Abnormalities in elastic fibers and other connective-tissue components of floppy mitral valve

Quantified planar collagen distribution in healthy and degenerative mitral valve: biomechanical and clinical implications

Degenerative mitral valve disease is a common valvular disease with two arguably distinct phenotypes: fibroelastic deficiency and Barlow's disease. These phenotypes significantly alter the microstructures of the leaflets, particularly the collagen fibers, which are the main mechanical load carriers. The predominant method of investigation is histological sections. However, the sections are cut transmurally and provide a lateral view of the microstructure of the leaflet, while the mechanics and function are determined by the planar arrangement of the collagen fibers. This study, for the first time, quantitatively examined planar collagen distribution quantitatively in health and disease using second harmonic generation microscopy throughout the thickness of the mitral valve leaflets. Twenty diseased samples from eighteen patients and six control samples were included in this study. Healthy tissue had highly aligned collagen fibers. In fibroelastic deficiency they are less aligned and in Barlow's disease they are completely dispersed. In both diseases, collagen fibers have two preferred orientations, which, in contrast to the almost constant one orientation in healthy tissues, also vary across the thickness. The results indicate altered in vivo mechanical stresses and strains on the mitral valve leaflets as a result of disease-related collagen remodeling, which in turn triggers further remodeling.

Arrhythmic Mitral Valve Prolapse: A Comprehensive Review

Mitral valve prolapse (MVP) is a prevalent cardiac disorder that impacts approximately 2% to 3% of the overall population. While most patients experience a benign clinical course, there is evidence suggesting that a subgroup of MVP patients face an increased risk of sudden cardiac death (SCD). Although a conclusive causal link between MVP and SCD remains to be firmly established, various factors have been associated with arrhythmic mitral valve prolapse (AMVP). This study aims to provide a comprehensive review encompassing the historical background, epidemiology, pathology, clinical manifestations, electrocardiogram (ECG) findings, and treatment of AMVP patients. A key focus is on utilizing multimodal imaging techniques to accurately diagnose AMVP and to highlight the role of mitral annular disjunction (MAD) in AMVP.

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.

The role of elastin on the mechanical properties of the anterior leaflet in porcine tricuspid valves

Elastin is present in the extracellular matrix (ECM) of connective tissues, and its mechanical properties are well documented. In Marfan syndrome, however, the inability to properly code for the protein fibrillin-1 prematurely leads to the degradation and loss of elastin fiber integrity in the ECM. In this study, the role of elastin in the ECM of the anterior leaflet of the tricuspid valve was investigated by examining the biomechanical behavior of porcine leaflets before and after the application of the enzyme elastase. Five loading protocols were applied to the leaflet specimens in two groups (elastase-treated and control samples). The mechanical response following elastase application yielded a significantly stiffer material in both the radial and circumferential directions. At a physiological level of stress (85 kPa), the elastase group had an average strain of 26.21% and 6.32% in the radial and circumferential directions, respectively, at baseline prior to elastase application. Following elastase treatment, the average strain was 5.28% and 0.97% in the radial and circumferential directions, respectively. No statistically significant change was found in the control group following sham treatment with phosphate-buffered saline (PBS). Two-photon microscopy images confirmed that after the removal of elastin, the collagen fibers displayed a loss of undulation. With a significant reduction in radial compliance, the ability to withstand physiological loads may be compromised. As such, an extracellular matrix that is structurally deficient in elastin may hinder normal tricuspid valve function.

Chest pain and palpitations in postmenopausal women with mitral valve prolapse: is there a gastro-oesophageal origin?

BACKGROUND AND AIM

Mitral valve prolapse (MVP) is a common disease in women, causing chest pain and palpitation due to structural and functional valve abnormality, and is sometimes associated with gastro-oesophageal reflux disease (GERD). This is a challenging clinical problem in clinical practice and requires targeted diagnostic assessment to identify the underlying causes of the symptoms, because treatment needs to be tailored, according to the causes themselves, to resolve the symptoms.

AIM

To assess the prevalence of GERD in a population of postmenopausal women affected by MVP and determine if there is any correlation between the two conditions.

METHODS

The MVP diagnosis was performed using echocardiograpy examination, according to American Society Echocardiography criteria. Two hundred and eighty-nine consecutive MVP women, symptomatic for chest pain and palpitation, were included; 250 consecutive women without MVP, symptomatic for chest pain and palpitation, were the control group (CG). The GERD diagnosis was made according to 2013 American College Gastroenterology criteria; women affected by thyroid disorders, all heart disease, including mitral disease with moderate or severe mitral regurgitation, and gastrointestinal diseases assessed using gastroscopy were excluded.

RESULTS

Among 289 women with MVP, 31 (11%) women were affected by GERD, and among 250 in the CG, 11 (4.4%) women were affected by GERD: Chi-squared 8.1; odds ratio 2.7; P < 0.0044. Twenty-six (9%) women affected by GERD, with MVP, presented with mild mitral regurgitation, and 7 (2.8%) women in the CG presented with mild mitral regurgitation as well: Chi-squared 8.95; odds ratio 3.4; 95% CI, P < 0.0028.

DISCUSSION AND CONCLUSIONS

GERD is relatively common in women with MVP. Moreover, women with MVP are approximately three times more likely to be affected by GERD; the two conditions are correlated in a statistically high significant way. GERD assessment needs to be included into routine follow-up strategies in women with MVP to optimise medical therapy, improvinge symptom relief for better quality of life.

