Novel hypertrophic cardiomyopathy phenotype: segmental hypertrophy isolated to the posterobasal left ventricular free wall

Mitral Annular Disjunction in the Context of Mitral Valve Prolapse: Identifying the At-Risk Patient

Mitral annular disjunction (MAD), a separation between the left atrium/mitral valve annulus and the left ventricular myocardium, is frequently seen in patients with arrhythmic mitral valve prolapse. Although an association exists between MAD and ventricular arrhythmias, little is known regarding the identification of individuals at high risk. Multimodality imaging including echocardiography, computed tomography, cardiac magnetic resonance, and positron emission tomography can play an important role in both the diagnosis and risk stratification of MAD. Due to a paucity of data, clinical decision making in a patient with MAD is challenging and remains largely empirical. Although MAD itself can be corrected surgically, the prevention and treatment of associated arrhythmias may require medical therapy, catheter ablation, and an implantable cardioverter-defibrillator. Prospective data are required to define the role of implantable cardioverter-defibrillators, targeted catheter ablation, and surgical correction in selected, at-risk patients.

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.

Transthoracic echocardiography for arrhythmic mitral valve prolapse: Phenotypic characterization as first step

Mitral valve prolapse (MVP) is the most frequent valvulopathy with a prevalence of 1.2%-2.4% in general population and it is characterized by a benign course. Although it can be associated with some complications, ventricular arrhythmias (VA) and sudden cardiac death (SCD) as ultimate expressions, are the most worrying. The estimated risk of SCD in MVP is between 0.2% and 1.9% per year including both MVP patients with left ventricular (LV) dysfunction due to severe MR and MVP patients without significant MR. The latter ones constitute a particular phenotype called "malignant MVP" characterized by bileaflet myxomatous prolapse, ECG repolarization abnormalities and complex VAs (c-VAs) with polymorphic/right bundle branch block morphology (RBBB) and LV fibrosis of the papillary muscles (PMs) and inferobasal wall secondary to mechanical stretching visualized as late gadolinium enhancement (LGE) areas by cardiac magnetic resonance (CMR). In MVP, the first diagnostic approach is transthoracic echocardiography (TTE) that defines the presence of mitral annular disjunction (MAD) which seems to be associated with "arrhythmic MVP" (AMVP). From an ECG point of view, AMVP is characterized by frequent premature ventricular contractions (PVCs) arising from one or both PMs, fascicular tissue, and outflow tract, as well as by T-wave inversion in the inferolateral leads. The aim of the present paper is to describe TTE red flags that could identify MVP patients at high risk to develop complex arrhythmias as supported by the corresponding findings of LGE-CMR and anatomy studies. TTE could be a co-partner in phenotyping high-risk arrhythmic MVP patients.

Diagnosis of Mitral Valve Prolapse: Much More than Simple Prolapse. Multimodality Approach to Risk Stratification and Therapeutic Management

Mitral valve prolapse (MVP) is the most common valvular disease with a prevalence of 2%. It has generally a benign course; however, recent findings suggested an association between MVP and complex arrhythmias and eventually cardiac arrest and for this reason, it is also called arrhythmogenic MVP. Subjects who experience this complication are in general young women, with thickened mitral leaflets or bileaflet prolapse not necessarily associated with severe mitral regurgitation (MR). The nature of the relation between MVP and cardiac arrest is not clearly understood. Actually, the challenging task is to find the cluster of prognostic factors including T-wave inversion, polymorphic premature ventricular contractions, bileaflet prolapse, MR severity, but most importantly, those parameters of hypercontractility, mitral annulus disjunction (MAD), and myocardial fibrosis using a multimodality approach. Transthoracic echocardiography is the first-line imaging modality for the diagnosis of MVP, but also for detecting MAD and hypercontractility, followed by cardiac magnetic resonance for tissue characterization and detection of myocardial and papillary muscle fibrosis, using either late gadolinium enhancement (at the basal segment of the inferolateral wall and papillary muscles) (macro-fibrosis), or diffuse fibrosis by T1 mapping (native and post contrast T1). Moreover, there are also preliminary data on positron emission tomography utilizing 18F-fluorodeoxyglucose as a tool for providing evidence of early myocardial inflammation. The objective of this review article is to provide the clinician with an overview and a practical clinical approach to MVP for risk stratification and treatment guidance.

Mitral valve prolapse morphofunctional features by cardiovascular magnetic resonance: more than just a valvular disease

INTRODUCTION

Mitral valve (MV) prolapse (MVP) is a primary valvular abnormality. We hypothesized that additionally there are concomitant abnormalities of the left ventricle (LV) and MV apparatus in this entity even in the absence of significant mitral regurgitation (MR).

OBJECTIVE

To characterize MV and LV anatomic and functional features in MVP with preserved LV ejection fraction, with and without significant MR, using cardiovascular magnetic resonance (CMR).

METHODS

Consecutive MVP patients (n = 80, mean 52 years, 37% males) with preserved LV ejection fraction, and 44 controls (46 years, 52% males) by CMR were included, as well as 13 additional patients with "borderline" MVP. From cine images we quantified LV volumes, MV and LV anatomic measurements (including angle between diastolic and systolic annular planes, annular displacement, and basal inferolateral hypertrophy) and, using feature tracking, longitudinal and circumferential peak systolic strains.

