Diagnostic Cardiovascular Magnetic Resonance Imaging Criteria in Noncompaction Cardiomyopathy and the Yield of Genetic Testing

Genetic, clinical and imaging implications of a noncompaction phenotype population with preserved ejection fraction

Introduction

The genotype of symptomatic left ventricular noncompaction phenotype (LVNC) subjects with preserved left ventricular ejection fraction (LVEF) and its effect on clinical presentation are less well studied. We aimed to characterize the genetic, cardiac magnetic resonance (CMR) and clinical background, and genotype-phenotype relationship in LVNC with preserved LVEF.

Methods

We included 54 symptomatic LVNC individuals (LVEF: 65 ± 5%) whose samples were analyzed with a 174-gene next-generation sequencing panel and 54 control (C) subjects. The results were evaluated using the criteria of the American College of Medical Genetics and Genomics. Medical data suggesting a higher risk of cardiovascular complications were considered "red flags".

Results

Of the LVNC population, 24% carried pathogenic or likely pathogenic (P) mutations; 56% carried variants of uncertain significance (VUS); and 20% were free from cardiomyopathy-related mutations. Regarding the CMR parameters, the LVNC and C groups differed significantly, while the three genetic subgroups were comparable. We found a significant relationship between red flags and genotype; furthermore, the number of red flags in a single subject differed significantly among the genetic subgroups (p = 0.002) and correlated with the genotype (r = 0.457, p = 0.01). In 6 out of 7 LVNC subjects diagnosed in childhood, P or VUS mutations were found.

Discussion

The large number of P mutations and the association between red flags and genotype underline the importance of genetic-assisted risk stratification in symptomatic LVNC with preserved LVEF.

Cardiomyopathies in children: An overview

Paediatric cardiomyopathies form a heterogeneous group of disorders characterized by structural and electrical abnormalities of the heart muscle, commonly due to a gene variant of the myocardial cell structure. Mostly inherited as a dominant or occasionally recessive trait, they might be part of a syndromic disorder of underlying metabolic or neuromuscular defects or combine early developing extracardiac abnormalities (i.e., Naxos disease). The annual incidence of 1 per 100,000 children appears higher during the first two years of life. Dilated and hypertrophic cardiomyopathy phenotypes share an incidence of 60% and 25%, respectively. Arrhythmogenic right ventricular cardiomyopathy (ARVC), restrictive cardiomyopathy, and left ventricular noncompaction are less commonly diagnosed. Adverse events such as severe heart failure, heart transplantation, or death usually appear early after the initial presentation. In ARVC patients, high-intensity aerobic exercise has been associated with worse clinical outcomes and increased penetrance in at-risk genotype-positive relatives. Acute myocarditis in children has an incidence of 1.4-2.1 cases/per 100,000 children per year, with a 6-14% mortality rate during the acute phase. A genetic defect is considered responsible for the progression to dilated cardiomyopathy phenotype. Similarly, a dilated or arrhythmogenic cardiomyopathy phenotype might emerge with an episode of acute myocarditis in childhood or adolescence. This review provides an overview of childhood cardiomyopathies focusing on clinical presentation, outcome, and pathology.

Genetic landscape in Russian patients with familial left ventricular noncompaction

Background

Left ventricular noncompaction (LVNC) cardiomyopathy is a disorder that can be complicated by heart failure, arrhythmias, thromboembolism, and sudden cardiac death. The aim of this study is to clarify the genetic landscape of LVNC in a large cohort of well-phenotyped Russian patients with LVNC, including 48 families (n=214).

Methods

All index patients underwent clinical examination and genetic analysis, as well as family members who agreed to participate in the clinical study and/or in the genetic testing. The genetic testing included next generation sequencing and genetic classification according to ACMG guidelines.

Results

A total of 55 alleles of 54 pathogenic and likely pathogenic variants in 24 genes were identified, with the largest number in the MYH7 and TTN genes. A significant proportion of variants -8 of 54 (14.8%) -have not been described earlier in other populations and may be specific to LVNC patients in Russia. In LVNC patients, the presence of each subsequent variant is associated with increased odds of having more severe LVNC subtypes than isolated LVNC with preserved ejection fraction. The corresponding odds ratio is 2.77 (1.37 -7.37; p <0.001) per variant after adjustment for sex, age, and family.

