Regional annular geometry in patients with mitral regurgitation: implications for annuloplasty ring selection

Entire Mitral Valve Reconstruction Using Porcine Extracellular Matrix: Adding a Ring Annuloplasty

PURPOSE

This study investigated the implications of inserting a flexible annuloplasty ring after reconstructing the entire mitral valve in a porcine model using a previously investigated tube graft design made of 2-ply small intestinal submucosa extracellular matrix (CorMatrix®).

METHODS

An acute model with eight 80-kg pigs, each acting as its own control, was used. The entire mitral valve was reconstructed with a 2-ply small intestinal submucosa extracellular matrix tube graft (CorMatrix®). Subsequently, a Simulus® flexible ring was inserted. The characterization was based on mitral annular geometry and valvular dynamics with sonomicrometry and echocardiography.

RESULTS

After adding the ring annuloplasty, the in-plane annular dynamics were more constant throughout the cardiac cycle compared to the reconstruction alone. However, the commissure-commissure distance was statistically significantly decreased [35.0 ± 3.4 mm vs. 27.4 ± 1.9 mm, P < 0.001, diff =  - 7.6 mm, 95% CI, - 9.8 to (-5.4) mm] after ring insertion, changing the physiological annular D-shape into a circular shape which created folds at the coaptation zone resulting in a central regurgitant jet on color Doppler.

CONCLUSION

We successfully reconstructed the entire mitral valve using 2-ply small intestinal submucosal extracellular matrix (CorMatrix®) combined with a flexible annuloplasty. The annuloplasty reduced the unphysiological systolic widening previously found with this reconstructive technique. However, the Simulus flex ring changed the physiological annular D-shape into a circular shape and hindered a correct unfolding of the leaflets. Thus, we do not recommend a flexible ring in conjunction with this reconstructive technique; further investigations are needed to discover a more suitable remodelling annuloplasty.

Computational Modeling of the Subject-Specific Effects of Annuloplasty Ring Sizing on the Mitral Valve to Repair Functional Mitral Regurgitation

Surgical repair of functional mitral regurgitation (FMR) that occurs in nearly 60% of heart failure (HF) patients is currently performed with undersizing mitral annuloplasty (UMA), which lacks short- and long-term durability. Heterogeneity in valve geometry makes tailoring this repair to each patient challenging, and predictive models that can help with planning this surgery are lacking. In this study, we present a 3D echo-derived computational model, to enable subject-specific, pre-surgical planning of the repair. Three computational models of the mitral valve were created from 3D echo data obtained in three pigs with HF and FMR. An annuloplasty ring model in seven sizes was created, each ring was deployed, and post-repair valve closure was simulated. The results indicate that large annuloplasty rings (> 32 mm) were not effective in eliminating regurgitant gaps nor in restoring leaflet coaptation or reducing leaflet stresses and chordal tension. Smaller rings (≤ 32 mm) restored better systolic valve closure in all investigated cases,but excessive valve tethering and restricted motion of the leaflets were still present. This computational study demonstrates that for effective correction of FMR, the extent of annular reduction differs between subjects, and overly reducing the annulus has deleterious effects on the valve.

Utilization of Engineering Advances for Detailed Biomechanical Characterization of the Mitral-Ventricular Relationship to Optimize Repair Strategies: A Comprehensive Review

The geometrical details and biomechanical relationships of the mitral valve-left ventricular apparatus are very complex and have posed as an area of research interest for decades. These characteristics play a major role in identifying and perfecting the optimal approaches to treat diseases of this system when the restoration of biomechanical and mechano-biological conditions becomes the main target. Over the years, engineering approaches have helped to revolutionize the field in this regard. Furthermore, advanced modelling modalities have contributed greatly to the development of novel devices and less invasive strategies. This article provides an overview and narrative of the evolution of mitral valve therapy with special focus on two diseases frequently encountered by cardiac surgeons and interventional cardiologists: ischemic and degenerative mitral regurgitation.

Level of agreement between three-dimensional transthoracic and transesophageal echocardiography for mitral annulus evaluation: A feasibility and comparison study

INTRODUCTION

Mitral annulus assessment is of utmost importance for the management of patients with mitral valve (MV) abnormalities, as it helps to determine the decision for surgical or transcatheter treatment. Three-dimensional (3D) transesophageal echocardiography (TOE) has been the only reliable echocardiographic method for the evaluation of the mitral annulus by now. However, newer transthoracic echocardiography (TTE) 3D probes have enabled to provide accurate measurements as well and become a valuable tool when TOE is contraindicated. The aim of this study is to assess the feasibility of 3D TTE analysis of mitral annulus and the level of agreement with 3D TOE measurements.

METHODS

A total of 121 consecutive patients were assessed with 3D TTE and TOE. All mitral annulus parameters were retrospectively analyzed with the dedicated 4D autoMVQ application. Bland-Altman analysis and intraclass correlation coefficient were used for the comparison and agreement between the two methods. Half of our patients had normal mitral valves and served as control group, while the other half had various mitral valve pathologies.

