Biventricular noncompaction: a case report

Left ventricular noncompaction in Ibadan, Nigeria

BACKGROUND

There has been an increase in the reporting of cases of left ventricular noncompaction (LVNC) cardiomyopathy in medical literature due to advances in medical imaging. Patients with LVNC may be asymptomatic or may present with arrhythmias, heart failure, thromboembolism or sudden death. LVNC is typically diagnosed by echocardiography, although there are higher-resolution cardiac imaging techniques such as cardiac magnetic resonance imaging (MRI) to make the diagnosis. The objective of the study is to report on a series of 9 cases of LVNC cardiomyopathy seen at the University College Hospital, Ibadan. Cases of LVNC seen between September 1, 2015 and July 31, 2022 in our echocardiography service  is being reported.

RESULTS

There were a total of 6 men and 3 women. Mean age at presentation was 52.89 ± 15.02 years. The most common mode of presentation was heart failure (6 patients). Hypertension was the most common comorbidity (6 patients). Three patients had an ejection fraction of less than 40% and the mean ratio of noncompacted to compacted segment at end-systole was 2.80 ± 0.48. The most common areas of trabecular localization were the LV lateral wall and the apex. Beta blockers were highly useful in the management of the patients.

CONCLUSIONS

LVNC cardiomyopathy is not uncommon in our environment and a high index of suspicion is often required.

PRDM16 Is a Compact Myocardium-Enriched Transcription Factor Required to Maintain Compact Myocardial Cardiomyocyte Identity in Left Ventricle

BACKGROUND

Left ventricular noncompaction cardiomyopathy (LVNC) was discovered half a century ago as a cardiomyopathy with excessive trabeculation and a thin ventricular wall. In the decades since, numerous studies have demonstrated that LVNC primarily has an effect on left ventricles (LVs) and is often associated with LV dilation and dysfunction. However, in part because of the lack of suitable mouse models that faithfully mirror the selective LV vulnerability in patients, mechanisms underlying the susceptibility of LVs to dilation and dysfunction in LVNC remain unknown. Genetic studies have revealed that deletions and mutations in PRDM16 (PR domain-containing 16) cause LVNC, but previous conditional Prdm16 knockout mouse models do not mirror the LVNC phenotype in patients, and the underlying molecular mechanisms by which PRDM16 deficiency causes LVNC are still unclear.

METHODS

Prdm16 cardiomyocyte-specific knockout (Prdm16cKO) mice were generated and analyzed for cardiac phenotypes. RNA sequencing and chromatin immunoprecipitation deep sequencing were performed to identify direct transcriptional targets of PRDM16 in cardiomyocytes. Single-cell RNA sequencing in combination with spatial transcriptomics was used to determine cardiomyocyte identity at the single-cell level.

RESULTS

Cardiomyocyte-specific ablation of Prdm16 in mice caused LV-specific dilation and dysfunction, as well as biventricular noncompaction, which fully recapitulated LVNC in patients. PRDM16 functioned mechanistically as a compact myocardium-enriched transcription factor that activated compact myocardial genes while repressing trabecular myocardial genes in LV compact myocardium. Consequently, Prdm16cKO LV compact myocardial cardiomyocytes shifted from their normal transcriptomic identity to a transcriptional signature resembling trabecular myocardial cardiomyocytes or neurons. Chamber-specific transcriptional regulation by PRDM16 was attributable in part to its cooperation with LV-enriched transcription factors Tbx5 and Hand1.

CONCLUSIONS

These results demonstrate that disruption of proper specification of compact cardiomyocytes may play a key role in the pathogenesis of LVNC. They also shed light on underlying mechanisms of the LV-restricted transcriptional program governing LV chamber growth and maturation, providing a tangible explanation for the susceptibility of LV in a subset of LVNC cardiomyopathies.

State-of-the art review: Noncompaction cardiomyopathy in pediatric patients

Noncompaction cardiomyopathy (NCCM) is a disease characterized by hypertrabeculation, commonly hypothesized due to an arrest in compaction during fetal development. In 2006, NCCM was classified as a distinct form of cardiomyopathy (CMP) by the American Heart Association. NCCM in childhood is more frequently familial than when diagnosed in adulthood and is associated with other congenital heart diseases (CHDs), other genetic CMPs, and neuromuscular diseases (NMDs). It is yet a rare cardiac diseased with an estimated incidence of 0.12 per 100.000 in children up to 10 years of age. Diagnosing NCCM can be challenging due to non-uniform diagnostic criteria, unawareness, presumed other CMPs, and presence of CHD. Therefore, the incidence of NCCM in children might be an underestimation. Nonetheless, NCCM is the third most common cardiomyopathy in childhood and is associated with heart failure, arrhythmias, and/or thromboembolic events. This state-of-the-art review provides an overview on pediatric NCCM. In addition, we discuss the natural history, epidemiology, genetics, clinical presentation, outcome, and therapeutic options of NCCM in pediatric patients, including fetuses, neonates, infants, and children. Furthermore, we provide a simple classification of different forms of the disease. Finally, the differences between the pediatric population and the adult population are described.

