Correlation between clinical and histologic patterns of degenerative mitral valve insufficiency: a histomorphometric study of 130 excised segments

A balanced mitral leaflet and large ring strategy avoids systolic anterior motion in Barlow's disease

OBJECTIVES

Mitral valve repair for Barlow's disease offers good outcomes but excessive and myxomatous valvular tissue is associated with systolic anterior motion. Although valvular disease might progress after repair and cause long-term systolic anterior motion, few reports focus on this aspect. Herein, we will review our 16-year experience with mitral valve repair for Barlow's disease and systolic anterior motion incidence.

METHODS

We retrospectively reviewed surgical outcomes of 92 cases of mitral valve repair using a balanced leaflet/large ring strategy plus median sternotomy for Barlow's disease (median age 45.1 ± 12.7 years old [19-72], 37 females) from 2004 to 2019. Concomitant surgeries, except for tricuspid valve or anti-arrhythmic surgeries, were excluded.

RESULTS

The follow-up period was 5.8 ± 4.4 years with no deaths. Patients had mitral regurgitation of grade 3/4 (15 cases) or 4/4 (77 cases) due to anterior leaflet (3 cases), posterior leaflet (75 cases), or bileaflet (14 cases) prolapse, with chord elongation (39 cases), chord rupture (22 cases), or a combination of both (14 cases). All cases required ring annuloplasty (median size of 33.0 ± 5.4 mm) combined with leaflet resection (91 cases), chord intervention (12 cases), or indentation closure (2 cases). No case had short- or long-term SAM. The freedom-from-mitral-regurgitation (of greater than grade 2/4) rate was 94.1% over 5 years and 76.0% over 10 years without reoperation.

CONCLUSIONS

Our two-pronged strategy for mitral valve repair in Barlow's disease avoids systolic anterior motion over the long-term, with good outcomes.

Five-year outcomes of different techniques for minimally invasive mitral valve repair in Barlow's disease

OBJECTIVES

Barlow's disease is a specific sub-form of mitral valve (MV) disease, characterized by diffuse excessive tissue and multi segment prolapse. The anterolateral mini-thoracotomy represents the standard access for MV regurgitation in many centres. It still remains unclear which surgical technique provides the best results. Therefore, the aim of this study was to compare operative safety and mid-term outcomes after (i) isolated annuloplasty, (ii) use of additional artificial chordae or (iii) leaflet resection in patients suffering from Barlow's disease undergoing minimally invasive MV repair.

METHODS

A consecutive series of patients suffering from Barlow's disease undergoing minimally invasive MV surgery between 2001 and 2020 were analysed (n = 246). Patients were grouped and analysed according to the used surgical technique. The primary outcome was a modified Mitral Valve Academic Research Consortium combined end-point of mortality, reoperation due to repair failure or reoccurrence of severe mitral regurgitation within 5 years. The secondary outcome included operative success and safety up to 30 days.

RESULTS

No significant difference was found between the 3 surgical techniques with regard to operative safety (P = 0.774). The primary outcome did not differ between groups (P = 0.244). Operative success was achieved in 93.5% and was lowest in the isolated annuloplasty group (77.1%). Conversion to MV replacement was increased in patients undergoing isolated annuloplasty (P < 0.001).

CONCLUSIONS

Isolated annuloplasty, use of additional artificial chordae and leaflet resection represent feasible techniques in Barlow patients undergoing minimally invasive MV surgery with comparable 5-year results. In view of the increased conversion rate in the annuloplasty group, the pathology should not be oversimplified.

Infant Barlow's Disease in Association with Atrial Septal Defect

CLINICAL DATA

Female, seven years old, referred to our service complaining about congestive heart failure symptoms due to mitral valve regurgitation and atrial septal defect. Technical description: Echocardiographic findings compatible with Barlow's disease and atrial septal defect, ostium secundum type.

OPERATION

She was submitted to mitral valvuloplasty with chordal shortening and prosthetic posterior ring (Gregori-Braile®) along with patch atrioseptoplasty.

COMMENTS

Mitral valve regurgitation is a rare congenital heart disease and Barlow's disease is probably rarer. Mitral valve repair is the treatment of choice.

Mid-term clinical outcomes of totally endoscopic repair for mitral regurgitation in Barlow's disease

OBJECTIVE

This study aimed to confirm the safety and feasibility of totally endoscopic repair for mitral regurgitation (MR) in Barlow's disease.

METHODS

From June 2018 to December 2022, 21 consecutive Barlow's disease patients (aged 33 ± 12 years; 57.1% male) underwent totally endoscopic mitral valve (MV) repair with leaflets folding, multiple artificial chordae implantation and ring annuloplasty. The safety and feasibility of this technique was evaluated by its mid-term clinical outcomes.

RESULTS

There was no operative death or complications. The mean cardiopulmonary bypass (CPB) time was 190 ± 41 (128-267) min, and the aortic cross-clamp time was 145 ± 32 (66-200) min. The average number of artificial chordae implantation was 2.9 ± 0.7 (1-4) pairs. The mean MV coaptation length was 1.4 ± 0.3 (0.8-1.8) cm, and the median transvalvular gradient was 1 [interquartile range (IQR), 1-2] mmHg. During a median follow-up time of 24 (IQR, 10-38) months, all patients showed persistent effective valve function with no significant MR or systolic anterior motion.

CONCLUSIONS

Totally endoscopic repair was a safe, effective, and reproducible procedure with satisfied mid-term clinical outcomes for MR in Barlow's disease. However, further randomized and long-term follow-up studies were warranted to determine its clinical effects.

Degenerative mitral regurgitation

Degenerative mitral regurgitation is a major threat to public health and affects at least 24 million people worldwide, with an estimated 0.88 million disability-adjusted life years and 34,000 deaths in 2019. Improving access to diagnostic testing and to timely curative therapies such as surgical mitral valve repair will improve the outcomes of many individuals. Imaging such as echocardiography and cardiac magnetic resonance allow accurate diagnosis and have provided new insights for a better definition of the most appropriate timing for intervention. Advances in surgical techniques allow minimally invasive treatment with durable results that last for ≥20 years. Transcatheter therapies can provide good results in select patients who are considered high risk for surgery and have a suitable anatomy; the durability of such repairs is up to 5 years. Translational science has provided new knowledge on the pathophysiology of degenerative mitral regurgitation and may pave the road to the development of medical therapies that could be used to halt the progression of the disease.