RESULTS

AutoMVQ analysis was not feasible in 11 out of 121 TTE examinations (91% feasibility) and in 4 out of 121 TOE examinations (96% feasibility). Mitral annular area and perimeter were slightly larger in TTE than those measured by TOE (12.7 ± 3.6 vs. 12.4 ± 3.2 cm² for area and 12.7 ± 1.7 vs. 12.5 ± 1.6 cm for perimeter), however still showing strong correlation (r = .942 and r = .922, respectively). The majority of mitral valve measurements (anterior-posterior, medial-lateral and commissural diameter, aorto-mitral angle and anterior leaflet length) were similar among the two methods with strong correlation (r > .80). Inter-trigonal distance, posterior leaflet length and tenting height showed weaker agreement between TTE and TOE (r = .687, r = .687, r = .634, respectively). Mitral annular dimensions (by 3D area) were found to be significantly larger in patients with MV pathology (13.5 ± 3.5 vs. 11 ± 2.3 cm² ), atrial fibrillation (14.4 ± 3 vs. 11.4 ± 2.8 cm² ), left ventricular (13.8 ± 3.1 vs. 11.7 ± 3.1cm² ) and left atrial dilatation (13 ± 3.3 vs. 10.6 ± 2.3cm² ) compared to the individuals in the control group (p < .001 for all comparisons).

CONCLUSIONS

Assessment of the MV with 3D TTE with dedicated MVQ software is feasible and accurate, showing strong correlation and agreement with TOE measurements.

Mitral Annulus Geometry and Dynamic Motion Changes in Patients With Aortic Regurgitation: A Three-Dimensional Transesophageal Echocardiographic Study

OBJECTIVE

The aim of the present study was to investigate the mitral annulus (MA) geometry and dynamic motion changes in patients with aortic regurgitation (AR) before and after aortic valve replacement (AVR). Moreover, the difference in the effect of the type of prosthetic aortic valve on MA was compared.

DESIGN

Prospective observational study.

SETTING

Cardiac operating room at a single hospital.

PARTICIPANTS

Eighty-two patients with isolated moderate-to-severe AR who underwent AVR. Forty patients with normal valves were enrolled as controls.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The MA geometry and dynamic motion throughout the cardiac cycle were evaluated semiautomatically by three-dimensional transesophageal echocardiography. The severity of functional mitral regurgitation was intraoperatively evaluated. All patients were divided into 2 groups depending on the type of prosthetic valve (mechanical valve and bioprosthetic valve groups). Before AVR, compared with the control group without AR, the AR group demonstrated larger MA dimensions and the MA geometry was flatter. The contraction fraction of the MA area, perimeter, and height during the whole cardiac cycle were larger in the AR group (p < 0.05 for all). After AVR, most MA geometric and dynamic parameters decreased and functional mitral regurgitation also improved. In the postoperative subset analyses, the mechanical valve group showed a larger contraction fraction of the MA area and perimeter than the bioprosthetic valve group (p < 0.05 for both).

CONCLUSIONS

The MA geometry and dynamic motion changed markedly in patients with AR. These spatial and dynamic changes were restored to a certain extent after surgical correction of the aortic valve. However, the effects produced by mechanical and bioprosthetic valves on MA were different.

In vivo assessment of mitral valve leaflet remodelling following myocardial infarction

Each year, more than 40,000 people undergo mitral valve (MV) repair surgery domestically to treat regurgitation caused by myocardial infarction (MI). Although continual MV tissue remodelling following repair is believed to be a major contributor to regurgitation recurrence, the effects of the post-MI state on MV remodelling remain poorly understood. This lack of understanding limits our ability to predict the remodelling of the MV both post-MI and post-surgery to facilitate surgical planning. As a necessary first step, the present study was undertaken to noninvasively quantify the effects of MI on MV remodelling in terms of leaflet geometry and deformation. MI was induced in eight adult Dorset sheep, and real-time three-dimensional echocardiographic (rt-3DE) scans were collected pre-MI as well as at 0, 4, and 8 weeks post-MI. A previously validated image-based morphing pipeline was used to register corresponding open- and closed-state scans and extract local in-plane strains throughout the leaflet surface at systole. We determined that MI induced permanent changes in leaflet dimensions in the diastolic configuration, which increased with time to 4 weeks, then stabilised. MI substantially affected the systolic shape of the MV, and the range of stretch experienced by the MV leaflet at peak systole was substantially reduced when referred to the current time-point. Interestingly, when we referred the leaflet strains to the pre-MI configuration, the systolic strains remained very similar throughout the post-MI period. Overall, we observed that post-MI ventricular remodeling induced permanent changes in the MV leaflet shape. This predominantly affected the MV's diastolic configuration, leading in turn to a significant decrease in the range of stretch experienced by the leaflet when referenced to the current diastolic configuration. These findings are consistent with our previous work that demonstrated increased plastic (i.e. non-recoverable) leaflet deformations post-MI, that was completely accounted for by the associated changes in collagen fiber structure. Moreover, we demonstrated through noninvasive methods that the state of the MV leaflet can elucidate the progression and extent of MV adaptation following MI and is thus highly relevant to the design of current and novel patient specific minimally invasive surgical repair strategies.

Mitral valve prolapse in patients with atrial septal defect: A quantitative three-dimensional echocardiographic analysis

INTRODUCTION AND OBJECTIVES

Mitral valve (MV) prolapse is highly prevalent in patients with atrial septal defect (ASD). Abnormal left ventricular geometry has been proposed as the main mechanism of MV prolapse in ASD, however, the changes in the morphology of the MV apparatus remain to be clarified. Our aim was to assess the MV geometry in patients with ASD and MV prolapse.