Semaphorin 3E/PlexinD1 signaling is required for cardiac ventricular compaction

Left ventricular noncompaction (LVNC) is one of the most common forms of genetic cardiomyopathy characterized by excessive trabeculation and impaired myocardial compaction during fetal development. Patients with LVNC are at higher risk of developing left/right ventricular failure or both. Although the key regulators for cardiac chamber development are well studied, the role of semaphorin (Sema)/plexin signaling in this process remains poorly understood. In this article, we demonstrate that genetic deletion of Plxnd1, a class-3 Sema receptor in endothelial cells, leads to severe cardiac chamber defects. They were characterized by excessive trabeculation and noncompaction similar to patients with LVNC. Loss of Plxnd1 results in decreased expression of extracellular matrix proteolytic genes, leading to excessive deposition of cardiac jelly. We demonstrate that Plxnd1 deficiency is associated with an increase in Notch1 expression and its downstream target genes. In addition, inhibition of the Notch signaling pathway partially rescues the excessive trabeculation and noncompaction phenotype present in Plxnd1 mutants. Furthermore, we demonstrate that Semaphorin 3E (Sema3E), one of PlexinD1's known ligands, is expressed in the developing heart and is required for myocardial compaction. Collectively, our study uncovers what we believe to be a previously undescribed role of the Sema3E/PlexinD1 signaling pathway in myocardial trabeculation and the compaction process.

Cardiomyopathy Phenotypes and Outcomes for Children With Left Ventricular Myocardial Noncompaction: Results From the Pediatric Cardiomyopathy Registry

BACKGROUND

Left ventricular noncompaction (LVNC) is a distinct form of cardiomyopathy characterized by hypertrabeculation of the left ventricle. The LVNC phenotype may occur in isolation or with other cardiomyopathy phenotypes. Prognosis is incompletely characterized in children.

METHODS AND RESULTS

According to diagnoses from the National Heart, Lung, and Blood Institute-funded Pediatric Cardiomyopathy Registry from 1990 to 2008, 155 of 3,219 children (4.8%) had LVNC. Each LVNC patient was also classified as having an associated echocardiographically diagnosed cardiomyopathy phenotype: dilated (DCM), hypertrophic (HCM), restrictive (RCM), isolated, or indeterminate. The time to death or transplantation differed among the phenotypic groups (P = .035). Time to listing for cardiac transplantation significantly differed by phenotype (P < .001), as did time to transplantation (P = .015). The hazard ratio for death/transplantation (with isolated LVNC as the reference group) was 4.26 (95% confidence interval [CI] 0.78-23.3) for HCM, 6.35 (95% CI 1.52-26.6) for DCM, and 5.66 (95% CI 1.04-30.9) for the indeterminate phenotype. Most events occurred in the 1st year after diagnosis.

CONCLUSIONS

LVNC is present in at least 5% of children with cardiomyopathy. The specific LVNC-associated cardiomyopathy phenotype predicts the risk of death or transplantation and should inform clinical management.

Left ventricular non-compaction cardiomyopathy

Left ventricular non-compaction, the most recently classified form of cardiomyopathy, is characterised by abnormal trabeculations in the left ventricle, most frequently at the apex. It can be associated with left ventricular dilation or hypertrophy, systolic or diastolic dysfunction, or both, or various forms of congenital heart disease. Affected individuals are at risk of left or right ventricular failure, or both. Heart failure symptoms can be induced by exercise or be persistent at rest, but many patients are asymptomatic. Patients on chronic treatment for compensated heart failure sometimes present acutely with decompensated heart failure. Other life-threatening risks of left ventricular non-compaction are ventricular arrhythmias or complete atrioventricular block, presenting clinically as syncope, and sudden death. Genetic inheritance arises in at least 30-50% of patients, and several genes that cause left ventricular non-compaction have been identified. These genes seem generally to encode sarcomeric (contractile apparatus) or cytoskeletal proteins, although, in the case of left ventricular non-compaction with congenital heart disease, disturbance of the NOTCH signalling pathway seems part of a final common pathway for this form of the disease. Disrupted mitochondrial function and metabolic abnormalities have a causal role too. Treatments focus on improvement of cardiac efficiency and reduction of mechanical stress in patients with systolic dysfunction. Further, treatment of arrhythmia and implantation of an automatic implantable cardioverter-defibrillator for prevention of sudden death are mainstays of therapy when deemed necessary and appropriate. Patients with left ventricular non-compaction and congenital heart disease often need surgical or catheter-based interventions. Despite progress in diagnosis and treatment in the past 10 years, understanding of the disorder and outcomes need to be improved.