Conclusion

Overall, the genetic analysis of LVNC patients, accompanied by cardiomyopathy-related family history analysis, resulted in a high diagnostic yield of 89.6%. These results suggest that genetic screening should be applied to the diagnosis and prognosis of LVNC patients.

RBM20 nucleotide sequence variant in a family with a dilated phenotype of left ventricular non-compaction

Aim. To demonstrate two generations of a family with a progressive course of left ventricular non-compaction (LVNC) and the presence of a RBM20 gene variant.

Material and methods. Based on the multicenter registry of patients with LVNC, a family with LVNC with a dilated phenotype was selected at the National Medical Research Center for Therapy and Preventive Medicine. Next generation sequencing was performed on a Nextseq 550 systen (Illumina, USA). For clinical interpretation, nucleotide sequence variants in the genes associated with LVNC development were selected according to the available literature data, with frequencies <0,5% in the gnomAD database. The identified variants were verified using Sanger sequencing on an Applied Biosystem 3500 Genetic Analyzer (Thermo Fisher Scientific, USA).

Results. The article presents the results of clinical, paraclinical and molecular genetic studies of two generations of a family diagnosed with LVNC with a dilated phenotype and the progression of isolated LVNC to a dilated type. As a result of a molecular genetic study, all family members with the LVNC were found to have a likely pathogenic variant in the RBM20 NP_001127835.2:p.Pro638Leu (rs267607003) gene. RBM20 is a key splicing regulator that controls the processing of several important transcripts predominantly expressed in striated muscle, especially cardiac tissue. RBM20 gene variants can lead to disruption of splicing at several points and, as a result, to cardiomyopathy progression. Most known pathogenic RBM20 variants are associated with dilated cardiomyopathy; however, a number of studies have found RBM20 gene variants in patients with LVNC. The segregation of nucleotide sequence variant with symptoms in two generations testifies in favor of the association of the detected variant with LVNC development.

Conclusion. Currently, the boundaries of the cardiomyopathy genetics are expanding. Pathogenic and likely pathogenic RBM20 gene variants are associated primarily with a dilated phenotype and a high risk of sudden cardiac death. The article presents the results of a survey of two generations of a family with LVNC and progressive myocardial remodeling.

30-minute CMR for common clinical indications: a Society for Cardiovascular Magnetic Resonance white paper

BACKGROUND

Despite decades of accruing evidence supporting the clinical utility of cardiovascular magnetic resonance (CMR), adoption of CMR in routine cardiovascular practice remains limited in many regions of the world. Persistent use of long scan times of 60 min or more contributes to limited adoption, though techniques available on most scanners afford routine CMR examination within 30 min. Incorporating such techniques into standardize protocols can answer common clinical questions in daily practice, including those related to heart failure, cardiomyopathy, ventricular arrhythmia, ischemic heart disease, and non-ischemic myocardial injury. BODY: In this white paper, we describe CMR protocols of 30 min or shorter duration with routine techniques with or without stress perfusion, plus specific approaches in patient and scanner room preparation for efficiency. Minimum requirements for the scanner gradient system, coil hardware and pulse sequences are detailed. Recent advances such as quantitative myocardial mapping and other add-on acquisitions can be incorporated into the proposed protocols without significant extension of scan duration for most patients.

CONCLUSION

Common questions in clinical cardiovascular practice can be answered in routine CMR protocols under 30 min; their incorporation warrants consideration to facilitate increased access to CMR worldwide.

Correlation between left ventricular fractal dimension and impaired strain assessed by cardiac MRI feature tracking in patients with left ventricular noncompaction and normal left ventricular ejection fraction

OBJECTIVES

To investigate the correlation between the extent of excessive trabeculation assessed by fractal dimension (FD) and myocardial contractility assessed by cardiac MRI feature tracking in patients with left ventricular noncompaction (LVNC) and normal left ventricular ejection fraction (LVEF).

METHODS

Forty-one LVNC patients with normal LVEF (≥ 50%) and 41 healthy controls were retrospectively included. All patients fulfilled three available diagnostic criteria on MRI. Cardiac MRI feature tracking was performed on cine images to determine left ventricular (LV) peak strains in three directions: global radial strain (GRS), global circumferential strain (GCS), and global longitudinal strain (GLS). The complexity of excessive trabeculation was quantified by fractal analysis on short-axis cine stacks.