METHODS

We evaluated 99 patients (73% female, median age 40 years) with ASD who underwent a three-dimensional transesophageal echocardiogram. Three-dimensional analysis of the MV was done using dedicated automated software. Transthoracic echocardiographic parameters were assessed post ASD closure in 28 patients.

RESULTS

MV prolapse was found in 39% of patients. Although smaller left ventricular dimensions and greater interatrial shunt were found in patients with MV prolapse compared with those without prolapse, there was no difference in the subvalvular parameters. MV prolapse was associated with larger mitral anterior-posterior diameter, anterolateral-posteromedial diameter, anterior perimeter, posterior perimeter, total perimeter, and anterior leaflet area (all p < 0.05). Mitral regurgitation was more frequent in patients with MV prolapse (80 vs. 48%, p = 0.002).

CONCLUSIONS

In patients with ASD, the main mechanism of MV prolapse is the presence of an organic primary process of the MV apparatus (excessive anterior mitral leaflet tissue and mitral annular enlargement).

A toolbox for generating scalable mitral valve morphometric models

The mitral valve is a complex anatomical structure, whose shape is key to several traits of its function and disease, being crucial for the success of surgical repair and implantation of medical devices. The aim of this study was to develop a parametric, scalable, and clinically useful model of the mitral valve, enabling the biomechanical evaluation of mitral repair techniques through finite element simulations. MATLAB was used to parameterize the valve: the annular boundary was sampled from a porcine mitral valve mesh model and landmark points and relevant boundaries were selected for the parameterization of leaflets using polynomial fitting. Several geometric parameters describing the annulus, leaflet shape and papillary muscle position were implemented and used to scale the model according to patient dimensions. The developed model, available as a toolbox, allows for the generation of a population of models using patient-specific dimensions obtained from medical imaging or averaged dimensions evaluated from empirical equations based on the Golden Proportion. The average model developed using this framework accurately represents mitral valve shapes, associated with relative errors reaching less than 10% for annular and leaflet length dimensions, and less than 24% in comparison with clinical data. Moreover, model generation takes less than 5 min of computing time, and the toolbox can account for individual morphological variations and be employed to evaluate mitral valve biomechanics; following further development and validation, it will aid clinicians when choosing the best patient-specific clinical intervention and improve the design process of new medical devices.

Annular Dynamics and Leaflet Geometry in Patch Reconstruction of the Posterior Mitral Leaflet After Adding a Flexible Annuloplasty Ring

PURPOSE

Patch reconstruction of the posterior mitral leaflet using small intestinal submucosa extracellular matrix has been successfully performed in a porcine study. The patch reconstruction, however, resulted in non-physiological systolic widening of the mitral annulus, suggesting the need for an annuloplasty ring. The objective was to characterize the impact on annular dynamics and leaflet geometry of adding a flexible annuloplasty ring to the posterior mitral leaflet patch reconstruction.

METHODS

Measurements were performed in an acute 80-kg porcine model, with seven pigs acting as their own controls. The posterior mitral leaflet was reconstructed with a 2-ply small intestinal submucosa extracellular matrix patch (CorMatrix®). Additionally, a Simulus® Flexible Annuloplasty Ring (Medtronic Inc., Minneapolis, MN, USA) was inserted. Mitral annular dynamics were evaluated using sonomicrometry, and leaflet geometry was described using echocardiography.

RESULTS

The annuloplasty ring reduced mitral annular dimensions and restricted cyclic changes in mitral annular area (126 ± 19 vs. 30 ± 13 mm², p < 0.001), septal-lateral and commisure-commisure distances. Ring annuloplasty prevented systolic widening in the mitral annulus after posterior mitral leaflet reconstruction. The annular saddle shape and leaflet coaptation length (8.7 ± 2.3 vs. 9.7 ± 1.3 mm, p = 0.221) were comparable before and after ring insertion.

CONCLUSIONS

The flexible annuloplasty ring resulted in a downsized annulus with restriction of cyclic annular changes in the reconstructed mitral valve. Ring insertion preserved the annular saddle shape and coaptation length. The ring annuloplasty counteracted the non-physiological annular dynamics, and this may improve durability of the posterior mitral leaflet patch reconstruction.

Optimized mitral annuloplasty ring design reduces loading in the posterior annulus

OBJECTIVE

The study objective was to develop a novel annuloplasty ring with regional flexibility and assess its suture force dynamics in healthy ovine subjects compared with fully rigid or fully flexible rings.

METHODS

Materially heterogeneous rings were created with rigid anterior and posterior, and flexible commissural segments. These rings were created to match the geometry of the Profile 3D ring (Medtronic, Minneapolis, Minn). Each ring was instrumented with 10 force transducers to measure cyclic suture forces (FC) and undersized annuloplasty was performed in 6 healthy ovine subjects. Each FC was recorded and examined for cardiac cycles reaching a maximum left ventricular pressure of 100, 125, and 150 mm Hg. FC was compared with previously reported values from fully rigid Profile 3D and fully flexible prototype rings.

RESULTS

Relative to the fully rigid ring, the heterogeneous ring exhibited 48% reduction in FC at its commissural (rigid vs heterogeneous: 1.80 ± 0.94 N vs 0.95 ± 0.52 N; P < .001) and 32% reduction in posterior (1.90 ± 0.92 N vs 1.29 ± 0.91 N; P < .001) regions, but not in its anterior region (2.45 ± 1.21 N vs 2.23 ± 1.22 N; P = .279). Relative to the fully flexible ring, the heterogeneous ring exhibited no significant differences in FC in any region.

