Evolving Concepts and Technologies in Mitral Valve Repair

Large Animal Translational Validation of 3 Mitral Valve Repair Operations for Mitral Regurgitation Using a Mitral Valve Prolapse Model: A Comprehensive In Vivo Biomechanical Engineering Analysis

BACKGROUND

Various mitral repair techniques have been described. Though these repair techniques can be highly effective when performed correctly in suitable patients, limited quantitative biomechanical data are available. Validation and thorough biomechanical evaluation of these repair techniques from translational large animal in vivo studies in a standardized, translatable fashion are lacking. We sought to evaluate and validate biomechanical differences among different mitral repair techniques and further optimize repair operations using a large animal mitral valve prolapse model.

METHODS

Male Dorset sheep (n=20) had P2 chordae severed to create the mitral valve prolapse model. Fiber Bragg grating force sensors were implanted to measure chordal forces. Ten sheep underwent 3 randomized, paired mitral valve repair operations: neochord repair, nonresectional leaflet remodeling, and triangular resection. The other 10 sheep underwent neochord repair with 2, 4, and 6 neochordae. Data were collected at baseline, mitral valve prolapse, and after each repair.

RESULTS

All mitral repair techniques successfully eliminated regurgitation. Compared with mitral valve prolapse (0.54±0.18 N), repair using neochord (0.37±0.20 N; P=0.02) and remodeling techniques (0.30±0.15 N; P=0.001) reduced secondary chordae peak force. Neochord repair further decreased primary chordae peak force (0.21±0.14 N) to baseline levels (0.20±0.17 N; P=0.83), and was associated with lower primary chordae peak force compared with the remodeling (0.34±0.18 N; P=0.02) and triangular resectional techniques (0.36±0.27 N; P=0.03). Specifically, repair using 2 neochordae resulted in higher peak primary chordal forces (0.28±0.21 N) compared with those using 4 (0.22±0.16 N; P=0.02) or 6 neochordae (0.19±0.16 N; P=0.002). No difference in peak primary chordal forces was observed between 4 and 6 neochordae (P=0.05). Peak forces on the neochordae were the lowest using 6 neochordae (0.09±0.11 N) compared with those of 4 neochordae (0.15±0.14 N; P=0.01) and 2 neochordae (0.29±0.18 N; P=0.001).

CONCLUSIONS

Significant biomechanical differences were observed underlying different mitral repair techniques in a translational large animal model. Neochord repair was associated with the lowest primary chordae peak force compared to the remodeling and triangular resectional techniques. Additionally, neochord repair using at least 4 neochordae was associated with lower chordal forces on the primary chordae and the neochordae. This study provided key insights about mitral valve repair optimization and may further improve repair durability.

Strategies for surface coatings of implantable cardiac medical devices

Cardiac medical devices (CMDs) are required when the patient's cardiac capacity or activity is compromised. To guarantee its correct functionality, the building materials in the development of CMDs must focus on several fundamental properties such as strength, stiffness, rigidity, corrosion resistance, etc. The challenge is more significant because CMDs are generally built with at least one metallic and one polymeric part. However, not only the properties of the materials need to be taken into consideration. The biocompatibility of the materials represents one of the major causes of the success of CMDs in the short and long term. Otherwise, the material will lead to several problems of hemocompatibility (e.g., protein adsorption, platelet aggregation, thrombus formation, bacterial infection, and finally, the rejection of the CMDs). To enhance the hemocompatibility of selected materials, surface modification represents a suitable solution. The surface modification involves the attachment of chemical compounds or bioactive compounds to the surface of the material. These coatings interact with the blood and avoid hemocompatibility and infection issues. This work reviews two main topics: 1) the materials employed in developing CMDs and their key characteristics, and 2) the surface modifications reported in the literature, clinical trials, and those that have reached the market. With the aim of providing to the research community, considerations regarding the choice of materials for CMDs, together with the advantages and disadvantages of the surface modifications and the limitations of the studies performed.

Papillary muscle rupture of the mitral valve following blunt thoracic trauma

Blunt cardiac injury is caused by large deceleration forces seen in motor vehicle accidents and can range from non-life-threatening arrhythmias to potentially fatal cardiac conditions such as valve disruption. A 28-year-old man presented following a motor vehicle accident involving direct blunt-force chest trauma. He developed papillary muscle rupture resulting in mitral valve dysfunction. Diagnosis was delayed due to concomitant chest pathology. Diagnosis of cardiac valvular injuries may be difficult due to concomitant injuries in a trauma patient. Though rare, papillary muscle rupture should be included in the differential diagnosis following blunt thoracic trauma, particularly involving persistent hypoxemia.

3D mitral annulus echocardiography assessment in patients affected by degenerative mitral regurgitation who underwent mitral valve repair with flexible band

BACKGROUND

Degenerative mitral valve (MV) regurgitation (DMR) shows significative mitral annulus (MA) alterations; mitral valve repair (MVR) seeks to restore annular geometry and function, and the current use of flexible band seams to respect most annular mobility reducing parietal stress. Parameters of MV geometry obtained by 3D transesophageal echocardiography (3D-TTE) analysis are crucial for surgical planning and postoperative success. The aim of this study was to assess, by means of a dedicated software, the variations of MA geometry and function in patients affected by DMR compared to controls and after MVR with flexible band.

METHODS

We enrolled 32 patients (cases) with severe DMR who underwent MVR using flexible band; we compare this group with 20 controls. The TEE with 3D MV images acquisition was performed in both groups and then analyzed in postprocessing by using a dedicated software.

