The Risk of Sudden Unexpected Cardiac Death in Children: Epidemiology, Clinical Causes, and Prevention

Missed or Delayed Diagnosis of Heart Disease by the General Pediatrician

Missed or delayed heart disease diagnoses pose a major challenge in pediatric primary care. Many cardiac conditions present with subtle or nonspecific symptoms that resemble benign childhood illnesses, making their prompt recognition difficult. This review describes congenital and acquired heart diseases prone to diagnostic delays, including critical congenital heart disease, coarctation of the aorta, atrial and ventricular septal defects, myocarditis, Kawasaki disease, heart failure, and pulmonary arterial hypertension. The atypical presentations of these disorders and the associated diagnostic pitfalls are emphasized. Furthermore, the importance of alarming symptoms and signs, such as chest pain, palpitations, syncope, and abnormal heart murmurs, is underscored. A structured approach to these red flags is presented to assist primary care pediatricians in identifying children at risk, initiating appropriate management, and referring them for specialized evaluation. The importance of preparticipation screening for athletes is also discussed, highlighting how it can be applied to all children during routine health visits to identify those with heart disease. Appropriate training is essential to increase pediatricians' ability to recognize and manage cardiac patients.

Arrhythmogenic Left Ventricular Cardiomyopathy: From Diagnosis to Risk Management

PURPOSE OF REVIEW

Left ventricular arrhythmogenic cardiomyopathy (ALVC) is a rare and poorly characterized cardiomyopathy that has recently been reclassified in the group of non-dilated left ventricular cardiomyopathies. This review aims to summarize the background, diagnosis, and sudden cardiac death risk in patients presenting this cardiomyopathy.

RECENT FINDINGS

Although there is currently a lack of data on this condition, arrhythmogenic left ventricular dysplasia can be considered a specific disease of the left ventricle (LV). We have collected the latest evidence about the management and the risks associated with this cardiomyopathy.

SUMMARY

Left ventricular arrhythmogenic cardiomyopathy is still poorly characterized. ALVC is characterized by fibrofatty replacement in the left ventricular myocardium, with variable phenotypic expression. Diagnosis is based on a multiparametric approach, including cardiac magnetic resonance (CMR) and genetic testing, and is important for sudden cardiac death (SCD) risk stratification and management. Recent guidelines have improved the management of left ventricular arrhythmogenic cardiomyopathy. Further studies are necessary to improve knowledge of this cardiomyopathy.

Multimodality Imaging in Arrhythmogenic Left Ventricular Cardiomyopathy

The term arrhythmogenic cardiomyopathy (ACM) describes a large spectrum of myocardial diseases characterized by progressive fibrotic or fibrofatty replacement, which gives the substrate for the occurrence of ventricular tachyarrhythmias and the development of ventricular dysfunction. This condition may exclusively affect the left ventricle, leading to the introduction of the term arrhythmogenic left ventricular cardiomyopathy (ALVC). The clinical features of ALVC are progressive fibrotic replacement with the absence or mild dilation of the LV and the occurrence of ventricular arrhythmias within the left ventricle. In 2019, the diagnostic criteria for the diagnosis of ALVC, based on family history and clinical, electrocardiographic, and imaging features, have been proposed. However, since the significant clinical and imaging overlap with other cardiac diseases, genetic testing with the demonstration of a pathogenic variant in an ACM-related gene is required for diagnostic confirmation. In ALVC, the multimodality imaging approach comprises different imaging techniques, such as echocardiography, cardiac magnetic resonance, and cardiac nuclear imaging. It provides essential information for the diagnosis, differential diagnosis, sudden cardiac death risk stratification, and management purposes. This review aims to elucidate the current role of the different multimodality imaging techniques in patients with ALVC.