Arrhythmogenic Mitral Valve Prolapse and Sudden Cardiac Death: An Update and Current Perspectives

Mitral valve prolapse (MVP) affects about 2% to 3% of the general population, mostly women, and is the most common cause of primary chronic mitral regurgitation (MR) in western countries. The natural history is heterogeneous and widely determined by the severity of MR. Although most patients remain asymptomatic with a near-normal life expectancy, approximately 5% to 10 % progress to severe MR. As largely recognized, left ventricular (LV) dysfunction due to chronic volume overload per se identifies a subgroup at risk of cardiac death. However, there is rising evidence of a link between MVP and life threating ventricular arrhythmias (VAs)/sudden cardiac death (SCD) in a small subset of middle-aged patients without significant MR, heart failure and remodeled hearts. The present review focuses on the underlying mechanism of electric instability and unexpected cardiac death in this subset of young patients, from the myocardial scarring of the LV infero-lateral wall due to mechanical stretch exerted by the prolapsing leaflets and mitral annular disjunction, to the inflammation's impact on fibrosis pathways along with a constitutional hyperadrenergic state. The heterogeneity of clinical course reveals a necessity of risk stratification, preferably through noninvasive multimodality imaging, that will help to identify and prevent adverse scenarios in young MVP patients.

Therapeutic CCR2 Blockade Prevents Inflammation and Alleviates Myxomatous Valve Disease in Marfan Syndrome

Myxomatous valve disease (MVD) can lead to cardiac dysfunction and heart failure, yet medical therapies are lacking. C-C chemokine receptor type 2 (CCR2)+ immune cell infiltration promotes mitral valve inflammation in a Marfan syndrome (MFS) mouse model. The CCR2 genetic knockout reduces inflammation with downregulated proteases and improved extracellular matrix integrity. Pharmacological inhibition of CCR2+ cell infiltration by RS504393 prevents the initiation and progression of MVD, indicated by restored protease expression, improved extracellular matrix organization, and reduced valve leaflet thickness in MFS mice. Thus, the CCR2 antagonist RS504393 is a promising therapy for the treatment of MVD in MFS.

An autopsy case of sudden unexpected death with Barlow's disease

A 45-year-old man was clinically diagnosed with mitral valve regurgitation 2 years before death. The autopsy showed left ventricular hypertrophy and mitral valve prolapse of the bileaflet with billowing valve and excessively thickened leaflet, the findings of which were consistent with Barlow's disease. Microscopically, destruction of the three-layer structure of the mitral valve and advanced interstitial fibrosis of the left ventricular wall were evident. Additionally, a marked but limited reduction in conduction fibers was found in the branching point of the left and right branches, as seen in cases of idiopathic complete atrioventricular block. Genetic investigation using whole-exome sequencing showed some genetic variants with uncertain significance. In patients with Barlow's disease, a marked reduction of conduction fibers might be a subtype of sudden cardiac death. The overlap of some arrhythmogenic substrate in the heart may increase the risk of sudden cardiac death with asymptomatic Barlow's disease.

The Role of Transforming Growth Factor-β Signaling in Myxomatous Mitral Valve Degeneration

Mitral valve prolapse (MVP) due to myxomatous degeneration is one of the most important chronic degenerative cardiovascular diseases in people and dogs. It is a common cause of heart failure leading to significant morbidity and mortality in both species. Human MVP is usually classified into primary or non-syndromic, including Barlow’s Disease (BD), fibro-elastic deficiency (FED) and Filamin-A mutation, and secondary or syndromic forms (typically familial), such as Marfan syndrome (MFS), Ehlers-Danlos syndrome, and Loeys–Dietz syndrome. Despite different etiologies the diseased valves share pathological features consistent with myxomatous degeneration. To reflect this common pathology the condition is often called myxomatous mitral valve degeneration (disease) (MMVD) and this term is universally used to describe the analogous condition in the dog. MMVD in both species is characterized by leaflet thickening and deformity, disorganized extracellular matrix, increased transformation of the quiescent valve interstitial cell (qVICs) to an activated state (aVICs), also known as activated myofibroblasts. Significant alterations in these cellular activities contribute to the initiation and progression of MMVD due to the increased expression of transforming growth factor-β (TGF-β) superfamily cytokines and the dysregulation of the TGF-β signaling pathways. Further understanding the molecular mechanisms of MMVD is needed to identify pharmacological manipulation strategies of the signaling pathway that might regulate VIC differentiation and so control the disease onset and development. This review briefly summarizes current understanding of the histopathology, cellular activities, molecular mechanisms and pathogenesis of MMVD in dogs and humans, and in more detail reviews the evidence for the role of TGF-β.

Mitral Regurgitation in Patients Undergoing Noncardiac Surgery

Mitral regurgitation (MR) is one of the most frequently encountered types of valvular heart disease in the United States. Patients with significant MR (moderate-to-severe or severe) undergoing noncardiac surgery have an increased risk of perioperative cardiovascular complications. MR can arise from a diverse array of causes that fall into 2 broad categories: primary (diseases intrinsic to the valvular apparatus) and secondary (diseases that disrupt normal valve function via effects on the left ventricle or mitral annulus). This article highlights key guideline updates from the American College of Cardiologists (ACC) and the American Heart Association (AHA) that inform decision-making for the anesthesiologist caring for a patient with MR undergoing noncardiac surgery. The pathophysiology and natural history of acute and chronic MR, staging of chronic primary and secondary MR, and considerations for timing of valvular corrective surgery are reviewed. These topics are then applied to a discussion of anesthetic management, including preoperative risk evaluation, anesthetic selection, hemodynamic goals, and intraoperative monitoring of the noncardiac surgical patient with MR.

The current diagnosis and treatment of high-risk patients with chronic primary and secondary mitral valve regurgitation

Mitral valve regurgitation (MR) is due primarily to either primary degeneration of the mitral valve with Barlow's or fibroelastic disease or is secondary to ischemic or nonischemic cardiomyopathies. Echocardiography is essential to assess MR etiology and severity, the remodeling of cardiac chambers and to characterize longitudinal chamber changes to determine optimal therapies. Surgery is recommended for severe primary MR if persistent symptoms are present or if left ventricle dysfunction is present with an EF <60% or a left ventricle end-systolic diameter ≥40 mm. For secondary MR, therapy of heart failure with vasodilators and diuretics improves forward cardiac output. Coronary artery bypass grafts (CABG) or percutaneous coronary intervention (PCI) should be considered for severe MR due to ischemia. This review summarizes the pathophysiology, the characteristics, the management and the different interventions for high risk patients with chronic primary and secondary MR.

