Porth's Essentials of Pathophysiology, 4e

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Circulatory Function

U N I T 5

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

 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. ■■ 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).

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.