A four-dimensional study of the aortic root dynamics

External aortic annuloplasty with a dedicated expansible ring improves outcomes in remodeling root repair compared with homemade Dacron ring

OBJECTIVES

In remodeling valve-sparing root replacement with external annuloplasty, we compare long-term outcomes of a calibrated expansible extra-aortic ring with a homemade Dacron ring.

METHODS

All patients (2003-2020) operated for root aneurysm with/without aortic insufficiency (AI) were included. The standardized CAVIAAR (conservation aortique valvulaire dans les insuffisances aortiques et anévrysmes de la racine-Valve sparing in aortic insufficiencies and root aneurysms) technique was root remodeling and external annuloplasty ring with the EXTRA-AORTIC Ring or homemade Dacron ring.

RESULTS

Among 486 patients (age 52.3 ± 14.0 years) operated for root aneurysm, 375 (repair rate: 77.1%) underwent root remodeling with annuloplasty (extra-aortic ring, n = 289, vs Dacron ring, n = 86). At 10 years (median follow-up, 4.08 years' interquartile range, 1.95-7.61), unmatched and matched analysis showed that patients with extra-aortic ring had greater survival, similar to the general population (93.3% vs 79.9%, P = .097), lower reoperation incidence (2.0% vs 9.7%, P = .0098), and lower AI grade >2 recurrence (1.9% vs 11.2%, P = .0042), compared with patients with a Dacron ring. Mixed-effect model showed that with extra-aortic ring annuloplasty, annular dilation over time (P = .0033) was prevented and, compared with the homemade Dacron ring, root expansibility was better preserved (3.22% vs 2.12%, P = .002) and mean transvalvular gradient was lower (6.58 mm Hg vs 7.94 mm Hg, P = .001). Tricuspid and bicuspid valves with extra-aortic ring had similar reoperation (4.3% vs 0.85%, P = .65) and AI grade >2 incidence (2.7% vs 1.2%, P = .61), expansibility (P = .29), and diameter (P = .47), whereas mean transvalvular gradient was lower for tricuspid valves (5.58 mm Hg vs 7.60 mm Hg, P = .004).

CONCLUSIONS

Valve-sparing root remodeling with calibrated expansible extra-aortic ring annuloplasty improves the outcomes of reoperation and recurrent AI compared with a homemade Dacron ring. It prevents dilation and maintains physiological root dynamics for durable valve repair.

Strain estimation in aortic roots from 4D echocardiographic images using medial modeling and deformable registration

Even though the central role of mechanics in the cardiovascular system is widely recognized, estimating mechanical deformation and strains in-vivo remains an ongoing practical challenge. Herein, we present a semi-automated framework to estimate strains from four-dimensional (4D) echocardiographic images and apply it to the aortic roots of patients with normal trileaflet aortic valves (TAV) and congenital bicuspid aortic valves (BAV). The method is based on fully nonlinear shell-based kinematics, which divides the strains into in-plane (shear and dilatational) and out-of-plane components. The results indicate that, even for size-matched non-aneurysmal aortic roots, BAV patients experience larger regional shear strains in their aortic roots. This elevated strains might be a contributing factor to the higher risk of aneurysm development in BAV patients. The proposed framework is openly available and applicable to any tubular structures.

Retrograde dye perfusion of the proximal aorta - A postmortem technical study

Introduction

Multiple cardiovascular conditions can lead to unexpected fatality, which is defined as sudden cardiac death. One of these potentially underlying conditions is aortic regurgitation, which can be caused by discrete changes of the geometry of the proximal aorta. To analyze aortic valve competency and furthermore to elucidate underlying pathological alterations of the coronary arteries and the vasa vasorum a perfusion method to simulate a diastolic state was designed.

Material and methods

A postmortem approach with retrograde perfusion of the ascending aorta with methylene blue was applied to three bodies. The procedure comprised cannulation of the brachiocephalic trunk, clamping of the aortic arch between brachiocephalic trunk and left carotid artery, infusion of 250 ml of methylene blue, and optical clearing of the superficial tissue layers after perfusion. Organs were examined directly following perfusion and after optical clearing.

Results

Assessment and visualization of aortic valve competency and the vasa vasorum were possible in all three instances. Visualization of the coronary perfusion was impaired by postmortem thrombus formation. Optical clearing did not provide additional information.

Discussion

The method presented here is a time- and cost-efficient way of visualizing aortic valve competency and the vasa vasorum. The visualization of the vasa vasorum highlights the potential of this method in basic research on diseases of the great arteries and coronaries. However, for a time-efficient functional analysis of the coronaries, other methods must be applied.

Dynamic Volumetric Assessment of the Aortic Root: The Influence of Bicuspid Aortic Valve Competence

BACKGROUND

Aortic root evaluation is conventionally based on 2-dimensional measurements at a single phase of the cardiac cycle. This work presents an image analysis method for assessing dynamic 3-dimensional changes in the aortic root of minimally calcified bicuspid aortic valves (BAVs) with and without moderate to severe aortic regurgitation.

METHODS

The aortic root was segmented over the full cardiac cycle in 3-dimensional transesophageal echocardiographic images acquired from 19 patients with minimally calcified BAVs and from 16 patients with physiologically normal tricuspid aortic valves (TAVs). The size and dynamics of the aortic root were assessed using the following image-derived measurements: absolute mean root volume and mean area at the level of the ventriculoaortic junction, sinuses of Valsalva, and sinotubular junction, as well as normalized root volume change and normalized area change of the ventriculoaortic junction, sinuses of Valsalva, and sinotubular junction over the cardiac cycle.