Minimally-invasive mitral valve repair of symmetric and asymmetric Barlow´s disease

Objectives

Barlow´s disease represents a wide spectrum of mitral valve pathologies associated with regurgitation (MR), excess leaflet tissue, and prolapse. Repair strategies range from complex repairs with annuloplasty plus neochords through resection to annuloplasty-only. The latter requires symmetric prolapse patterns and central regurgitant jets. We aimed to assess repair success and durability, survival, and intraoperative outcomes with symmetric and asymmetric Barlow’s disease.

Methods

Between 09/10 and 03/20, 103 patients (of 1939 with mitral valve surgery) presented with Barlow´s disease. All received surgery through mini-thoracotomy with annuloplasty plus neochords (n = 71) or annuloplasty-only (n = 31). One valve was replaced for endocarditis (repair rate: 99%).

Results

Annuloplasty-only patients were older (64 ± 16 vs. 55 ± 11 years, p = 0.008) and presented with higher risk (EuroSCORE II: 4.2 ± 4.9 vs. 1.6 ± 1.7, p = 0.007). Annuloplasty-only patients had shorter cross-clamp times (53 ± 18 min vs. 76 ± 23 min, p < 0.001) and received more tricuspid annuloplasty (15.5% vs. 48.4%, p < 0.001). Operating times were similar (170 ± 41 min vs. 164 ± 35, p = 0.455). In three patients, annuloplasty-only caused intraoperative systolic anterior motion (SAM), which was fully resolved by neochords to the posterior leaflet. There were no conversions to sternotomy or deaths at 30-days. Three patients required reoperation for recurrent MR (at 25 days, 2.8 and 7.8 years). At the latest follow-up, there was no MR in 81.4%, mild in 14.7%, and moderate in 2.9%. Three patients died due to non-cardiac reasons. Surviving patients report the absence of relevant symptoms.

Conclusions

Minimally-invasive Barlow’s repair is safe with good durability. Annuloplasty-only may be a simple solution for complex but symmetric pathologies. However, it may carry an increased risk of intraoperative SAM.

Characterization of Degenerative Mitral Valve Disease: Differences between Fibroelastic Deficiency and Barlow's Disease

Degenerative mitral valve disease causing mitral valve prolapse is the most common cause of primary mitral regurgitation, with two distinct phenotypes generally recognized with some major differences, i.e., fibroelastic deficiency (FED) and Barlow’s disease. The aim of this review was to describe the main histological, clinical and echocardiographic features of patients with FED and Barlow’s disease, highlighting the differences in diagnosis, risk stratification and patient management, but also the still significant gaps in understanding the exact pathophysiology of these two phenotypes.

Cardiac Imaging for Risk Assessment of Malignant Ventricular Arrhythmias in Patients With Mitral Valve Prolapse

Recent studies have described the occurrence of complex ventricular arrhythmias and sudden cardiac death among patients with mitral valve prolapse (MVP). The reported incidence rate of sudden cardiac death or ventricular tachycardia is about 1–1.5% among patients with MVP. Various imaging markers have been associated with this increased risk, including mitral annular disjunction, replacement fibrosis by late gadolinium enhancement, and mechanical dispersion. In this review, we briefly discuss how multimodality cardiac imaging can be applied to identify MVP patients with high risk of sudden cardiac death and complex ventricular arrhythmias.

Resolving the Disproportionate Left Ventricular Enlargement in Mitral Valve Prolapse Due to Barlow Disease: Insights From Cardiovascular Magnetic Resonance

OBJECTIVES

This study hypothesized that left ventricular (LV) enlargement in Barlow disease can be explained by accounting for the total volume load that consists of transvalvular mitral regurgitation (MR) and the prolapse volume.

BACKGROUND

Barlow disease is characterized by long prolapsing mitral leaflets that can harbor a significant amount of blood-the prolapse volume-at end-systole. The LV in Barlow disease can be disproportionately enlarged relative to MR severity, leading to speculation of Barlow cardiomyopathy.

METHODS

Cardiac magnetic resonance (CMR) was used to compare MR, prolapse volume, and heart chambers remodeling in patients with Barlow disease (bileaflet prolapse [BLP]) and in single leaflet prolapse (SLP).

RESULTS

A total of 157 patients (81 with BLP, 76 with SLP) were included. Patients with SLP were older and more had hypertension. Patients with BLP had more heart failure. Indexed LV end-diastolic volume was larger in BLP despite similar transvalvular MR. However, the prolapse volume was larger in BLP, which led to larger total volume load compared with SLP. Increasing tertiles of prolapse volume and MR both led to an incremental increase in LV end-diastolic volume in BLP. Using the total volume load improved the correlation with indexed LV end-diastolic volume in the BLP group, which closely matched that of SLP. A multivariable model that incorporated the prolapse volume explained left heart chamber enlargement better than a MR-based model, independent of prolapse category.

CONCLUSIONS

The prolapse volume is part of the total volume load exerted on the LV during the cardiac cycle and could help explain the disproportionate LV enlargement relative to MR severity noted in Barlow disease.

Stress-induced remodelling of the mitral valve: a model for leaflet thickening and superimposed tissue formation in mitral valve disease

AIMS

In mitral valve prolapse (MVP), leaflet thickening has recently been suggested to be due, in addition to a myxomatous degeneration, to the presence of a superimposed tissue (SIT), defined as an additional fibrous layer on top of the original leaflet. The mechanisms of SIT formation are currently unknown. We hypothesized that SIT formation would result from excessive leaflet stress and we used a unique ex vivo model to assess the correlation between leaflet remodelling and the type and location of mechanical stress and to elucidate the mechanisms underlying SIT formation.

METHODS AND RESULTS

Human diseased mitral valves (MVs; n = 21) were histologically analysed for SIT formation and original leaflet thickening. The SIT comprised of various compositions of extracellular matrix and could reach more than 50% of total leaflet thickness. Original leaflet and SIT thickness did not show significant correlation (r = -0.27, P = 0.23), suggesting different regulatory mechanisms. To study the role of the mechanical environment on MV remodelling, mouse MV were cultured in their natural position in the heart and subjected to various haemodynamic conditions representing specific phases of the cardiac cycle and the MVP configuration. SIT formation was induced in the ex vivo model, mostly present on the atrial side, and clearly dependent on the duration, type, and extent of mechanical stress. Specific stainings and lineage tracing experiments showed that SIT comprises of macrophages and myofibroblasts and is associated with the activation of the transforming growth factor-beta and bone morphogenetic protein signalling pathways. Migration of valvular interstitial cells and macrophages through breakages of the endothelial cell lining contributed to SIT formation.