Biomechanics of mitral valve leaflets: Second harmonic generation microscopy, biaxial mechanical tests and tissue modeling

Collagen fibers are the main load carrier in the mitral valve (MV) leaflets. Their orientation and dispersion are an important factor for the mechanical behavior. Most recent studies of collagen fibers in MVs lack either entire thickness study or high transmural resolution. The present study uses second harmonic generation (SHG) microscopy in combination with planar biaxial mechanical tests to better model and examine collagen fibers and mechanical properties of MV leaflets. SHG in combination with tissue clearing enables the collagen fibers to be examined through the entire thickness of the MV leaflets. Planar biaxial mechanical tests, on the other hand, enable the characterization of the mechanical tissue behavior, which is represented by a structural tissue model. Twelve porcine MV leaflets are examined. The SHG recording shows that the mean fiber angle for all samples varies on average by ±12° over the entire thickness and the collagen fiber dispersion changes strongly over the thickness. A constitutive model based on the generalized structure tensor approach is used for the associated tissue characterization. The model represents the tissue with three mechanical parameters plus the mean fiber direction and the dispersion, and predicts the biomechanical response of the leaflets with a good agreement (average r²=0.94). It is found that the collagen structure can be represented by a mean direction and a dispersion with a single family of fibers despite the variation in the collagen fiber direction and the dispersion over the entire thickness of MV leaflets. STATEMENT OF SIGNIFICANCE: Despite its prominent role in the mechanical behavior of mitral valve (MV) leaflets, the collagen structure has not yet been investigated over the entire thickness with high transmural resolution. The present study quantifies the detailed through thickness collagen fiber structure and examines the effects of its variation on MV tissue modeling. This is important because the study evaluates the assumption that the collagen fibers can be modeled with a representative single fiber family despite the variation across the thickness. In addition, the current comprehensive data set paves the way for quantifying the disruption of collagen fibers in myxomatous MV leaflets associated with disrupted collagen fibers.

Characterization of the electrophysiological substrate in patients with Barlow's disease

BACKGROUND

Myxomatous mitral valve prolapse (MVP) and mitral-annular disjunction (Barlow disease) are at-risk for ventricular arrhythmias (VA). Fibrosis involving the papillary muscles and/or the infero-basal left ventricular (LV) wall was reported at autopsy in sudden cardiac death (SCD) patients with MVP.

OBJECTIVES

We investigated the electrophysiological substrate subtending VA in MVP patients with Barlow disease phenotype.

METHODS

Twenty-three patients with VA were enrolled, including five with syncope and four with a history of SCD. Unipolar (Uni < 8.3 mV) and bipolar (Bi < 1.5 mV) low-voltage areas were analyzed with electro-anatomical mapping (EAM), and VA inducibility was evaluated with programmed ventricular stimulation (PES). Electrophysiological parameters were correlated with VA patterns, electrocardiogram (ECG) inferior negative T wave (nTW), and late gadolinium enhancement (LGE) assessed by cardiac magnetic resonance.

RESULTS

Premature ventricular complex (PVC) burden was 12 061.9 ± 12 994.6/24 h with a papillary-muscle type (PM-PVC) in 18 patients (68%). Twelve-lead ECG showed nTW in 12 patients (43.5%). A large Uni less than 8.3 mV area (62.4 ± 45.5 cm² ) was detected in the basal infero-lateral LV region in 12 (73%) patients, and in the papillary muscles (2.2 ± 2.9 cm² ) in 5 (30%) of 15 patients undergoing EAM. A concomitant Bi less than 1.5 mV area (5.0 ± 1.0 cm² ) was identified in two patients. A history of SCD, and the presence of nTW, and LGE were associated with a greater Uni less than 8.3 mV extension: (32.8 ± 3.1 cm² vs. 9.2 ± 8.7 cm² ), nTW (20.1 ± 11.0 vs. 4.1 ± 3.8 cm² ), and LGE (19.2 ± 11.7 cm² vs. 1.0 ± 2.0 cm² , p = .013), respectively. All patients with PM-PVC had a Uni less than 8.3 mV area. Sustained VA (ventricular tachycardia 2 and VF 2) were induced by PES only in four patients (one with resuscitated SCD).

CONCLUSIONS

Low unipolar low voltage areas can be identified with EAM in the basal inferolateral LV region and in the papillary muscles as a potential electrophysiological substrate for VA and SCD in patients with MVP and Barlow disease phenotype.

Electrophysiological Substrate in Patients with Barlow's Disease

Mitral valve prolapse (MVP) is the most common valvular heart disease, affecting 2-3% of the general population. Barlow's disease is a clinical syndrome characterised by MVP. Initially thought a benign condition, MVP is now recognised as a cause of sudden cardiac death and ventricular arrhythmias. The development of new imaging techniques has contributed recently to the identification of novel risk factors. Catheter ablation of ventricular arrhythmias in patients affected by MVP is traditionally considered challenging. In this review, the authors summarise the evidence on arrhythmogenesis in the context of MVP, along with risk stratification of sudden cardiac death and the available treatment options, including new catheter ablation techniques.

Antemortem and Post-Mortem Characteristics of Lethal Mitral Valve Prolapse Among All Countywide Sudden Deaths

OBJECTIVES

The goal of this study was to investigate the characteristics of mitral valve prolapse (MVP) in a post-mortem study of consecutive sudden cardiac deaths (SCDs) in subjects up to 90 years of age.

BACKGROUND

Up to 2.3% of subjects with MVPs experience SCD, but by convention SCD is rarely confirmed by autopsy. In a post-mortem study of persons <40 years of age, 7% of SCDs were caused by MVP; bileaflet involvement, mitral annular disjunction (MAD), and replacement fibrosis were common.

METHODS

In the San Francisco POST SCD (Postmortem Systematic Investigation of Sudden Cardiac Death) study, autopsies have been performed on >1,000 consecutive World Health Organization-defined (presumed) cases of SCD in subjects aged 18 to 90 years since 2011; a total of 603 were adjudicated. Autopsy-defined sudden arrhythmic death (SAD) required absence of nonarrhythmic cause; MVP diagnosis required leaflet billowing. One hundred antemortem echocardiograms were revised to identify additional MVPs missed on autopsy.

RESULTS

Among the 603 presumed SCDs, 339 (56%) were autopsy-defined SADs, with MVP identified in 7 (1%). Six additional MVPs were identified by review of echocardiograms, for a prevalence of at least 2% among 603 presumed SCDs and 4% among 339 SADs (vs. 264 non-SADs; p = 0.02). All 6 additional MVPs had monoleaflet rather than bileaflet involvement and mild mitral regurgitation, ruling out hemodynamic cause. Less than one-half had MAD with replacement fibrosis, but all had multisite interstitial fibrosis.