RESULTS

Normalized volume change over the cardiac cycle was significantly greater in BAV roots with moderate to severe regurgitation than in normal TAV roots and in BAV roots with no or mild regurgitation. Aortic root dynamics were most significantly different at the mid-level of the sinuses of Valsalva in BAVs with moderate to severe regurgitation than in competent TAVs and BAVs.

CONCLUSIONS

Echocardiographic reconstruction of the aortic root demonstrates significant differences in dynamics of BAV roots with moderate to severe regurgitation relative to physiologically normal TAVs and competent BAVs. This finding may have implications for risk of future dilatation, dissection, or rupture, which warrant further investigation.

Aortic valve neocuspidisation using xenologous pericardium versus bioprosthetic valve replacement

BACKGROUND

Surgical aortic valve replacement (SAVR) for aortic valve stenosis (AS) patients with small aortic root is associated with a higher rate of prosthesis-patient mismatch and suboptimal clinical outcomes. Aortic valve neocuspidisation using xenologous pericardium (xAVNeo) has shown favorable hemodynamic performance. The aim was to compare 6-year clinical outcomes of xAVNeo with SAVR.

METHODS

Between 2003-2018, 412 patients with severe AS and small aortic root received either xAVNeo (N=114) or bioprosthesis (N=298). After propensity matching, the cohort included 222 patients. The primary endpoints were early-, 6-year mortality and freedom from reoperation. Mean follow-up averaged 3.4±3.1 years and was 95% complete.

RESULTS

Early mortality was 8.1% for the SAVR group vs 9.9% for the xAVNeo group, OR 1.25 [CI95% 0.51-2.89]. The estimated survival probabilities at 6 years for the SAVR and xAVNeo cohorts were 89.9% and 88.8%, respectively, OR 1.07 [0.49-2.34]. Progressive degeneration of the neo-cusps resulted in mean gradients increase from 6.1±2.3 mmHg to 22.7±11.5 mmHg ( p<0.0001 ); cusp sclerosis was the most common indication for reoperation in the xAVNeo group with a linearised rate of 1.92% vs. 0.26% per patient-year, rate ratio = 7.41 [CI95% 0.95-333.7]. The freedom from reoperation was 84.8% at 6 years, inferior to that of the SAVR group (100%).

CONCLUSIONS

Early clinical outcome and 6-year survival following xAVNeo and SAVR was comparable. However, xAVNeo using bovine pericardium was associated with a higher rate of structural valve deterioration and inferior freedom from reoperation when compared to SAVR.

Leaflet kinematics after the Yacoub and Florida-sleeve operations: results of an in vitro study

OBJECTIVES

The Florida-sleeve is a valve-sparing technique that causes minimal interference to leaflet kinematics and aortic root dynamism. The aim of this in vitro study was to evaluate the effects of the Florida-sleeve and Yacoub techniques on aortic leaflet kinematics.

METHODS

Two groups of 6 whole porcine hearts were treated with either the Florida-sleeve technique or the Yacoub technique and tested in a pulsatile loop. Valve fluid dynamics, coronary flow analysis and valve echocardiograms were performed both before and after the procedures.

RESULTS

Both procedures showed no difference in rapid valve opening time as compared with their respective baseline values. The Florida-sleeve procedure showed a shorter slow closing time (192 ± 19 ms vs baseline 244 ± 14 ms, P = 0.016) and increased slow closing velocity (-1.5 ± 0.4 cm/s vs baseline -0.8 ± 0.4 cm/s, P = 0.038). In the rapid valve closing phase, the Yacoub procedure showed a trend towards slower closing valve velocity (-16 ± 9 cm/s vs baseline -25 ± 9 cm/s, P = 0.07). The Yacoub procedure showed larger leaflet displacement at the end of the slow valve closing time that was 2.0 ± 0.5 cm vs baseline 1.5 ± 0.3 cm, P = 0.044. When comparing the Florida-sleeve and Yacoub procedures, the former showed statistically significant shorter slow valve closing time (P = 0.017).

CONCLUSIONS

This study showed that the Florida-sleeve technique alters the slow closing phase of the aortic valve leaflet kinematics when compared with both the normal baseline and Yacoub procedure, while the latter showed a larger leaflet displacement before the rapid closing valve phase.

Aortic annulus and the importance of annuloplasty

Dystrophic aortic insufficiency accounts for the majority of Western cases of aortic insufficiency and can be divided into the three phenotypes of isolated aortic insufficiency, dilated aortic root, and dilated ascending aorta. Each of these phenotypes is associated with a dilated annulus and/or sinotubular junction. Recent international guidelines recommend reimplantation or remodeling with aortic annuloplasty for valve-sparing root replacement, as well as consideration of aortic valve repair in cases of aortic insufficiency. A dilated aortic annulus is a major risk factor for failure of aortic valve repair procedures, indicating the need to address the annulus at the time of aortic valve or root repair. Calibrated annuloplasty should be performed at sub- and supravalular levels in order to restore the ratio of the sinotubular junction and annulus and be adapted according to the phenotype of the root and ascending aorta. Standardization of aortic valve repair techniques with use of a calibrated annuloplasty will improve dissemination of techniques and rate of aortic valve repair. Current medical evidence shows that aortic valve repair is safe, produces better quality of life, and reduces valve-related mortality compared to prosthetic valve replacement.

Reexamining remodelling in children

OBJECTIVES

Some studies have suggested that root remodelling is unsuitable as valve-sparing aortic root replacement in children because of the increased risk of valve failure. This study reviewed our experience with root remodelling in children.

METHODS

All patients who underwent root remodelling at the age of ≤18 years between 1999 and 2016 were evaluated. In 2004, cusp effective height was measured intraoperatively and prolapse was corrected with central plication on the cusp. Suture annuloplasty was introduced after 2009 for annular dilatation.

