Isolated cleft of the posterior mitral valve leaflet in a patient with Marfan syndrome

Aortic disease and cardiomyopathy in patients with a novel DNMT3A gene variant causing Tatton-Brown-Rahman syndrome

Tatton-Brown-Rahman syndrome (TBRS) is a rare congenital genetic disorder caused by autosomal dominant pathogenic variants in the DNA methyltransferase DNMT3A gene. Typical TBRS clinical features are overgrowth, intellectual disability, and minor facial anomalies. However, since the syndrome was first described in 2014, a widening spectrum of abnormalities is being described. Cardiovascular abnormalities are less commonly reported but can be a major complication of the syndrome. This article describes a family of three individuals diagnosed with TBRS in adulthood and highlights the variable expression of cardiovascular features. A 34-year-old proband presented with progressive aortic dilatation, mitral valve (MV) regurgitation, left ventricular (LV) dilatation, and ventricular arrhythmias. The affected family members (mother and brother) were diagnosed with MV regurgitation, LV dilatation, and arrhythmias. Exome sequencing and computational protein analysis suggested that the novel familial DNMT3A mutation Ser775Tyr is located in the methyltransferase domain, however, distant from the active site or DNA-binding loops. Nevertheless, this bulky substitution may have a significant effect on DNMT3A protein structure, dynamics, and function. Analysis of peripheral blood cfDNA and transcriptome showed shortened mononucleosome fragments and altered gene expression in a number of genes related to cardiovascular health and of yet undescribed function, including several lncRNAs. This highlights the importance of epigenetic regulation by DNMT3A on cardiovascular system development and function. From the clinical perspective, we suggest that new patients diagnosed with congenital DNMT3A variants and TBRS require close examination and follow-up for aortic dilatation and valvular disease because these conditions can progress rapidly. Moreover, personalized treatments, based on the specific DNMT3A variants and the different pathways of their function loss, can be envisioned in the future.

Cleft posterior mitral valve leaflet: The added value of 3-dimensional echocardiography

A 65-year-old female patient diagnosed with degenerative aortic valve disease and severe regurgitation on transthoracic echocardiography (TTE) also had severe mitral regurgitation (MR), but the exact mechanism of MR could not be determined. Transesophageal echocardiography (TEE) showed limited leaflet coaptation and a severe central MR jet. Further three-dimensional (3D) imaging revealed an indentation in the middle of P2 scallop almost reaching the annulus. This was consistent with the diagnosis of cleft posterior mitral valve leaflet. Unlike cleft anterior leaflet which can be clear on TTE short-axis images, cleft posterior leaflet may only be visible using 3D TEE. The identification of cleft posterior leaflet is essential in guiding surgical valve repair.

Diagnosis of Isolated Cleft Mitral Valve Using Three-Dimensional Echocardiography

BACKGROUND

The prevalence of isolated cleft mitral valve (MV; no concomitant congenital heart disease or degenerative MV disease) with significant mitral regurgitation (MR) diagnosed using two-dimensional echocardiography (2DE) has been reported to be very low. Three-dimensional echocardiography (3DE) has enabled a more comprehensive visualization of the MV and detailed understanding of the mechanisms of MR and can potentially reveal isolated cleft MV that is not recognized with 2DE. The aim of this study was to determine, using 3DE, the prevalence, location, and associated MV annular and left ventricular characteristics of isolated cleft MV, in the absence of associated congenital heart disease, in patients with significant MR.

METHODS

A total of 1,092 patients with unexplained moderate or greater MR on two-dimensional transthoracic echocardiography who were referred for three-dimensional transesophageal echocardiography between 2005 and 2017 (n = 626) were retrospectively studied. Left ventricular dimensions and function were determined, and quantitative MR assessment and three-dimensional analysis of the MV annulus was performed.

RESULTS

Twenty-one patients (prevalence 3.3%) were diagnosed with isolated cleft MV using three-dimensional transesophageal echocardiography but not 2DE. The majority of these patients (n = 16) were noted to have anterior cleft MVs, with most located in the mid-A1 (n = 10) or mid-A3 (n = 5) scallops. Posterior clefts were less common (n = 5) and occurred at the site of the natural scallop indentations (three between P1 and P2 and two between P2 and P3). Among patients with either anterior or posterior MV cleft, there were no differences in left ventricular ejection fraction or three-dimensional MV geometry (annular distance, height, circumference, and area). There was a trend toward worse MR severity in patients with anterior cleft MV.

CONCLUSIONS

In patients with otherwise unexplained significant MR referred for transesophageal echocardiography, 3DE uncovered a considerably higher prevalence of isolated cleft MV than previously reported by 2DE, with the majority located in the anterior MV. Although the annular geometry was similar between patients with anterior and posterior cleft MVs, a trend toward more severe MR in anterior clefts may reflect underlying abnormalities in the embryologic development of the anterior MV leaflet. Evaluation of MV pathology is improved by 3DE, which should be used routinely in the setting significant MR.

The Trileaflet Mitral Valve

With the advent of 3-dimensional echocardiography, visualization of the mitral valve has greatly improved. Recently, there has been an increase in reporting of a distinct entity called the "trileaflet mitral valve" using 3-dimensional echocardiography. It is controversial whether this is a new entity or an improved visualization of isolated mitral valve clefts or trifoliate left atrioventricular valve in the setting of an atrioventricular septal defect (AVSD) with intact septum. We present a case of a trifoliate valve, interpreting our findings based on a systematic review of previous publication on trileaflet mitral valves, isolated clefts in the mural (posterior) leaflet of the mitral valve, and trifoliate left atrioventricular valves with AVSD and intact septal structures. We describe the latter entity as a left atrioventricular valve because it never achieves the features of a normal mitral valve. We compare the features of isolated clefts of the mural leaflet of the mitral valve with trifoliate left atrioventricular valve found in the setting of AVSDs with intact septal structures to illustrate the current controversy regarding these conditions. In conclusion, our review suggested the reported trileaflet left atrioventricular valves is likely a misnomer because of a lack of consideration of embryologic development and nomenclature, rather than a greater appreciation and identification of a new distinct disease entity.