RESULTS

There were no anthropometrics differences between cases and controls, both presented normal left ventricular ejection fraction. DMR group showed a significant increase of annulus dimensional parameters (p = .001) and alteration of nonplanarity comparing to controls (p < .05). The annuloplasty with flexible band induces a considerable reduction of MV dimensions comparing to preoperative data and restores physiological mobility and nonplanarity. There were no statistical differences between postoperative DMR and controls data, except for nonplanarity parameters (p ~.05), maybe influenced by hemodynamic settings.

CONCLUSIONS

MVR with annuloplasty using flexible band appears able to reinstate a more physiological anatomic conformation of the MA, without compromising its dynamic properties.

Structural and biomechanical characterizations of acellular porcine mitral valve scaffolds: anterior leaflets, posterior leaflets, and chordae tendineae

Mitral valve (MV) tissue engineering is still in its early stage, and one major challenge in MV tissue engineering is to identify appropriate scaffold materials. With the potential of acellular MV scaffolds being demonstrated recently, it is important to have a full understanding of the biomechanics of the native MV components and their acellular scaffolds. In this study, we have successfully characterized the structural and mechanical properties of porcine MV components, including anterior leaflet (AL), posterior leaflet (PL), strut chordae, and basal chordae, before and after decellularization. Quantitative DNA assay showed more than 90% reduction in DNA content, and Griffonia simplicifolia (GS) lectin immunohistochemistry confirmed the complete lack of porcine α-Gal antigen in the acellular MV components. In the acellular AL and PL, the atrialis, spongiosa, and fibrosa trilayered structure, along with its ECM constitutes, i.e., collagen fibers, elastin fibers, and portion of GAGs, were preserved. Nevertheless, the ECM of both AL and PL experienced a certain degree of disruption, exhibiting a less dense, porous ECM morphology. The overall anatomical morphology of the strut and basal chordae were also maintained after decellularization, with longitudinal morphology experiencing minimum disruption, but the cross-sectional morphology exhibiting evenly-distributed porous structure. In the acellular AL and PL, the nonlinear anisotropic biaxial mechanical behavior was overall preserved; however, uniaxial tensile tests showed that the removal of cellular content and the disruption of structural ECM did result in small decreases in maximum tensile modulus, tissue extensibility, failure stress, and failure strain for both MV leaflets and chordae.

Canine mitral valve size as measured by computed tomography

OBJECTIVE

To measure the mitral annulus in dogs. Our hypothesis was that mitral measurement would be possible and consistent among observers using CT.

SAMPLE

Thoracic CT scans of dogs without known heart disease.

PROCEDURES

Five trained investigators measured 4 aspects of the mitral valve and the fourth thoracic vertebrae (T4) length using multiplanar reformatting tools. Ten randomly chosen animals were measured by all investigators to determine interobserver reliability.

RESULTS

There were 233 CT scans eligible for inclusion. Dogs weighed 2 to 96 kg (mean, 28.1 kg), with a variety of breeds represented. Golden Retrievers (n = 28) and Labrador Retrievers (n = 37) were overrepresented. The intraclass correlations were all greater than 0.9, showing excellent agreement between observers. The means and SDs of each measurement were as follows: trigone-to-trigone distance, 17.2 ± 4.7 mm; the remaining circumference, 79.0 ± 17.5 mm; commissure-to-commissure distance, 30.8 ± 6.5 mm; septal leaflet-to-lateral leaflet distance, 26.3 ± 6.0 mm; T4 length, 16.9 ± 3.1 mm; and the total circumference normalized by T4, 5.7 ± 0.7 mm.

CLINICAL RELEVANCE

This study provides information that may help in the development of future treatment for mitral valve dysfunction and subsequent annular enlargement.

A multiparameter algorithm to guide repair of degenerative mitral regurgitation

PURPOSE

Degenerative mitral regurgitation repair using a measured algorithm could increase the precision and reproducibility of repair outcomes.

METHODS

Direct and echocardiographic measurements guide the repair to achieve a coaptation length of 5 to 10 mm and minimize the risk of systolic anterior motion. Leaflet reconstruction restored the normal 2 to 1 ratio of anterior to posterior leaflet length without residual prolapse or restriction. The choice of ring size was based on anterior leaflet length, the distance from the leaflet coaptation point to the septum, and the anterior-posterior ring dimension. Freedom from reoperation and mitral regurgitation recurrence were based on multistate models.

RESULTS

One thousand fifty-one patients had mitral surgery and 1026 (97.6%) were repaired. A2 length was 27.2 ± 4.5 mm; and the reconstructed posterior leaflet was 13.9 ± 2.3 mm. Median ring size was 34 mm and strongly correlated to A2 length (R = 0.76; P < .001). The coaptation length at P2 after repair was 6.4 ± 1.7 mm and 87% of measurements were between 5 and 10 mm. Results at predischarge and 10 years, respectively, included mild regurgitation (7.5% and 26.1%), moderate (0.7% and 15.6%), moderate to severe (0% and 1.4%), and severe (0% and 0%), with mean mitral gradient values 3.5 ± 1.5 and 2.9 ± 1.2 mm Hg, respectively. Systolic anterior motion at discharge and last follow-up were 0.2% and 1.1%, respectively. Ten-year freedom from mitral valve reoperation was 99.7%.

CONCLUSIONS

A simple, reproducible, measured algorithm for degenerative mitral valve repair provides excellent early and late results and is a useful adjunct to established surgical techniques.

Relationship of surgeon experience and outcomes of surgery for degenerative mitral valve disease

OBJECTIVE

To assess the impact of surgeon experience on the outcomes of degenerative mitral valve disease.

METHODS

We reviewed all patients who had surgery for degenerative mitral valve disease between 2011 and 2016. Experienced surgeon was defined as performing ≥ 25 mitral valve operations/year. Patient characteristics and outcomes were compared. Competing risk analysis was performed to identify factors associated with mitral regurgitation (MR) recurrence. Survival analysis for mortality was done using Kaplan Meier curve and Cox proportional hazard method.