RESULTS

There were 17 consecutive patients. The median age at operation was 14 (2.8-18) years. Aortic valve morphology was tricuspid in 10 patients, bicuspid in 5 patients, unicuspid in 1 patient and a pulmonary autograft in 1 patient. Marfan syndrome, Loeys-Dietz syndrome and other connective tissue diseases were present in 11, 1 and 2 patients, respectively. Five patients had more than moderate aortic regurgitation. The median graft size used for root remodelling was 24 (18-26) mm. Cusp repair and annuloplasty were performed in 15 and 14 patients, respectively. The mean follow-up time was 6.5 ± 4.3 years. One patient with preoperatively severely depressed ventricular function died in the hospital from persistent heart failure. One patient (operated on before 2004) required aortic valve reoperation due to cusp prolapse. One patient with a unicuspid valve had developed moderate aortic regurgitation, and the other 14 patients had mild or less regurgitation. The median diameter of the sinus of Valsalva at the last follow-up was 36 (30-43) mm, Z-score of 1.5 (-3.5 to 3.9).

CONCLUSIONS

Root remodelling can be performed in children with favourable results by appropriate cusp repair and annuloplasty.

Aortic Root Dynamics in Sleeve Aortic Sparing Procedure: Echocardiographic and Computational Studies

In Sleeve procedure, the leaflets-sinus unit is maintained. We hypothesized that this feature partially preserves aortic root (AR) dynamics and leaflets kinematics and limits tensions in the leaflets. We tested our hypothesis based on in vivo and computational assessment of leaflets and AR dynamics. AR and aortic leaflet kinematics was assessed by transthoracic echocardiography in 10 patients treated with the Sleeve procedure and in 10 healthy patients. Numerical calculations with the Finite Element Method were performed to support the analysis of the clinical results and provide a better understanding of the behavior of the AR treated via the Sleeve procedure. Echocardiographic evidence showed that AR expansion in the Sleeve group was partially preserved as compared to the Control group (2.9 ± 2.5% vs 7.7 ± 6.3%, P = 0.038) and of the sinotubular junction (2.9 ± 1.5% vs 7.3 ± 3.8%, P = 0.003), and significantly preserved at the Valsalva sinuses level (6.7 ± 2.6% vs 9.5 ± 4.3%) with not statistically significant differences (P = 0.11). In none of the cardiac phases, differences in aortic valve leaflets kinematics were measured between the 2 groups; computational results were rather consistent with this evidence. Computational results well matched echocardiographic evidences, allowing for their mechanistic interpretation. Near-normal opening and closing characteristics can be accomplished by a technique that preserves the shape and the dynamics of the Valsalva sinuses. Whether the substantial preservation of the AR distensibility and leaflets kinematics observed in this study will favorably affect long-term valve durability it remains to be ascertained.

Geometric changes in the aortic valve annulus during the cardiac cycle: impact on aortic valve repair

OBJECTIVES

The growing experience in aortic valve (AV) repair showed that annular stabilization is a crucial component to achieve stable long-term results after AV repair. Dynamic changes in the AV annulus during the cardiac cycle may have an impact on annuloplasty design.

METHODS

We retrospectively analysed full cardiac cycle multislice computed tomography data from 58 consecutive patients (mean age 75.9 ± 6.5 years, 36% men) with normally functioning tricuspid AVs (normal AV subgroup). The following computed tomography parameters were measured during systole and diastole: maximum, minimum and mean AV annulus diameter, AV annular area and AV annular perimeter. The AV annular eccentricity index was calculated (%) [(max AV annulus × 100/min AV annulus) - 100] in systole and diastole. Subsequently, multislice computed tomography data from 20 patients with severe aortic regurgitation were analysed [aortic valve regurgitation (AR) subgroup].

RESULTS

In the normal AV subgroup, there was a significant decrease in the mean AV annulus diameter from systole to diastole (i.e. 24.6 ± 2.5 mm vs 23.9 ± 2.4 mm, respectively; P < 0.001), which occurred predominantly in the short annular axis (i.e. 21.2 ± 2.4 mm in systole vs 19.9 ± 2.3 mm in diastole; P < 0.001). The mean AV annular area decreased significantly in diastole (i.e. 467.5 ± 94.5 mm2 in systole vs 444.8 ± 86.1 mm2 in diastole; P = 0.012). The annular eccentricity index increased significantly in diastole (33.0 ± 12.2% in systole vs 41.4 ± 13.5% in diastole; P < 0.001). Furthermore, we found an inverse linear correlation between the mean AV annulus diameter and the annular eccentricity index (r = -0.40, P = 0.034). The diastolic annular eccentricity index was significantly reduced in the AR subgroup (i.e. 41.4 ± 13.5% in the normal AV subgroup vs 33.7 ± 14.8% in the AR cohort; P = 0.035).

CONCLUSIONS

The normal AV annulus undergoes important geometric deformation during the cardiac cycle that is significantly reduced in diastole in the AR scenario. A novel AV annuloplasty system should ideally adapt for this marked diastolic annular eccentricity and thereby allow for dynamic aortic root changes during the cardiac cycle.

Structural valve deterioration does not alter tissue valves' radiopaque landmarks: Implications for valve-in-valve therapy

BACKGROUND

Valve-in-valve is established as a safe and efficient alternative to redo surgery in the treatment of structural valve deterioration (SVD). In vitro models rely on the radiopaque landmarks of undeteriorated tissue valves to establish the optimal implantation level of the transcatheter heart valves inside the deteriorated valves. In computed assisted procedures, the radiopaque landmarks of the deteriorated valves may be used to guide valve implantation through image fusion. The purpose of this study is to determine whether SVD alters the radiopaque landmarks of stented tissue valves.