CONCLUSIONS

Mechanical stresses induce specific cellular and molecular changes in the MV that result in SIT formation. These observations provide the first insights in the mechanism of SIT formation and represent an initial step to identify potential novel and early treatment for MVP.

Understanding Non-P2 Mitral Regurgitation Using Real-Time Three-Dimensional Transesophageal Echocardiography: Characterization and Factors Leading to Underestimation

BACKGROUND

P2 prolapse is a common cause of degenerative mitral regurgitation (MR); echocardiographic characteristics of non-P2 prolapse are less known. Because of the eccentric nature of degenerative MR jets, the evaluation of MR severity is challenging. The aim of this study was to test the hypotheses that (1) the percentage of severe MR determined by transthoracic echocardiography (TTE) would be lower compared with that determined by transesophageal echocardiography (TEE) in patients with non-P2 prolapse and also in a subgroup with "horizontal MR" (a horizontal jet seen on TTE that hugs the leaflets without reaching the atrial wall, particularly found in non-P2 prolapse) and (2) the directions of MR jets between TTE and real-time (RT) three-dimensional (3D) TEE would be discordant.

METHODS

One hundred eighteen patients with moderate to severe and severe degenerative MR defined by TEE were studied. The percentage of severe MR between TTE and TEE was compared in P2 and non-P2 prolapse groups and in horizontal and nonhorizontal MR groups. Additionally, differences in the directions of the MR jets between TTE and RT 3D TEE were assessed.

RESULTS

Eighty-six percent of patients had severe MR according to TEE. TTE underestimated severe MR in the non-P2 group (severe MR on TTE, 57%; severe MR on TEE, 85%; P < .001) but not in the P2 group (severe MR on TTE, 79%; severe MR on TEE, 91%; P = .157). Most "horizontal" MR jets were found in the non-P2 group (85%), and this subgroup showed even more underestimation of severe MR on TTE (TTE, 22%; TEE, 89%; P < .001). There was discordance in MR jet direction between two-dimensional TTE and RT 3D TEE in 41% of patients.

CONCLUSIONS

Non-P2 and "horizontal" MR are significantly underestimated on TTE compared with TEE. There is substantial discordance in the direction of the MR jet between RT 3D TEE and TTE. Therefore, TEE should be considered when these subgroups of MR are observed on TTE.

Mechanics and Microstructure of the Atrioventricular Heart Valve Chordae Tendineae: A Review

The atrioventricular heart valves (AHVs) are responsible for directing unidirectional blood flow through the heart by properly opening and closing the valve leaflets, which are supported in their function by the chordae tendineae and the papillary muscles. Specifically, the chordae tendineae are critical to distributing forces during systolic closure from the leaflets to the papillary muscles, preventing leaflet prolapse and consequent regurgitation. Current therapies for chordae failure have issues of disease recurrence or suboptimal treatment outcomes. To improve those therapies, researchers have sought to better understand the mechanics and microstructure of the chordae tendineae of the AHVs. The intricate structures of the chordae tendineae have become of increasing interest in recent literature, and there are several key findings that have not been comprehensively summarized in one review. Therefore, in this review paper, we will provide a summary of the current state of biomechanical and microstructural characterizations of the chordae tendineae, and also discuss perspectives for future studies that will aid in a better understanding of the tissue mechanics-microstructure linking of the AHVs' chordae tendineae, and thereby improve the therapeutics for heart valve diseases caused by chordae failures.

Quantitative Description of Mitral Valve Geometry Using Real-Time Three-Dimensional Echocardiography

Objectives

Leaflet and annular geometry are important determinants of mitral valve (MV) stress. Repair techniques which optimize valvular geometry will reduce stress and potentially increase repair durability. The development of such procedures will require image processing methodologies that provide a quantitative description of three-dimensional valvular geometry. Using three-dimensional echocardiography in conjunction with novel geometric modeling and rendering techniques, we have developed a high-resolution, quantitative, three-dimensional methodology for imaging the human MV.

Methods

Five normal adults underwent MV imaging using real-time three-dimensional echocardiography. Using specially designed image analysis software, multiple valvular geometric parameters, including the magnitude and orientation of leaflet curvature, leaflet surface area, annular height, intercommissural width, septolateral annular diameter, and annular area were determined for each subject. Image rendering techniques that allow for the clear and concise presentation of this detailed information are also presented.

Results

Although three-dimensional annular and leaflet geometry were found to be highly conserved among normal human subjects, substantial regional variation in leaflet geometry was observed. Interestingly, leaflet geometric heterogeneity was most pronounced in the midposterior leaflet, the region most commonly involved in leaflet flail in subjects with myxomatous disease.

Conclusions

The image processing and graphical rendering techniques that we have developed can be used to provide a complete description of three-dimensional MV geometry in human subjects. Widespread application of these techniques to normal subjects and patients with MV disease will provide insight into the geometric basis of both valvular pathology and repair durability.

Clinical and echocardiographic factors associated with mitral plasticity in patients with chronic inferior myocardial infarction

Aims

Ischaemic mitral regurgitation (IMR) is consequence of left ventricular (LV) remodelling after myocardial infarction. In some cases, the mitral valve enlarges to compensate for LV remodelling and tenting, improving its coaptation; a process termed 'plasticity'. We sought to identify clinical and echocardiographic factors associated with plasticity in patients with chronic inferior myocardial infarction (CII).

Methods and results

This study included 91 revascularized CII patients and 46 controls. Plasticity and IMR severity were evaluated by 2D transthoracic echocardiography. Compared with controls, CII patients were older (59 vs. 25 years) and mostly men (80% vs. 46%), both P < 0.001. Chronic inferior myocardial infarction patients also had significant LV remodelling: larger LV volumes, larger mitral tenting areas, larger coaptation depths, longer mitral leaflets and chords, and worse mitral regurgitation (all P ≤ 0.03). Of 91 CII patients, 60 had mitral plasticity (longer anterior and posterior leaflets and longer posterior chords, all P < 0.001), despite not exhibiting significantly larger LV volumes, tenting area or coaptation depth, when compared with patients with no plasticity. Contralateral (anterior) papillary muscle-to-annulus length tended to be increased in CII plasticity patients (P = 0.05). Also they had less moderate and severe IMR (both P < 0.04) compared with non-plasticity CII patients. Multivariate analysis demonstrated independent associations between plasticity and smoking [odds ratio (OR) 0.03, 0.002-0.57; P = 0.019], duration of type-2 diabetes (OR 1.19, 1.007-1.42; P = 0.04) and haemoglobin (OR 2.17, 1.25-3.76; P = 0.005).

