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U N I T 5
Circulatory Function
Heart Disease in Infants
and Children
Heart disease in children encompasses both congeni-
tal and acquired disorders. Approximately 1 of every
125 infants born has a congenital heart defect, making
this the most common form of structural birth defect.
61
Advances in diagnostic methods and surgical treatment
have greatly increased the long-term survival and posi-
tive outcomes for children born with congenital heart
defects. Although thousands of infants born each year
will have a congenital heart disease, other children will
develop an acquired heart disease, such as Kawasaki dis-
ease. Other acquired disorders that affect children, the
cardiomyopathies and rheumatic fever, were discussed
earlier in the chapter.
Fetal and Perinatal Circulation
The fetal circulation is different anatomically and physi-
ologically from the postnatal circulation. Before birth,
oxygenation of blood occurs through the placenta; after
birth it occurs through the lungs. The fetus is main-
tained in a low-oxygen state (PO
2
30 to 35 mm Hg;
hemoglobin O
2
saturation 60% to 70%). To compen-
sate, fetal cardiac output is higher than at any other time
in life (400 to 500 mL/kg/minute) and fetal hemoglobin
has a higher affinity for oxygen.
62
Also, the pulmonary
vessels in the fetus are markedly constricted because of
the fluid-filled lungs and the heightened hypoxic stim-
ulus for vasoconstriction that is present in the fetus.
CHART 19-2
Conditions Associated with Secondary
Cardiomyopathies*
Autoimmune Disorders
Systemic lupus erythematosus
Rheumatoid arthritis
Scleroderma
Polyarteritis nodosa
Endocrine Disorders
Acromegaly
Diabetes mellitus
Hypothyroidism and hyperthyroidism
Hyperparathyroidism
Familial Storage Diseases
Glycogen storage disease
Mucopolysaccharidoses
Hemochromatosis
Infiltrative Disorders
Amyloidosis
Sarcoidosis
Radiation-induced fibrosis
Neuromuscular/Neurologic Disorders
Friedreich ataxia
Muscular dystrophy
Neurofibromatosis
Nutritional Deficiencies
Thiamine (beriberi)
Protein (kwashiorkor)
Toxins
Alcohol and its metabolites
Arsenic
Chemotherapeutic agents (anthracyclines [doxorubicin,
daunorubicin], cyclophosphamide)
Catecholamines
Hydrocarbons
*Not intended to be inclusive.
SUMMARY CONCEPTS
■■
The cardiomyopathies, which involve both
mechanical and electrical etiologies of myocardial
dysfunction, are classified as either primary or
secondary based on whether they are confined
to the myocardium or are associated with other
disease conditions. Symptoms related to most
cardiomyopathies, whether primary or secondary,
are those associated with heart failure and
sudden cardiac death.Treatment focuses on
symptom management and prevention of lethal
arrhythmias.
■■
The primary cardiomyopathies include
genetic, mixed, or acquired types. The genetic
cardiomyopathies include hypertrophic
cardiomyopathy and arrhythmogenic
right ventricular dysplasia. The mixed
cardiomyopathies, which include dilated
and restrictive cardiomyopathies, are of
both genetic and acquired origin. Acquired
cardiomyopathies include those that have
their origin in the inflammatory process
(e.g., myocarditis), stress (takotsubo
cardiomyopathy), or pregnancy (peripartum
cardiomyopathy). In many cases the cause is
unknown, in which case it is referred to as an
idiopathic cardiomyopathy.
■■
The secondary cardiomyopathies are heart
diseases in which myocardial involvement occurs
as part of a multisystem disorder.They include
cardiomyopathies associated with drugs, diabetes
mellitus, muscular dystrophy, autoimmune
disorders, and cancer treatment agents (radiation
and chemotherapeutic drugs).