METHODS

Our approach was based on the computation of relevant anatomical measurements from CT images. Radiopaque landmarks of degenerated bioprostheses and the corresponding undeteriorated valves were extracted to create surface meshes and cloud points using grey-level thresholding. 3D registration using an iterative closest point algorithm was used to align the corresponding cloud points, while the modified Hausdorff Distance was applied to determine the differences between them.

RESULTS

The proposed evaluation was performed on 19 degenerated tissue valves. 15 valves were scanned from patients evaluated for valve-in-valve procedures, and 4 bioprostheses were scanned after surgical extraction during redo aortic valve replacement. All the degenerated valves were compared to the corresponding undeteriorated models. Overall, the mean difference between degenerated and undeteriorated valves was 0.33 ± 0.12 mm. The maximum observed registration error was 0.66 mm.

CONCLUSIONS

Our study demonstrates no significant difference between the radiopaque landmarks of deteriorated and undeteriorated bioprostheses after the occurrence of SVD. Our findings suggest therefore that SVD does not alter radiopaque landmarks of stented tissue valves. These results validate in-vitro studies of optimal transcatheter heart valves implantation inside deteriorated tissue valves based on their radiopaque landmarks, and allow the use of non-deteriorated valves' imaging features in computer assisted valve-in-valve procedures.

Predictors of Aortic Valve Repair Failure

Aortic valve repair is the preferred approach for the treatment of severe aortic insufficiency (AI), as it allows patients to keep their native aortic valve, thus substantially reducing the risk of prosthesis-related complications. Several studies have documented excellent long-term outcomes of aortic valve repair. The major complication of this operation is AI recurrence, with ensuingneed for reoperation. The surgical experience accumulated over the last two decades has allowed for better understanding of the mechanisms of recurrent AI after aortic valve repair. Herein, we review the current state of knowledge on predictors of aortic valve repair failure. These include unaddressed annular dilation, residual cusp prolapse or retraction, commissural orientation, and use of patch material. This enhanced understanding has led to the development of increasingly refined techniques and improved patient outcomes. Continued follow-up and detailed data collection at the time of surgery, together with three-dimensional echo imaging, will allow further improvements in aortic valve repair.

Comparison of Dacron ring and suture annuloplasty for aortic valve repair-a porcine study

Background

A subvalvular annuloplasty is often used for aortic valve repair in patients with isolated aortic regurgitation with aortic annulus dilatation. Our aim was to characterize and compare annulus geometry and dynamics of the Dacron ring and suture annuloplasty and compare it with the native aortic annulus under standardized conditions.

Methods

We randomized 29 pigs of 80 kg into a Dacron ring group, a suture annuloplasty group and a native control group. The assessment was performed using sonomicrometry crystals for evaluation of dynamic geometry, and pressure measurements and echocardiography to evaluate valve performance.

Results

Aortic annulus area (AAA) was significantly reduced in the Dacron and Suture group compared with the Native group. Expansibility was similar and within normal physiologic limits in all three groups (Native: 12%±7%; Dacron: 11%±3%; Suture: 10%±4%). The largest segmental expansion was observed at the right coronary sinus (RC) in the Native and Dacron group but in the Suture group there was no significant difference between segments. The aortic annulus was primarily oval in systole and became more circular in diastole in the Native and Dacron group, however, in the Suture group, the sphericity remained relatively unchanged throughout the cardiac cycle.

Conclusions

This study is the first to describe and compare detailed segmental geometry of the Dacron ring and suture annuloplasty in a standardized porcine model. The two annuloplasties effectively downsized the aortic annulus, while expansibility was maintained. Each annuloplasty had its own geometrical characteristics, but the Dacron ring was more similar to the native aortic annulus than the suture annuloplasty. This study suggests that the Dacron ring offers a more physiological and standardized support by mimicking the geometry and dynamics of the native aortic annulus and thus is a preferable choice over the suture annuloplasty for valve-sparing aortic root procedures.

Rationale for aortic annuloplasty to standardise aortic valve repair

Available evidence shows that aortic valve repair reduces valve-related mortality and improves quality of life compared to prosthetic aortic valve replacement. One of the most important predictors of bicuspid and tricuspid aortic valve repair failure is the absence of treating a dilated aortic annulus greater than 25-28 mm. Competency of the aortic valve depends on multiple factors including the diameter of the annulus, sinotubular junction, valve cusps and commissures. Dystrophic aortic insufficiency (AI) is the commonest cause of AI in the Western world and is characterised by dilatation of the aortic annulus (≥25 mm), sinuses and/or sinotubular junction (≥30 mm). Depending on whether the sinuses of Valsalva and/or tubular ascending aorta are dilated, three phenotypes can be identified: dilated aortic root, dilated ascending aorta and isolated AI. All three phenotypes are associated with a dilated aortic annulus. Aortic annuloplasty reduces the dilated aortic annulus and improves the surface of coaptation, as in the case of mitral valve repair. In treating AI, it is also important to restore the physiological sinotubular junction/annulus ratio, which can be carried out with remodeling root repair + subvalvular annuloplasty (for dilated aortic root), tubular ascending aorta replacement + subvalvular annuloplasty (for dilated ascending aorta) and double sub- and supra-valvular annuloplasty (for isolated AI). Aortic annuloplasty is now considered an essential component of aortic valve repair and valve-sparing root surgery.

Asymmetric Dynamics of the Native Aortic Annulus Evaluated by Force Transducer and Sonomicrometry in a Porcine Model

PURPOSE

With new repair techniques of the aortic root and valve emerging, a detailed understanding of the dynamics of the aortic annulus and valve is required for optimal results. The objective of this study was to characterize geometrical changes and force distribution of the native porcine aortic annulus throughout the cardiac cycle.