The heart in RASopathies

The cardiovascular phenotype associated with RASopathies has expanded far beyond the original descriptions of pulmonary valve stenosis by Dr Jaqueline Noonan in 1968 and hypertrophic cardiomyopathy by Hirsch et al. in 1975. Because of the common underlying RAS/MAPK pathway dysregulation, RASopathy syndromes usually present with a typical spectrum of overlapping cardiovascular anomalies, although less common cardiac defects can occur. The identification of the causative genetic variants has enabled the recognition of specific correlations between genotype and cardiac phenotype. Characterization and understanding of genotype-phenotype associations is not only important for counseling a family of an infant with a new diagnosis of a RASopathy condition but is also critical for their clinical prognosis with respect to cardiac disease, neurodevelopment and other organ system involvement over the lifetime of the patient. This review will focus on the cardiac manifestations of the most common RASopathy syndromes, the relationship between cardiac defects and causal genetic variation, the contribution of cardiovascular abnormalities to morbidity and mortality and the most relevant follow-up issues for patients affected by RAS/MAPK pathway diseases, with respect to cardiac clinical outcomes and management, in children and in the adult population.

Clinical genetic testing in four highly suspected pediatric restrictive cardiomyopathy cases

BACKGROUND

Restrictive cardiomyopathy (RCM) presents a high risk for sudden cardiac death in pediatric patients. Constrictive pericarditis (CP) exhibits a similar clinical presentation to RCM and requires differential diagnosis. While mutations of genes that encode sarcomeric and cytoskeletal proteins may lead to RCM, infection, rather than gene mutation, is the main cause of CP. Genetic testing may be helpful in the clinical diagnosis of RCM.

METHODS

In this case series study, we screened for TNNI3, TNNT2, and DES gene mutations that are known to be etiologically linked to RCM in four pediatric patients with suspected RCM.

RESULTS

We identified one novel heterozygous mutation, c.517C>T (substitution, position 517 C → T) (amino acid conversion, p.Leu173Phe), and two already known heterozygous mutations, c.508C>T (substitution, position 508, C → T) (amino acid conversion, p.Arg170Trp) and c.575G>A (substitution, position 575, G → A) (amino acid conversion, p.Arg192His), in the TNNI3 gene in three of the four patients.

CONCLUSION

Our findings support the notion that genetic testing may be helpful in the clinical diagnosis of RCM.

Multimodality Imaging in Cardiomyopathies with Hypertrophic Phenotypes

Multimodality imaging is a comprehensive strategy to investigate left ventricular hypertrophy (LVH), providing morphologic, functional, and often clinical information to clinicians. Hypertrophic cardiomyopathy (HCM) is defined by an increased LV wall thickness not only explainable by abnormal loading conditions. In the context of HCM, multimodality imaging, by different imaging techniques, such as echocardiography, cardiac magnetic resonance, cardiac computer tomography, and cardiac nuclear imaging, provides essential information for diagnosis, sudden cardiac death stratification, and management. Furthermore, it is essential to uncover the specific cause of HCM, such as Fabry disease and cardiac amyloidosis, which can benefit of specific treatments. This review aims to elucidate the current role of multimodality imaging in adult patients with HCM.

Genetic Clues on Implantable Cardioverter-Defibrillator Placement in Young-Age Hypertrophic Cardiomyopathy: A Case Report of Novel MYH7 Mutation and Literature Review