CONCLUSIONS

In a countywide post-mortem study of all adult cases of SCD, MVP prevalence was at least 4% of SADs, but one-half were missed on autopsy. Monoleaflet MVP was often underdiagnosed post-mortem. Compared with young cases of SCD, lethal MVP in older cases of SCD did not consistently have bileaflet anatomy, replacement fibrosis, or MAD.

Echocardiographic screening for mitral valve prolapse in Turkish school children

We determined the frequency of mitral valve prolapse (MVP) in healthy Turkish school children using the current echocardiographic diagnostic criteria. This epidemiological survey was performed on 2550 school children. All children were screened with echocardiography and the family of children with MVP were also screened. The prolapse of mitral leaflets into left atrium ≥ 2 mm in parasternal long-axis view was used as diagnostic criteria. MVP was classified as classical or non-classical according to anterior mitral leaflet thickness. The thickness of anterior mitral leaflet, the extent of prolapse, and the presence of mitral regurgitation were evaluated. The children were also questioned about the associated symptoms. The prevalence of MVP was 1.25% in children with a mean age of 11.1 ± 2.9 years. The prevalence was 0.9%, 1.2%, and 1.6% in 5-9 years, 10-13 years, and 14-18 years of age, respectively. 43.7% of the cases were classical MVP. The frequency of auscultation findings was 34.3%. 11/34 children had mitral regurgitation. There was no statistically significant difference between classical MVP and non-classical MVP in terms of mitral regurgitation, physical examination findings, and symptoms. Anxiety (37.5%) was the most common symptom. The frequency of MVP in the first-degree relatives of children with MVP was 11/84 (13.1%). Most patients with MVP don't have auscultation findings and symptoms, therefore echocardiography is an important tool in the diagnosis of MVP. It is also reasonable to screen first degree relatives of MVP patients with echocardiography.

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.

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.

A single nucleotide deletion resulting in a frameshift in exon 4 of TAB2 is associated with a polyvalular syndrome

OBJECTIVE

Polyvalvularmyxomatous degeneration is a rare clinical condition. A 51-year-old male patient presented at our centre with all four heart valves with myxomatous degeneration and severe mitral and aortic regurgitation due to leaflet prolapse. The patient referred five further family members with valvular heart disease at different stages of presentation. The aim of this study was to investigate the genetic basis of this familial polyvalvularmyxomatous degeneration which was associated with mild dysmorphic facial anomalies and short stature.

DESIGN

A detailed family history was recorded. Nine members of the family, affected or not by valvular heart disease, were studied clinically, echocardiographically and by detailed genetic analyses.

RESULTS

Six of the nine family members had echocardiographic features of different degrees of degenerative heart valve disease. In addition, the affected subjects shared similar mild dysmorphic facial anomalies and short stature. Exome sequencing identified a rare heterozygous single nucleotide deletion in the TAB2 gene in all affected family members, which was absent in the unaffected members.

CONCLUSIONS

A variant in the TAB2 gene is proposed as the cause of syndromic congenital heart disease, displaying congenital myxomatous degenerative heart valve disease, mild dysmorphic fascial anomalies and short stature in this family.

Development and Evaluation of a Tissue-Engineered Fibrin-based Canine Mitral Valve Three-dimensional Cell Culture System

Myxomatous mitral valve disease is the most common cardiac disease of the dog, but examination of the associated cellular and molecular events has relied on the use of cadaveric valve tissue, in which functional studies cannot be undertaken. The aim of this study was to develop a three-dimensional (3D) cell co-culture model as an experimental platform to examine disease pathogenesis. Mitral valve interstitial (VIC) and endothelial (VEC) cells were cultured from normal and diseased canine (VIC only) valves. VICs were embedded in a fibrin-based hydrogel matrix and one surface was lined with VECs. The 3D static cultures (constructs) were examined qualitatively and semiquantitatively by light microscopy, immunofluorescence microscopy and protein immunoblotting. Some constructs were manipulated and the endothelium damaged, and the response examined. The construct gross morphology and histology demonstrated native tissue-like features and comparable expression patterns of cellular (α-smooth muscle actin [SMA] and embryonic smooth muscle myosin heavy chain [SMemb]) and extracellular matrix associated markers (matrix metalloproteinase [MMP]-1 and MMP-3), reminiscent of diseased valves. There were no differences between constructs containing normal valve VICs and VECs (type 1) and those containing diseased valve VICs and normal valve VECs (type 2). Mechanical manipulation and endothelial damage (type 3) tended to decrease α-SMA and SMemb expression, suggesting reversal of VIC activation, but with retention of SMemb⁺ cells adjacent to the wounded endothelium consistent with response to injury. Fibrin-based 3D mitral valve constructs can be produced using primary cell cultures derived from canine mitral valves, and show a phenotype reminiscent of diseased valves. The constructs demonstrate a response to endothelial damage indicating their utility as experimental platforms.

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.

Myxomatous Degeneration of the Canine Mitral Valve: From Gross Changes to Molecular Events

Myxomatous mitral valve disease (MMVD) is the single most common acquired heart disease of the dog, but is also of emerging importance in human medicine, with some features of the disease shared between both species. There has been increased understanding of this disease in recent years, with most research aiming to elucidate the cellular and molecular events of disease pathogenesis. For gross and histological changes, much of our understanding is based on historical studies and there has been no comprehensive reappraisal of the pathology of MMVD. This paper reviews the gross, histological, ultrastructural, cellular and molecular changes in canine MMVD.