METHODS

Measurements were performed in an acute 80 kg porcine model (n = 7) using sonomicrometry crystals in the aortic annulus for evaluation of geometry and dynamics, annular force transducer evaluating force distribution, and pressure measurements and echocardiography evaluating valve performance.

RESULTS

Overall, segmental force distribution and geometrical changes differed between different segments of the aortic annulus. The highest force development was found at the left/right interleaflet triangle (2.87 ± 2.1 N) and the largest segmental expansion was observed at the right-coronary and left-coronary sinus. The aortic annulus changed configuration throughout the cardiac cycle and became more oval in systole.

CONCLUSIONS

This study is the first to describe detailed segmental dynamics and force distribution of the native aortic annulus in a porcine model in vivo. The heterogenous behavior of the aortic annulus suggests that different segments demand different support for repair of the aortic root and valve.

Biomechanical characterization and comparison of different aortic root surgical techniques

OBJECTIVES

Understanding the biomechanical impact of aortic valve-sparing techniques is important in an era in which surgical techniques are developing and are increasingly being used based on biomechanical understanding that is essential in the refining of existing techniques. The objective of this study was to describe how the valve-sparing remodelling (Yacoub) and reimplantation (David Type-1) techniques affect the biomechanics of the native aortic root in terms of force distribution and geometrical changes.

METHODS

Two force transducers were implanted into 22 pigs, randomized to 1 of 3 groups (David = 7, native = 7 and Yacoub = 8) along with 11 sonomicrometry crystals and 2 pressure catheters. Force and geometry data were combined to obtain the local structural stiffness in different segments of the aortic root.

RESULTS

The radial structural stiffness was not different between groups (P = 0.064) at the annular level; however, the David technique seemed to stabilize the aortic annulus more than the Yacoub technique. In the sinotubular junction, the native group was more compliant (P = 0.036) with the right-left coronary segment than the intervention groups. Overall, the native aortic root appeared to be more dynamic at both the annular level and the sinotubular junction than both intervention groups.

CONCLUSIONS

In conclusion, the David procedure may stabilize the aortic annulus more than the Yacoub procedure, whereas the leaflet opening area was larger in the latter (P = 0.030). No difference (P = 0.309) was found in valve-opening delay between groups. The 2 interventions show similar characteristics at the sinotubular junction, whereas the David technique seemed more restrictive at the annular level than the Yacoub technique.

A systematic approach to 3D echocardiographic assessment of the aortic root

[first paragraph of article]Severe aortic regurgitation (AR) and/or severe abnormalities of the aortic root and the tubular ascending aorta (TAA) are indications for surgical treatment. The correct diagnosis, the choice of optimal treatment, as well as optimal timing of surgery, mainly depend on findings obtained by echocardiography - which is usually the initial diagnostic modality applied in clinical practice. Therefore, an appropriate morphological and functional quantification of the aortic valve (AV) and the aortic root complex is required. Aside from the need of standardization to provide a precise objective evaluation, the use of modern echocardiographic technologies - especially 3D-echocardiography -are less often implemented in clinical routine. The present manuscript focuses on the advantages of transthoracic and transesophageal 3D-echocardiography (TTE, TEE) for an improved assessment of the AV and the aortic root complex to provide accurate and comprehensive measurements for making the correct diagnosis and defining further therapeutic strategies.

Dynamics of the aortic annulus in 4D CT angiography for transcatheter aortic valve implantation patients

BACKGROUND

Transcatheter aortic valve implantation (TAVI) is a well-established treatment for patients with severe aortic valve stenosis. This procedure requires pre-operative planning by assessment of aortic dimensions on CT Angiography (CTA). It is well-known that the aortic root dimensions vary over the heart cycle. However, sizing is commonly performed at either mid-systole or end-diastole only, which has resulted in an inadequate understanding of its full dynamic behavior.

STUDY GOAL

We studied the variation in annulus measurements during the cardiac cycle and determined if this variation is dependent on the amount of calcification at the annulus.

METHODS

We measured and compared aortic root annular dimensions and calcium volume in CTA acquisitions at 10 cardiac cycle phases in 51 aortic stenosis patients. Sub-group analysis was performed based on the volume of calcium by splitting the population into mildly and severely calcified valves subgroups.

RESULTS

For most annulus measurements, the largest differences were found between 10% and 70 to 80% cardiac cycle phases. Mean difference (±standard deviation) in annular minimum diameter, maximum diameter, area, and aspect ratio between mid-systole and end-diastole phases were 1.0 ± 0.29 mm (p = 0.065), 0.30 ± 0.24 mm (p = 0.7), 24.1 ± 7.6 mm2 (p < 0.001), and 0.041 ± 0.012 (p = 0.039) respectively. Calcium volume measurements varied strongly during the cardiac cycle. The dynamic annulus area was behaving differently between mildly and severely calcified subgroups (p = 0.02). Furthermore, patients with severe aortic calcification were associated with larger annulus diameters.

CONCLUSION

There is a significant variation of annulus area and calcium volume measurement during the cardiac cycle. In our measurements, only the dynamic variation of the annulus area is dependent on the severity of the aortic calcification. For TAVI candidates, the annulus area is significantly larger in mid-systole compared to end-diastole.