CONCLUSIONS

The reduced FC of the heterogeneous ring relative to the fully rigid ring suggests a promising approach to reduce suture loading while preserving the annular remodeling capability of fully rigid rings. Future studies in diseased subjects are necessary to explore repair effectiveness of this ring.

Geometric description for the anatomy of the mitral valve: A review

The mitral valve is a complex anatomical structure whose physiological functioning relies on the biomechanical properties and structural integrity of its components. Their compromise can lead to mitral valve dysfunction, associated with morbidity and mortality. Therefore, a review on the morphometry of the mitral valve is crucial, more specifically on the importance of valve dimensions and shape for its function. This review initially provides a brief background on the anatomy and physiology of the mitral valve, followed by an analysis of the morphological information available. A characterisation of mathematical descriptions of several parts of the valve is performed and the impact of different dimensions and shape changes in disease is then outlined. Finally, a section regarding future directions and recommendations for the use of morphometric information in clinical analysis of the mitral valve is presented.

Predicting the Number of Edge-to-Edge Repair Devices Needed to Adequately Treat Mitral Regurgitation Using Transesophageal Echocardiography

OBJECTIVES

Increased utilization and highly variable costs seen with percutaneous mitral valve edge-to-edge repair have made cost cutting strategies of significant interest. Mitral regurgitation etiology, the number of devices used, and experience all play a role in variability. Currently a paucity of data exists in predicting the number of devices. Any associations found between echocardiography parameters and the number of devices used could help with pre-procedure planning and device placement strategies, ultimately reducing variability and costs.

DESIGN

In this retrospective analysis the authors evaluated the ability of established and novel three-dimensional (3D) mitral regurgitation measures, namely 3D vena contracta area and vena contracta length, to predict the number of devices used. Other factors evaluated include mitral valve area and ejection fraction. All factors were compared using the Mann Whitney rank sum tests.

PARTICIPANTS

Patients over 18 years old undergoing the MitraClip procedure.

SETTING

Catheterization Laboratory.

MAIN RESULTS

No relationship was found between 3D parameters and the number of devices used, but mitral valve area was strongly associated with the use of multiple devices.

CONCLUSION

The 3D parameters of interest were not associated with the use of multiple devices, but the mitral valve area was associated. Further studies are needed to determine if this relationship is predictive.

On the simulation of mitral valve function in health, disease, and treatment

The mitral valve (MV) is the heart valve that regulates blood ?ow between the left atrium and left ventricle (LV). In situations where the MV fails to fully cover the left atrioventricular ori?ce during systole, the resulting regurgitation causes pulmonary congestion, leading to heart failure and/or stroke. The causes of MV insuf?ciency can be either primary (e.g. myxomatous degeneration) where the valvular tissue is organically diseased, or secondary (typically inducded by ischemic cardiomyopathy) termed ischemic mitral regurgitation (IMR), is brought on by adverse LV remodeling. IMR is present in up to 40% of patients and more than doubles the probability of cardiovascular morbidity after 3.5 years. There is now agreement that adjunctive procedures are required to treat IMR caused by lea?et tethering. However, there is no consensus regarding the best procedure. Multicenter registries and randomized trials would be necessary to prove which procedure is superior. Given the number of proposed procedures and the complexity and duration of such studies, it is highly unlikely that IMR procedure optimization will be achieved by prospective clinical trials. There is thus an urgent need for cell and tissue physiologically based quantitative assessments of MV function to better design surgical solutions and associated therapies. Novel computational approaches directed towards optimized surgical repair procedures can substantially reduce the need for such trial-and-error approaches. We present the details of our MV modeling techniques, with an emphasis on what is known and investigated at various length scales.

Comprehensive Assessment of Mitral Valve Geometry and Cardiac Remodeling With 3-Dimensional Echocardiography After Percutaneous Mitral Valve Repair

MitraClip is a validated treatment for significant mitral regurgitation (MR) in high-risk patients. Aims of the study were to evaluate immediate changes in mitral valve (MV) geometry induced by MitraClip and correlations between baseline geometry and cardiac remodeling. Eighty patients who underwent MitraClip for primary (48%) or secondary (52%) MR were enrolled. Intraoperative transesophageal echocardiographic 3D images were acquired immediately before and after the procedure for MV annulus (MVA) morphology analysis. Transthoracic 3D echocardiography was performed preoperatively and at 6 months follow-up (6MFU). Patients were classified on the basis of MR reduction (ΔMR) at 6MFU as Optimal (ΔMR ≥ 2) or Suboptimal (ΔMR < 2). An optimal result was reached in 60 (75%) patients, whereas 20 subjects showed a ΔMR< 2 at 6MFU. The Optimal showed significantly smaller baseline MVA (antero-posterior diameter 4.05 ± 0.59 vs 4.43 ± 0.68 cm; anterolateral-posteromedial diameter 4.38 ± 0.56 vs 4.70 ± 0.73 cm; MVA circumference 14.1 ± 1.7 vs 15.1 ± 2.3 cm; and 3D area 14.8 ± 3.9 vs 17.4 ± 5.3 cm²), lower sphericity index and nonplanar angle compared with Suboptimal. A value of antero-posterior diameter ≥4.44cm was identified (receiver-operating characteristic curve) as a possible cut-off for preoperative identification of Suboptimal patients. Postoperatively, MitraClip induced reduction of MVA flattening (nonplanar angle), sphericity index, and size (as expressed by antero-posterior diameter, MVA circumference and area). At 6MFU, the Optimal showed significant decrease in left ventricular volumes and pulmonary artery systolic pressure. In conclusion, MitraClip induces remarkable changes in MVA geometry and favorable left ventricular remodeling is detected in patients with optimal mid-term outcome; a preprocedural antero-posterior diameter <4.44cm seems to be a potential predictor of mid-term optimal result.