Conclusion

Mitral plasticity results in less moderate and severe IMR. Longer time-duration of diabetes mellitus and higher haemoglobin level are independently associated with mitral plasticity, while smoking independently associates with no plasticity. Increased anterior papillary muscle-to-annulus length in CII patients with plasticity suggests complex LV remodelling mechanisms are involved in plasticity.

Transvalvular pressure gradients for different methods of mitral valve repair: only neochordoplasty achieves native valve gradients

OBJECTIVES

Many surgical and interventional methods are available to restore patency for patients with degenerative severe mitral valve regurgitation. Leaflet resection and neochordoplasty, which both include ring annuloplasty, are the most frequently performed techniques for the repair of posterior mitral leaflet flail. It is unclear which technique results in the best haemodynamics. In this study, we investigated the effect of different mitral valve reconstruction techniques on mitral valve haemodynamics and diastolic transvalvular pressure gradient in an ex vivo porcine model.

METHODS

Eight porcine mitral valves were tested under pulsatile flow conditions in an in vitro pulsatile flow loop for haemodynamic quantification. Severe acute posterior mitral leaflet flail was created by resecting the posterior marginal chorda. The acute mitral valve regurgitation was corrected using 4 different repair techniques, in each valve, in a strictly successive order: (i) neochordoplasty with polytetrafluoroethylene sutures alone and (ii) with ring annuloplasty, (iii) edge-to-edge repair and (iv) triangular leaflet resection, both with ring annuloplasty. Valve haemodynamics were measured and quantified for all valve configurations (native, rupture and each surgical reconstruction). The results were analysed using a validated statistical linear mixed model, and the P-values were calculated using a 2-sided Wald test.

RESULTS

All surgical reconstruction techniques were able to sufficiently correct the acute mitral valve regurgitation. Neochordoplasty without ring annuloplasty was the only reconstruction technique that resulted in haemodynamic properties similar to the native mitral valve (P-values from 0.071 to 0.901). The diastolic transvalvular gradient remained within the physiological range for all reconstructions but was significantly higher than in the native valve for neochordoplasty with ring annuloplasty (P < 0.000), edge-to-edge repair (P < 0.000) and leaflet resection (P < 0.000). Neochordoplasty without ring annuloplasty resulted in a significantly better pressure gradient than neochordoplasty with a ring annuloplasty (P < 0.000). Additionally, neochordoplasty with a ring annuloplasty resulted in significantly lower transvalvular pressure gradients than edge-to-edge repair (P < 0.000) and leaflet resection (P < 0.000).

CONCLUSIONS

Neochordoplasty with or without ring annuloplasty was the reconstruction technique that almost achieved native physiological haemodynamics after repair of posterior mitral leaflet flail after acute isolated chordal rupture in our ex vivo porcine model.

Comparison of Outcomes of Mitral Valve Repair for Leaflet Prolapse with Advanced versus Mild/Moderate Myxomatous Degeneration

There is limited information on long-term outcomes of mitral valve repair for mitral regurgitation (MR) caused by different degrees of myxomatous degeneration. The aim of this study was to compare the surgical results of patients with advanced and mild/moderate myxomatous mitral valve degeneration (MVD). We identified 130 patients (25 advanced and 105 mild/moderate MVD patients) who underwent mitral valve repair for MR and were pathologically diagnosed as myxomatous degeneration. Follow-up was 100% complete (mean length, 5.1 ± 1.8 years). Survival differed significantly between the advanced and mild/moderate MVD groups (76.0 ± 9.7% versus 95.0 ± 5.4% at 8 years, P < 0.001). The univariate predictors of mortality were advanced myxomatous degeneration, recurrent MR, and early series (surgeries before 2011). The mild/moderate MVD group had higher freedom from a moderate or severe MR rate compared with the advanced MVD group (77.4 ± 4.5% versus 50.5 ± 10.2% at 7 years, P = 0.003). Multivariable Cox analysis revealed advanced myxomatous degeneration and residual MR as independent predictors of recurrent moderate or severe MR. A total of 25 patients (19.2%) had persistent atrial fibrillation (AF) after repair. In multivariate analysis, advanced myxomatous degeneration was found to be an independent predictor of postoperative persistent AF.In conclusion, the long-term outcomes of mitral valve repair in patients with advanced MVD are poorer than in those with mild/moderate MVD. Advanced myxomatous degeneration is an independent predictor of recurrent moderate or severe MR and postoperative persistent AF in MVD patients performing repair, which deserves more attention before and after surgery.

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.

New insights into mitral valve dystrophy: a Filamin-A genotype-phenotype and outcome study

Aims

Filamin-A (FLNA) was identified as the first gene of non-syndromic mitral valve dystrophy (FLNA-MVD). We aimed to assess the phenotype of FLNA-MVD and its impact on prognosis.

Methods and results

We investigated the disease in 246 subjects (72 mutated) from four FLNA-MVD families harbouring three different FLNA mutations. Phenotype was characterized by a comprehensive echocardiography focusing on mitral valve apparatus in comparison with control relatives. In this X-linked disease valves lesions were severe in men and moderate in women. Most men had classical features of mitral valve prolapse (MVP), but without chordal rupture. By contrast to regular MVP, mitral leaflet motion was clearly restricted in diastole and papillary muscles position was closer to mitral annulus. Valvular abnormalities were similar in the four families, in adults and young patients from early childhood suggestive of a developmental disease. In addition, mitral valve lesions worsened over time as encountered in degenerative conditions. Polyvalvular involvement was frequent in males and non-diagnostic forms frequent in females. Overall survival was moderately impaired in men (P = 0.011). Cardiac surgery rate (mainly valvular) was increased (33.3 ± 9.8 vs. 5.0 ± 4.9%, P < 0.0001; hazard ratio 10.5 [95% confidence interval: 2.9-37.9]) owing mainly to a lifetime increased risk in men (76.8 ± 14.1 vs. 9.1 ± 8.7%, P < 0.0001).

Conclusion

FLNA-MVD is a developmental and degenerative disease with complex phenotypic expression which can influence patient management. FLNA-MVD has unique features with both MVP and paradoxical restricted motion in diastole, sub-valvular mitral apparatus impairment and polyvalvular lesions in males. FLNA-MVD conveys a substantial lifetime risk of valve surgery in men.

Genomic analysis in patients with myxomatous mitral valve prolapse: current state of knowledge

Background

Myxomatous mitral valve prolapse is a common cardiac abnormality. Morbus Barlow is characterized by excess myxomatous leaflet tissue, bileaflet prolapse or billowing, chordae elongation and annular dilatation with or without calcification. Extensive myxoid degeneration with destruction of the normal three-layered leaflet tissue architecture is observed histologically in such patients. Autosomal dominant inheritance with an age and sex-dependent expression has long been recognised. This review explores the current understanding of the genetics of bileaflet prolapse, with a focus on genetic analysis and the role for echocardiographical screening of the first degree relatives of affected patients.