RESULTS

Compared with controls, patients with LVNC had impaired GRS, GCS, and GLS (all p < 0.05). The global, maximal, and regional FD values of the LVNC population were all significantly higher than those of the controls (all p < 0.05). Global FD was positively correlated with the end-diastolic volume index, end-systolic volume index, and stroke volume index (r = 0.483, 0.505, and 0.335, respectively, all p < 0.05), but negatively correlated with GRS and GCS (r =  - 0.458 and 0.508, respectively, both p < 0.001). Moreover, apical FD was also weakly associated with LVEF and GLS (r =  - 0.249 and 0.252, respectively, both p < 0.05).

CONCLUSION

In patients with LVNC, LV systolic dysfunction was detected early by cardiac MRI feature tracking despite the presence of normal LVEF and was associated with excessive trabecular complexity assessed by FD.

KEY POINTS

• Left ventricular global strain was already impaired in patients with extremely prominent excessive trabeculation but normal left ventricular ejection fraction. • An increased fractal dimension was associated with impaired deformation in left ventricular noncompaction.

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.

Reduced Systolic Function and Not Genetic Variants Determine Outcome in Pediatric and Adult Left Ventricular Noncompaction Cardiomyopathy

Background: Left ventricular noncompaction cardiomyopathy (LVNC CMP) is a genetic cardiomyopathy. Genotype-phenotype correlation and clinical outcome of genetic variants in pediatric and adult LVNC CMP patients are still unclear. Methods: The retrospective multicenter study was conducted in unrelated index patients with LVNC CMP, diagnosed between the years 1987 and 2017, and all available family members. All index patients underwent next-generation sequencing for genetic variants in 174 target genes using the Illumina TruSight Cardio Sequencing Panel. Major adverse cardiac events (MACE) included mechanical circulatory support, heart transplantation, survivor of cardiac death, and/or all-cause death as combined endpoint. Results: Study population included 149 LVNC CMP patients with a median age of 27.8 (9.2-44.8) years at diagnosis; 58% of them were symptomatic, 18% suffered from non-sustained and sustained arrhythmias, and 17% had an implantable cardioverter defibrillator (ICD) implanted. 55/137 patients (40%) were ≤ 18 years at diagnosis. A total of 134 variants were identified in 87/113 (77%) index patients. 93 variants were classified as variant of unknown significance (VUS), 24 as likely pathogenic and 15 as pathogenic. The genetic yield of (likely) pathogenic variants was 35/113 (31%) index patients. Variants occurred most frequently in MYH7 (n=19), TTN (n = 10) and MYBPC3 (n = 8). Altogether, sarcomere gene variants constituted 42.5% (n = 57) of all variants. The presence or absence of (likely) pathogenic variants or variants in specific genes did not allow risk stratification for MACE. Reduced left ventricular (LV) systolic function and increased left ventricular end-diastolic diameter (LVEDD) were risk factors for event-free survival in the Kaplan-Meier analysis. Through multivariate analysis we identified reduced LV systolic function as the main risk factor for MACE. Patients with reduced LV systolic function were at a 4.6-fold higher risk for MACE. Conclusions: Genetic variants did not predict the risk of developing a MACE, neither in the pediatric nor in the adult cohort. Multivariate analysis emphasized reduced LV systolic function as the main independent factor that is elevating the risk for MACE. Genetic screening is useful for cascade screening to identify family members at risk for developing LVNC CMP.

An Appreciation of Anatomy in the Molecular World

Robert H. Anderson is one of the most important and accomplished cardiac anatomists of the last decades, having made major contributions to our understanding of the anatomy of normal hearts and the pathologies of acquired and congenital heart diseases. While cardiac anatomy as a research discipline has become largely subservient to molecular biology, anatomists like Professor Anderson demonstrate anatomy has much to offer. Here, we provide cases of early anatomical insights on the heart that were rediscovered, and expanded on, by molecular techniques: migration of neural crest cells to the heart was deduced from histological observations (1908) and independently shown again with experimental interventions; pharyngeal mesoderm is added to the embryonic heart (1973) in what is now defined as the molecularly distinguishable second heart field; chambers develop from the heart tube as regional pouches in what is now considered the ballooning model by the molecular identification of regional differentiation and proliferation. The anatomical discovery of the conduction system by Purkinje, His, Tawara, Keith, and Flack is a special case because the main findings were never neglected in later molecular studies. Professor Anderson has successfully demonstrated that sound knowledge of anatomy is indispensable for proper understanding of cardiac development.