RESULTS

There were 575 patients treated by 9 surgeons for severe MR caused by degenerative mitral valve disease between 2011 and 2016. Three experienced surgeons performed 77.2% of the operations. Patients treated by less experienced surgeons had worse comorbidity profile and were more likely to have an urgent or emergent operation (p = .001). Experienced surgeons were more likely to attempt repair (p = .024), to succeed in repair (94.7% vs. 87%; p = .001), had shorter cross-clamp times (p = .001), and achieved higher repair rate (81.3% vs. 69.7%; p = .005). Experienced surgeons were more likely to use neochordae (p = .001) and less likely to use chordae transfer (p = .001). Surgeon experience was not associated with recurrence of moderate or higher degree of MR after repair but was an independent risk factor for mortality (HR = 2.64; p = .002).

CONCLUSIONS

Techniques of degenerative mitral valve surgery differ with surgeon experience, with higher rates of repair and better outcomes associated with more experienced surgeons.

Multimodality Cardiac Imaging for Procedural Planning and Guidance of Transcatheter Mitral Valve Replacement and Mitral Paravalvular Leak Closure

Transcatheter mitral valve interventions are an evolving and growing field in which multimodality cardiac imaging is essential for diagnosis, procedural planning, and intraprocedural guidance. Currently, transcatheter mitral valve-in-valve with a balloon-expandable valve is the only form of transcatheter mitral valve replacement (TMVR) approved by the FDA, but valve-in-ring and valve-in-mitral annular calcification interventions are increasingly being performed. Additionally, there are several devices under investigation for implantation in a native annulus. Paravalvular leak (PVL) is a known complication of surgical or transcatheter valve implantation, where regurgitant flow occurs between the prosthetic sewing ring and the native mitral annulus. We sought to describe the role and applications of multimodality cardiac imaging for TMVR, and PVL closure, including the use of Cardiovascular Computed Tomography Angiography and 3-Dimensional Transesophageal Echocardiography for diagnosis, prosthetic valve evaluation, pre-procedural planning, and intraprocedural guidance, as well as evolving technologies such as fusion imaging and 3D printing.

Radiofrequency ablation alters the microstructural organization of healthy and enzymatically digested porcine mitral valves

BACKGROUND

Myxomatous mitral valve degeneration is a common cause of mitral regurgitation and is often associated with mitral valve prolapse. With no known targets to pharmacologically treat mitral valve prolapse, surgery is often the only treatment option. Recently, radiofrequency ablation has been proposed as a percutaneous alternative to surgical resection for the reduction of mitral valve leaflet area.

OBJECTIVE

Using an in vitro model of porcine mitral valve anterior leaflet enlargement following enzymatic digestion, we sought to investigate mechanisms by which radiofrequency ablation alters the geometry, microstructural organization, and mechanical properties of healthy and digested leaflets.

METHODS

Paired measurements before and after ablation revealed the impact of radiofrequency ablation on leaflet properties. Multiphoton imaging was used to characterize changes in the structure and organization of the valvular extracellular matrix; planar biaxial mechanical testing and constitutive modeling were used to estimate mechanical properties of healthy and digested leaflets.

RESULTS

Enzymatic digestion increased leaflet area and thickness to a similar extent as clinical mitral valve disease. Radiofrequency ablation altered extracellular matrix alignment and reduced the area of digested leaflets to that of control. Additionally, enzymatic digestion resulted in fiber alignment and reorientation toward the radial direction, causing increased forces during ablation and a structural stiffening which was improved by radiofrequency ablation.

CONCLUSION

Radiofrequency ablation induces radial extracellular matrix alignment and effectively reduces the area of enlarged mitral valve leaflets. Hence, this technique may be a therapeutic approach for myxomatous mitral valve disease and is thus an avenue for future study.

Long-Term Results of Mitral Repair With Complete Semi-Rigid Rings vs Posterior Flexible Bands

BACKGROUND

The aim of the study was to evaluate whether the type of ring used had an impact on the long-term results of mitral repair for degenerative mitral regurgitation (MR), due to posterior leaflet prolapse, treated with quadrangular or triangular resection.

METHODS

From January 2002 to December 2008, 1406 patients with severe MR due to posterior leaflet prolapse underwent mitral repair. Of these patients, we selected 452 consecutive patients treated with the same repair approach. Mitral annuloplasty to complete the repair was performed with a posterior flexible band (n = 260) or a complete semi-rigid ring (n = 192). The 2 groups were comparable at baseline, and their clinical and echocardiographic outcomes were compared at long-term follow-up.

RESULTS

Overall survival at 14 years was similar (P = .29). The cumulative incidence function of cardiac death, with noncardiac death as competing risk, showed no difference (P = .71). At 14 years, probability of recurrence of MR greater than or equal to 3+ was 1.11% in the flexible band group and 3.25% in the semi-rigid ring group (P = .073). At 14 years, probability of recurrence of MR greater than or equal to 2 was 13.49% in the band group vs 10.78% in the semi-rigid ring group (P = .897).

CONCLUSIONS

In patients requiring mitral valve repair for posterior leaflet prolapse, treated with the same repair approach, the type of annuloplasty ring has no impact on the incidence of cardiac death and recurrence of MR at 14 years. Whether these findings remain stable at longer follow-up should be further investigated.