Stabilized Collagen and Elastin-Based Scaffolds for Mitral Valve Tissue Engineering

There is a significant clinical need for new approaches to treatment of mitral valve disease. The aim of this study was to develop a tissue-engineered mitral valve scaffold possessing appropriate composition and structure to ensure ideal characteristics of mitral valves, such as large orifice, rapid opening and closure, maintenance of mitral annulus-papillary muscle continuity, in vivo biocompatibility and extended durability. An extracellular matrix-based scaffold was generated, based on the native porcine mitral valve as starting material and a technique for porcine cell removal without causing damage to the matrix components. To stabilize these structures and slow down their degradation, acellular scaffolds were treated with penta-galloyl glucose (PGG), a well-characterized polyphenol with high affinity for collagen and elastin. Biaxial mechanical testing presented similar characteristics for the PGG-treated scaffolds compared to fresh tissues. The extracellular matrix components, crucial for maintaining the valve shape and function, were well preserved in leaflets, and in chordae, as shown by their resistance to collagenase and elastin. When extracted with strong detergents, the PGG-treated scaffolds released a reduced amount of soluble matrix peptides, compared to untreated scaffolds; this correlated with diminished activation of fibroblasts seeded on scaffolds treated with PGG. Cell-seeded scaffolds conditioned for 5 weeks in a valve bioreactor showed good cell viability. Finally, rat subdermal implantation studies showed that PGG-treated mitral valve scaffolds were biocompatible, nonimmunogenic, noninflammatory, and noncalcifying. In conclusion, a biocompatible mitral valve scaffold was developed, which preserved the biochemical composition and structural integrity of the valve, essential for its highly dynamic mechanical demands, and its biologic durability.

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.

Mitral valve prolapse is associated with altered extracellular matrix gene expression patterns

Mitral valve prolapse (MVP) is the leading indication for isolated mitral valve surgery in the United States. Disorganization of collagens and glycosaminoglycans in the valvular extracellular matrix (ECM) are histological hallmarks of MVP. We performed a transcriptome analysis to study the alterations in ECM-related gene expression in humans with sporadic MVP. Mitral valve specimens were obtained from individuals undergoing valve repair for MVP (n=7 patients) and from non-beating heart-tissue donors (n=3 controls). Purified RNA was subjected to whole-transcriptome microarray analysis. Microarray results were validated by quantitative reverse transcription polymerase chain reaction (RT-qPCR). Gene ontology enrichment analysis was performed. 2046 unique genes showed significant differential expression (false discovery rate <0.5%). After demonstrating appropriate sample clustering, microarray results were globally validated using a subset of 22 differentially expressed genes by RT-qPCR (Pearson's correlation r=0.65, p=0.001). Gene ontology enrichment analyses performed with ErmineJ and DAVID Bioinformatics Database demonstrated overrepresentation of ECM components (p<0.05). Functional annotation clustering calculated enrichment of ECM-related ontology groups (enrichment score=4.1). ECM-related gene expression is significantly altered in MVP. Our study is consistent with the histologically observed alterations in collagen and mucopolysaccharide profiles of myxomatous mitral valves. Furthermore, whole-transcriptome analyses suggest dysregulation of multiple pathways, including TGF-beta signaling.

Evolution of Mitral Valve Prolapse: Insights From the Framingham Heart Study

BACKGROUND

Longitudinal studies of mitral valve prolapse (MVP) progression among unselected individuals in the community, including those with nondiagnostic MVP morphologies (NDMs), are lacking.

METHODS AND RESULTS

We measured longitudinal changes in annular diameter, leaflet displacement, thickness, anterior/posterior leaflet projections onto the annulus, coaptation height, and mitral regurgitation jet height in 261 Framingham Offspring participants at examination 5 who had available follow-up imaging 3 to 16 years later. Study participants included MVP (n=63); NDMs, minimal systolic displacement (n=50) and the abnormal anterior coaptation phenotype (n=10, with coaptation height >40% of the annulus similar to posterior MVP); plus 138 healthy referents without MVP or NDMs. At follow-up, individuals with MVP (52% women, 57±11 years) had greater increases of leaflet displacement, thickness, and jet height than referents (all P<0.05). Eleven participants with MVP (17%) had moderate or more severe mitral regurgitation (jet height ≥5 mm) and 5 others (8%) underwent mitral valve repair. Of the individuals with NDM, 8 (80%) participants with abnormal anterior coaptation progressed to posterior MVP; 17 (34%) subjects with minimal systolic displacement were reclassified as either posterior MVP (12) or abnormal anterior coaptation (5). In comparison with the 33 participants with minimal systolic displacement who did not progress, the 17 who progressed had greater leaflet displacement, thickness, coaptation height, and mitral regurgitation jet height (all P<0.05).

CONCLUSIONS

NDM may evolve into MVP, highlighting the clinical significance of mild MVP expression. MVP progresses to significant mitral regurgitation over a period of 3 to 16 years in one-fourth of individuals in the community. Changes in mitral leaflet morphology are associated with both NDM and MVP progression.

New biomarkers for primary mitral regurgitation

Background

Mitral regurgitation is a frequent valvular heart disease affecting around 2.5 % of the population with prevalence directly related to aging. Degeneration of mitral valve is broadly considered as a passive ongoing pathophysiological process and little is known about its physiological deregulation. The purpose of this study was to highlight new biomarkers of mitral regurgitation in order to decipher the underlying pathological mechanism as well as to allow the diagnosis and the monitoring of the disease.

Results

Modulation of various blood proteins expression was examined in patients suffering from different grades of mitral regurgitation (mild, moderate and severe) compared to healthy controls. To this end, several routine clinical assays and the multi analyte profile technology targeting 184 proteins were used. High-density lipoprotein, apolipoprotein-A1, haptoglobin and haptoglobin-α2 chain levels significantly decreased proportionally to the degree of mitral regurgitation when compared to controls. High-density lipoprotein and apolipoprotein-A1 levels were associated with effective regurgitant orifice area and regurgitant volume. Apolipoprotein-A1 was an independent predictor of severe mitral regurgitation. Moreover, with ordinal logistic regression, apolipoprotein-A1 remained the only independent factor associated with mitral regurgitation. In addition, myxomatous mitral valves were studied by immunocytochemistry. We observed an increase of LC3, the marker of autophagy, in myxomatous mitral valves compared with healthy mitral valves.

