Cardiovascular System

Approximately 50% of all children have innocent heart murmurs. Screening and referral of children with murmurs assists in distinguishing between innocent and organic murmurs. Assessment of cardiac and vascular function is an essential component of many hospitalizations, particularly when surgery is performed and when drugs are administered. When cardiac problems have been identified, knowledgeable assessment aids in monitoring the effectiveness of treatment regimens and in early detection of complications.

The heart is a muscular four-chambered organ located in the mediastinum. The upper chambers of the heart are the atria; the lower chambers are the ventricles. Septa divide the two ventricles and the two atria. Four valves prevent the backflow of blood into the chambers. The tricuspid valve, located between the right atrium and ventricle, and the bicuspid, or mitral valve, located between the left atrium and ventricle, are the atrioventricular valves. The pulmonic valve, located in the pulmonary artery, and the aortic valve, in the aorta, are the semilunar valves. Closure of the four valves produces vibrations that are thought to be responsible for heart sounds. S₁ refers to the “lubb” sound produced by closure of the atrioventricular valves, and S₂ to the “dubb” sound produced by closure of the semilunar valves. Table 16-1 summarizes the various sounds and their characteristics.

In its initial stage of development the heart is a straight tube. Between the second and tenth weeks of gestation it undergoes a series of changes to become a four-chambered organ. The heart begins beating during the third week of gestation. During fetal life it primarily distributes the oxygen and nutrients that have been supplied through the placenta. The fetal lungs are largely bypassed by shunts that exist during fetal life. At birth these shunts begin to close as pulmonary vascular resistance drops. Pulmonary vascular resistance approximates adult levels by 6 weeks. Pulmonary vascular resistance is still relatively high in the first month of life, and cardiac defects such as ventricular septal defect might not be detected.

The heart is large in relation to body size in the infant. It lies somewhat horizontally and occupies a large portion of the thoracic cavity. Growth of the lungs causes the heart to assume a lower position, and by 7 years of age the heart has assumed an adult position that is more oblique and lower. Heart size increases in adolescence in conjunction with rapid growth.

At birth ventricular walls are similar in thickness, but with circulatory demands the left ventricle increases in thickness. The thinness of the ventricle produces a low systolic pressure in the newborn. The systolic pressure rises after birth until it approximates adult levels by puberty. Blood vessels lengthen and thicken in response to increased pressures.

The child can sit or lie. Allow the child to handle the stethoscope. Listening to the parent’s or nurse’s heart or to their own hearts is often effective in dispelling anxieties in young patients. Ask the parent or child about heart disease in family members. Inquire whether the child has had difficulty in feeding (infant), undue fatigue, intolerance for exercise, poor weight gain, weakness, cyanosis, edema, dizziness, epistaxis, squatting, frequent respiratory tract infections, or delayed development. Ask the parent whether the mother had any infection or took medications during pregnancy, age of mother at infant’s birth, and presence of maternal diabetes or alcohol use. Inquire whether the child had problems at birth, such as low birth weight, prematurity, congenital infection, or respiratory difficulty. Inquire about temperament of the child and family responses to illness.

Assessment	Findings
Inspection
Observe the child’s body posture.	Clinical Alert
	Squatting is seen in tetralogy of
	Fallot.
	Persistent slight hyperextension of the neck in infants can indicate hypoxia.
	Restlessness accompanied by abdominal pain, pallor, vomiting, unconsolable crying, and shock can indicate acute myocardial infarction in susceptible children.
Observe the child for cyanosis, mottling, and edema.	Clinical Alert
	Cyanosis, pallor, and mottling can indicate heart disease. Edema can indicate congestive heart failure. Edema of sacral and periorbital areas is more common in younger children.
	Edema of the extremities is more common in older children but in the younger child can more likely indicate renal failure.
	Cyanosis increases with crying in children with an atrioventricular canal defect and with some other cardiac defects.

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Assessment	Findings
Observe the child for signs of respiratory difficulty (grunting, costal retractions, flaring of the nares, adventitious chest sounds) and hacking cough.	Clinical Alert
	Respiratory difficulties and congested cough can indicate congestive heart failure or respiratory infection.
Inspect the child’s nailbeds for clubbing, lengthening, widening, and splinter hemorrhages (thin, black lines).	Clinical Alert
	Clubbing indicates hypoxia.
	Splinter hemorrhages indicate emboli and might indicate bacterial endocarditis.
	Symmetric chest expansion is normal.