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Explore the amazing journey of heart development in children, from embryology to postnatal changes and common defects. Learn about congenital heart conditions and their complications. Understand obstructive and mixed defects.
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Alterations of Cardiovascular Function in Children Chapter 31
Developmental Anatomy of the Cardiovascular System • Embryology • Cardiogenesis begins at approximately 3 weeks’ gestation • The heart arises from the mesenchyme • Develops as an enlarged blood vessel with a large lumen and muscular wall • Midsection grows faster than the ends • The heart tube elongates and rotates to the right, creating a bulboventricular loop • Fetal heart contractions begin by approximately the 28th day
Developmental Anatomy of the Cardiovascular System • Cardiac septation • Endocardial cushions • Septum primum and the septum secundum • Ostium primum • Ostium secundum • Foramen ovale • Ductus arteriosus
Transitional Circulation • Circulatory changes take place that affect blood flow, vascular resistance, and oxygen tension • Closure of fetal shunts • Ductus venosus • Foramen ovale • Ductus arteriosus
Postnatal Development • Changes in the position of the heart • Changes in the size of the right ventricle • Hemodynamics • Decreased pulmonary vascular resistance • Increased systemic vascular resistance • Heart rate ranges from 100 to 180 beats per minute • Newborns have a high oxygen demand
Congenital Heart Defects • Underlying cause is known in only 10% of defects • Prenatal, environmental, and genetic risk factors • Maternal rubella, insulin-dependent diabetes, alcoholism, PKU, and hypercalcemia • Drugs • Chromosome aberrations
Complications of Congenital Heart Defects • Congestive heart failure • Hypoxemia • Cyanosis • Eisenmenger syndrome
Defects Increasing Pulmonary Blood Flow • Patent ductus arteriosus (PDA) • Failure of the ductus arteriosus to close • PDA allows blood to shunt from the pulmonary artery to the aorta
Defects Increasing Pulmonary Blood Flow • Atrial septal defect • Abnormal communication between the atria • Three major types • Ostium primum defect • Ostium secundum defect • Sinus venosus defect
Defects Increasing Pulmonary Blood Flow • Ventricular septal defect (VSD) • Abnormal communication between the ventricles • Most common type of congenital heart lesion • Types • Perimembranous VSD • Muscular VSD • Supracristal VSD • AV canal VSD
Defects Increasing Pulmonary Blood Flow • Atrioventricular canal defect (AVC) • Results from nonfusion of the endocardial cushions • Demonstrates abnormalities in the atrial and ventricular septa and atrioventricular valves • Complete, partial, and transitional AVCs
Defects Decreasing Pulmonary Blood Flow • Tetralogy of Fallot • Syndrome represented by four defects • Ventricular septal defect (VSD) • Overriding aorta straddles the VSD • Pulmonary valve stenosis • Right ventricle hypertrophy
Defects Decreasing Pulmonary Blood Flow • Tricuspid atresia • Imperforate tricuspid valve • Lack of communication between the right atrium and right ventricle • Additional defects • Septal defect • Hypoplastic or absent right ventricle • Enlarged mitral valve and left ventricle • Pulmonic stenosis
Obstructive Defects • Coarctation of the aorta • Narrowing of the lumen of the aorta that impedes blood flow • Coarctation of the aorta is almost always in a juxtaductal position, but it can occur anywhere between the origin of the aortic arch and the bifurcation of the aorta in the lower abdomen
Obstructive Defects • Aortic stenosis • Narrowing of the aortic outflow tract • Caused by malformation or fusion of the cusps • Causes an increased workload on the left ventricle
Obstructive Defects • Pulmonary stenosis • Narrowing of the pulmonary outflow tract • Abnormal thickening of the valve leaflets • Narrowing of the valve • Pulmonary semilunar valve atresia
Obstructive Defects • Hypoplastic left heart syndrome • Abnormal development of the left-sided cardiac structures • Obstruction to blood flow from the left ventricular outflow tract • Under development of the left ventricle, aorta and aortic arch, and mitral atresia or stenosis
Mixed Defects • Transposition of the great arteries • Aorta arises from the right ventricle and the pulmonary artery arises from the left ventricle • Results in two separate, parallel circuits • Unoxygenated blood circulates continuously through the systemic circulation • Oxygenated blood circulates continuously through the pulmonary circulation • Extrauterine survival requires communication between the two circuits
Mixed Defects • Total anomalous pulmonary venous connection (TAPVC) • Pulmonary veins connect to the right side of the heart, directly or indirectly through one or more systemic veins that drain into the right atrium
Mixed Defects • Truncus arteriosus • Failure of the embryonic artery and the truncus arteriosus to divide into the pulmonary artery and the aorta • The trunk straddles an always present VSD
Acquired Cardiovascular Disorders • Kawasaki disease • Also known as mucocutaneous lymph node syndrome • Acute, self-limiting systemic vasculitis that may result in cardiac sequelae
Kawasaki Disease • Stages • One (0-12 days): capillaries, venules, arterioles, and the heart become inflamed • Two (12-35 days): inflammation of larger vessels; coronary aneurysms appear • Three (26-40 days): medium-sized arteries begin granulation process; small vessel inflammation decreases • Four (day 40 and beyond): scarring of vessels, thickening of tunica intima, calcification, coronary artery stenosis
Kawasaki Disease • Diagnosis (5 of 6 major findings) • Fever for 5 or more days (unresponsive to antibiotics) • Bilateral conjunctivitis without exudation • Erythema of oral mucosa (strawberry tongue) • Changes in the extremities, such as peripheral edema and erythema with desquamation of palms and soles • Polymorphous rash • Cervical lymphadenopathy
Acquired Cardiovascular Disorders • Systemic hypertension • Hypertension in children differs from adult hypertension • Often have an underlying disease • Renal disease or coarctation of the aorta • A cause of the hypertension in children is almost always found • Children with hypertension are commonly asymptomatic
Acquired Cardiovascular Disorders • Childhood obesity • Multivariable and multidimensional • Risk factors • Race, socioeconomic status, and lack of health insurance • Childhood nutrition, level of physical activity, and engagement of sedentary activities (TV, computer use, etc.) • Association with parental obesity