The Use of a Preoperative Mitral Valve Model to Guide Mitral Valve Repair

BACKGROUND

Mitral valve repair is commonly used to address degenerative or functional changes to the mitral valve apparatus and surrounding ventricular anatomy. Preoperative transoesophageal echocardiogram (TOE) is routinely used to evaluate and identify the precise anatomic location of mitral valve pathology in order to guide repair. However, surgeons currently lack specific guidance regarding the approximate dimensions of the mitral valve they should aim for in order to achieve optimal valve function and avoid adverse outcomes. Therefore, through an observational study, we aimed to develop and test the accuracy of a preliminary mathematical model which represents the geometric relationship between various clinically relevant components of the mitral valve and its surrounding structures.

METHODS

Using established trigonometric principles, the geometric relationship shared between several mitral valve components was represented in a two-dimensional (2D) model and described in a mathematical equation. The output variable of the model is the anteroposterior diameter of the mitral valve. To assess the accuracy of the mathematical model, we compared the model-predicted anteroposterior (AP) diameter against AP diameter measured by postoperative TOE in 42 cases.

RESULTS

The root mean squared error (RMSE) of model predicted AP diameter compared to measured AP diameter was 0.43 cm. The mean absolute percentage error (MAPE) of the model was 17.7%. In 34 out of 42 cases, model-predicted AP diameters were within 25% of AP diameters measured by postoperative TOE.

CONCLUSIONS

Preliminary testing of a simple mathematical model has shown its relative accuracy in representing the geometric relationship between several mitral valve variables. Further research and refinement of the model is required in order to improve its accuracy. We are encouraged that, with further improvement, the model has the potential for clinical application.

A new simplified technique for artificial chordae implantation in mitral valve repair with its early results

Background

Many techniques in mitral valve repair (MVR) have been reported with successful long-term results. The aim of this study is to present our simplified technique in artificial chordae replacement for MVR, and reporting its short-term outcomes.

Methods

We present a prospective single-surgeon experience. A new simplified artificial chordae implantation technique has been used to repair mitral valves. Postoperative echocardiography at 0, 6, then every 12 months is used to control the results. Endpoints involved freedom from mitral regurgitation (MR), reoperation and major adverse cardiac and cerebrovascular events (MACCE).

Results

Between 01/2016 and 01/2018, 57 consecutive patients undergo MVR using this technique are evaluated. Mean age was 63.6±10.1 years and 68.4% were male. Mitral valve pathology was mainly degenerative (52, 91.2%) or healed endocarditis (5, 8.8%). Besides chordae replacement (3.6±1.1 per patient), annuloplasty was used in all patients to correct annulus dilation and stabilize the repair. Mean cross-clamping time was 53±13.4 minutes in isolated MVR and 69.4±31.1 minutes in concomitant procedures. Postoperative outcomes reported two mortalities. Discharge echocardiography reported mild MR in 4 patients and the rest of patients had non-to trace regurgitation. Follow-up results within a mean of 19.3±8.5 months reported no significant MR or need for reoperation and three more (non-valve related) mortalities.

Conclusions

Our simplified technique allows to reduce the number of used chordae and re-correction if needed, which consequently reduces cross-clamping and bypass time especially in endoscopic MVR. Good intraoperative and short-term results are reported. These results are still under investigation to prove long-term stability of the repair.

Degenerative Mitral Valve Repair Restores Life Expectancy

BACKGROUND

Mitral valve repair (MVr) for severe, degenerative mitral regurgitation is the gold standard, because medical management carries poor prognosis. However, despite clear benefit of MVr, many eligible patients are untreated. This study investigated whether MVr restores patients to normal life expectancy, at any age of operation, by comparing long-term survival of patients after MVr with the life expectancy of the general United States population.

METHODS

This retrospective study investigated 1011 patients with degenerative mitral regurgitation who underwent isolated MVr between 2003 and 2017. Parametric distribution analysis was applied to long-term post-MVr mortality data, and Weibull probability plots provided the best-fit distribution by Anderson-Darling Goodness-of-Fit testing. Confidence intervals of the estimated distribution were used to compare additional life expectancy after MVr to the general US population across multiple decades of life. Patients after MVr were categorized by age into decade (range, 20-89 years).

RESULTS

The life expectancy of patients after MVr matched the life expectancy of the general US population at any age between 40 and 89 years. Lower-bound one-sided 95% confidence intervals for additional life expectancy were not appreciably different from corresponding median additional life expectancy of the general population. There were few deaths in the 20- to 39-year-old group, limiting predictability, but survival also appeared normative.

CONCLUSIONS

These findings suggest that degenerative MVr restores anticipated life expectancy to that of the general population, regardless of age. Although our findings underscore the importance of repair for degenerative mitral disease, larger studies with longer term follow-up are needed to reinforce this finding, particularly for younger patients.

Mapping the spatial variation of mitral valve elastic properties using air-pulse optical coherence elastography

The mitral valve is a highly heterogeneous tissue composed of two leaflets, anterior and posterior, whose unique composition and regional differences in material properties are essential to overall valve function. While mitral valve mechanics have been studied for many decades, traditional testing methods limit the spatial resolution of measurements and can be destructive. Optical coherence elastography (OCE) is an emerging method for measuring viscoelastic properties of tissues in a noninvasive, nondestructive manner. In this study, we employed air-pulse OCE to measure the spatial variation in mitral valve elastic properties with micro-scale resolution at 1 mm increments along the radial length of the leaflets. We analyzed differences between the leaflets, as well as between regions of the valve. We found that the anterior leaflet has a higher elastic wave velocity, which is reported as a surrogate for stiffness, than the posterior leaflet, most notably at the annular edge of the sample. In addition, we found a spatial elastic gradient in the anterior leaflet, where the annular edge was found to have a greater elastic wave velocity than the free edge. This gradient was less pronounced in the posterior leaflet. These patterns were confirmed using established uniaxial tensile testing methods. Overall, the anterior leaflet was stiffer and had greater heterogeneity in its mechanical properties than the posterior leaflet. This study measures differences between the two mitral leaflets with greater resolution than previously feasible and demonstrates a method that may be suitable for assessing valve mechanics following repair or during the engineering of synthetic valve replacements.