Conclusion

These potential biomarkers of mitral regurgitation highlighted different cellular processes that could be modified in myxomatous degenerescence: reverse cholesterol transport, antioxidant properties and autophagy.

Electronic supplementary material

The online version of this article (doi:10.1186/s12014-015-9097-2) contains supplementary material, which is available to authorized users.

Investigation of the Matrix Metalloproteinase-2 Gene in Patients with Non-Syndromic Mitral Valve Prolapse

Non-syndromic mitral valve prolapse (MVP) is a common degenerative valvulopathy, predisposing to arrhythmia and sudden death. The etiology of MVP is suspected to be under genetic control, as supported by familial cases and its manifestation in genetic syndrome (e.g., Marfan syndrome). One candidate etiological mechanism is a perturbation of the extracellular matrix (ECM) remodeling of the valve. To test this hypothesis, we assessed the role of genetic variants in the matrix metalloproteinase 2 gene (MMP2) known to regulate the ECM turnover by direct degradation of proteins and for which transgenic mice develop MVP. Direct sequencing of exons of MMP2 in 47 unrelated patients and segregation analyses in families did not reveal any causative mutation. We studied eight common single nucleotide polymorphisms (TagSNPs), which summarize the genetic information at the MMP2 locus. The association study in two case controls sets (N_Cases = 1073 and N_Controls = 1635) provided suggestive evidence for the association of rs1556888 located downstream MMP2 with the risk of MVP, especially in patients with the fibroelastic defiency form. Our study does not support the contribution of MMP2 rare variation in the etiology to MVP in humans, though further genetic and molecular investigation is required to confirm our current suggestive association of one common variant.

Familial clustering of mitral valve prolapse in the community

BACKGROUND

Knowledge of mitral valve prolapse (MVP) inheritance is based on pedigree observation and M-mode echocardiography. The extent of familial clustering of MVP among unselected individuals in the community using current, more specific echocardiographic criteria is unknown. In addition, the importance of nondiagnostic MVP morphologies (NDMs; first described in large pedigrees) has not been investigated in the general population. We hypothesized that parental MVP and NDMs increase the risk of offspring MVP.

METHODS AND RESULTS

Study participants were 3679 Generation 3 individuals with available parental data in the Offspring or the New Offspring Spouse cohorts. MVP and NDMs were distinguished by leaflet displacement >2 versus ≤2 mm beyond the mitral annulus, respectively. We compared MVP prevalence in Generation 3 participants with at least 1 parent with MVP (n=186) with that in individuals without parental MVP (n=3493). Among 3679 participants (53% women; mean age, 40±9 years), 49 (1%) had MVP. Parental MVP was associated with a higher prevalence of MVP in Generation 3 participants (10 of 186, 5.4%) compared with no parental MVP (39 of 3493, 1.1%; adjusted odds ratio, 4.51; 95% confidence interval, 2.13-9.54; P<0.0001). When parental NDMs were examined alone, the prevalence of Generation 3 MVP remained higher (12 of 484, 2.5%) compared with those without parental MVP or NDMs (27 of 3009, 0.9%; adjusted odds ratio, 2.52; 95% confidence interval, 1.25-5.10; P=0.01).

CONCLUSIONS

Parental MVP and NDMs are associated with increased prevalence of offspring MVP, highlighting the genetic substrate of MVP and the potential clinical significance of NDMs in the community.

Alk3 mediated Bmp signaling controls the contribution of epicardially derived cells to the tissues of the atrioventricular junction

Recent studies using mouse models for cell fate tracing of epicardial derived cells (EPDCs) have demonstrated that at the atrioventricular (AV) junction EPDCs contribute to the mesenchyme of the AV sulcus, the annulus fibrosus, and the parietal leaflets of the AV valves. There is little insight, however, into the mechanisms that govern the contribution of EPDCs to these tissues. While it has been demonstrated that bone morphogenetic protein (Bmp) signaling is required for AV cushion formation, its role in regulating EPDC contribution to the AV junction remains unexplored. To determine the role of Bmp signaling in the contribution of EPDCs to the AV junction, the Bmp receptor activin-like kinase 3 (Alk3; or Bmpr1a) was conditionally deleted in the epicardium and EPDCs using the mWt1/IRES/GFP-Cre (Wt1(Cre)) mouse. Embryonic Wt1(Cre);Alk3(fl/fl) specimens showed a significantly smaller AV sulcus and a severely underdeveloped annulus fibrosus. Electrophysiological analysis of adult Wt1(Cre);Alk3(fl/fl) mice showed, unexpectedly, no ventricular pre-excitation. Cell fate tracing revealed a significant decrease in the number of EPDCs within the parietal leaflets of the AV valves. Postnatal Wt1(Cre);Alk3(fl/fl) specimens showed myxomatous changes in the leaflets of the mitral valve. Together these observations indicate that Alk3 mediated Bmp signaling is important in the cascade of events that regulate the contribution of EPDCs to the AV sulcus, annulus fibrosus, and the parietal leaflets of the AV valves. Furthermore, this study shows that EPDCs do not only play a critical role in early developmental events at the AV junction, but that they also are important in the normal maturation of the AV valves.

Clinical and pathological features of degenerative mitral valve disease: billowing mitral leaflet versus fibroelastic deficiency

PURPOSE

Degenerative mitral valve disease is distinguished with billowing mitral leaflet (BML) or fibroelastic deficiency (FED). The purpose of this study is to evaluate the clinical characteristics and the pathohistological differences between BML and FED.

METHODS

A total of 73 patients who diagnosed as degenerative mitral valve disease pathologically after mitral valve surgery for severe mitral regurgitation were enrolled. On the basis of echocardiographic features and gross appearances, they were classified as BML (9 cases) and FED (64 cases).

RESULTS

In the BML group, multiple segments of the leaflet showed billowing with elongated chordae. Therefore excessive valve tissue needed to be removed by multiple resection and suture. The FED patients had focal myxomatous changes with ruptured chordae, a single resection and suture was frequently employed. In pathological examination, the valve thickness of the BML was nearly twice as thick as the FED, and the mucopolysaccharide accumulation of the Spongiosa in the BML was over 50%, while 30% in the FED.

