In vivo assessment of aortic root geometry in normal controls using 3D analysis of computed tomography

Aortic valve cusp size and shape in dilated trileaflet aortic roots

OBJECTIVES

The objective of the study was to quantify the differences in cusp size and shape in patients with normal and dilated trileaflet aortic roots and in dilated roots with or without aortic regurgitation.

METHODS

A retrospective analysis of computed tomography studies in patients with normal and dilated trileaflet aortic roots was performed measuring root and cusp dimensions. Normal root size was defined as sinuses of Valsalva diameter less than 40 mm, dilated as 45 mm or greater. Root measurements normalized to basal ring diameter and cusp measurements normalized to geometric height were analyzed to assess the shape. Additionally, comparison of dilated roots with or without aortic regurgitation was made.

RESULTS

We analyzed 146 normal and 104 dilated aortic roots and 73 propensity-matched pairs. Dilated roots were larger in all dimensions and had increased ratio between commissural and basal ring diameter (1.58 ± 0.23 vs 1.11 ± 0.10, P < .001). Cusps in dilated roots were larger in all measured dimensions and were elongated with increased normalized cusp insertion length (3.64 ± 0.39 vs 3.26 ± 0.20, P < .001) and normalized free margin length (2.53 ± 0.30 vs 2.16 ± 0.19, P < .001). In patients with dilated root and no cusp prolapse (n = 83), those with moderate or severe aortic regurgitation had larger commissural diameter but similar cusp dimensions compared with those with no or mild aortic regurgitation.

CONCLUSIONS

The cusps in dilated roots elongate transversely and to a lesser degree radially. Functional aortic regurgitation is caused by extensive commissural dilatation and not by inadequate cusp adaptation.

Three-dimensional modelling of aortic leaflet coaptation and load-bearing surfaces: in silico design of aortic valve neocuspidizations

OBJECTIVES

Three-dimensional (3D) modelling of aortic leaflets remains difficult due to insufficient resolution of medical imaging. We aimed to model the coaptation and load-bearing surfaces of the aortic leaflets and adapt this workflow to aid in the design of aortic valve neocuspidizations.

METHODS

Geometric morphometrics, using landmarks and semilandmarks, was applied to the geometric determinants of the aortic leaflets from computed tomography, followed by an isogeometric analysis using Non-Uniform Rational Basis Splines (NURBS). Ten aortic valve models were generated, measuring determinants of leaflet geometry defined as 3D NURBS curves, and leaflet coaptation and load-bearing surfaces were defined as 3D NURBS surfaces. Neocuspidizations were obtained by either shifting the upper central coaptation landmark towards the sinotubular junction or using parametric neo-landmarks placed on a centreline drawn between the centroid of the aortic root base and centroid of a circle circumscribing the 3 upper commissural landmarks.

RESULTS

The ratio of the leaflet free margin length to the geometric height was 1.83, whereas the ratio of the commissural coaptation height to the central coaptation height was 1.93. The median coaptation surface was 137 mm2 (IQR 58) and the median load-bearing surface was 203 mm2 (60) per leaflet. Neocuspidization multiplied the central coaptation height by 3.7 and the coaptation surfaces by 1.97 and 1.92 using the native coaptation axis and centroid coaptation axis, respectively.

CONCLUSIONS

Geometric morphometrics reliably defined the coaptation and load-bearing surfaces of aortic leaflets, enabling an experimental 3D design for the in silico neocuspidization of aortic valves.

Updated 2022 ACC/AHA Guideline Improves Concordance Between TTE and CT in Monitoring Marfan Snydrome and Related Disorders, but Relevant Measurement Differences Remain Frequent

Background

Patients diagnosed with Marfan syndrome or a related syndrome require frequent aorta monitoring using imaging techniques like transthoracic echocardiography (TTE) and computed tomography (CT). Accurate aortic measurement is crucial, as even slight enlargement (>2 mm) often necessitates surgical intervention. The 2022 ACC/AHA guideline for Aortic Disease Diagnosis and Management includes updated imaging recommendations. We aimed to compare these with the 2010 guideline.

Methods

This retrospective study involved 137 patients with Marfan syndrome or a related disorder, undergoing TTE and ECG-triggered CT. Aortic diameter measurements were taken based on the old 2010 guideline (TTE: inner edge to inner edge, CT: external diameter) and the new 2022 guideline (TTE: leading edge to leading edge, CT: internal diameter). Bland-Altman plots compared measurement differences.