Comparison of the mitral valve morphologies of Cavalier King Charles Spaniels and dogs of other breeds using 3D transthoracic echocardiography

Background

Myxomatous mitral valve disease (MMVD) is more prevalent in Cavalier King Charles Spaniels (CKCSs) compared to dogs of other breeds at a given age. Abnormal valvular stress is thought to contribute to the development and progression of MMVD, and a relationship exists between mitral valve (MV) morphology and stress acting on the valve.

Objectives

To determine whether the MV morphology of healthy adult CKCSs differs from the morphology of healthy adult dogs of other breeds determined by RT‐3DTTE.

Animals

Thirty‐five healthy CKCSs and 41 healthy dogs of other breeds.

Methods

Prospective cross‐sectional study. Dogs underwent physical examination, conventional echocardiography, and RT‐3DTTE. RT–3DTTE datasets were analyzed using dedicated software for MV morphologic analysis. Morphologic variables were compared between CKCSs and dogs of other breeds.

Results

The MV of healthy CKCSs had a smaller annulus height (0.46 ± 0.11 vs. 0.56 ± 0.17; P = .0021), tenting height (0.26 ± 0.12 vs. 0.42 ± 0.18; P < .001), tenting area (0.42 ± 0.15 vs. 0.79 ± 0.34; P < .001), normalized tenting volume (0.09 [0.05–0.13] vs. 0.14 [0.10–0.20]; P < .001), and normalized area of the posterior leaflet (0.57 ± 0.15 vs. 0.66 ± 0.18; P = .016) compared to healthy dogs of other breeds; this results in CKCSs having a flatter MV with reduced tenting, compared to the MV of other breeds.

Conclusions and Clinical Importance

These morphologic features could confer a mechanical disadvantage and play a role in the predisposition of CKCSs to the early development of MMVD.

Effects of Decreased Annular Height and Annular Saddle-Shaped Non-Planarity in Degenerative Severe Mitral Regurgitation with Normal Left Ventricular Ejection Fraction: Real-Time 3D Transesophageal Echocardiography

Background

The extent of mitral annular (MA) remodeling and dysfunction is correlated with the severity of mitral regurgitation (MR) as well as left atrial (LA) and left ventricular (LV) dilation. MA dysfunction may be a useful prognostic factor for operative timing and MR recurrence after successful mitral valve (MV) repair. The aim of this study was to evaluate additive prognostic factors of MA non-planarity using real-time 3D transesophageal echocardiography (RT3D-TEE) analysis in patients with chronic severe MR and preserved LV systolic function.

Methods

Forty-seven patients with chronic severe MR and preserved LV systolic function scheduled for MV repair were prospectively enrolled. Echocardiographic studies were performed before surgery and postoperatively within 2 weeks and at least 6 months after surgery. RT3D-TEE was performed before the operation and immediately post-operative.

Results

Mean age was 55.4 ± 15.1 years and 24 were male. Annulus height/body surface area (BSA) obtained via RT3D-TEE was correlated with the degree of postoperative LA remodeling. Patients were divided into two groups by average baseline annulus height/BSA. Patients with normal annular height had a smaller postoperative LV end-diastolic dimension, LV end-systolic dimension and LA volume index than patients with decreased annular height. Preoperative annulus height/BSA values strongly predicted postoperative LA remodeling.

Conclusion

MA height may be a useful prognostic factor for determining the timing of surgery in patients with chronic primary MR. Annulus height/BSA assessed via RT3D-TEE may provide additional information predictive of postoperative LA remodeling after successful MV repair.

Image Segmentation and Modeling of the Pediatric Tricuspid Valve in Hypoplastic Left Heart Syndrome

Hypoplastic left heart syndrome (HLHS) is a single-ventricle congenital heart disease that is fatal if left unpalliated. In HLHS patients, the tricuspid valve is the only functioning atrioventricular valve, and its competence is therefore critical. This work demonstrates the first automated strategy for segmentation, modeling, and morphometry of the tricuspid valve in transthoracic 3D echocardiographic (3DE) images of pediatric patients with HLHS. After initial landmark placement, the automated segmentation step uses multi-atlas label fusion and the modeling approach uses deformable modeling with medial axis representation to produce patient-specific models of the tricuspid valve that can be comprehensively and quantitatively assessed. In a group of 16 pediatric patients, valve segmentation and modeling attains an accuracy (mean boundary displacement) of 0.8 ± 0.2 mm relative to manual tracing and shows consistency in annular and leaflet measurements. In the future, such image-based tools have the potential to improve understanding and evaluation of tricuspid valve morphology in HLHS and guide strategies for patient care.