3D printed mitral valve models: affordable simulation for robotic mitral valve repair

OBJECTIVES

3D printed mitral valve (MV) models that capture the suture response of real tissue may be utilized as surgical training tools. Leveraging clinical imaging modalities, 3D computerized modelling and 3D printing technology to produce affordable models complements currently available virtual simulators and paves the way for patient- and pathology-specific preoperative rehearsal.

METHODS

We used polyvinyl alcohol, a dissolvable thermoplastic, to 3D print moulds that were casted with liquid platinum-cure silicone yielding flexible, low-cost MV models capable of simulating valvular tissue. Silicone-moulded MV models were fabricated for 2 morphologies: the normal MV and the P2 flail. The moulded valves were plication and suture tested in a laparoscopic trainer box with a da Vinci Si robotic surgical system. One cardiothoracic surgery fellow and 1 attending surgeon qualitatively evaluated the ability of the valves to recapitulate tissue feel through surveys utilizing the 5-point Likert-type scale to grade impressions of the valves.

RESULTS

Valves produced with the moulding and casting method maintained anatomical dimensions within 3% of directly 3D printed acrylonitrile butadiene styrene controls for both morphologies. Likert-type scale mean scores corresponded with a realistic material response to sutures (5.0/5), tensile strength that is similar to real MV tissue (5.0/5) and anatomical appearance resembling real MVs (5.0/5), indicating that evaluators 'agreed' that these aspects of the model were appropriate for training. Evaluators 'somewhat agreed' that the overall model durability was appropriate for training (4.0/5) due to the mounting design. Qualitative differences in repair quality were notable between fellow and attending surgeon.

CONCLUSIONS

3D computer-aided design, 3D printing and fabrication techniques can be applied to fabricate affordable, high-quality educational models for technical training that are capable of differentiating proficiency levels among users.

Mechanical properties of a new thermally deformable mitral valve annuloplasty ring and its effects on the mitral valve

Ideally, an annuloplasty ring's shape should be changed intraoperatively if mitral valve repair is unsuccessful because of a short coaptation length or systolic anterior motion. Several post-implantation adjustable rings have been developed, but they are not freely deformable and are unsuitable for asymmetric repair of the valvular annulus. We developed a novel thermally deformable mitral annuloplasty ring to address these problems and assessed the ring's mechanical properties and its effect on the mitral valve anatomy. This ring was made of polycaprolactone. Tensile and bending tests were performed to evaluate the ring's mechanical properties. The ratio of the transverse and septal-lateral length was determined as 4:3. Using 10 pig hearts, we measured the post-deformation coaptation length and minimum distance from the coaptation to the ventricular septum, which is a factor of abnormal systolic anterior motion of the mitral valve. In the mechanical tests, the ring's yield point was greater than the deformation force of the annulus in humans. In pigs with deformation from "4:3" to "4:2", the coaptation length was significantly increased in each mitral valve part. In pigs with deformation from "4:3" to "4:4", the minimum distance from the coaptation to the ventricular septum was significantly increased. Asymmetrical ring deformation increased the coaptation length only at the deformed area. In conclusion, this new thermally deformable mitral annuloplasty ring could be "order-made" to effectively change the coaptation length in all parts of the mitral valve and the distance from the coaptation to septum post-deformation via intraoperative heating.

Advanced Imaging Techniques for Mitral Regurgitation

Mitral regurgitation (MR) is one of the most commonly encountered valvular lesions in clinical practice. MR can be either primary (degenerative) or secondary (functional) depending on the etiology of MR and the pathology of the mitral valve (MV). Echocardiography is the primary diagnostic tool for MR and is key in determining this etiology as well as MR severity. While clinicians usually turn to 2 Dimensional echocardiography as first-line imaging, 3 Dimensional echocardiography (3DE) has continually shown to be superior in terms of describing MV anatomy and pathology. This review article elaborates on 3DE techniques, modalities, and advances in software. Furthermore, the article demonstrates how 3DE has reformed MR evaluation and has played a vital role in determining patient management.

Multi-resolution geometric modeling of the mitral heart valve leaflets

An essential element of cardiac function, the mitral valve (MV) ensures proper directional blood flow between the left heart chambers. Over the past two decades, computational simulations have made marked advancements toward providing powerful predictive tools to better understand valvular function and improve treatments for MV disease. However, challenges remain in the development of robust means for the quantification and representation of MV leaflet geometry. In this study, we present a novel modeling pipeline to quantitatively characterize and represent MV leaflet surface geometry. Our methodology utilized a two-part additive decomposition of the MV geometric features to decouple the macro-level general leaflet shape descriptors from the leaflet fine-scale features. First, the general shapes of five ovine MV leaflets were modeled using superquadric surfaces. Second, the finer-scale geometric details were captured, quantified, and reconstructed via a 2D Fourier analysis with an additional sparsity constraint. This spectral approach allowed us to easily control the level of geometric details in the reconstructed geometry. The results revealed that our methodology provided a robust and accurate approach to develop MV-specific models with an adjustable level of spatial resolution and geometric detail. Such fully customizable models provide the necessary means to perform computational simulations of the MV at a range of geometric accuracies in order to identify the level of complexity required to achieve predictive MV simulations.

A Review of the Use of Cardiac Computed Tomography for Evaluating the Mitral Valve before and after Mitral Valve Repair

The role of cardiac computed tomography (CT) for evaluating the mitral valve (MV) has been limited since echocardiography is the main method of evaluation. However, recent advances in cardiac CT have enable detailed evaluation of the anatomy and geometry of the MV. We describe assessments of the anatomy and coaptation geometric parameters of normal MVs, and also review repair of diseased/damaged MV. We also discuss pre- and post-surgical imaging of MV pathology using cardiac CT and various CT images. We found that cardiac CT could be used as an alternative imaging modality to echocardiography for pre-operative MV evaluation and to predict clinical outcomes following repair.