Results

Using the 2022 guideline significantly reduced differences outside the clinical agreement limit from 49% to 26% for the aortic sinus and from 41% to 29% for the ascending aorta. Mean differences were -0.30 mm for the aortic sinus and +1.12 mm for the ascending aorta using the 2022 guideline, compared to -2.66 mm and +1.21 mm using the 2010 guideline.

Conclusion

This study demonstrates for the first time that the 2022 ACC/AHA guideline improves concordance between ECG-triggered CT and TTE measurements in Marfan syndrome patients, crucial for preventing life-threatening aortic complications. However, the frequency of differences >2 mm remains high.

Clinical Relevance/Application

Accurate aortic diameter measurement is vital for patients at risk of fatal aortic complications. While the 2022 guideline enhances concordance between imaging modalities, frequent differences >2 mm persist, potentially impacting decisions on aortic repair. The risk of repeat radiation exposure from ECG-triggered CT, considered the 'gold standard', continues to be justified.

Aortic valve leaflet and root dimensions in normal tricuspid aortic valves: A computed tomography study

BACKGROUND AND AIM OF THE STUDY

The aim of this study was to use coronary computed tomography in patients with normal tricuspid aortic valves to perform detailed aortic root and aortic valve geometric analysis with a focus on the asymmetry of the three leaflets.

METHODS

Retrospective analysis of anonymized coronary computed tomography angiograms was performed using dedicated software, where manual aortic root segmentation and marking of several points of interest were followed by automated measurements of aortic root and leaflets. Asymmetry of the three leaflets in individual patients was assessed by calculating absolute and relative differences between the largest and the smallest of the three leaflets.

RESULTS

We analyzed 70 aortic valves, the mean patient age was 53 ± 11 years, and 50% (n = 35) of patients were female. All aortic valves were tricuspid, without calcifications and aortic roots were of normal dimensions. Some degree of asymmetry was present in all analyzed valves. Absolute and relative differences for free margin length were 3.2 ± 1.4 mm and 9.3 ± 3.8%, respectively. The largest relative difference was noted in the coaptation area (36.5 ± 16.5%) and the smallest in leaflet effective height (6.1 ± 4.8%). Using predefined cutoff criteria for absolute differences in leaflet dimensions, 86% of the valves were classified as asymmetric.

CONCLUSIONS

Most normal tricuspid aortic valves show some degree of asymmetry. Equal free margin length of the three leaflets is not needed for normal tricuspid aortic valve function. Leaflet effective height showed the least amount of asymmetry confirming its importance in keeping the aortic valve competent.

Design of an aortic polymeric valve with asymmetric leaflets and evaluation of its performance by finite element method

BACKGROUND

The geometry of leaflets plays a significant role in prosthetic valves' (PVs) performance. Typically, natural aortic valves have three unequal leaflets, which differ in size. The present study aims to design an asymmetric tri-leaflet polymeric valve with one large and two small leaflets based on commissure lengths and leaflet eccentricities.

METHODS

Eccentricity was related to commissure lengths based on the deformation of the free margins for the fully-opened state of leaflets. The polystyrene-block-polyethylene-polypropylene-block-polystyrene polymer characterized the material properties of the leaflets. The Finite Element Method (FEM) was used to evaluate performance parameters, including maximum geometric orifice area (GOA), average GOA, maximum von Mises stress, and leaflet's coaptation surface area (CSA).

RESULTS

Asymmetric valves with no eccentricity provided a low level of GOA because the asymmetric form of small leaflets caused them to close faster than the large leaflet, leading to a sudden drop in the GOA during systole. As the radial curve tends towards a straight line, an undesirable coaptation occurs, and peak stress increases despite higher GOAs. A new radial curve consisting of two straight lines connected by an arc that provided 25.64 mm² coaptation surface area (CAS) and 117.54 mm² average GOA, was proposed to improve coaptation and GOA.

CONCLUSION

The radial curve of leaflets affects the valve's performance more than other geometric parameters. The combination of straight lines and arcs for radial curves was selected as the reference model for asymmetric valves with one large and two small leaflets.

