Adapting to a new environment: postnatal maturation of the human cardiomyocyte.

The postnatal mammalian heart undergoes remarkable developmental changes, which are stimulated by the transition from the intrauterine to extrauterine environment. With birth, increased oxygen levels promote metabolic, structural and biophysical maturation of cardiomyocytes, resulting in mature muscle with increased efficiency, contractility and electrical conduction. In this Topical Review article, we highlight key studies that inform our current understanding of human cardiomyocyte maturation. Collectively, these studies suggest that human atrial and ventricular myocytes evolve quickly within the first year but might not reach a fully mature adult phenotype until nearly the first decade of life. However, it is important to note that fetal, neonatal and paediatric cardiac physiology studies are hindered by a number of limitations, including the scarcity of human tissue, small sample size and a heavy reliance on diseased tissue samples, often without age-matched healthy controls. Future developmental studies are warranted to expand our understanding of normal cardiac physiology/pathophysiology and inform age-appropriate treatment strategies for cardiac disease.

The Heart of the Matter: A Path to Building Diversity in Pediatric Cardiology.

Our essay discusses the impact of underrepresentation in medical training, with a focus on pediatric cardiology. We use the perspective of a physician who is underrepresented in medicine (URiM), and has chosen to pursue a career in pediatric cardiology, to initiate an analysis of the current path toward pediatric cardiology and the factors in undergraduate and graduate medical education which could currently be optimized to improve diversity in training. We argue that a lack of diversity among physicians leads to worse patient outcomes, and we describe steps to improve representation in the field. In order to improve representation in pediatric cardiology, we must reflect upon our current practices and implement systemic changes within cardiology training program recruitment and retention practices. These changes should include continuous mentorship of URiM trainees interested in cardiology and prioritization of research that investigates social determinants of health which may disproportionally affect minority patients.

Acute Myocardial Dysfunction and Hypereosinophilic Infiltrative Myocarditis Secondary to New-Onset Pediatric Acute Lymphoblastic Leukemia.

Myocardial infiltration by eosinophils leads to myocardial inflammation and fibrosis, resulting in restrictive hemodynamics. We describe an uncommon presentation of eosinophilic predominant acute lymphoblastic leukemia that manifested with hypereosinophilic infiltrative myocarditis. (Level of Difficulty: Advanced.).