CONCLUSION

BML presents the characteristic valve thickening due to its abnormal production of mucopolysaccharide. Since excessive tissue was voluminous in the BML, high-grade plasty techniques, such as combination of multiple resection and chordal reconstruction were required.

Mild expression of mitral valve prolapse in the Framingham offspring: expanding the phenotypic spectrum

BACKGROUND

Mitral valve (MV) prolapse (MVP) is a common disorder associated with mitral regurgitation, endocarditis, heart failure, and sudden death. Nondiagnostic morphologies have been described in the familial context and may represent early expression of MVP in those genetically predisposed. The aim of this study was to explore the spectrum of MVP abnormalities in the community and compare their clinical and echocardiographic features.

METHODS

We measured annular diameter MV leaflet displacement, thickness, anterior and posterior leaflet projections onto the annulus, MV leaflet coaptation height (posterior MV leaflet projection/annular diameter), and MR jet height in 296 individuals of the Framingham Offspring Study with MVP (n = 77), the "abnormal anterior coaptation" (AAC) phenotype (n = 11) or "minimal systolic displacement" (MSD) (n = 57), and 151 age-matched and sex-matched referents with no MVP or its nondiagnostic forms.

RESULTS

AAC did not meet diagnostic displacement criteria but resembled MVP with regard to annular diameter and leaflet thickness (P > .05 for both). AAC was similar to posterior MVP with regard to posterior leaflet asymmetry and an anteriorly shifted coaptation (P = .91). Compared to patients with MSD and referents, patients with AAC had greater leaflet coaptation height, thickness, and annular diameter (P < .05 for all). MSD shared the posterior leaflet asymmetry with MVP, but the coaptation point was more posterior (coaptation height = 31% vs. 42%, P < .0001), as seen in referents. A higher proportion of patients with MVP had jet height ≥ 2 mm (mild or greater MR) compared with the other participants (44% vs. 16%, P < .0001).

CONCLUSIONS

Nondiagnostic morphologies are observed in the community and share the common feature of posterior leaflet asymmetry with MVP. AAC and MSD may thus represent early expressions of MVP. Longitudinal studies are warranted to elucidate the natural history of these phenotypes.

Why aortic elasticity differs among classical and non-classical mitral valve prolapsed?

BACKGROUND

Mitral valve prolapse (MVP) is the most common valvular heart disease and characterized by the displacement of an abnormally thickened mitral valve leaflet into the left atrium during systole. There are two types of MVP, broadly classified as classic (thickness ≥5 mm) and non-classic (thickness <5 mm) according to the morphology of the leaflets. We aimed to investigate elastic properties of the aorta in young male patients with classical and non-classical MVP.

MATERIAL/METHODS

In the present study, 63 young adult males (mean age: 22.7 ± 4.2) were included. Patients were divided into classic MVP (n = 27) and non-classic MVP (n = 36) groups. Aortic strain, aortic distensibility and aortic stiffness index were calculated by using aortic diameters obtained by echocardiography and blood pressures measured by sphygmomanometer.

RESULTS

There was no significant difference between the groups in terms of age, body mass index, left ventricular mass and ejection fraction. When comparing the MVP group it was found that aortic strain and aortic distensibility were increased (p = 0.0027, p = 0.016, respectively) whereas the aortic stiffness index was decreased (p = 0.06) in the classical MVP group.

CONCLUSION

We concluded that the elastic properties of the aorta is increased in patients with classic MVP. Further large scale studies should be performed to understand of morphological and physiological properties of the aorta in patients with MVP.

Multi-scale biomechanical remodeling in aging and genetic mutant murine mitral valve leaflets: insights into Marfan syndrome

Mitral valve degeneration is a key component of the pathophysiology of Marfan syndrome. The biomechanical consequences of aging and genetic mutation in mitral valves are poorly understood because of limited tools to study this in mouse models. Our aim was to determine the global biomechanical and local cell-matrix deformation relationships in the aging and Marfan related Fbn1 mutated murine mitral valve. To conduct this investigation, a novel stretching apparatus and gripping method was implemented to directly quantify both global tissue biomechanics and local cellular deformation and matrix fiber realignment in murine mitral valves. Excised mitral valve leaflets from wild-type and Fbn1 mutant mice from 2 weeks to 10 months in age were tested in circumferential orientation under continuous laser optical imaging. Mouse mitral valves stiffen with age, correlating with increases in collagen fraction and matrix fiber alignment. Fbn1 mutation resulted in significantly more compliant valves (modulus 1.34 ± 0.12 vs. 2.51 ± 0.31 MPa, respectively, P<.01) at 4 months, corresponding with an increase in proportion of GAGs and decrease in elastin fraction. Local cellular deformation and fiber alignment change linearly with global tissue stretch, and these slopes become more extreme with aging. In comparison, Fbn1 mutated valves have decoupled cellular deformation and fiber alignment with tissue stretch. Taken together, quantitative understanding of multi-scale murine planar tissue biomechanics is essential for establishing consequences of aging and genetic mutations. Decoupling of local cell-matrix deformation kinematics with global tissue stretch may be an important mechanism of normal and pathological biomechanical remodeling in valves.

Structural analysis of chordae tendineae in degenerative disease of the mitral valve

BACKGROUND

Degenerative disease of the mitral valve (DDMV) is always accompanied by lengthening and/or rupture of chordae tendineae. However, the mechanisms and the mode of chordal rupture remain controversial, and the pathologic anatomy of the apparently healthy chordae has mostly been overlooked. We analyze the structural aspects of both ruptured and intact chordae tendineae in DDMV.

METHODS AND RESULTS

Structural and ultrastructural microscopic analyses indicate that both the extracellular matrix and the interstitial cells are severely affected. Degenerative chordae show alterations in the synthesis and deposition of collagen and elastin, disorganization of collagen bundles and rupture of collagen fibres, accumulation of proteoglycans and of cellular and vesicular remnants, and cell transformation into a myofibroblast phenotype. Structural disruption makes the spongiosa and the dense collagenous core separate and break. Degeneration of the chordae is segmental, affecting both chordae that are clearly abnormal, and chordae that appear healthy on visual inspection.