Three-Dimensional Echocardiography Compared With Computed Tomography to Determine Mitral Annulus Size Before Transcatheter Mitral Valve Implantation

BACKGROUND

Previously, through the use of computed tomography (CT), it has been proposed that D-shaped versus saddle-shaped mitral annulus (MA) segmentation is more biomechanically appropriate to determine transcatheter mitral valve implantation size and eligibility.

METHODS AND RESULTS

Forty-one patients with severe mitral regurgitation being considered for transcatheter mitral valve implantation who had undergone cardiac CT and 3-dimensional transesophageal echocardiography (3D-TEE) were retrospectively evaluated. A standardized segmentation protocol for the D-shaped MA was developed using Philips Q-Laboratory mitral valve quantification software. MA dimensions were compared using Spearman's rank correlation and Bland-Altman analysis. Inter- and intraobserver agreement was quantified by intraclass correlation coefficient and Bland-Altman analysis. Mean age was 77±14 years; 71% male (n=29); mitral regurgitation pathogenesis was functional in 54% (n=22) and myxomatous in 46% (n=19). Mean MA area and circumference by 3D-TEE and CT were 11.3±2.7 versus 11.4±3.0 (P=0.67) and 124.1±15.6 versus 123.9±15.5 (P=0.79), respectively, with excellent correlation between modalities (r=0.84 and r=0.86; P<0.0001) and no systematic bias (-0.20±1.8 cm(2) [-3.7 cm(2); 3.3 cm(2)], 0.37±9 mm [-18.0 mm; 17.27 mm]). Mean septal-to-lateral and inter-trigone distances by 3D-TEE and CT were 33.2±4.7 versus 32.5±4.4 (P=0.24) and 31.7±3.5 versus 32.6±3.6 (P=0.06), respectively, with good correlation (r=0.69 and r=0.71; P<0.0001) and no systematic bias (0.77±3.8 mm [-6.7 mm; 8.2 mm], -1.5±3.1 mm [-4.6 mm; 7.6 mm]). There was excellent intra- and interobserver agreement according to intraclass correlation coefficients >0.90 for all parameters.

CONCLUSIONS

Similar to cardiac CT, 3D-TEE allows for D-shaped MA segmentation with no systematic difference in MA dimensions between modalities. This study supports the utilization of 3D-TEE as a complementary tool to CT assessment of the D-shaped MA to determine transcatheter mitral valve implantation size.

Mitral Valve Chordae Tendineae: Topological and Geometrical Characterization

Mitral valve (MV) closure depends upon the proper function of each component of the valve apparatus, which includes the annulus, leaflets, and chordae tendineae (CT). Geometry plays a major role in MV mechanics and thus highly impacts the accuracy of computational models simulating MV function and repair. While the physiological geometry of the leaflets and annulus have been previously investigated, little effort has been made to quantitatively and objectively describe CT geometry. The CT constitute a fibrous tendon-like structure projecting from the papillary muscles (PMs) to the leaflets, thereby evenly distributing the loads placed on the MV during closure. Because CT play a major role in determining the shape and stress state of the MV as a whole, their geometry must be well characterized. In the present work, a novel and comprehensive investigation of MV CT geometry was performed to more fully quantify CT anatomy. In vitro micro-tomography 3D images of ovine MVs were acquired, segmented, then analyzed using a curve-skeleton transform. The resulting data was used to construct B-spline geometric representations of the CT structures, enriched with a continuous field of cross-sectional area (CSA) data. Next, Reeb graph models were developed to analyze overall topological patterns, along with dimensional attributes such as segment lengths, 3D orientations, and CSA. Reeb graph results revealed that the topology of ovine MV CT followed a full binary tree structure. Moreover, individual chords are mostly planar geometries that together form a 3D load-bearing support for the MV leaflets. We further demonstrated that, unlike flow-based branching patterns, while individual CT branches became thinner as they propagated further away from the PM heads towards the leaflets, the total CSA almost doubled. Overall, our findings indicate a certain level of regularity in structure, and suggest that population-based MV CT geometric models can be generated to improve current MV repair procedures.

Ischemic mitral valve prolapse

Ischemic mitral prolapse (IMP) is a pathologic entity encountered in about one-third among the patients undergoing surgery for ischemic mitral regurgitation (IMR). IMP is generally the result of a papillary muscle injury consequent to myocardial, but the recent literature is progressively unveiling a more complex pathogenesis. The mechanisms underlying its development regards the impairment of one or more components of the mitral apparatus, which comprises the annulus, the chordae tendineae, the papillary muscle and the left ventricular wall. IMP is not only a disorder of valvular function, but also entails coexistent aspects of a geometric disturbance of the mitral valve configuration and of the left ventricular function and dimension and a correct understanding of all these aspects is crucial to guide and tailor the correct therapeutic strategy to be adopted. Localization of prolapse, anatomic features of the prolapsed leaflets and the subvalvular apparatus should be carefully evaluated as also constituting the major determinants defining patient's outcomes. This review will summarize our current understanding of the pathophysiology and clinical evidence on IMP with a particular focus on the surgical treatment.

Modeling the Myxomatous Mitral Valve With Three-Dimensional Echocardiography

BACKGROUND

Degenerative mitral valve disease is associated with variable and complex defects in valve morphology. Three-dimensional echocardiography (3DE) has shown promise in aiding preoperative planning for patients with this disease but to date has not been as transformative as initially predicted. The clinical usefulness of 3DE has been limited by the laborious methods currently required to extract quantitative data from the images.

