Trabeculation and left ventricular hypertrabeculation/noncompaction

Genetics and Clinical Features of Noncompaction Cardiomyopathy in the Fetal Population

Objectives: Noncompaction Cardiomyopathy (NCCM) has been classified as primary genetic cardiomyopathy and has gained increasing clinical awareness; however, little is known about NCCM in the fetal population. We aimed to investigate the clinical characteristics and genetic spectrum of a fetal population with NCCM. Methods: We retrospectively reviewed all fetuses with a prenatal diagnosis of NCCM at a single center between October 2010 and December 2019. These cases were investigated for gestational age at diagnosis, gender, left or biventricular involvement, associated cardiac phenotypes, outcomes, and genetic testing data. Results: We identified 37 fetuses with NCCM out of 49,898 fetuses, indicating that the incidence of NCCM in the fetal population was 0.07%. Of the 37 fetuses, 26 were male, ten were female and one was of unknown gender. NCCM involvement biventricle is the most common (n = 16, 43%), followed by confined to the left ventricle (n = 14, 38%). Nineteen (51%) had additional congenital heart defects, with right-sided lesions being the most common (n = 14, 74%), followed by ventricular septal defects (n = 10, 53%). Hydrops fetalis was present in 12 cases (32%), of which four were atypical (pericardial effusion only). Sequencing analysis was performed at autopsy (n = 19) or postnatally (n = 1) on 20 fetuses. Of the 20 fetuses undergoing copy number variation sequencing and whole-exome sequencing, nine (47%) had positive genetic results, including one with a pathogenic copy number variant and eight with pathogenic/likely pathogenic variants. Non-sarcomere gene mutations accounted for the vast majority (n = 7). In contrast, sarcomere gene mutations occurred in only one case (TPM1), and no mutations were identified in the three most common sarcomere genes (MYH7, TTN, and MYBPC3) of pediatric and adult patients. Pathogenic/likely pathogenic variants were significantly more frequent in fetuses with congenital heart defects than those without congenital heart defects. Conclusions: Our data demonstrate that fetal NCCM is a unique entity. Compared with pediatric and adult NCCM, fetal NCCM is more prone to biventricle involvement, more likely to be complicated with congenital heart defects, and has a distinct genetic spectrum.

Loss of Function Mutations in NNT Are Associated With Left Ventricular Noncompaction

BACKGROUND

Left ventricular noncompaction (LVNC) is an autosomal-dominant, genetically heterogeneous cardiomyopathy with variable severity, which may co-occur with cardiac hypertrophy.

METHODS AND RESULTS

Here, we generated whole exome sequence data from multiple members from 5 families with LVNC. In 4 of 5 families, the candidate causative mutation segregates with disease in known LVNC genes MYH7 and TPM1. Subsequent sequencing of MYH7 in a larger LVNC cohort identified 7 novel likely disease causing variants. In the fifth family, we identified a frameshift mutation in NNT, a nuclear-encoded mitochondrial protein, not implicated previously in human cardiomyopathies. Resequencing of NNT in additional LVNC families identified a second likely pathogenic missense allele. Suppression of nnt in zebrafish caused early ventricular malformation and contractility defects, probably driven by altered cardiomyocyte proliferation. In vivo complementation studies showed that mutant human NNT failed to rescue nnt morpholino-induced heart dysfunction, indicating a probable haploinsufficiency mechanism.

CONCLUSIONS

Together, our data expand the genetic spectrum of LVNC and demonstrate how the intersection of whole exome sequence with in vivo functional studies can accelerate the identification of genes that drive human genetic disorders.

Mutations in the NOTCH pathway regulator MIB1 cause left ventricular noncompaction cardiomyopathy

Left ventricular noncompaction (LVNC) causes prominent ventricular trabeculations and reduces cardiac systolic function. The clinical presentation of LVNC ranges from asymptomatic to heart failure. We show that germline mutations in human MIB1 (mindbomb homolog 1), which encodes an E3 ubiquitin ligase that promotes endocytosis of the NOTCH ligands DELTA and JAGGED, cause LVNC in autosomal-dominant pedigrees, with affected individuals showing reduced NOTCH1 activity and reduced expression of target genes. Functional studies in cells and zebrafish embryos and in silico modeling indicate that MIB1 functions as a dimer, which is disrupted by the human mutations. Targeted inactivation of Mib1 in mouse myocardium causes LVNC, a phenotype mimicked by inactivation of myocardial Jagged1 or endocardial Notch1. Myocardial Mib1 mutants show reduced ventricular Notch1 activity, expansion of compact myocardium to proliferative, immature trabeculae and abnormal expression of cardiac development and disease genes. These results implicate NOTCH signaling in LVNC and indicate that MIB1 mutations arrest chamber myocardium development, preventing trabecular maturation and compaction.