Transcatheter Aortic Valve Replacement and MitraClip to Reverse Heart Failure

Valvular heart diseases such as aortic stenosis and mitral regurgitation are often associated with heart failure, which in turn increases patients' Surgical Thoracic Society (STS) score. A high STS score means the patient is high risk for surgical aortic valve replacement and mitral valve repair/replacement. Transcatheter aortic valve replacement and percutaneous mitral valve repair offer a minimally invasive alternative for the treatment of valvular heart disease in patients with severe heart failure. We aim to review the current evidence on the safety, efficacy, and outcomes of these devices in patients with severe heart failure.

Computational virtual evaluation of the effect of annuloplasty ring shape

Mitral regurgitation (MR) is a result of mitral valve (MV) pathology. Its etiology can be categorized as degenerative or functional MR. Ring annuloplasty aims to reconfigure a dilated mitral annulus to its normal size and shape. We investigated the effect of annuloplasty ring shape on MR outcome using our established 3-dimensional (3-D) echocardiography-based computational MV evaluation protocols. Virtual patient MV models were created from 3-D transesophageal echocardiographic data in patients with MR because of mitral annular dilation. Two distinct annuloplasty rings (Physio II and GeoForm) were designed and virtually implanted to the patient MVs. Dynamic finite element simulations of MV function were performed for each MV after virtual ring annuloplasty of either ring, and physiologic and biomechanical characteristics of MV function were compared. Excessive stress values appeared primarily in the midanterior and midposterior regions, and lack of leaflet coaptation was found in pre-annuloplasty patient MVs. Both rings demonstrated marked reduction of stresses and efficient leaflet coaptation. The Physio II ring demonstrated more evenly distributed stress reduction across the leaflets and annulus compared with the GeoForm ring. Conversely, the highly nonplanar curvature of the GeoForm ring more effectively increased leaflet coaptation compared with the Physio II ring. This indicates that the shape of annuloplasty ring affects post-annuloplasty physiologic and biomechanical conditions, which can lead to tissue alteration over a longer period after ring annuloplasty. This virtual ring annuloplasty simulation strategy provides detailed physiologic and biomechanical information and may help better plan the optimal ring selection and improved patient-specific MV repairs.

Primary mitral valve regurgitation: Update and review

Mitral regurgitation is the second most common valvular disorder requiring surgical intervention worldwide. This review summarizes the current understanding of primary, degenerative mitral regurgitation with respect to etiology, comprehensive assessment, natural history and management. The new concept of staging of the valvular disorders, newer predictors of adverse and controversy of “watchful waiting” versus “early surgical intervention” for severe, asymptomatic, primary mitral regurgitation are addressed.

Anatomical features of acute mitral valve repair dysfunction: Additional value of three-dimensional echocardiography

Recurrence of mitral regurgitation after mitral valve repair is correlated with unfavourable left ventricular remodelling and poor outcome. This pictorial review describes the echocardiographic features of three types of acute mitral valve repair dysfunction, and the additional value of three-dimensional echocardiography.

Ex Vivo Methods for Informing Computational Models of the Mitral Valve

Computational modeling of the mitral valve (MV) has potential applications for determining optimal MV repair techniques and risk of recurrent mitral regurgitation. Two key concerns for informing these models are (1) sensitivity of model performance to the accuracy of the input geometry, and, (2) acquisition of comprehensive data sets against which the simulation can be validated across clinically relevant geometries. Addressing the first concern, ex vivo micro-computed tomography (microCT) was used to image MVs at high resolution (~40 micron voxel size). Because MVs distorted substantially during static imaging, glutaraldehyde fixation was used prior to microCT. After fixation, MV leaflet distortions were significantly smaller (p < 0.005), and detail of the chordal tree was appreciably greater. Addressing the second concern, a left heart simulator was designed to reproduce MV geometric perturbations seen in vivo in functional mitral regurgitation and after subsequent repair, and maintain compatibility with microCT. By permuting individual excised ovine MVs (n = 5) through each state (healthy, diseased and repaired), and imaging with microCT in each state, a comprehensive data set was produced. Using this data set, work is ongoing to construct and validate high-fidelity MV biomechanical models. These models will seek to link MV function across clinically relevant states.

Dynamic changes in the ischemic mitral annulus: Implications for ring sizing

OBJECTIVES

Contrary to the rest of the mitral annulus, inter-trigonal distance is known to be relatively less dynamic during the cardiac cycle. Therefore, intertrigonal distance is considered a suitable benchmark for annuloplasty ring sizing during mitral valve (MV) surgery. The entire mitral annulus dilates and flattens in patients with ischemic mitral regurgitation (IMR). It is assumed that the fibrous trigone of the heart and the intertrigonal distance does not dilate. In this study, we sought to demonstrate the changes in mitral annular geometry in patients with IMR and specifically analyze the changes in intertrigonal distance during the cardiac cycle.

METHODS

Intraoperative three-dimensional transesophageal echocardiographic data obtained from 26 patients with normal MVs undergoing nonvalvular cardiac surgery and 36 patients with IMR undergoing valve repair were dynamically analyzed using Philips Qlab ® software.

RESULTS

Overall, regurgitant valves were larger in area and less dynamic than normal valves. Both normal and regurgitant groups displayed a significant change in annular area (AA) during the cardiac cycle (P < 0.01 and P < 0.05, respectively). Anteroposterior and anterolateral-posteromedial diameters and inter-trigonal distance increased through systole (P < 0.05 for all) in accordance with the AAs in both groups. However, inter-trigonal distance showed the least percentage change across the cardiac cycle and its reduced dynamism was validated in both cohorts (P > 0.05).