METHODS

To maximize the utility of 3DE for preoperative valve evaluation, this work describes an automated 3DE image analysis method for generating models of the mitral valve that are well suited for both qualitative and quantitative assessment. The method is unique in that it captures detailed alterations in mitral leaflet and annular morphology and produces image-derived models with locally varying leaflet thickness. The method is evaluated on midsystolic transesophageal 3DE images acquired from 22 subjects with myxomatous degeneration and from 22 subjects with normal mitral valve morphology.

RESULTS

Relative to manual image analysis, the automated method accurately represents both normal and complex leaflet geometries with a mean boundary displacement error on the order of one image voxel. A detailed quantitative analysis of the valves is presented and reveals statistically significant differences between normal and myxomatous valves with respect to numerous aspects of annular and leaflet geometry.

CONCLUSIONS

This work demonstrates a successful methodology for the relatively rapid quantitative description of the complex mitral valve distortions associated with myxomatous degeneration. The methodology has the potential to significantly improve surgical planning for patients with complex mitral valve disease.

Comparison of saddle-shape flexibility and elliptical-shape stability between Cosgrove-Edwards and Memo-3D annuloplasty rings using three-dimensional analysis software

OBJECTIVE

To compare three-dimensional dynamics between implanted Cosgrove-Edwards and Sorin Memo-3D annuloplasty rings during the cardiac cycle.

METHODS

We examined 11 Cosgrove-Edwards rings and 20 Sorin Memo-3D rings after mitral plasty using real-time three-dimensional transesophageal echocardiography. We evaluated ring height, ellipticity, and geometry during one cardiac cycle. Four evenly spaced phases each selected during systole and diastole were assessed using REAL VIEW software.

RESULTS

The height of the Cosgrove-Edwards and Sorin Memo-3D rings was similar (2.3 ± 0.8 vs. 1.9 ± 0.9 mm, p = 0.44). The maximum difference in ring height during one cardiac cycle (change in height) was larger for the Cosgrove-Edwards than the Sorin Memo-3D rings (2.3 ± 0.8 vs. 1.5 ± 0.6 mm, p = 0.014). Ellipticity and the maximum difference in ellipticity during one cardiac cycle (change in ellipticity) were larger for Cosgrove-Edwards than Sorin Memo-3D rings (80.0 ± 9.1 vs. 72.0 ± 4.8 %, p = 0.014, respectively, and 12.0 ± 3.1 vs. 6.0 ± 1.8 %, p < 0.001).

CONCLUSIONS

Cosgrove-Edwards rings were more flexible, whereas Sorin Memo-3D rings maintained the elliptical shape more effectively.

Preoperative Three-Dimensional Valve Analysis Predicts Recurrent Ischemic Mitral Regurgitation After Mitral Annuloplasty

BACKGROUND

Valve repair for ischemic mitral regurgitation (IMR) with undersized annuloplasty rings is characterized by high IMR recurrence rates. Patient-specific preoperative imaging-based risk stratification for recurrent IMR would optimize results. We sought to determine if prerepair three-dimensional (3D) echocardiography combined with a novel valve-modeling algorithm would be predictive of IMR recurrence 6 months after repair.

METHODS

Intraoperative transesophageal real-time 3D echocardiography was performed in 50 patients undergoing undersized ring annuloplasty for IMR and in 21 patients with normal mitral valves. A customized image analysis protocol was used to assess 3D annular geometry and regional leaflet tethering. IMR recurrence (≥ grade 2) was assessed with two-dimensional transthoracic echocardiography 6 months after repair.

RESULTS

Preoperative annular geometry was similar in all IMR patients, and preoperative leaflet tethering was significantly higher in patients with recurrent IMR (n=13) than in patients in whom IMR did not recur (n=37) (tethering index: 3.91 ± 1.01 vs 2.90 ± 1.17, p = 0.008; tethering angles of A3: 23.5° ± 8.9° vs 14.4° ± 11.4°, p = 0.012; P2: 44.4° ± 8.8° vs 28.2° ± 17.0°, p = 0.002; and P3: 35.2° ± 6.0° vs. 18.6° ± 12.7°, p < 0.001). Multivariate logistic regression analysis revealed the preoperative P3 tethering angle as an independent predictor of IMR recurrence with an optimal cutoff value of 29.9° (area under the curve, 0.92; 95% confidence interval, 0.84 to 1.00; p < 0.001).

CONCLUSIONS

3D echocardiography combined with valve modeling is predictive of recurrent IMR. Preoperative regional leaflet tethering of segment P3 is a strong independent predictor of IMR recurrence after undersized ring annuloplasty. In patients with a preoperative P3 tethering angle of 29.9° or larger, chordal-sparing valve replacement rather than valve repair should be strongly considered.

Predictive factors of long-term results following valve repair in ischemic mitral valve prolapse

BACKGROUND

In patients with ischemic mitral regurgitation, leaflet prolapse requires an accurate evaluation since surgical approach depends on valvular and subvalvular characteristics. This study aims to describe a cohort of patients over a long-term follow up, analyzing survival, reoperation and predictive factors of surgical outcomes.