Isolated Left Ventricular Noncompaction in Sub-Saharan Africa: A Clinical and Echocardiographic Perspective

Background—

Isolated left ventricular noncompaction (ILVNC) is a cardiomyopathy caused by intrauterine failure of the myocardium to compact. Common clinical complications are heart failure, arrhythmias, and cardioembolism. A paucity of data exists relating to clinical and echocardiographic features of ILVNC in Africans.

Methods and Results—

This study is a single-center, prospective case-control study, whereby subjects attending a dedicated cardiomyopathy clinic were screened for and diagnosed with ILVNC, provided they had no other associated structural heart disease and fulfilled all the accompanying echocardiographic criteria: (1) end-systolic ratio of noncompacted layer to compacted layer >2, (2) presence of >3 prominent apical trabeculations, and (3) deep intertrabecular recesses that fill with blood from the ventricular cavity visualized using color Doppler ultrasound. Fifty-four subjects were identified, age 45.4±13.1 years (mean±SD), 95% confidence interval 3.6 to 10.2, 55.6% male, and 63.0% New York Health Association Class II, and prevalence of LVNC in our clinic was 6.9%, 95% confidence interval 3.6 to 10.2. Heart failure because of systolic dysfunction was the most common clinical presentation (53 subjects, 98.1%). Left ventricular end-diastolic diameter was 61.4±7.2 mm (mean±SD) and ejection fraction 26.7±11.9% (mean±SD). Common sites of noncompaction were the apical (100%), midinferior (74.1%), and midlateral (64.8%) walls. Right ventricular noncompaction occurred in 12 subjects (22.2%). Pulmonary hypertension was documented in 45 cases (83.3%). Right ventricular dilation was noted in 40 subjects (74.1%), while right ventricular function was depressed in 32 (59.3%). Tricuspid S' was 9.6±2.8 cm/s (mean±SD). No echocardiographic features suggestive of ILVNC were noted in a healthy control group of African descent.

Conclusions—

ILVNC in patients of African descent can be characterized by biventricular abnormality and pulmonary hypertension, in addition to isolated left-sided abnormality.

An unusual case of congenitally corrected transposition of the great arteries associated with noncompaction-like remodeling of the morphological right ventricle

Congenitally corrected transposition of the great arteries is a rare disease characterized by atrio-ventricular and ventriculo-arterial discordance (double discordance) and is associated with other cardiac anomalies in the majority of cases. The important associated anomalies include ventricular septal defect, abnormalities of left atrioventricular valve, subpulmonary stenosis, and conduction abnormalities. However, the noncompaction-like remodeling of the subaortic, morphologic right ventricle is not a commonly reported association. We, report a case of congenitally corrected transposition of the great arteries in a 40-year-old male patient, who had noncompaction-like remodeling of the morphologic right ventricle with severe ventricular dysfunction. He also had, left-sided Ebstein's anomaly, severe left atrioventricular valve regurgitation and a 2:1 atrioventricular conduction block.

Left ventricular non-compaction and its cardiac and neurologic implications

Left ventricular non-compaction, also known as left ventricular hypertrabeculation (LVHT), is a morphological abnormality of the left ventricular myocardium, characterised by a meshwork of myocardial strings, interlacing, and orderless in arrangement. LVHT is most frequently located in the apex and the lateral wall and may occur with or without other congenital or acquired cardiac abnormalities. LVHT is believed to be congenital in the majority of the cases but may develop during life in single cases (acquired LVHT). Congenital LVHT is believed to result from defective late-stage embryonic development of the myocardial architecture. The pathogenesis of acquired LVHT remains speculative. LVHT is most frequently found on transthoracic echocardiography and cardiac MRI but may be visualised also with other imaging techniques. In the majority of the cases, LVHT is associated with hereditary cardiac, neuromuscular, non-cardiac/non-muscle disease, or chromosomal aberrations. In the majority of the cases, LVHT is complicated by ventricular arrhythmias, systolic dysfunction, cardiac embolism, or sudden cardiac death. LVHT per se does not require a specific treatment. Only in case of complications, such as ventricular arrhythmias, cardioembolism, or systolic dysfunction, adequate therapy is indicated. Though initially assessed as poor, the prognosis of LVHT has meanwhile improved, most likely due to the increased awareness for the abnormality and the timely administration of adequate therapy.

Atrial right-to-left shunt without pulmonary hypertension in a patient with biventricular non-compaction cardiomyopathy accompanied by ventricular and atrial septal defects

Echocardiography and magnetic resonance imaging revealed biventricular non-compaction cardiomyopathy with ventricular (VSD) and atrial (ASD) septal defects in an unconscious, 23-year-old hypoxemic man. Doppler echocardiography showed a left-to-right shunt across the VSD and a right-to-left shunt across the ASD. Cardiac catheterization revealed elevated right atrial pressure, although pulmonary pressure was normal. We considered that the atrial right-to-left shunt had induced the hypoxemia, which was related mainly to right ventricular dysfunction in this biventricular non-compaction cardiomyopathy, but it was not related to pulmonary hypertension.