Background: Hypertrophic cardiomyopathy (HCM) is the second most common cardiomyopathy in childhood with a life-threatening risk. Implantable cardioverter-defibrillator (ICD) placement is recommended for early prevention if there are two or more clinical risk factors. Pediatric patients with HCM are at a higher risk of sudden cardiac death (SCD), but there are limited reports on indications for ICD implantation in children. Herein we describe the case of Myh7 mutation-induced HCM and cardiac arrest in a patient and evaluated information originating from genetic background to guide ICD administration. Case Presentation: The patient was a girl aged 7 years and 8 months who had been diagnosed with cardiomyopathy in utero 8 years prior. She had had recurrent cardiac arrests within the last 4 years. Electrocardiography indicated abnormalities in conduction, and ST segment changes. Echocardiography indicated significant left ventricular hypertrophy and hypertrophic systolic interventricular septum. Cardiac magnetic resonance imaging depicted general heart enlargement with hypertrophy, and delayed enhancement in myocardium with perfusion defect was also evident. Whole exon sequencing identified a de novo c.2723T>C (p.L908P) heterozygous mutation in the MYH7 gene. MYH7 p.L908P predicted unstable protein structure and impaired function. The patient was scheduled for ICD implantation. There were no complications after ICD implantation, and she was discharged from hospital on the 10th day. Regular oral beta-blockers, amiodarone, spironolactone, and enalapril were administered, and she was required to attend hospital regularly for follow-up. During follow-up there were no cardiac arrests. Literature review of clinical prognoses associated with genetic mutations of MYH7, MYBPC3, TNNI3, TNNT2, and TPM1 in pediatric HCM patients with and without ICD implantation indicated that they were totally differently. Previous reports also indicated that gene mutations predicted earlier onset of cardiac hypertrophy, and increase likelihood of SCD. Conclusion: Variant burden and variant type contribute to the risk of adverse events in pediatric HCM. Early recognition and intervention are vital in children. Gene mutation could be considered an indication for early ICD placement during standard risk stratification of HCM patients. Whether this extends to the majority of pediatric patients requires further investigation.

Clinical Profile and Risk Factors for Cardiac Death in Pediatric Patients With Primary Dilated Cardiomyopathy at a Tertiary Medical Center in China

AIM

We sought to identify the clinical characteristics and risk factors for cardiac mortality in pediatric patients with primary dilated cardiomyopathy (DCM) in China.

METHODS

A total of 138 pediatric patients who were consecutively diagnosed with primary DCM from January 2011 to December 2020 were included. We assessed patients' clinical symptoms and performed laboratory examinations, electrocardiography, and echocardiography.

RESULTS

Of these patients, 79 (57%) had severe systolic dysfunction (left ventricular ejection fraction of < 30%), 79 (57.2%) developed DCM before 12 months of age, 62 (45%) were male, 121 (87.7%) presented with advanced heart failure (cardiac functional class III/IV), and 54 (39.1%) presented with arrhythmia. At a median follow-up of 12 months, the overall cardiac mortality rate was 33%, and 40 of 46 deaths occurred within 6 months following DCM diagnosis. A multivariate Cox regression analysis identified several independent cardiac death predictors, including an age of 12 months to 5 years [hazard ratio (HR) 2.799; 95% confidence interval (CI) 1.160-6.758; P = 0.022] or 10-15 years (HR 3.617; 95% CI 1.336-9.788; P = 0.011) at diagnosis, an elevated serum alanine aminotransferase (ALT) concentration (≥ 51.5 U/L) (HR 2.219; 95% CI 1.06-4.574; P = 0.031), and use of mechanical ventilation (HR 4.223; 95% CI 1.763-10.114; P = 0.001).

CONCLUSION

The mortality rate of primary DCM without transplantation is high. Age, an elevated serum ALT concentration, and the need for mechanical ventilation predict mortality in patients with primary DCM, providing new insights into DCM risk stratification.

Case report: Removal of a subcutaneous implantable cardiac defibrillator in a pediatric patient with hypertrophic cardiomyopathy after a septal myectomy. Insights on current indications of type of ICD in children with hypertrophic cardiomyopathy and left ventricular tract obstruction

Hypertrophic cardiomyopathy is a heart muscle disease with an annual incidence between 0.24 and 0.47/100000 in childhood. Sudden cardiac death is the most common cause of death in this population. Although some medical treatment can decrease the risk of sudden cardiac death, implantable cardioverter defibrillator continues to be the most reliable treatment. Different types of devices and programming strategies can be used in patients with hypertrophic cardiomyopathy depending on each center and specific patient condition. We report a pediatric patient affected with hypertrophic cardiomyopathy who had and ICD implantation in primary prevention. Four years later he developed symptomatic left ventricular outflow tract obstruction and a surgical septal myectomy was performed. After the myectomy the patient developed complete left bundle branch block on his 12 lead ECG, and unfortunately none of the S-ICD vectors were suitable after the myectomy and it had to be explanted and replaced for a new transvenous ICD.