CONCLUSIONS

Annular dimensions in regurgitant valves are dynamic and can be measured feasibly and accurately using echocardiography. The echocardiographically identified inter-trigonal distance does not change significantly during the cardiac cycle.

Mid-term results of mitral valve repair for ischemic mitral regurgitation with ETlogix ring: A single-center study

BACKGROUND

Ischemic mitral regurgitation (IMR) is a common complication of coronary artery disease and represents an independent predictor of mortality. In the IMR the pattern of mitral valve annular dilatation is asymmetrical: this can explain the long-term incidence of recurrent mitral regurgitation after surgical annular size reduction with a symmetrical ring. The aim of this study is to analyze early and mid-term results of mitral valve repair (MVR) with the CMA IMR ETlogix ring, specifically developed for the surgical correction of IMR.

METHODS

Retrospectively, we studied 157 consecutive patients who underwent MVR with the CMA ETlogix ring for the treatment of grade ≥2 IMR in our center between June 2006 and December 2012. We reported clinical and echocardiographic early and mid-term results of this surgical technique.

RESULTS

Postoperative 30days mortality was 6.3%. Postoperative echocardiography evaluation at discharge revealed the absence of residual MR in 70%, mild MR in 26.5% and moderate MR in 3.5% of patients respectively. Median echographic follow-up time was 28 (3-84) months: survival rate was 92.1% at 32months; free from mitral valve reoperation rate was 97.5% and grade >2 MR recurrence free survival rate was 96.6%.

CONCLUSION

There are a few reports in the literature concerning the mid-term results of IMR surgical correction with CMA Etlogix ring. Our study, taking into account a large series of patients and an important follow-up period, demonstrates the effectiveness of this surgical repair technique reporting a low mid-term incidence of recurrent MR.

Myxomatous Mitral Valve with Prolapse and Flail Scallop

Background

Myxomatous mitral valve with prolapse are classically seen with abnormal leaflet apposition during contraction of the heart. Hemodynamic disorders can result from eccentric mitral regurgitation usually caused by chordae tendinae rupture or papillary muscle dysfunction. Echocardiography is the gold standard for evaluation of leaflet flail and prolapse due to high sensitivity and specificity. Though most mitral valve prolapse are asymptomatic those that cause severe regurgitation need emergent surgical intervention to prevent disease progression.

Case Report

We report a 54 year old Hispanic male who presented with progressively worsening dyspnea and palpitations. Initial evaluation was significant for atrial fibrillation on electrocardiogram with subsequent echocardiography revealing myxomatous mitral valve with prolapse. Following surgical repair of the mitral valve, the dyspnea and palpitations resolved.

Conclusions

Mitral valve prolapse is a common valvular abnormality but the pathogenic cause of myxomatous valves has not been elucidated. Several theories describe multiple superfamilies of proteins to be involved in the process. Proper identification of these severe mitral regurgitation due to these disease valves will help relieve symptomatic mitral valve prolapse patients.

Emerging Concepts in Transesophageal Echocardiography

Introduced in 1977, transesophageal echocardiography (TEE) offered imaging through a new acoustic window sitting directly behind the heart, allowing improved evaluation of many cardiac conditions. Shortly thereafter, TEE was applied to the intraoperative environment, as investigators quickly recognized that continuous cardiac evaluation and monitoring during surgery, particularly cardiac operations, were now possible. Among the many applications for perioperative TEE, this review will focus on four recent advances: three-dimensional TEE imaging, continuous TEE monitoring in the intensive care unit, strain imaging, and assessment of diastolic ventricular function.

Quantitative Imaging Assessment of an Alternative Approach to Surgical Mitral Valve Leaflet Resection: An Acute Porcine Study

This study reports the initial in vivo use of a combined radiofrequency ablation and cryo-anchoring (RFC) catheter as an alternative to surgical mitral valve (MV) leaflet resection. Radiofrequency ablation thermally shrinks enlarged collagenous tissues, providing an alternative to leaflet resection, and cryo-anchoring provides reversible attachment of a catheter to freely mobile MV leaflets. Excised porcine MVs (n = 9) were tested in a left heart flow simulator to establish treatment efficacy criteria. Resected leaflet area was quantified by tracking markers on the leaflet surface, and leaflet length reductions were directly measured on echocardiography. Leaflet area decreased by 38 ± 2.7%, and leaflet length decreased by 9.2 ± 1.8% following RFC catheter treatment. The RFC catheter was then tested acutely in healthy pigs (n = 5) under epicardial echocardiographic guidance, open-chest without cardiopulmonary bypass, using mid-ventricular free wall access. Leaflet length was quantified using echocardiography. Quantitative assessment of MV leaflet length revealed that leaflet resection was successful in 4 of 5 pigs, with a leaflet length reduction of 13.3 ± 4.6%. Histological, mechanical, and gross pathological findings also confirmed that RFC catheter treatment was efficacious. The RFC catheter significantly reduces MV leaflet size in an acute animal model, providing a possible percutaneous alternative to surgical leaflet resection.