A novel approach to the quantification of aortic root in vivo structural mechanics

Understanding aortic root in vivo biomechanics can help in elucidating key mechanisms involved in aortic root pathologies and in the outcome of their surgical treatment. Numerical models can provide useful quantitative information. For this to be reliable, detailed aortic root anatomy should be captured. Also, since the aortic root is never unloaded throughout the cardiac cycle, the modeled geometry should be consistent with the in vivo loads acting on it. Achieving such consistency is still a challenge, which was tackled only by few numerical studies. Here we propose and describe in detail a new approach to the finite element modeling of aortic root in vivo structural mechanics. Our approach exploits the anatomical information yielded by magnetic resonance imaging by reconstructing the 3-dimensional end-diastolic geometry of the aortic root and makes the reconstructed geometry consistent with end-diastolic loading conditions through the estimation of the corresponding prestresses field. We implemented our approach through a semiautomated modeling pipeline, and we applied it to quantify aortic root biomechanics in 4 healthy participants. Computed results highlighted that including prestresses into the model allowed for pressurizing the aortic root to the end-diastolic pressure while matching the image-based ground truth data. Aortic root dynamics, tissues strains, and stresses computed at relevant time points through the cardiac cycle were consistent with a broad set of data from previous computational and in vivo studies, strongly suggesting the potential of the method. Also, results highlighted the major role played by the anatomy in driving aortic root biomechanics.

3D physiological model of the aortic valve incorporating small coronary arteries

The diseases of the coronary arteries and the aortic root are still the leading causes of mortality and morbidity worldwide. In this study, a 3D global fluid-structure interaction of the aortic root with inclusion of anatomically inspired small coronary arteries using the finite element method is presented. This innovative model allows to study the impact and interaction of root biomechanics on coronary hemodynamics and brings a new understanding to small coronary vessels hemodynamics. For the first time, the velocity profiles and shear stresses are reported in distal coronary arteries as a result of the aortic flow conditions in a global fluid-structure interaction model.

An Expansible Aortic Ring in Aortic Root Remodeling: Exact Position, Pulsatility, Effectiveness, and Stability in Three-Dimensional CT Study

BACKGROUND

The aim of this study was to assess effectiveness, stability, position, and expansibility of an expansible aortic annuloplasty ring with computed tomography (CT).

METHODS

Ten men (median age 51 years) scheduled for aortic root remodeling with implantation of external annuloplasty ring underwent contrast-enhanced CT of the aortic root preoperatively, postoperatively, and at a median of 21 months after operation. A reconstructed transverse double oblique view of the aortic base (AB) and of the new defined annuloplasty ring base (ARB; plane of the lower edge of the ring) in systole and diastole were obtained. The diameters, perimeter, and area were measured. In addition, the distances between AB and ARB in the nadir of each sinus were measured.

RESULTS

We found 12% reduction of the postoperative AB and 19% of ARB perimeter in both systole (p = 0.004, p < 0.001, respectively) and diastole (p = 0.001, p < 0.001, respectively) compared with preoperative. There was 22% reduction of the postoperative AB area in systole and 24% in diastole (p = 0.002, p = 0.001, respectively) and 33% reduction of the ARB area in systole and 32% in diastole (p < 0.001 for both) compared with the preoperative period. Nearly all measured variables in the follow-up period showed a slight increase compared with the postoperative period; however, they did not reach statistical significance. The postoperative systolic-diastolic differences in the three measured variables at the level of AB and ARB were statistically significant and were maintained throughout the follow-up period. The base of the ring was implanted 2 ± 2 mm at the right, 0 ± 1 mm at the left above the AB, and 2 (-3 to 2) mm at the noncoronary nadir below the AB.

CONCLUSIONS

This study demonstrates imaging evidence of the effectiveness, stability, and pulsatility of the annuloplasty ring in aortic root remodeling in follow-up and describes the exact position of the ring at the base of the aortic root.

Volume Measurements in Aortic Root Assessment Using Two-Dimensional Echocardiography

BACKGROUND

Aortic dilatation is associated with the presence of aortic diseases. Current guidelines for assessing the aortic root (AoR) depend on linear measurements acquired by two-dimensional (2D) echocardiography. We considered that real-time three-dimensional echocardiography, which correlates better with AoR volume obtained by computed tomography, is widely unavailable, and therefore, there is a need to determine the AoR volume using 2D echocardiography.

METHODS

Fifty-one consecutive apparently healthy volunteers were recruited and subsequently divided into three age groups. Specified planes of acquisition and previously defined landmarks were identified, and phases of the cardiac cycle that allowed for measurement standardization were used. Volume was determined by the modified Simpson’s method.

RESULTS

Although the average diastolic and systolic volume measurements of the AoR dimensions were not significantly different across the three age groups in the study population, a highly significant difference was observed in the volume measurements between male and female normotensive persons, P < 0.01 in each case. AoR volume measurements were five times in the diseased compared with the normotensive individuals; however, linear measurements were only 1.5 times in size of the normal individuals. Both point and interval estimates of the volume measurements of AoR in adult normotensives in three age groups were presented as baseline information.

CONCLUSIONS

We hereby present a novel way to determine the AoR volume using 2D echocardiography and the normal reference range with respect to age and gender. We also established the relevance of our measurement by comparing the normal population with two isolated diseased aortas.

Immersed boundary-finite element model of fluid-structure interaction in the aortic root

It has long been recognized that aortic root elasticity helps to ensure efficient aortic valve closure, but our understanding of the functional importance of the elasticity and geometry of the aortic root continues to e-volve as increasingly detailed in vivo imaging data become available. Herein, we describe a fluid-structure interaction model of the aortic root, including the aortic valve leaflets, the sinsuses of Valsalva, the aortic annulus, and the sinotubular junction, that employs a version of Peskin's immersed boundary (IB) method with a finite element (FE) description of the structural elasticity. As in earlier work, we use a fiber-based model of the valve leaflets, but this study extends earlier IB models of the aortic root by employing an incompressible hyperelastic model of the mechanics of the sinuses and ascending aorta using a constitutive law fit to experimental data from human aortic root tissue. In vivo pressure loading is accounted for by a backward displacement method that determines the unloaded configurations of the root model. Our model yields realistic cardiac output at physiological pressures, with low transvalvular pressure differences during forward flow, minimal regurgitation during valve closure, and realistic pressure loads when the valve is closed during diastole. Further, results from high-resolution computations indicate that although the detailed leaflet and root kinematics show some grid sensitivity, our IB model of the aortic root nonetheless produces essentially grid-converged flow rates and pressures at practical grid spacings for the high-Reynolds number flows of the aortic root. These results thereby clarify minimum grid resolutions required by such models when used as stand-alone models of the aortic valve as well as when used to provide models of the outflow valves in models of left ventricular fluid dynamics.

