Sudden death in mitral valve prolapse with Holter monitoring-documented ventricular fibrillation: evidence of coexisting arrhythmogenic right ventricular cardiomyopathy

Arrhythmic Mitral Valve Prolapse: New Menaces of the Known Disease

Mitral  valve prolapse  (MVP) has  long  been  the subject  of intense  discussions regarding the prognosis and  follow-up tactics.  In most  cases,  this condition has a benign prognosis. However, recent autopsy and follow-up studies have shown risks of developing  sudden cardiac death (SCD) in some subgroups of patients who have this clinical phenomenon. The proposed  literature review uses the population  of patients with MVP with the highest probability  of developing  life-threatening ventricular tachyarrhythmias. Patients with the presence of a complex  of changes, including  bicuspid  MVP, negative T waves in the inferior and lateral leads on a standard  12-lead electrocardiogram (ECG), and a special anatomical  phenomenon called mitral annular  disjunction  (MAD), are at high  risk of developing  ventricular  ectopias  and VSS.  A reflection  of the high  risk of SCD  in such patients  is the increase of ventricular ectopy according to Holter monitoring. The presence of a bicuspid  MVP and the MAD  phenomenon, which is a separation  of the line of attachment  of the posterior mitral leaflet from the basal inferior wall segment  towards  the atrial wall, determines the presence of a special form of MVP,  the so-called  arrhythmogenic MVP.  Hence,  in most cases MVP has a benign  prognosis. However, patients with the aforementioned ar- rhythmic  MVP  signs  must  be given  particular  attention  and  annual  follow-up including  ECG  control,  Holter  monitoring and  echocardiographic examination of the heart to reduce the risk of ventricular tachyarrhythmias and SCD development.

Mitral Annular Disjunction: Associated Pathologies and Clinical Consequences

PURPOSE OF REVIEW

To provide an overview of mitral annular disjunction (MAD) and to discuss important challenges in diagnosis and management of MAD.

RECENT FINDINGS

MAD has regained interest in the context of sudden cardiac death (SCD) in patients with mitral valve prolapse (MVP), coined as the "arrhythmic" MVP syndrome. In addition, MAD in isolation was recently suggested to be associated with severe arrhythmia and SCD. There is a lack of consensus on the definition of MAD and the imaging modality to be used for diagnosing MAD, and the therapeutic implications of MAD remain uncertain. Furthermore, the exact mechanism underlying the association of MAD with SCD remains largely unexplored.

Mitral Valve Prolapse and Sudden Cardiac Death: A Systematic Review

Background

The relationship between mitral valve prolapse (MVP) and sudden cardiac death (SCD) remains controversial. In this systematic review, we evaluate the relationship between isolated MVP and SCD to better define a potential high‐risk subtype. In addition, we determine whether premortem parameters could predict SCD in patients with MVP and the incidence of SCD in MVP.

Methods and Results

Electronic searches were conducted in PubMed and Embase for all English literature articles published between 1960 and 2018 regarding MVP and SCD or cardiac arrest. We also identified articles investigating predictors of ventricular arrhythmias or SCD and cohort studies reporting SCD outcomes in MVP. From 2180 citations, there were 79 articles describing 161 cases of MVP with SCD or cardiac arrest. The median age was 30 years and 69% of cases were female. Cardiac arrest occurred during situations of stress in 47% and was caused by ventricular fibrillation in 81%. Premature ventricular complexes on Holter monitoring (92%) were common. Most cases had bileaflet involvement (70%) with redundancy (99%) and nonsevere mitral regurgitation (83%). From 22 articles describing predictors for ventricular arrhythmias or SCD in MVP, leaflet redundancy was the only independent predictor of SCD. The incidence of SCD with MVP was estimated at 217 events per 100 000 person‐years.