Relationship Between Leaflets and Root in Normal Aortic Valve Based on Computed Tomography Imaging: Implication for Aortic Valve Repair

Objective: By assessing the normal dimensions and the relationship between the aortic root and leaflets in Chinese population, the objective of this three-dimensional computed tomography (3DCT)-based study was to establish a matching reference for leaflets and aortic root for aortic valve (AV) repair.

Method: Electrocardiogram-gated multi-detector CT was performed on 168 Chinese participants with a normal aortic valve. Measurements of the aortic annuli and leaflets were obtained. The correlations between and the ratios of the specific root and leaflet measurements were analyzed. The references for the leaflet and root dimensions were suggested based on geometric height (gH) using a linear regression equation. The utility of the ratios was tested with CT images of 15 patients who underwent aortic valve repair.

Result: The mean annulus diameter (AD), sino-tubular junction (STJ) diameter, geometric height (gH), effective height (eH), free margin length (FML), commissural height (ComH), inter-commissural distance (ICD), and coaptation height (CH) were 22.4 ± 1.7 mm, 27.3 ± 2, 0.4 mm, 15.5 ± 1.7 mm, 8.9 ± 1.2 mm, 32.0 ± 3.4 mm, 17.9 ± 1.9 mm, 23.1 ± 2.3 mm, and 3.1 ± 0.6 mm, respectively. The gH/AD, FML/ICD, and eH/ComH ratios were 0.69 ± 0.07, 1.38 ± 0.08, and 0.50 ± 0.07, respectively. The gH correlated with all other leaflet and root measurements (P < 0.01), whereas the FML demonstrated a better correlation with ICD compared with gH (R² = 0.75, and R² = 0.37, respectively). The FML/ICD and eH/ComH ratios might be used to assess leaflet-root mismatch and post-repair leaflet billowing.

Conclusion: The normal aortic valve measurements based on 3DCT revealed a specific relationship between the root and leaflets; and this will guide the development of an objective method of aortic valve repair.

Understanding the Aortic Root Using Computed Tomographic Assessment: A Potential Pathway to Improved Customized Surgical Repair

There is continued interest in surgical repair of both the congenitally malformed aortic valve, and the valve with acquired dysfunction. Aortic valvar repair based on a geometric approach has demonstrated improved durability and outcomes. Such an approach requires a thorough comprehension of the complex 3-dimensional anatomy of both the normal and congenitally malformed aortic root. In this review, we provide an understanding of this anatomy based on the features that can accurately be revealed by contrast-enhanced computed tomographic imaging. We highlight the complimentary role that such imaging, with multiplanar reformatting and 3-dimensional reconstructions, can play in selection of patients, and subsequent presurgical planning for valvar repair. The technique compliments other established techniques for perioperative imaging, with echocardiography maintaining its central role in assessment, and enhances direct surgical evaluation. This additive morphological and functional information holds the potential for improving selection of patients, surgical planning, subsequent surgical repair, and hopefully the subsequent outcomes.

Application of Artificial Intelligence to Cardiovascular Computed Tomography

Cardiovascular computed tomography (CT) is among the most active fields with ongoing technical innovation related to image acquisition and analysis. Artificial intelligence can be incorporated into various clinical applications of cardiovascular CT, including imaging of the heart valves and coronary arteries, as well as imaging to evaluate myocardial function and congenital heart disease. This review summarizes the latest research on the application of deep learning to cardiovascular CT. The areas covered range from image quality improvement to automatic analysis of CT images, including methods such as calcium scoring, image segmentation, and coronary artery evaluation.

Normative Aortic Valvar Measurements in Adults Using Cardiac Computed Tomography - A Potential Guide to Further Sophisticate Aortic Valve-Sparing Surgery

BACKGROUND

A thorough understanding of the anatomy of the aortic valve is necessary for aortic valve-sparing surgery. Normal valvar dimensions and their relationships in the living heart, however, have yet to be fully investigated in a 3-dimensional fashion.

METHODS AND RESULTS

In total, 123 consecutive patients (66±12 years, Men 63%) who underwent coronary computed tomographic angiography were enrolled. Mid-diastolic morphology of the aortic roots, including height of the interleaflet triangles, geometric height, free margin length of each leaflet, effective height, and coaptation length were measured using multiplanar reconstruction images. Average height of the interleaflet triangle, geometric height, free margin length, effective height, and the coaptation length were 17.3±1.8, 14.7±1.3, 32.6±3.6, 8.6±1.4, and 3.2±0.8 mm, respectively. The right coronary aortic leaflet displayed the longest free margin length and shortest geometric height. Geometric height, free margin length, and effective height showed positive correlations with aortic root dimensions. Coaptation length, however, remained constant regardless of aortic root dimensions.