CONCLUSIONS

Changes in both matrix synthesis and degradation disturb the ordered collagen arrangement and modify the structural and physical properties of the chordae. Progressive structural disruption of the diseased chordae is the cause of chordal rupture. Mitral surgery corrects the damage, but the underlying causes of DDMV are not corrected. Thus, progression of the disease and affectation of additional chordae may be at the basis of the late complications and the recurrent mitral regurgitation which occurs several years after surgery. Our results indicate that a more aggressive approach to surgery may be needed.

The mechanobiology of mitral valve function, degeneration, and repair

In degenerative valve disease, the highly organized mitral valve leaflet matrix stratification is progressively destroyed and replaced with proteoglycan rich, mechanically inadequate tissue. This is driven by the actions of originally quiescent valve interstitial cells that become active contractile and migratory myofibroblasts. While treatment for myxomatous mitral valve disease in humans ranges from repair to total replacement, therapies in dogs focus on treating the consequences of the resulting mitral regurgitation. The fundamental gap in our understanding is how the resident valve cells respond to altered mechanical signals to drive tissue remodeling. Despite the pathological similarities and high clinical occurrence, surprisingly little mechanistic insight has been gleaned from the dog. This review presents what is known about mitral valve mechanobiology from clinical, in vivo, and in vitro data. There are a number of experimental strategies already available to pursue this significant opportunity, but success requires the collaboration between veterinary clinicians, scientists, and engineers.

Pathology, protein expression and signaling in myxomatous mitral valve degeneration: comparison of dogs and humans

Myxomatous degenerative mitral valve disease (MMVD) is a common heart disease in dogs. Although several morphological similarities occur between human and canine MMVD differences exist. However, in advanced stages the accumulation of proteoglycans is the main finding in both species. The extracellular matrix (ECM) in normal canine and human mitral valves is similar. In MMVD of both species proteoglycans is the major alteration, although specific changes in collagen distribution exists. The valvular expression pattern of matrix metalloproteinases (MMPs) and of their inhibitors (TIMPs) differs, in part, between dogs and humans. The MMPs and TIMPs expression patterns are similar in normal canine and human mitral valves, but they are quite different during degenerative progression. Valve endothelial cells (VEC) and interstitial cells (VIC) are phenotypically transformed in canine and human MMVD. Inflammation is an unlikely cause of valve degeneration in humans and dogs. There are several lines of evidence suggesting that transforming growth factor β1 (TGF β1) and serotonin signaling may mediate valve degeneration in humans and dogs. Although human and canine MMVD share structural similarities, there are some differences in ECM changes, enzyme expression and cell transformation, which may reflect a varied pathogenesis of these diseases.

Differentiating the aging of the mitral valve from human and canine myxomatous degeneration

During the course of both canine and human aging, the mitral valve remodels in generally predictable ways. The connection between these aging changes and the morbidity and mortality that accompany pathologic conditions has not been made clear. By exploring work that has investigated the specific valvular changes in both age and disease, with respect to the cells and the extracellular matrix found within the mitral valve, heretofore unexplored connections between age and myxomatous valve disease can be found. This review addresses several studies that have been conducted to explore such age and disease related changes in extracellular matrix, valvular endothelial and interstitial cells, and valve innervation, and also reviews attempts to correlate aging and myxomatous disease. Such connections can highlight avenues for future research and help provide insight as to when an individual diverts from an aging pattern into a diseased pathway. Recognizing these patterns and opportunities could result in earlier intervention and the hope of reduced morbidity and mortality for patients.

Transforming growth factor beta signaling in adult cardiovascular diseases and repair

The majority of children with congenital heart disease now live into adulthood due to the remarkable surgical and medical advances that have taken place over the past half century. Because of this, adults now represent the largest age group with adult cardiovascular diseases. It includes patients with heart diseases that were not detected or not treated during childhood, those whose defects were surgically corrected but now need revision due to maladaptive responses to the procedure, those with exercise problems and those with age-related degenerative diseases. Because adult cardiovascular diseases in this population are relatively new, they are not well understood. It is therefore necessary to understand the molecular and physiological pathways involved if we are to improve treatments. Since there is a developmental basis to adult cardiovascular disease, transforming growth factor beta (TGFβ) signaling pathways that are essential for proper cardiovascular development may also play critical roles in the homeostatic, repair and stress response processes involved in adult cardiovascular diseases. Consequently, we have chosen to summarize the current information on a subset of TGFβ ligand and receptor genes and related effector genes that, when dysregulated, are known to lead to cardiovascular diseases and adult cardiovascular deficiencies and/or pathologies. A better understanding of the TGFβ signaling network in cardiovascular disease and repair will impact genetic and physiologic investigations of cardiovascular diseases in elderly patients and lead to an improvement in clinical interventions.

Cellular mechanisms in mitral valve disease

The mitral valve is a living structure comprised of specific structural components which contain a heterogeneous population of cells. The cells include an amalgam of interstitial cells within the valve and a continuous covering of endothelial cells, each of which play a role in responding to the mechanical forces that the valve experiences, to maintain the function and durability of the valve. Attention on the characteristics and function of valve cells has focused mainly on those in the aortic valve, with relatively few studies addressing the role of these cells in the physiological and pathophysiological function of the mitral valve. This article reviews what is known about the function of cells within the mitral valve and how the changes in the physical and chemical environments can affect their function in the different types of mitral valve disease. Investigating the contribution of the cellular components of the mitral valve to valve function in health and disease will aid the understanding of how the durability and function of the valve are regulated, and possibly highlight molecular and pharmacological targets for the development of novel treatments for mitral valve disease.

Does the association between mitral valve prolapse and panic disorder really exist?