Conclusions

Isolated MVP and SCD predominantly affects young females with redundant bileaflet prolapse, with cardiac arrest usually occurring as a result of ventricular arrhythmias. To better understand the complex relationship between MVP and SCD, standardized reporting of clinical, electrophysiological, and cardiac imaging parameters with longitudinal follow‐up is required.

Mitral Valve Prolapse, Ventricular Arrhythmias, and Sudden Death

Despite a 2% to 3% prevalence of echocardiographically defined mitral valve prolapse (MVP) in the general population, the actual burden, risk stratification, and treatment of the so-called arrhythmic MVP are unknown. The clinical profile is characterized by a patient, usually female, with mostly bileaflet myxomatous disease, mid-systolic click, repolarization abnormalities in the inferior leads, and complex ventricular arrhythmias with polymorphic/right bundle branch block morphology, without significant regurgitation. Among the various pathophysiologic mechanisms of electrical instability, left ventricular fibrosis in the papillary muscles and inferobasal wall, mitral annulus disjunction, and systolic curling have been recently described by pathological and cardiac magnetic resonance studies in sudden death victims and patients with arrhythmic MVP. In addition, premature ventricular beats arising from the Purkinje tissue as ventricular fibrillation triggers have been documented by electrophysiologic studies in MVP patients with aborted sudden death.

The genesis of malignant ventricular arrhythmias in MVP probably recognizes the combination of the substrate (regional myocardial hypertrophy and fibrosis, Purkinje fibers) and the trigger (mechanical stretch) eliciting premature ventricular beats because of a primary morphofunctional abnormality of the mitral valve annulus.

The main clinical challenge is how to identify patients with arrhythmic MVP (which imaging technique and in which patient) and how to treat them to prevent sudden death. Thus, there is a necessity for prospective multicenter studies focusing on the prognostic role of cardiac magnetic resonance and electrophysiologic studies and on the therapeutic efficacy of targeted catheter ablation and mitral valve surgery in reducing the risk of life-threatening arrhythmias, as well as the role of implantable cardioverter defibrillators for primary prevention.

Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC/D): A Systematic Literature Review

Arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) is a genetic form of cardiomyopathy (CM) usually transmitted with an autosomal dominant pattern. It primary affects the right ventricle (RV), but may involve the left ventricle (LV) and culminate in biventricular heart failure (HF), life threatening ventricular arrhythmias and sudden cardiac death (SCD). It accounts for 11%-22% of cases of SCD in the young athlete population. Pathologically is characterized by myocardial atrophy, fibrofatty replacement and chamber dilation. Diagnosis is often difficult due to the nonspecific nature of the disease and the broad spectrum of phenotypic variations. Therefore consensus diagnostic criteria have been developed and combined electrocardiography, echocardiography, cardiac magnetic resonance imaging (CMRI) and myocardial biopsy. Early detection, family screening and risk stratification are the cornerstones in the diagnostic evaluation. Implantable cardioverter-defibrillator (ICD) implantation, ablative procedures and heart transplantation are currently the main therapeutic options.

Genetics of right ventricular cardiomyopathy

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited heart muscle disease that may result in arrhythmia, heart failure, and sudden death. The hallmark pathological findings are progressive myocyte loss and fibrofatty replacement, with a predilection for the right ventricle. However, variants of ARVC that preferentially affect the left ventricle are increasingly recognized. ARVC is distinguished from dilated cardiomyopathy by a propensity toward ventricular arrhythmia and sudden death in the absence of significant ventricular dysfunction. In the majority of families, ARVC shows autosomal dominant inheritance with incomplete penetrance. Recessive forms are also described, often in association with cutaneous disorders. Causative mutations have so far been identified in plakoglobin, desmoplakin, and plakophilin, all of which encode key components of the desmosome. Desmosomes are protein complexes that anchor intermediate filaments to the cytoplasmic membrane in adjoining cells, thereby forming a three-dimensional scaffolding that provides tissues with mechanical strength. Unraveling of the genetic etiology of ARVC has elicited a new model for pathogenesis. Impaired functioning of cell adhesion junctions during exposure to shear stress may lead to myocyte detachment and death, accompanied by inflammation and fibrofatty repair. At least three mechanisms contribute to the arrhythmic substrate: bouts of myocarditis, fibrous and adipose infiltrates that facilitate macroreentry, and gap junction remodeling secondary to altered mechanical coupling. The latter may underlie arrhythmogenicity in early disease. Although ARVC can be considered a disease of the desmosome, a variety of other genetic defects give rise to phenocopies, which may ultimately enhance our understanding of the broad phenotypic spectrum.