CONCLUSIONS

Diversities, as well as characteristic relationships among each value involving the aortic root, were identified using living-heart datasets. The aortic leaflets demonstrated compensatory elongation along with aortic root dilatation to maintain constant coaptation length. These measurements will serve as the standard value for revealing the underlying mechanism of aortic regurgitation to plan optimal aortic valve-sparing surgery.

Preoperative Cardiac Computed Tomography Characteristics Associated with Recurrent Aortic Regurgitation after Aortic Valve Re-Implantation

Objective

To identify the preoperative cardiac computed tomography (CT) factors influencing postoperative recurrent aortic regurgitation (AR) in patients who underwent aortic valve repair with the re-implantation technique (David operation) due to AR.

Materials and Methods

A total of 117 patients (age, 49.4 ± 15.6 years; 83 males) who underwent the David operation for AR were included in this retrospective study. Aortic root profiles including the aortic regurgitant orifice area (ARO) and the aortic cusp asymmetry ratio of the areas (ASR_area), which is defined as the maximum/minimum areas among the three cusp areas at the level of the commissures, were measured on preoperative cardiac CT scans. Clinical and CT findings were compared between a group with recurrent AR grade < 3 (no, trivial, or mild AR) and recurrent ≥ 3 + AR. To determine the optimal cut-off values of ASR and ARO, the receiver operating characteristic (ROC) curve was used. Cox regression analysis was used for the analysis of the factors affecting recurrent 3 + AR.

Results

Postoperatively, recurrent 3 + AR developed in 17 (14.5%) patients and occurred within a median of 268 days (interquartile range: 78–582 days). The cut-off ARO value for discriminating the patients with recurrent 3 + AR was > 24 mm² (sensitivity, 76.5%; specificity 64.8%), and the area under the ROC curve (AUC) was 0.72. For ASR_area, the cut-off value was > 1.58 (sensitivity, 76.5%; specificity, 58.0%) and the AUC was 0.64. Multivariable Cox regression showed that ARO > 24 mm² (hazard ratio = 3.79, p = 0.020) was a potential independent parameter for recurrent 3 + AR. ROC for the linear regression model showed that the AUC for both ARO and ASR_area was 0.73 (95% confidence interval, 0.64–0.81, p < 0.001).

Conclusion

ARO and ASR_area detected on preoperative cardiac CT would be potentially helpful for identifying AR patients who may benefit from the David operation.

Three-dimensional volumetric measurement of the aortic root compared to standard two-dimensional measurements using cardiac computed tomography

INTRODUCTION

Two-dimensional measurements are self-evidently limited when seeking accurately to represent the three-dimensional complexity of the aortic root. Volumetric measurement, therefore, seems an ideal alternative for a more accurate assessment.

MATERIALS AND METHODS

We retrospectively analyzed 123 individuals undergoing cardiac computed tomography. We measured the dimensions of the sinuses of Valsalva using routine multiplanar short axis imaging. Three conventional two-dimensional methods were applied to measure the dimensions of the sinuses. These involved bisecting center of sinus-to-center of interleaflet triangle measures, along with center of sinus-to-center of sinus, and largest sinus-to-sinus measurements. We then quantified the volumes of the root using the volume-rendering method.

RESULTS

The mean dimensions of the sinuses were significantly greater when measured using the largest sinus-to-sinus method as opposed to center of sinus-to-center of interleaflet triangle and center of sinus-to-center of sinus methods (33.6 ± 3.6 mm vs. 31.1 ± 3.1 mm and 30.9 ± 3.3 mm, p < .0001). The mean root volume of 13.6 ± 4.2 ml showed the strongest correlation with the mean dimensions of the sinuses of Valsalva measured using the bisecting method (R² = .8401, p < .0001).

CONCLUSIONS

By using two- and three-dimensional measurements, we have provided average data for the structurally normal aortic root. The differences and correlations encountered should be noted when evaluating and following changes in the diseased root.