OBJECTIVE

Although the possible relationship between panic disorder and mitral valve prolapse (MVP) attracted considerable research interest in the 1980s and 1990s, the reported prevalence of MVP in these patients has been inconsistent and widely variable. Clinical and epidemiologic studies have produced controversial data on possible association or definite causal relationship between these 2 entities. The primary objective of the present review was to summarize the current state of knowledge on the association between panic disorder and MVP, including the influence of diagnostic criteria for MVP on the controversial results.

DATA SOURCES

We searched MEDLINE, LILACS, and EMBASE databases using the keywords panic and mitral. Inclusion criteria were articles concerning the reciprocal association of MVP and panic disorder, published from the earliest dates available through December 2006.

STUDY SELECTION

All relevant articles published in English, Spanish, or Portuguese and reporting original data related to the association of MVP and panic disorder were included. Forty articles fulfilling the criteria for inclusion in this review were identified.

DATA SYNTHESIS

Even though the reported prevalence of MVP in panic disorder varied from 0% to 57%, a significant association between the 2 disorders was documented in 17 of the 40 studies. Such inconsistent results were due to sampling biases in case or control groups, widely different diagnostic criteria for MVP, and lack of reliability of MVP diagnosis. None of the reviewed studies used the current state-of-the-art diagnostic criteria for MVP to evaluate the volunteers. Apparently, the more elaborate the study methodology, the lower the chance to observe a significant relationship between these 2 conditions.

CONCLUSIONS

Published results are insufficient to definitely establish or to exclude an association between MVP and panic disorder. If any relationship does actually exist, it could be said to be infrequent and mainly occur in subjects with minor variants of MVP. To clarify this intriguing issue, future studies should mainly focus on the observed methodological biases and particularly should use the current criteria for MVP as the standard for evaluation.

CMR predictors of mitral regurgitation in mitral valve prolapse

OBJECTIVES

We sought to assess the correlation between mitral valve characteristics and severity of mitral regurgitation (MR) in subjects with mitral valve prolapse (MVP) undergoing cardiac magnetic resonance (CMR) imaging.

BACKGROUND

Compared with extensive echocardiographic studies, CMR predictors of MVP-related MR are unknown. The severity of MR at the time of diagnosis has prognostic implication for patients; therefore, the identification of determinants of MR and its progression may be important for risk stratification, follow-up recommendations, and surgical decision making.

METHODS

Seventy-one MVP patients (age 54 ± 11 years, 58% males, left ventricular [LV] ejection fraction 65 ± 5%) underwent cine CMR to assess annular dimensions, maximum systolic anterior and posterior leaflet displacement, papillary muscle (PM) distance to coaptation point and prolapsed leaflets, as well as diastolic anterior and posterior leaflet thickness and length, and LV volumes and mass. Velocity-encoded CMR was used to obtain aortic outflow and to quantify MR volume.

RESULTS

Using multiple linear regression analysis including all variables, LV mass (p < 0.001), anterior leaflet length (p = 0.006), and posterior displacement (p = 0.01) were the best determinants of MR volume with a model-adjusted R(2) = 0.6. When the analysis was restricted to valvular characteristics, MR volume correlated with anterior mitral leaflet length (p < 0.001), posterior mitral leaflet displacement (p = 0.003), posterior leaflet thickness (p = 0.008), and the presence of flail (p = 0.005) with a model-adjusted R(2) = 0.5. We also demonstrated acceptable intraobserver and interobserver variability in these measurements.

CONCLUSIONS

Anterior leaflet length, posterior leaflet displacement, posterior leaflet thickness, and the presence of flail are the best CMR valvular determinants of MVP-related MR. The acceptable intraobserver and interobserver variability of our measurements confirms the role of CMR as an imaging modality for assessment of MVP patients with significant MR.

Fibrillin-1 gene intron 56 polymorphism in Turkish children with mitral valve prolapse

OBJECTIVE

Mitral valvar prolapse is the most common anomaly of the mitral valve apparatus throughout childhood. Fibrillin is one of the structural components of the elastin-associated microfibrils found in the mitral valve. A case-controlled study has performed to investigate the relationship between fibrillin 1 gene intron 56 polymorphism and risk of mitral valvar prolapse in Turkish children.

PATIENTS AND METHODS

A total of 77 patients with mitral valvar prolapse diagnosed by clinical evaluation and echocardiography and 89 normal children of same age and sex were studied. The fibrillin-1 gene intron 56 polymorphism was identified by the polymerase chain reaction-based restriction analysis.

RESULTS

There was a significant difference in the distribution of fibrillin-1 gene intron 56 genotypes (p = 0.0001) and allelic frequency (p = 0.0001) between the cases and the controls.

CONCLUSIONS

Patients with mitral valvar prolapse have higher frequencies of fibrillin-1 gene intron 56 GC genotypes. Healthy children have higher frequencies of fibrillin-1 gene intron 56 CC genotypes. We speculate that the higher frequency of fibrillin-1 gene intron 56 G-allele increases the risk of mitral valvar prolapse.

Immunohistochemical characterization of the extracellular matrix in normal mitral valves and in chronic valve disease (endocardiosis) in dogs

This study aimed to characterize the composition and distribution of the extracellular matrix (ECM) components in normal canine mitral valves (MV) and in chronic heart valve disease (CVD). MV of 50 dogs (normal (n=9), mild (n=13), moderate (n=17), severe (n=11) CVD) were investigated macroscopically, histologically (H.-E., picrosirius red) and immunohistochemically (collagen I, III, IV, V, VI, elastin, laminin, fibronectin, heparan sulphate). In normal MV, ECM components were expressed in a typical layered pattern. In mild CVD, basement membrane components (laminin, collagen IV, fibronectin) were increased. Advanced CVD was characterized by myxomatous nodular lesions displaying a marginal and a central region comprised mainly of collagen I, VI and fibronectin in the former and collagen I and III in the latter. Collagen IV and laminin appeared multifocally in marked CVD. In conclusion, not only an accumulation of proteoglycans, but also a distinctly altered expression of basement membrane components, and collagens characterizes CVD.