Arrhythmogenic right ventricular cardiomyopathy: clinicopathologic correlation based on a revised definition of pathologic patterns

Different morphologic features of arrhythmogenic right ventricular cardiomyopathy (ARVC) have been described. However, it is still unclear whether they correspond to distinct forms of the same disease. A pathologic study was performed on a series of ARVC (15 from heart transplant and 12 from autopsy) from 2 Italian referral university hospitals. Based on both myocellular features and the nature of myocardial replacement, hearts were divided into 2 groups: infiltrative, with a lacelike pattern of transmural fatty infiltration and strands of normal residual cardiomyocytes (n = 11); and cardiomyopathic, with massive myocardial replacement by fibro fatty tissue and cardiomyopathic changes (such as hypertrophy and myofibril loss) of residual cardiomyocytes (n = 16). Hearts from the infiltrative group were mostly obtained at autopsy of patients who died suddenly. Fatty substitution was limited almost exclusively to the right ventricle. Mitral valve dysplasia (prolapse or cleft) was frequently present. Hearts from the cardiomyopathic group came mainly from heart transplants for congestive heart failure. Fibro fatty replacement was more extensive, usually biventricular. Active myocarditis and features suggestive of myocardial transdifferentiation were also observed. Despite these differences in clinical outcome and morphologic features, patients from the 2 groups showed similar mean age, sex distribution, occurrence of threatening ventricular arrhythmias, and prevalence of family history of sudden death, arrhythmias, or cardiomyopathy. Infiltrative and cardiomyopathic patterns represent different clinical and pathologic subsets of ARVC. Myocellular features are an important clue in the distinction between the two entities. The differentiation between the 2 patterns is feasible on endomyocardial biopsy and could give important prognostic information.

Gene for arrhythmogenic right ventricular cardiomyopathy with diffuse nonepidermolytic palmoplantar keratoderma and woolly hair (Naxos disease) maps to 17q21

BACKGROUND

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a heart muscle disease of unknown etiology that causes arrhythmias, heart failure, and sudden death. Diagnosis can be difficult, and this hampers investigation of its molecular basis. Forms of ARVC in which gene penetrance and disease expression are greater should facilitate genetic study. We undertook a clinical and genetic investigation of Naxos disease, originally described by Protonotarios in 1986. This disease constitutes the triad of ARVC, diffuse nonepidermolytic palmoplantar keratoderma, and woolly hair.

METHODS AND RESULTS

We evaluated the population of Naxos, Greece, to identify probands, which was followed by family screening. Twenty-one affected persons from 9 families of 150 persons were identified. Linkage analysis was performed with microsatellite markers. The disease locus mapped to 17q21. A peak 2-point LOD score of 3.62 at theta=0.0 was found with a marker within intron 4 of the keratin 9 gene, a member of the type I (acidic) keratin family. A preserved homozygous disease haplotype was identified. Haplotype analysis delimited the disease interval.

CONCLUSIONS

Hair and skin abnormalities were found to be reliable markers of subsequent heart disease. This suggests the presence of a single mutant gene with novel cardiac, skin, and hair function or two or more tightly linked disease genes. Recessive inheritance of Naxos disease and a founder effect were demonstrated. Identification of a fully informative genetic marker linked to the disease and uncommon in the background population may be of use as a test to identify disease gene carriers.