Acute and Midterm Outcome After MitraClip Therapy in Patients With Severe Mitral Regurgitation and Left Ventricular Dysfunction

The clinical outcome of patients with severe primary and secondary mitral regurgitation (MR) and heart failure or significantly reduced left ventricular ejection fraction (LVEF) who underwent percutaneous mitral valve repair (pMVR) is yet not well known. This study compares midterm outcome of patients with severe left ventricular dysfunction (EF ≤30%) versus patients with slightly or moderately reduced or normal LVEF (EF >30%) after pMVR. One hundred thirty-six consecutive patients were enrolled: 42 patients displayed severe left ventricular dysfunction, group 1 (logistic EuroSCORE I 27.7 ± 21.8%; secondary MR in 37 patients), and 94 patients displayed slightly or moderately reduced or normal LVEF, group 2 (logistic EuroSCORE I 17 ± 18.2%; secondary MR in 21 patients). The primary efficacy endpoint was death of any cause, repeat mitral valve intervention, and/or New York Heart Association class ≥III, which was reached in 31% of patients in group 1 versus 40% in group 2 (p = 0.719) at a median follow-up of 371 days. MR, graded by transthoracic echocardiography, was reduced in both groups (p <0.001) and New York Heart Association class improved in each group (p <0.001), with no differences between groups (p >0.05). In conclusion, at midterm follow-up, the pMVR provided significant clinical benefits with comparable results achieved both in patients with significantly reduced and in patients with moderately reduced to normal LVEF. Thus, pMVR represents a feasible and effective treatment in high-risk patients who otherwise have limited therapeutic options and no safe option to reduce MR.

Long-term outcomes of mitral valve repair versus replacement for degenerative disease: a systematic review

The short-term advantage of mitral valve repair versus replacement for degenerative disease has been extensively documented. These advantages include lower operative mortality, improved survival, better preservation of left-ventricular function, shorter post-operative hospital stay, lower total costs, and fewer valve-related complications, including thromboembolism, anticoagulation-related bleeding events and late prosthetic dysfunction. More recent written data are available indicating the long-term advantage of repair versus replacement. While at some institutions, the repair rate for degenerative disease may exceed 90%, the national average in 2007 was only 69%. Making direct comparisons between mitral valve repair and replacement using the available studies does present some challenges however, as there are often differences in baseline characteristics between patient groups as well as other dissimilarities between studies. The purpose of this review is to systematically summarize the long-term survival and reoperation data of mitral valve repair versus replacement for degenerative disease. A PubMed search was done and resulted in 12 studies that met our study criteria for comparing mitral valve repair versus replacement for degenerative disease. A systematic review was then conducted abstracting survival and reoperation data.

Standards for heart valve surgery in a 'Heart Valve Centre of Excellence'

Surgical centres of excellence should include multidisciplinary teams with specialist expertise in imaging, clinical assessment and surgery for patients with heart valve disease. There should be structured training programmes for the staff involved in the periprocedural care of the patient and these should be overseen by national or international professional societies. Good results are usually associated with high individual and centre volumes, but this relationship is complex. Results of surgery should be published by centre and should include rates of residual regurgitation for mitral repairs and reoperation rates matched to the preoperative pathology and risk.

Comparing the endo-aortic balloon and the external aortic clamp in minimally invasive mitral valve surgery

OBJECTIVES

The aim of this study was to assess the differences in perioperative outcomes and complications between the endo-aortic balloon (EAB) and the external aortic clamp (EAC) during primary elective minimally invasive mitral valve surgery (MIMVS) in a single referral centre by one surgeon. Primary outcomes were cardiopulmonary bypass time (CPB), cross-clamp time (CX) and occurrence of postoperative cerebrovascular accidents (CVAs). Secondary outcomes were other perioperative parameters and complications.

METHODS

We retrospectively analysed 340 consecutive patients who underwent MIMVS for mitral regurgitation (MR), mitral stenosis or combined regurgitation/stenosis between November 2010 and March 2014 in a single referral centre. In total, 221 patients who underwent an isolated mitral valve repair or isolated mitral valve replacement or repair/replacement combined with an atrial fibrillation (AF)-ablation procedure were included. Patients who had previous cardiac surgery or concomitant tricuspid valve surgery, myxoma or atrial septal defect closure surgery were excluded.

RESULTS

A total of 57 patients (Group A) underwent MIMVS using the EAC and 164 patients (Group B) were operated using an EAB. Preoperative variables showed a significant difference in poor left ventricular function (LVF, P = 0.18) and moderate LVF (P = 0.019). No significant differences were found in CPB-time, cross-clamp time or postoperative CVA. Furthermore, no significant differences were found in complications, 30-day mortality or postoperative echocardiographical MR gradation. Hospital stay, however, was prolonged in Group A (P = 0.001) and maximum troponin T levels were significantly lower in Group B (P = 0.014). In Group B however, 10 procedures were converted (6%) from EAB to EAC.

CONCLUSIONS

There is no difference in use between the EAB and the EAC in terms of CPB-time and cross-clamp time, complications or MR gradation at discharge. Use of the EAC showed significantly higher postoperative levels of troponin T, implying more myocardial damage, compared with the EAB. In 6% of the cases however, patients were converted from the EAB to the EAC.

Therapeutic decision-making for patients with fluctuating mitral regurgitation

Mitral regurgitation (MR) is a common, progressive, and difficult-to-manage disease. MR is dynamic in nature, with physiological fluctuations occurring in response to various stimuli such as exercise and ischaemia, which can precipitate the development of symptoms and subsequent cardiac events. In both chronic primary and secondary MR, the dynamic behaviour of MR can be reliably examined during stress echocardiography. Dynamic fluctuation of MR can also have prognostic value; patients with a marked increase in regurgitant volume or who exhibit increased systolic pulmonary artery pressure during exercise have lower symptom-free survival than those who do not experience significant changes in MR and systolic pulmonary artery pressure during exercise. Identifying patients who have dynamic MR, and understanding the mechanisms underlying the condition, can potentially influence revascularization strategies (such as the surgical restoration of coronary blood flow) and interventional treatment (including cardiac resynchronization therapy and new approaches targeted to the mitral valve).