RESULTS

Significant MR was found in 46 (56%) MVP patients. Compared with controls, MVP patients had LV enlargement, basal inferolateral hypertrophy, higher posterior annular excursion, and reduced shortening of the papillary muscles. LV basal strains were significantly increased, particularly in several basal segments. These differences remained significant in patients without significant MR, and many persisted in "borderline" MVP.

CONCLUSIONS

In patients with MVP and preserved LV ejection fraction there is LV dilatation, basal inferolateral hypertrophy, exaggerated posterior annular displacement and increased basal deformation, even in the absence of significant MR or overt MVP. These findings suggest that MVP is a disease not only of the MV but also of the adjacent myocardium.

Morphofunctional Abnormalities of Mitral Annulus and Arrhythmic Mitral Valve Prolapse

Supplemental Digital Content is available in the text.

Background—

Arrhythmic mitral valve prolapse (MVP) is characterized by myxomatous leaflets and left ventricular (LV) fibrosis of papillary muscles and inferobasal wall. We searched for morphofunctional abnormalities of the mitral valve that could explain a regional mechanical myocardial stretch.

Methods and Results—

Thirty-six (27 female patients; median age: 44 years) arrhythmic MVP patients with LV late gadolinium enhancement on cardiac magnetic resonance and no or trivial mitral regurgitation, and 16 (6 female patients; median age: 40 years) MVP patients without LV late gadolinium enhancement were investigated by morphofunctional cardiac magnetic resonance. Mitral annulus disjunction (median: 4.8 versus 1.8 mm; P<0.001), end-systolic mitral annular diameters (median: 41.2 versus 31.5; P=0.004) and end-diastolic mitral annular diameters (median: 35.5 versus 31.5; P=0.042), prevalence of posterior systolic curling (34 [94%] versus 3 [19%]; P<0.001), and basal to mid LV wall thickness ratio >1.5 (22 [61%] versus 4 [25%]; P=0.016) were higher in MVP patients with late gadolinium enhancement than in those without. A linear correlation was found between mitral annulus disjunction and curling (R=0.85). A higher prevalence of auscultatory midsystolic click (26 [72%] versus 6 [38%]; P=0.018) was also noted. Histology of the mitral annulus showed a longer mitral annulus disjunction in 50 sudden death patients with MVP and LV fibrosis than in 20 patients without MVP (median: 3 versus 1.5 mm; P<0.001).

Conclusions—

Mitral annulus disjunction is a constant feature of arrhythmic MVP with LV fibrosis. The excessive mobility of the leaflets caused by posterior systolic curling accounts for a mechanical stretch of the inferobasal wall and papillary muscles, eventually leading to myocardial hypertrophy and scarring. These mitral annulus abnormalities, together with auscultatory midsystolic click, may identify MVP patients who would need arrhythmic risk stratification.

Hypertrophic angulation deformity of the basal interventricular septum combined with abnormality of the papillary muscle and chordae tendineae

A Chinese woman was admitted to our hospital because of syncope. Transthoracic echocardiography revealed a hypertrophic basal interventricular septum of 15 mm with a sharp angle protruding into the left ventricular outflow tract. Moreover, an anomalous anterolateral papillary muscle (maximum width of 11 mm) was inserted into the left ventricular outflow tract, with short chordae tendineae connecting both basal interventricular septum and anterior leaflet of the mitral valve. All of these abnormalities resulted in a left ventricular outflow gradient of 136 mmHg. Surgical septal myectomy of the sharp angle combined with partial papillary muscle resection and removal of the abnormal chordae tendineae was selected to relieve the left ventricular outflow obstruction. This was a rare combination of deformity of the angulation of the focal basal interventricular septum and abnormalities of the papillary muscle and chordae tendineae, which led to left ventricular outflow obstruction.

Relation of mitral valve prolapse to basal left ventricular hypertrophy as determined by cardiac magnetic resonance imaging

We aimed to characterize the extent and distribution of focal basal left ventricular (LV) hypertrophy in patients with mitral valve prolapse (MVP). Sixty-three patients (mean age: 58 ± 14 years) with MVP and 20 age-matched normal volunteers (mean age: 53 ± 11 years) were assessed using cardiac magnetic resonance imaging. We compared the ratio of basal to mid end-diastolic wall thickness in both groups and correlated it with clinical and imaging parameters. Of the 63 patients, 44 (70%) had posterior leaflet prolapse, 2 (3%) had anterior leaflet prolapse, and 17 (27%) had bileaflet prolapse. There was a significantly increased ratio of basal to mid-ventricular end-diastolic wall thickness in all segments of the left ventricle in those with MVP compared to the controls. The inferolateral (2.1 vs 1.0, p <0.01) and anterolateral (2.1 vs 1.1) ratios (p <0.01) were the greatest compared to the other myocardial segments. The degree of mitral annular excursion had a strong positive correlation with the degree of hypertrophy (r(2) = 0.81, p <0.01) and was an independent predictor in adjusted multivariate analysis (p <0.0001). Age, body mass index, LV end-diastolic volume index, LV end -systolic volume index, LV stroke volume index, degree of prolapse, and mitral regurgitation volume did not have any significant correlation with the degree of hypertrophy. In conclusion, MVP is associated with concentric basal LV hypertrophy and good correlation between the excursion of the mitral valve annulus and the degree of relative LV hypertrophy suggests that locally increased myocardial function could be responsible for this remodeling.