16-kDa prolactin and bromocriptine in postpartum cardiomyopathy

Peripartum cardiomyopathy (PPCM) is a potentially life-threatening heart disease emerging toward the end of pregnancy or in the first postpartal months in previously healthy women. Recent data suggest a central role of unbalanced peri-/postpartum oxidative stress that triggers the proteolytic cleavage of the nursing hormone prolactin (PRL) into a potent antiangiogenic, proapoptotic, and proinflammatory 16-kDa PRL fragment. This notion is supported by the observation that inhibition of PRL secretion by bromocriptine, a dopamine D2-receptor agonist, prevented the onset of disease in an animal model of PPCM and by first clinical experiences where bromocriptine seem to exert positive effects with respect to prevention or treatment of PPCM patients. Here, we highlight the current state of knowledge on diagnosis of PPCM, provide insights into the biology and pathophysiology of 16-kDa PRL and bromocriptine, and outline potential consequences for the clinical management and treatment options for PPCM patients.

Isolated ventricular noncompaction syndrome in a nigerian male: case report and review of the literature

Isolated ventricular non-compaction cardiomyopathy (IVNC) is a rare, morphologically distinct primary genetic cardiomyopathy, which is now gaining prominence as an important differential diagnosis in patients presenting with cardiac failure. We describe a case report of a Nigerian male with facial dysmorphism presenting with cardiac failure. This is followed by a review of the literature with focus on the diagnosis of this condition, which may be difficult especially in non-Caucasian populations.

Isolated non-compaction cardiomyopathy

BACKGROUND

Isolated non-compaction cardiomyopathy (NCCM) was first described in 1984. This disorder, a primary genetic cardiomyopathy, is now attracting increased attention.

METHOD

The current state of the epidemiology, pathogenesis, pathophysiology, clinical features, diagnosis, treatment, and prognosis of NCCM are discussed on the basis of a review of selected literature as well as the authors' personal experience.

RESULTS

The pathogenesis of NCCM is thought to involve a genetically determined disturbance of the myocardial compaction process during fetal endomyocardial morphogenesis. It is not accompanied by any other cardiac anomalies. Echocardiography is the diagnostic method of choice. The diagnosis is based on the following echocardiographic criteria: the presence of at least 4 prominent trabeculations and deep intertrabecular recesses, blood flow from the ventricular cavity into the intertrabecular recesses, and a typical bilaminar structure of the affected portion of the left ventricular myocardium. NCCM can also be diagnosed with magnetic resonance imaging of the heart. The clinical severity of NCCM is variable; its manifestations include heart failure, thromboembolic events, and arrhythmias. The treatment is symptom-based. Patients with symptomatic NCCM have a poor prognosis.

CONCLUSION

NCCM is a type of cardiomyopathy that was first described 25 years ago. Its molecular genetic basis is not yet fully clear, and the same is true of its diagnosis, treatment, and prognosis. Further study of these matters is needed.

Isolated noncompaction of the left ventricular myocardium -- a review of the literature two decades after the initial case description

Isolated noncompaction of the left ventricular myocardium (INVM), first described in 1984, is an unclassified cardiomyopathy and is assumed to occur as an arrest of the compaction process during the normal development of the heart. Between weeks 5 to 8 of human fetal development, the ventricular myocardium undergoes gradual compaction with transformation of the relatively large intertrabecular spaces into capillaries while the residual spaces within the trabecular meshwork gradually flatten or disappear. In the case of INVM, the spaces within the intertrabecular meshwork persist while no other cardiac abnormalities exist. Although there is substantial evidence supporting the developmental hypothesis, other pathogenetic processes responsible for INVM have been discussed. It can be assumed that INVM will be better understood in the future as the molecular genetic basis of cardiomyopathies will be further unravelled. Echocardiography has been shown to be the method of choice in diagnosis of INVM. The diagnostic criteria can be summarized as: 1) appearance of at least four prominent trabeculations and deep intertrabecular recesses; 2) appearance of blood flow from the ventricular cavity into the intertrabecular recesses as visualized by color Doppler imaging; 3) the segments of noncompacted myocardium mainly involve the apex and the inferior mid and lateral mid of the left ventricular wall and typically show a two-layered structure with an endsystolic ratio greater than two between the noncompacted subendocardial layer and the compacted subepicardial layer; 4) absence of coexisting cardiac abnormalities. Magnetic resonance imaging using modern gradient echo sequences has also been shown to diagnose INVM accurately. The clinical presentation of INVM is characterized by a high prevalence of heart failure, thromboembolic events and arrhythmias including ventricular tachycardia and atrial fibrillation. The establishment of a registry, which was initiated by the "Arbeitsgemeinschaft Leitende Kardiologische Krankenhausärzte (ALKK)" recently, may provide further clues for diagnosis, risk stratification, and management of this disease.