Methods

Systematic literature searches were performed using PubMed and Embase up to September 2017. In Disse et al.’s study (study one) first degree relatives of 25 patients with Morbus Barlow who underwent mitral valve repair were screened for bileaflet valve prolapse. In Nesta et al.’s study one family with three living generations of 43 individuals with 9 confirmed cases of MVP was screened. Genotyping was performed in four families for 344 microsatellite markers from Chromosome 1 to 16.

Results

In study one, autosomal dominant inheritance was shown in four pedigrees. Genome-wide linkage analysis of the most informative pedigree (24 individuals, three generations) showed a significant linkage for markers mapping to chromosome 16p. Linkage to this locus was confirmed in a second family within the same study, but was excluded in the remaining two pedigrees. In study two an autosomal dominant locus was mapped to chromosome 13. 8 of the 9 individuals affected were found to suffer from bileaflet prolapse.

Conclusions

Barlow’s disease is a heritable trait but the genetic causes remain largely elusive. Ch16p11.2-p12.1 is the only locus proven to be associated with bileaflet prolapse. Locus 13.q31.3-q32.1 was shown to cause bileaflet as well as posterior leaflet prolapse. This review intends to make physicians aware of genetic causes of myxomatous mitral valve prolapse, thereby emphasising the importance of cardiological examination of first-degree relatives of patients with Morbus Barlow. Integrated and more comprehensive studies are needed for identification of genes involved in this heterogenic disease. Further genomic studies may facilitate more individualised and accurate risk assessment and may help to develop possible preventive stategies for patients in the future.

Genetics of syndromic and non-syndromic mitral valve prolapse

Mitral valve prolapse (MVP) is a common condition that affects 2%-3% of the general population. MVP is thought to include syndromic forms such as Marfan syndrome and non-syndromic MVP, which is the most frequent form. Myxomatous degeneration and fibroelastic deficiency (FED) are regarded as two different forms of non-syndromic MVP. While FED is still considered a degenerative disease associated with ageing, frequent familial clustering has been demonstrated for myxomatous MVP. Familial and genetic studies led to the recognition of reduced penetrance and large phenotypic variability, and to the identification of prodromal or atypical forms as a part of the complex spectrum of the disease. Whereas autosomal dominant mode is the common inheritance pattern, an X linked form of non-syndromic MVP was recognised initially, related to Filamin-A gene, encoding for a cytoskeleton protein involved in mechanotransduction. This identification allowed a comprehensive description of a new subtype of MVP with a unique association of leaflet prolapse and paradoxical restricted motion in diastole. In autosomal dominant forms, three loci have been mapped to chromosomes 16p11-p12, 11p15.4 and 13q31-32. Although deciphering the underlying genetic defects is still a work in progress, DCHS1 mutations have been identified (11p15.4) in typical myxomatous disease, highlighting new molecular pathways and pathophysiological mechanisms leading to the development of MVP. Finally, a large international genome-wide association study demonstrated the implication of frequent variants in MVP development and opened new directions for future research. Hence, this review focuses on phenotypic, genetic and pathophysiological aspects of MVP.

Mitral Prolapse: An Old Mysterious Entity - The Incremental Role of Multimodality Imaging in Sports Eligibility

Mitral valve prolapse is generally a benign condition characterized by fibromyxomatous changes of the mitral leaflet with displacement into the left atrium and late-systolic regurgitation. Although it is an old clinical entity, it still arouses perplexity in diagnosis and clinical management. Complications, such as mitral regurgitation (MR), atrial fibrillation, congestive heart failure, endocarditis, ventricular arrhythmias, and sudden cardiac death (SCD), have been reported. A large proportion of the overall causes of SCD in young competitive athletes is explained by mitral valve prolapse. Recent studies have shown the fibrosis of the papillary muscles and inferobasal left ventricular wall in mitral valve prolapse, suggesting a possible origin of ventricular fatal arrhythmias. Athletes with mitral valve prolapse and MR should undergo annual evaluations including physical examination, echocardiogram, and exercise stress testing to evaluate the cardiovascular risks of competitive sports and obtain the eligibility. In this setting, multimodality imaging techniques – echocardiography, cardiac magnetic resonance, and cardiac computed tomography – should provide a broad spectrum of information, from diagnosis to clinical management of the major clinical profiles of the disease.

Mitral Valve Prolapse: Multimodality Imaging and Genetic Insights

Mitral valve prolapse (MVP) is a common heritable valvulopathy affecting approximately 2.4% of the population. It is the most important cause of primary mitral regurgitation (MR) requiring surgery. MVP is characterized by fibromyxomatous changes and displacement of one or both mitral leaflets into the left atrium. Echocardiography represents the primary diagnostic modality for assessment of MVP. Accurate quantitation of ventricular volumes and function for surgical planning in asymptomatic severe MR can be provided with both echocardiography and cardiac magnetic resonance. In addition, assessment of myocardial fibrosis using late gadolinium enhancement and T1 mapping allows better understanding of the impact of MVP on the myocardium. Imaging in MVP is important not only for diagnostic and prognostic purposes, but is also essential for detailed phenotyping in genetic studies. Genotype-phenotype studies in MVP pedigrees have allowed the identification of milder, non-diagnostic MVP morphologies by echocardiography. Such morphologies represent early expression of MVP in gene carriers. This review focuses on multimodality imaging and the phenotypic spectrum of MVP. Moreover, the review details the recent genetic discoveries that have increased our understanding of the pathophysiology of MVP, with clues to mechanisms and therapy.

Mitral Leaflet Changes Following Myocardial Infarction: Clinical Evidence for Maladaptive Valvular Remodeling

BACKGROUND

Ischemic mitral regurgitation (MR) is classically ascribed to functional restriction of normal leaflets, but recent studies have suggested post-myocardial infarction (MI) mitral valve (MV) leaflet fibrosis and thickening, challenging valve normality. Progression of leaflet thickness post-MI has not been studied. We hypothesized that excessive MV remodeling post-MI contributes to MR. Our objectives are to characterize MV changes after MI and relate them to MR.

