1.12], p=0.009). The inter-observer, inter-modality (MSCT, R-angio) variability in measurement at the level of coaptation for minimum diameter, maximum diameter and area were all low (respectively, mean ±SD:1.2% ±1.2; 1.7% ±1.8 and 2.0% ±1.3).

CONCLUSIONS

R-angio with motion-compensated reconstruction offers new possibilities for evaluation of the post-implantation geometry of percutaneous structural heart prostheses and the potential clinical effects.

Automatic aortic root landmark detection in CTA images for preprocedural planning of transcatheter aortic valve implantation

Transcatheter aortic valve implantation is currently a well-established minimal invasive treatment option for patients with severe aortic valve stenosis. CT Angiography is used for the pre-operative planning and sizing of the prosthesis. To reduce the inconsistency in sizing due to interobserver variability, we introduce and evaluate an automatic aortic root landmarks detection method to determine the sizing parameters. The proposed algorithm detects the sinotubular junction, two coronary ostia, and three valvular hinge points on a segmented aortic root surface. Using these aortic root landmarks, the automated method determines annulus radius, annulus orientation, and distance from annulus plane to right and left coronary ostia. Validation is performed by the comparison with manual measurements of two observers for 40 CTA image datasets. Detection of landmarks showed high accuracy where the mean distance between the automatically detected and reference landmarks was 2.81 ± 2.08 mm, comparable to the interobserver variation of 2.67 ± 2.52 mm. The mean annulus to coronary ostium distance was 16.9 ± 3.3 and 17.1 ± 3.3 mm for the automated and the reference manual measurements, respectively, with a mean paired difference of 1.89 ± 1.71 mm and interobserver mean paired difference of 1.38 ± 1.52 mm. Automated detection of aortic root landmarks enables automated sizing with good agreement with manual measurements, which suggests applicability of the presented method in current clinical practice.

Does the aortic annulus undergo conformational change throughout the cardiac cycle? A systematic review

Accurate annular sizing in transcatheter aortic valve implantation (TAVI) planning is essential. It is now widely recognized that the annulus is an oval structure in most patients, but it remains unclear if the annulus undergoes change in size and shape during the cardiac cycle that may impact prosthesis size selection. Our aim was to assess whether the aortic annulus undergoes dynamic conformational change during the cardiac cycle and to evaluate possible implications for prosthesis size selection. We performed a systematic search in PubMed and Embase databases and reviewed all available literature on aortic annulus measurements in at least two cardiac phases. Twenty-nine articles published from 2001 to 2014 were included. In total, 2021 subjects with and without aortic stenosis were evaluated with a mean age ranging from 11 ± 3.6 to 84.9 ± 7.2 years. Two- and three-dimensional echocardiography was performed in six studies each, magnetic resonance imaging was used in one and computed tomography in 17 studies. In general, the aortic annulus was more circular in systole and predominantly oval in diastole. Whereas the annular long-axis diameter showed insignificant change throughout the cycle, the short-axis diameter, area, and perimeter were significantly larger in systole compared with diastole. Hence, the aortic annulus does undergo dynamic changes during the cardiac cycle. In patients with large conformational changes, diastolic compared with systolic measurements can result in undersizing TAVI prostheses. Due to the complex annular anatomy and dynamic change, three-dimensional assessment in multiple phases has utmost importance in TAVI planning to improve prosthesis sizing.

MDCT evaluation of aortic root and aortic valve prior to TAVI. What is the optimal imaging time point in the cardiac cycle?

OBJECTIVES

To determine the optimal imaging time point for transcatheter aortic valve implantation (TAVI) therapy planning by comprehensive evaluation of the aortic root.

METHODS

Multidetector-row CT (MDCT) examination with retrospective ECG gating was retrospectively performed in 64 consecutive patients referred for pre-TAVI assessment. Eighteen different parameters of the aortic root were evaluated at 11 different time points in the cardiac cycle. Time points at which maximal (or minimal) sizes were determined, and dimension differences to other time points were evaluated. Theoretical prosthesis sizing based on different measurements was compared.

RESULTS

Largest dimensions were found between 10 and 20% of the cardiac cycle for annular short diameter (10%); mean diameter (10%); effective diameter and circumference-derived diameter (20%); distance from the annulus to right coronary artery ostium (10%); aortic root at the left coronary artery level (20%); aortic root at the widest portion of coronary sinuses (20%); and right leaflet length (20%). Prosthesis size selection differed depending on the chosen measurements in 25-75% of cases.

CONCLUSION

Significant changes in anatomical structures of the aortic root during the cardiac cycle are crucial for TAVI planning. Imaging in systole is mandatory to obtain maximal dimensions.

KEY POINTS

• Most aortic root structures undergo significant dimensional changes throughout the cardiac cycle. • The largest dimensions of aortic parameters should be determined to optimize TAVI. • Circumference-derived diameter showed maximum dimension at 20% of the cardiac cycle.