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5 APF of the heart and blood vessels in children. Circulation of the fetus and newborn
Muktarali kyzy B, teacher of «Child Diseases» Department. International Medical Faculty of Osh State University
Rajesh Akash, Umapathy Swetha , Arjunan Sanjay (Year 3rd),students of International Medical Faculty of Osh State University
Abstract
Children exhibit unique anatomical and physiological characteristics of the cardiovascular system that differ significantly from adults. These differences influence hemodynamics, oxygen delivery, and clinical manifestations of cardiac pathology. Fetal circulation is adapted to intrauterine life, ensuring oxygen supply via the placenta, while newborn circulation undergoes rapid transition immediately after birth. This article reviews the structural and functional specifics of the pediatric heart and blood vessels and outlines the critical transitions from fetal to neonatal circulation. Understanding these distinctions is essential for accurate clinical assessment and management of cardiovascular conditions in infants and children.
Introduction
The cardiovascular system of children undergoes continuous development from fetal life through adolescence. Fetal circulation is specialized for placental oxygenation, employing shunts such as the ductus venosus, foramen ovale, and ductus arteriosus. At birth, these shunts close due to physiological changes triggered by lung expansion and altered pressure gradients.
In early childhood, the myocardium, vascular elasticity, heart rate, and blood pressure remain distinct from adult patterns, influencing clinical signs and responses to disease. A detailed understanding of pediatric cardiovascular anatomy and physiology is therefore essential for pediatricians, cardiologists, and healthcare professionals.
Objectives
1. To describe the anatomical features of the heart and blood vessels in infants and children.
2. To outline the physiological characteristics of the pediatric cardiovascular system.
3. To explain the structure and function of fetal circulation.
4. To describe the transitional circulation changes occurring after birth.
5. To summarize clinical implications of these developmental features.
Methods
This article is based on:
• Review of pediatric anatomy and physiology textbooks.
• Analysis of current scientific literature on fetal and neonatal circulation.
• Comparative evaluation of cardiovascular features between fetal, neonatal, and pediatric stages.
• Synthesis of clinical guidelines and pediatric cardiology resources.
Keywords
Pediatric cardiovascular system; fetal circulation; newborn circulation; foramen ovale; ductus arteriosus; heart development; hemodynamics in children.
Results
1. Anatomical Features of the Heart in Children
• Heart size: Larger relative to body weight (0.8% of body mass in newborns vs. 0.5% in adults).
• Position: Horizontally placed; apex at 4th intercostal space in infants.
• Right vs. Left ventricle: Right ventricle is dominant at birth due to high pulmonary vascular resistance in fetal life.
• Myocardium: Immature, with fewer contractile elements and lower compliance.
• Coronary circulation: Higher metabolic demand leads to increased coronary perfusion.
2. Features of Blood Vessels in Children
• Arteries: More elastic but thinner; systolic pressure lower in infants.
Capillaries: Dense network; facilitates high metabolic needs.
• Veins: Wider lumen; venous return depends heavily on respiration.
• Pulse: Higher heart rate due to low stroke volume.
3. Fetal Circulation
Key components include:
• Placenta: Primary organ for gas exchange.
• Ductus venosus: Shunts oxygenated blood from umbilical vein to inferior vena cava.
• Foramen ovale: Allows blood to flow from right to left atrium, bypassing lungs.
• Ductus arteriosus: Connects pulmonary artery to aorta, further bypassing lungs.
Blood flow favors delivery of the most oxygenated blood to the brain and heart.
4. Transitional Circulation in the Newborn
After birth:
• First breath reduces pulmonary resistance.
• Increased pulmonary blood flow raises left atrial pressure.
• Foramen ovale closes functionally within minutes.
• Ductus arteriosus constricts due to rising oxygen levels (anatomic closure ~1–2 weeks).
• Ductus venosus closes within a few days.
• Systemic vascular resistance increases as placental circulation ends.
5. Clinical Implications
• Higher heart rates and lower blood pressures are normal in infants.
• Delayed closure of fetal shunts may lead to congenital heart disorders (e.g., PDA, PFO).
• Immature myocardium leads to limited ability to increase stroke volume—children compensate via heart rate.
• Vulnerability to dehydration due to low blood volume.
Discussion
The cardiovascular system of children is uniquely adapted for rapid growth and metabolic demands. Fetal circulation prioritizes oxygen delivery through placental exchange and specialized shunts, while the newborn must rapidly adapt to pulmonary respiration. These transitions require coordinated structural and physiological changes.
Failure of these transitions can result in common neonatal cardiac conditions such as persistent pulmonary hypertension, patent ductus arteriosus, or atrial septal defects. Moreover, the differences in myocardial structure and vascular properties explain why clinical signs of cardiac disease often differ from adults, with tachycardia and feeding difficulties commonly preceding overt heart failure in infants.
Understanding these anatomical and physiological distinctions is essential for accurate diagnosis, interpretation of vital signs, and management of pediatric cardiovascular diseases.
References
1. Rudolph AM. Congenital Diseases of the Heart: Clinical-Physiological Considerations. 3rd ed. Wiley-Blackwell.
2. Kliegman RM, St. Geme JW. Nelson Textbook of Pediatrics. 21st ed. Elsevier.
3. Sadler TW. Langman’s Medical Embryology. 14th ed.
4. Moore KL, Persaud TV. The Developing Human: Clinically Oriented Embryology.
5. Anderson RH, Baker EJ. Paediatric Cardiology. Springer.
6. American Heart Association. Guidelines for Pediatric Cardiac Assessment.