METHODS AND RESULTS

Three groups of 40 patients with serial echocardiograms over a mean of 23.4 months were identified from an echocardiography database: patients first studied early (6±12 days) and late (12±7 years) after an inferior MI and normal controls. MV thickness was correlated with MR. We studied the mechanisms for MV changes in a sheep model (6 apical MI versus 6 controls) followed for 8 weeks, with MV cellular and histopathologic analyses. Early post-MI, leaflet thickness was found to be similar to controls (2.6±0.5 vs 2.5±0.4 mm; P=0.23) but significantly increased over time (2.5±0.4 to 2.9±0.4 mm; P<0.01). In this group, patients tolerating maximal doses of renin-angiotensin blocking agents had less thickening (25% of patients; P<0.01). The late-MI group had increased thickness (3.2±0.5 vs 2.5±0.4 mm; P<0.01) without progression. At follow-up, 48% of post-MI patients had more than mild MR. Increased thickness was independently associated with MR. Experimentally, 8 weeks post-MI, MVs were 2-fold thicker than controls, with increased collagen, profibrotic transforming growth factor-β, and endothelial-to-mesenchymal transformation, confirmed by flow cytometry.

CONCLUSIONS

MV thickness increases post-MI and correlates with MR, suggesting an organic component to ischemic MR. MV fibrotic remodeling can indicate directions for future therapy.

Current Discoveries and Interventions for Barlow's Disease

Mitral valve prolapse is a common valve pathology. One particular type of mitral valve prolapse that can be difficult to treat is Barlow's disease. This review serves to give insight on the current discoveries and therapeutic interventions of Barlow's disease.

Effect of Losartan on Mitral Valve Changes After Myocardial Infarction

BACKGROUND

After myocardial infarction (MI), mitral valve (MV) tethering stimulates adaptive leaflet growth, but counterproductive leaflet thickening and fibrosis augment mitral regurgitation (MR), doubling heart failure and mortality. MV fibrosis post-MI is associated with excessive endothelial-to-mesenchymal transition (EMT), driven by transforming growth factor (TGF)-β overexpression. In vitro, losartan-mediated TGF-β inhibition reduces EMT of MV endothelial cells.

OBJECTIVES

This study tested the hypothesis that profibrotic MV changes post-MI are therapeutically accessible, specifically by losartan-mediated TGF-β inhibition.

METHODS

The study assessed 17 sheep, including 6 sham-operated control animals and 11 with apical MI and papillary muscle retraction short of producing MR; 6 of the 11 were treated with daily losartan, and 5 were untreated, with flexible epicardial mesh comparably limiting left ventricular (LV) remodeling. LV volumes, tethering, and MV area were quantified by using three-dimensional echocardiography at baseline and at 60 ± 6 days, and excised leaflets were analyzed by histopathology and flow cytometry.

RESULTS

Post-MI LV dilation and tethering were comparable in the losartan-treated and untreated LV constraint sheep. Telemetered sensors (n = 6) showed no significant losartan-induced changes in arterial pressure. Losartan strongly reduced leaflet thickness (0.9 ± 0.2 mm vs. 1.6 ± 0.2 mm; p < 0.05; 0.4 ± 0.1 mm sham animals), TGF-β, and downstream phosphorylated extracellular-signal-regulated kinase and EMT (27.2 ± 12.0% vs. 51.6 ± 11.7% α-smooth muscle actin-positive endothelial cells, p < 0.05; 7.2 ± 3.5% sham animals), cellular proliferation, collagen deposition, endothelial cell activation (vascular cell adhesion molecule-1 expression), neovascularization, and cells positive for cluster of differentiation (CD) 45, a hematopoietic marker associated with post-MI valve fibrosis. Leaflet area increased comparably (17%) in constrained and losartan-treated sheep.

CONCLUSIONS

Profibrotic changes of tethered MV leaflets post-MI can be modulated by losartan without eliminating adaptive growth. Understanding the cellular and molecular mechanisms could provide new opportunities to reduce ischemic MR.

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.

Comparative Histopathological Analysis of Mitral Valves in Barlow Disease and Fibroelastic Deficiency

Whether Barlow disease (BD) and fibroelastic deficiency (FED), the main causes of mitral valve prolapse (MVP), should be considered 2 distinct diseases remains unknown. Mitral valves from patients who required surgery for severe mitral regurgitation due to degenerative nonsyndromic MVP were analyzed. Intraoperative diagnosis of BD or FED was based on leaflet redundancy and thickness, number of segments involved, and annular dimension. The removed medial scallop of the posterior leaflet and attached chordae were used for histopathological and immunohistological assessment. Histologically, compared to normal controls (n = 3), BD (n = 14), and FED (n = 9) leaflets demonstrated an altered architecture and increased thickness. Leaflet thickness was greater and chordae thickness lower in BD than FED (P < 0.0001). In BD, increased thickness was owing to spongiosa expansion (proteoglycan accumulation) and intimal thickening on fibrosa and atrialis; in FED, local thickening was predominant on the fibrosa side, with accumulation of proteoglycan-like material around the chordae. Collagen accumulation was observed in FED leaflets and chords and decreased in BD. Fragmented elastin fibers were present in BD and FED; elastin decreased in BD but increased in FED leaflets and around chordae. Activated myofibroblasts accumulate in both diseased leaflets and chords, but more abundantly in FED chordae (P < 0.0001), independently of age, suggesting a role of these cells in chordal rupture. There were more CD34-positive cells in BD leaflets and in FED chordae (P < 0.01). In BD leaflets (but not chordae) proliferative Ki67-positive cells were more abundant (P < 0.01) and matrix metalloproteinase 2 levels were increased (P < 0.01) indicating tissue remodeling. Upregulation of transforming growth factor beta and pERK signaling pathways was evident in both diseases but more prominent in FED leaflets (continued on next page)(P < 0.001), with pERK upregulation in FED chordae (P < 0.0001). Most cellular and signaling markers were negligible in control valves. Quantitative immunohistopathological analyses demonstrated distinct changes between BD and FED valves: predominant matrix degradation in BD and increased profibrotic signaling pathways in FED, indicating that BD and FED are 2 different entities. These results may pave the way for genetic studies of MVP and development of preventive drug therapies.