METHODS AND RESULTS

From March 1994 to June 2011, 75 patients with ischemic mitral regurgitation and leaflet prolapse underwent surgical myocardial revascularization and mitral valve repair (90.7%) or replacement (9.3%). Our cohort was followed up until April 2015, with a mean follow up of 7 ± 3 years. Cardiac-related deaths occurred in 26 patients, with a mean survival of 114.2 months, including eight patients with in-hospital mortality. Reoperation was performed in 14 patients, due to valve repair failure. Twenty-six patients experienced moderate-to-severe mitral regurgitation. A preoperative LVEDD > 62 mm, LVESD > 52 mm, previous anteroseptal myocardial infarction, diffuse coronary artery disease, papillary anatomy type 1, partial rupture of the papillary muscle, A1-A2 scallop prolapse and postoperative mitral valve configuration (tenting area, tenting height, alfa-1 angle and alfa-2 angle) were identified as independent predictors of poor outcome. An index quantifying the stress on the annulus imparted by annuloplasty was elaborated and predicted endpoints.

CONCLUSION

Leaflet prolapse is an important entity in patients with ischemic mitral regurgitation, and its pathogenic mechanism mostly relies on papillary muscle lesion or elongation. Perioperative parameters describing geometric features of left ventricle, valvular and subvalvular components should be considered to provide a tailored approach for mitral valve repair, or to opt for immediate replacement in case of unfavorable geometry.

The butterfly technique

Butterfly resection is a mitral valve repair technique for prolapsing posterior leaflets. The aim of butterfly resection is to optimize the geometry of the resultant new leaflet, with controlled height reduction for a prolapsing segment, without annular reduction. We have reported the concept of its design, its advantages in preventing post-repair systolic anterior motion (SAM), and excellent early and medium-term results. The present illustrated article describes the technical details of how we design and perform the butterfly technique.

A simplified D-shaped model of the mitral annulus to facilitate CT-based sizing before transcatheter mitral valve implantation

BACKGROUND

The nonplanar, saddle-shaped structure of the mitral annulus has been well established through decades of anatomic and echocardiographic study. Its relevance for mitral annular assessment for transcatheter mitral valve implantation is uncertain.

OBJECTIVE

Our objectives are to define the methodology for CT-based simplified "D-shaped" mitral annular assessment for transcatheter mitral valve implantation and compare these measurements to traditional "saddle-shaped" mitral annular assessment.

METHODS

The annular contour was manually segmented, and fibrous trigones were identified using electrocardiogram-gated diastolic CT data sets of 28 patients with severe functional mitral regurgitation, yielding annular perimeter, projected area, trigone-to-trigone (TT) distance, and septal-lateral distance. In contrast to the traditional saddle-shaped annulus, the D-shaped annulus was defined as being limited anteriorly by the TT distance, excluding the aortomitral continuity. Hypothetical left ventricular outflow tract (LVOT) clearance was assessed.

RESULTS

Projected area, perimeter, and septal-lateral distance were found to be significantly smaller for the D-shaped annulus (11.2 ± 2.7 vs 13.0 ± 3.0 cm(2); 124.1 ± 15.1 vs 136.0 ± 15.5 mm; and 32.1 ± 4.0 vs 40.1 ± 4.9 mm, respectively; P < .001). TT distances were identical (32.7 ± 4.1 mm). Hypothetical LVOT clearance was significantly lower for the saddle-shaped annulus than for the D-shaped annulus (10.7 ± 2.2 vs 17.5 ± 3.0 mm; P < .001).

CONCLUSION

By truncating the anterior horn of the saddle-shaped annular contour at the TT distance, the resulting more planar and smaller D-shaped annulus projects less onto the LVOT, yielding a significantly larger hypothetical LVOT clearance than the saddle-shaped approach. CT-based mitral annular assessment may aid preprocedural sizing, ensuring appropriate patient and device selection.

In-vivo analysis of selectively flexible mitral annuloplasty rings using three-dimensional echocardiography

BACKGROUND

Selectively flexible rings, Colvin-Galloway (CG) Future and Carpentier-Edwards (CE) Physio II, are used for annuloplasty during mitral valve repair to facilitate dynamic annular motion while preventing annular dilation. In this study, we assessed the extent and nature of the flexibility of these rings in vivo, which has not been objectively demonstrated.

METHODS

Three-dimensional transesophageal echocardiography was used intraoperatively to acquire data regarding dynamic motion of mitral annuli and annuloplasty rings in 33 patients undergoing mitral repair (15 CG Future and 18 CE Physio II) and in 15 control patients. Data were analyzed to assess the dynamic changes in annular geometry after implantation of selectively flexible rings.

RESULTS

After annuloplasty, there was an immediate and significant decrease in annular displacement (p < 0.001) and annular displacement velocity (p < 0.01). Dynamic change in multiple variables including anteroposterior diameter (p < 0.001) and annular area (p < 0.001) was also significantly depressed. In comparison with normal mitral valves, partially flexible rings allowed limited dynamic motion: percentage changes in anteroposterior diameter (p < 0.001), anterolateral posteromedial diameter (p < 0.001), and total circumference (p < 0.001) were significantly lower. Compared with each other, the two rings resulted in similar changes in anterior annulus length (p = 0.93), posterior annular length (p = 0.82), and annular area (p = 0.31).

CONCLUSIONS

Mitral annular dynamics were uniformly depressed after implantation of these rings. Selective flexibility could not be demonstrated in vivo using echocardiographic data.