Early results of extra-aortic annuloplasty ring implantation on aortic annular dimensions

OBJECTIVES

Dilatation of the aortic annulus is a cause of recurrent aortic regurgitation following the Ross or Yacoub procedures. Use of an extra-aortic annuloplasty ring is a potentially useful adjunct procedure. The aim of this study was to analyze the early effectiveness and mid-term stability of this surgical approach.

METHODS

From 2011 to 2015, 50 patients (mean age, 43 ± 14 years) underwent adjunct extra-aortic annuloplasty ring implantation (n = 39 Dacron rings and n = 11 ExAo rings [CORONEO Inc, Montreal, Canada]). Median ring size was 28 mm (range, 27-32 mm). All patients had aortic regurgitation or a dilated aortic annulus. Concomitant surgical procedure was a valve-sparing remodeling procedure (n = 32) or a Ross procedure (n = 18). Baseline and follow-up echocardiographic systolic and diastolic aortic annular dimensions were prospectively collected. Longitudinal analyses were performed using mixed-effect models. Median follow-up was 12 months (98% complete).

RESULTS

Use of an extra-aortic annuloplasty ring resulted in a significant decrease in both systolic (27.9 ± 0.5 mm preoperatively vs 23.6 ± 0.3 mm at discharge, P < .001) and diastolic (24.8 ± 0.4 mm preoperatively vs 20.3 ± 0.3 mm at discharge, P < .001) dimensions. Mean systolic and diastolic dimensions remained statistically unchanged up to 2 years postoperatively, compared with their predischarge values. Systolic expansion of the annulus was conserved early after surgery (16% systolic expansion) and preserved up to 2 years after ring implantation.

CONCLUSIONS

Use of an extra-aortic annuloplasty ring is effective at reducing annular diameters. This remains stable at mid-term follow-up, with preservation of aortic annular dynamics. Longer-term studies are required to determine the continued stability and impact on long-term clinical outcomes.

Numerical analysis of the 3-dimensional aortic root morphology during the cardiac cycle

OBJECTIVES

The aim was to define the 3-dimensional (3D) geometrical changes of the aortic root and to determine the local shear stress profile of aortic root elements during the cardiac cycle.

METHODS

Six sonomicrometric crystals (200 Hz) were implanted into the aortic root of five pigs at the commissures and at the aortic root base (AoB). 3D aortic root deformation including volume, torsion and tilt angle were determined. Geometrical data with measured local flow and pressure conditions was used for computed fluid dynamics modelling of the aortic root.

RESULTS

Compared with end-diastole, the sinotubular junction and AoB have maximal expansion at peak ejection: 16.42 ± 6.36 and 7.60 ± 2.52%, and minimal at isovolaemic relaxation: 2.87 ± 1.62 and 1.85 ± 1.79%. Aortic root tilt and rotation angle were maximal at the end of diastole: 17.7 ± 8.8 and 21.2 ± 2.09°, and decreased to 15.24 ± 8.14 and 18.3 ± 0.1.94° at peak ejection. High shear stress >20 Pa was registered at peak ejection at coaptations, and during diastole at the superior two-thirds of the leaflets and intervalvular triangles (IVTs). The leaflet body, inferior one-third of the IVTs and valve nadir were exposed to moderate shear stress (8-16 Pa) during the cardiac cycle.

CONCLUSIONS

Aortic root geometry demonstrates precise 3D changes of tilt and rotation angle. Reduction of angles during ejection results in a straight cylinder with low shear stress that facilitates the ejection; the increase during diastole results in a tilted frustum with elevated shear stress. Findings can be used for comparative analysis of native and synthetic structures with individual compliance.

Sutureless aortic valve replacement for aortic incompetence

OBJECTIVE

Sutureless prostheses for surgical aortic valve replacement (AVR) are usually used in degenerative calcified aortic stenosis. Less is known on the application of sutureless prostheses for pure aortic incompetence.

METHODS

Between 2011 and 2014, 442 patients were operated on with the Perceval aortic sutureless valve implant. We identified 11 patients (10 female, mean age 70.5) who underwent sutureless AVR for pure aortic incompetence (off-label use). Three patients had a left ventricle ejection fraction of 30% or less. Mean logistic EuroSCORE was 15.2 (range 2.2-45.2). In five patients associated mitral procedures (three [60%] repair and two [40%] replacement) were performed. Four procedures were performed through a minimally invasive approach (three right minithoracotomies and one partial sternotomy).

RESULTS

Mean cardiopulmonary bypass time was 130.2 min and aortic cross clamp time was 82.2 min. Mean implanted prosthesis size was 24.5 ± 1.3 (median 25) mm (insignificant correlation with preoperative aortic valve annulus measurement by transthoracic echocardiography: 21.6 ± 1.5 [median 21] mm, Pearson's r = 0.373, p = 0.259). One patient died on 24th day after AVR associated with aortic arch replacement and hypothermic circulatory arrest (10 years after correction for type A aortic dissection). No residual para- or intravalvular leakage was present on discharge and 12-month follow-up. No migration of the prosthesis occurred.

CONCLUSION

Sutureless AVR is an option in selected patients with aortic incompetence. Preoperative aortic annulus measurement by echocardiography has poor predictive value for estimation of prosthetic valve size.