The mechanisms, diagnosis and management of mitral regurgitation in mitral valve prolapse and hypertrophic cardiomyopathy

Valvular disease is a frequent cardiac pathology leading to heart failure and, ultimately, death. Mitral regurgitation, defined as the inability of the two mitral leaflets to coapt, is a common valvular disease and a self sustained pathology. A better understanding of the mitral valve histological layers provides a better understanding of the leaflet and chordae changes in mitral valve prolapse. Mitral valve prolapse may occur in myxomatous degenerative abnormalities, connective tissue disorders or in sporadic isolated cases. It is the most common mitral abnormality of non-ischemic cause leading to severe surgery-requiring mitral regurgitation. In addition to standard echocardiographic investigations, newly implemented three-dimensional techniques are being used and they permit a better visualisation, from the so-called ‘surgical view’, and an improved evaluation of the mitral valve. Hypertrophic cardiomyopathy is the most frequent inherited myocardial disease caused by mutations in various genes encoding proteins of the cardiac sarcomere, leading to a marked left ventricular hypertrophy unexplained by other comorbidities. The pathological echocardiographic hallmarks of hypertrophic cardiomyopathy are left ventricular hypertrophy, left ventricular outflow tract obstruction and systolic anterior motion of the mitral valve. The systolic anterior motion of the mitral valve contributes to the development of mitral regurgitation and further narrows the left ventricular outflow tract, leading to more severe symptomatology. Cardiac magnetic resonance imaging accurately measures the left ventricular mass, the degree of diastolic function and it may also be used to distinguish phenotypic variants. The clinical outcome of patients with these pathologies is mostly determined by the selected option of treatment. The purpose of surgical correction regarding mitral valve involvement is to restore valvular competence. Surgery has proven to be the only useful treatment in preventing heart failure, improving symptomatology and reducing mortality. Our approach wishes to enhance the understanding of the mitral valve’s involvement in hypertrophic cardiomyopathy and mitral valve prolapse from genetic, haemodynamic and clinical perspectives, as well as to present novelties in the grand field of treatment.

Characterization of biomechanical properties of aged human and ovine mitral valve chordae tendineae

The mitral valve (MV) is a highly complex cardiac valve consisting of an annulus, anterior and posterior leaflets, chordae tendineae (chords) and two papillary muscles. The chordae tendineae mechanics play a pivotal role in proper MV function: the chords help maintain proper leaflet coaptation and rupture of the chordae tendineae due to disease or aging can lead to mitral valve insufficiency. Therefore, the aim of this study was to characterize the mechanical properties of aged human and ovine mitral chordae tendineae. The human and ovine chordal specimens were categorized by insertion location (i.e., marginal, basal and strut) and leaflet type (i.e., anterior and posterior). The results show that human and ovine chords of differing types vary largely in size but do not have significantly different elastic and failure properties. The excess fibrous tissue layers surrounding the central core of human chords added thickness to the chords but did not contribute to the overall strength of the chords. In general, the thinner marginal chords were stiffer than the thicker basal and strut chords, and the anterior chords were stiffer and weaker than the posterior chords. The human chords of all types were significantly stiffer than the corresponding ovine chords and exhibited much lower failure strains. These findings can be explained by the diminished crimp pattern of collagen fibers of the human mitral chords observed histologically. Moreover, the mechanical testing data was modeled with the nonlinear hyperelastic Ogden strain energy function to facilitate accurate computational modeling of the human MV.

Myocardial Infarction Alters Adaptation of the Tethered Mitral Valve

BACKGROUND

In patients with myocardial infarction (MI), leaflet tethering by displaced papillary muscles induces mitral regurgitation (MR), which doubles mortality. Mitral valves (MVs) are larger in such patients but fibrosis sets in counterproductively. The investigators previously reported that experimental tethering alone increases mitral valve area in association with endothelial-to-mesenchymal transition.

OBJECTIVES

The aim of this study was to explore the clinically relevant situation of tethering and MI, testing the hypothesis that ischemic milieu modifies mitral valve adaptation.

METHODS

Twenty-three adult sheep were examined. Under cardiopulmonary bypass, the papillary muscle tips in 6 sheep were retracted apically to replicate tethering, short of producing MR (tethered alone). Papillary muscle retraction was combined with apical MI created by coronary ligation in another 6 sheep (tethered plus MI), and left ventricular remodeling was limited by external constraint in 5 additional sheep (left ventricular constraint). Six sham-operated sheep were control subjects. Diastolic mitral valve surface area was quantified by 3-dimensional echocardiography at baseline and after 58 ± 5 days, followed by histopathology and flow cytometry of excised leaflets.

RESULTS

Tethered plus MI leaflets were markedly thicker than tethered-alone valves and sham control subjects. Leaflet area also increased significantly. Endothelial-to-mesenchymal transition, detected as α-smooth muscle actin-positive endothelial cells, significantly exceeded that in tethered-alone and control valves. Transforming growth factor-β, matrix metalloproteinase expression, and cellular proliferation were markedly increased. Uniquely, tethering plus MI showed endothelial activation with vascular adhesion molecule expression, neovascularization, and cells positive for CD45, considered a hematopoietic cell marker. Tethered plus MI findings were comparable with external ventricular constraint.

CONCLUSIONS

MI altered leaflet adaptation, including a profibrotic increase in valvular cell activation, CD45-positive cells, and matrix turnover. Understanding cellular and molecular mechanisms underlying leaflet adaptation and fibrosis could yield new therapeutic opportunities for reducing ischemic MR.

Differential MicroRNA Expression Profile in Myxomatous Mitral Valve Prolapse and Fibroelastic Deficiency Valves

Myxomatous mitral valve prolapse (MMVP) and fibroelastic deficiency (FED) are two common variants of degenerative mitral valve disease (DMVD), which is a leading cause of mitral regurgitation worldwide. While pathohistological studies have revealed differences in extracellular matrix content in MMVP and FED, the molecular mechanisms underlying these two disease entities remain to be elucidated. By using surgically removed valvular specimens from MMVP and FED patients that were categorized on the basis of echocardiographic, clinical and operative findings, a cluster of microRNAs that expressed differentially were identified. The expressions of has-miR-500, -3174, -17, -1193, -646, -1273e, -4298, -203, -505, and -939 showed significant differences between MMVP and FED after applying Bonferroni correction (p < 0.002174). The possible involvement of microRNAs in the pathogenesis of DMVD were further suggested by the presences of in silico predicted target sites on a number of genes reported to be involved in extracellular matrix homeostasis and marker genes for cellular composition of mitral valves, including decorin (DCN), aggrecan (ACAN), fibromodulin (FMOD), α actin 2 (ACTA2), extracellular matrix protein 2 (ECM2), desmin (DES), endothelial cell specific molecule 1 (ESM1), and platelet/ endothelial cell adhesion molecule 1 (PECAM1), as well as inverse correlations of selected microRNA and mRNA expression in MMVP and FED groups. Our results provide evidence that distinct molecular mechanisms underlie MMVP and FED. Moreover, the microRNAs identified may be targets for the future development of diagnostic biomarkers and therapeutics.