Cardiomyopathy is a myocardial disease that is accompanied by impaired heart function and often has a genetic cause. In pediatric cardiomyopathy, the presence of various gene variants highlights genetic diversity as a characteristic feature. Genetic forms can be autosomal dominant, autosomal recessive, X-linked, or mitochondrial, among others. Genetic cardiomyopathy is characterized by different clinical presentations of different variants within the same gene. Most gene variants are rare, and having the same hotspot or variant is uncommon. Even within the same family, these genetic variants can exhibit varying degrees of penetrance. Furthermore, even if individuals within the same family share the same genetic variant, their clinical courses and outcomes can differ significantly. For comprehensive patient care, consideration of the genetic background by genetic testing, including family members, is crucial.

Childhood-onset idiopathic cardiomyopathy is relatively rare, and its management requires sufficient knowledge and expertise of pediatric cardiologists. This review article was based on the presentations at the 20^th Educational Seminar Basic Course of the Japanese Society of Pediatric Cardiology and Cardiac Surgery on July 8, 2023. First, this review provided an overview of recent pharmacotherapy strategies for heart failure according to adult guidelines published in the US, Europe, and Japan. Subsequently, it delved into the clinical assessment and treatment of specific topics, including dilated cardiomyopathy, hypertrophic cardiomyopathy, and restrictive cardiomyopathy. Finally, it briefly introduced the current status of pediatric heart transplantation in Japan and our hospital.

The JCS 2023 Guidelines on the Diagnosis and Treatment of Myocarditis classifies myocarditis as acute, chronic active, chronic, chronic inflammatory cardiomyopathy, or postmyocarditis cardiomyopathy. Endomyocardial biopsy is the gold standard for the diagnosis of myocarditis, but cardiac magnetic resonance imaging (MRI) has become increasingly important in recent years. In cases with suggestive symptoms, signs, and clinical course accompanied by elevated cardiac troponin levels, cardiac MRI findings that meet the Lake Louise criteria can be used to diagnose acute myocarditis without endomyocardial biopsy. However, endomyocardial biopsy is essential for the definitive diagnosis of chronic active myocarditis and chronic inflammatory cardiomyopathy. In this review, we provided an overview of the diagnosis, treatment, and management of myocarditis in accordance with the 2023 revised guidelines, including our own case studies. The diagnosis of myocarditis cannot be based on clinical course and noninvasive tests alone, and it needs to be confirmed by myocardial biopsy or cardiac MRI. A certain number of cases that were clinically diagnosed as dilated cardiomyopathy were chronic active myocarditis and chronic inflammatory cardiomyopathy. Appropriate diagnosis, treatment, and management of these patients are expected to improve the outcomes of severe heart failure in both childhood and adulthood.

Fetal cardiac dysfunction differs from that in adults. Fetal hydrops is the last stage of fetal cardiac dysfunction; however, cardiac dysfunction does not necessarily occur simultaneously with fetal hydrops. A profound knowledge of fetal circulation and physiology is essential for comprehending the complexities of the fetal condition. Of the several parameters for evaluating fetal systolic, diastolic, and overall cardiac function, cardiovascular profile score (CVPS) is the most prominent. This score includes both arterial and venous Doppler patterns, in addition to fetal cardiac function. Assessment of each condition necessitates consideration of fetal physiology and etiology. In cases of high output status, cardiac output is the key factor, whereas conditions, such as Ebstein’s disease warrant attention to the Tei index and maximum velocity of tricuspid regurgitation. Proactive management of infants before the onset of fetal hydrops is preferable, notwithstanding the simultaneous concern of prematurity.

In children with size limitations and congenital heart disease with unique cardiac structures, selection of the lead and implantation method and provision of device therapy that considers the natural history are both important. New functional and pacing devices are emerging, and the number of implantations for these condition is expected to increase. This paper described recent clinical findings on device therapy for pediatric and congenital heart disease.

Although circulatory management is the primary therapeutic target in pediatric cardiovascular disease, respiratory management is also important for improving prognosis. To achieve this, ventilator settings should take into consideration not only oxygenation and gas exchange but also the following four factors: prevention of lung injury, optimization of work of breathing, improvement of patient ventilator interaction, and cardiopulmonary interactions. This study outlined the influence of these four factors on patients and the pitfalls of ventilation in children, particularly neonates and infants.

Anomalous right coronary artery from the pulmonary artery (ARCAPA) is a rare congenital heart disease. Our patient was a 1 year and 2 months old Japanese girl who was diagnosed based on cardiac echocardiography findings during follow-up for failure to thrive. The echocardiography showed a slightly larger left main coronary artery, the origin of the right coronary artery was not clearly detected, and color Doppler showed multiple blood flow signals in the ventricular septum. Coronary CT showed that the right coronary artery originated from the main pulmonary artery, confirming the diagnosis of ARCAPA. Left coronary artery angiography by cardiac catheterization showed that contrast medium flowed from the left coronary artery into the right coronary artery via the collateral vessels, and the main pulmonary artery was contrasted. Multiple blood flow signals in the ventricular septum on echocardiography were observed to be collateral blood vessels from the left coronary artery to the right coronary artery. ARCAPA can cause myocardial infarction and sudden death, and in this case, the right coronary artery was re-implanted into the aorta. Echocardiography was useful in the diagnosis of this disease with its characteristic findings.

Double aortic arch (DAA) is a common condition resulting in vascular ring formation. Prader–Willi syndrome (PWS) is a congenital malformation that causes feeding difficulties due to hypotonia, particularly in the neonatal to infancy period, and can sometimes lead to respiratory problems. Currently, there are no documented cases of PWS accompanied by DAA. Our patient was a girl diagnosed with PWS who was being monitored at another hospital. When the patient was 1 year and 6 months old, she was rushed to our hospital because of inspiratory stridor. After further examination, she was diagnosed as DAA. Although she had residual mild inspiratory stridor, no hypoxemia or difficulty in breathing forcefully was noted. Therefore, she was discharged and planned for elective surgery. Unfortunately, 17 days after discharge, she died while eating at home. In this case, hypotonia and respiratory problems associated with PWS made the diagnosis of DAA challenging and led to worsening of symptoms. Therefore, in patients with vascular rings who present with hypotonia and dysphagia, immediate diagnosis and treatment are essential.