Aortic valve leaflet replacement with bovine pericardium to preserve native dynamic capabilities of the aortic annulus

Valve replacement is typically the most appropriate option for treating aortic valve stenotic insufficiency. However, neither mechanical nor bioprosthetic replacement components preserve the circumferential expansion and contraction of a native aortic annulus during the cardiac cycle, because the prosthetic ring is affixed to the annulus. A 64-year-old man presented with a bicuspid and stenotic aortic valve, and the native annulus was too small to accommodate a porcine replacement valve. We fashioned new aortic leaflets from bovine pericardium with use of a template, and we affixed the sinotubular junction with use of inner and outer stabilization rings. Postoperative echocardiograms revealed coaptation of the 3 new leaflets with no regurgitation. At the patient's 5.5-year follow-up examination, echocardiograms showed flexible leaflet movement with a coaptation height of 7 mm, and expansion and contraction of the aortic annulus similar to that of a normal native annulus. The transvalvular pressure gradient was insignificant. If long-term durability of the new leaflets is confirmed, this method of leaflet replacement and fixation of the sinotubular junction might serve as an acceptable alternative to valve replacement in the treatment of aortic valve stenosis. We describe the patient's case and present our methods and observations.

The living aortic valve: From molecules to function

The aortic valve lies in a unique hemodynamic environment, one characterized by a range of stresses (shear stress, bending forces, loading forces and strain) that vary in intensity and direction throughout the cardiac cycle. Yet, despite its changing environment, the aortic valve opens and closes over 100,000 times a day and, in the majority of human beings, will function normally over a lifespan of 70–90 years. Until relatively recently heart valves were considered passive structures that play no active role in the functioning of a valve, or in the maintenance of its integrity and durability. However, through clinical experience and basic research the aortic valve can now be characterized as a living, dynamic organ with the capacity to adapt to its complex mechanical and biomechanical environment through active and passive communication between its constituent parts. The clinical relevance of a living valve substitute in patients requiring aortic valve replacement has been confirmed. This highlights the importance of using tissue engineering to develop heart valve substitutes containing living cells which have the ability to assume the complex functioning of the native valve.

Aortic valve reconstruction using autologous pericardium for ages over 80 years

Background

We performed original aortic valve reconstruction using autologous pericardium; the feasibility for elderly patients is reviewed.

Methods

From April 2007 through September 2011, aortic valve reconstruction was carried out in 86 patients over the age of 80 years. Twenty-seven patients were male and 59 were female. Mean age was 82.9 ± 2.5 years. Seventy-two patients had aortic stenosis and 14 had aortic regurgitation. Mean preoperative surgical annular diameter was 19.5 ± 2.5 mm. There were 80 (90.7%) cases of small aortic annulus. Mean preoperative logistic EuroSCORE was 22.9 ± 15.8.

Results

Isolated aortic valve reconstructions were performed in 51 patients. Concomitant procedures included coronary artery bypass grafting in 6, hemiarch aortic replacements in 6, 9 maze procedures, and some combinations. No conversion to valve replacement was required. Mean follow-up was 1243 days. There were 3 hospital deaths due to noncardiac causes. No reoperation was needed. Survival at 56 months was 87.0%. No thromboembolic event occurred. Echocardiography 3.5 years after surgery revealed an average peak pressure gradient of 14.6 ± 3.8 mm Hg. No moderate or severe regurgitation was recorded.

Conclusions

Aortic valve reconstruction is feasible for patients older than 80 years, resulting in good hemodynamics and a better quality of life, without anticoagulation.

Assessment of cyclic changes in the diameter of the aortic annulus using speckle-tracking trans-esophageal echocardiography

It is uncertain whether dynamic variation in the diameter of the aortic annulus occurs during the cardiac cycle in humans. The purpose of this study was to analyze cyclic changes of the aortic annulus using speckle-tracking trans-esophageal echocardiography. The subjects were 40 patients with aortic stenosis and 40 controls. Absolute and relative changes in the diameter of the aortic annulus and the times at which the maximum and minimum diameters occurred during the cardiac cycle were determined using speckle-tracking trans-esophageal echocardiography. The maximum and minimum diameters were 22.9 ± 2.7 and 20.0 ± 2.9 mm, respectively, in controls. The change in diameter of the aortic annulus was 2.9 ± 0.7 mm, and the relative change was 12.9 ± 3.5%. The maximum aortic annulus diameter was reached at the onset of aortic valve opening, and the minimum diameter occurred in the rapid filling phase. The change in diameter of the aortic annulus was significantly smaller (2.2 ± 0.6 mm vs. 2.9 ± 0.7 mm, p < 0.0001), and the time to reach the maximum diameter was significantly longer (98.5 ± 17.5 ms vs. 83.4 ± 18.2 ms, p = 0.0004), in the aortic stenosis group than in the control group. The study found that dynamic changes of the aortic annulus occur in the cardiac cycle and can be measured using speckle-tracking trans-esophageal echocardiography. We also found that aortic stenosis has an effect on the extent and timing of these changes. This suggests that accurate assessment of aortic annulus diameter requires consideration of the timing of the cardiac cycle.

Systematic Approach to Aortic Valvuloplasty in Children and Young Adults

Valve repair in children and young adults is an attractive alternative to replacement or Ross procedure. In the past, the various valvuloplasty techniques have addressed isolated valve pathology. Recently, however, a holistic approach involving repair of all aortic root structures has evolved and promised to be an excellent alternative to valve replacement. It provides good long-term results and avoids all the drawback of prosthetic valve insertion in this age group. Development of ideal patch material needed for valve repair and better understanding of the anatomy and function of the aortic root may further improve the short- and long-term outcomes of aortic valvuloplasty.