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KEY POINTS
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Key Points

  • Generally classified as dilated or hypertrophic cardiomyopathy.

  • Incidence is 1.2 per 100,000. Higher in males due to X-linked conditions.

  • Most common causes of hypertrophic cardiomyopathy are maternal diabetes, twin–twin transfusion, Noonan syndrome, inborn error of metabolism, and familial single-gene disorder.

  • Most common causes of dilated cardiomyopathy are infection, endocardial fibroelastosis, dysrhythmia, carnitine deficiency, and familial single-gene disorder.

  • Associated with high incidence of antenatal cardiac dysfunction and in utero mortality (except if due to maternal diabetes).

  • Twenty percent of cases are familial. Obtain a family history and consider evaluating both parents.

  • As many as 40% of cases require postnatal heart transplant.

  • Increasing numbers of causative mutations in genes for sarcomeric and cytoskeletal proteins have been identified. Most are inherited as autosomal dominant disorders with variable penetrance.

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CONDITION
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Cardiomyopathy refers to cardiac hypertrophy manifested by an increased interventricular septal size and/or free ventricular wall size in the absence of an increased cardiac load, accompanied by decreased cardiac function and by ventricular dilation (Michels et al., 1992). More broadly, cardiomyopathy is defined as a disease of the myocardium characterized by the presence of systolic or diastolic dysfunction or abnormal myocardial structure (Schwartz et al., 1996). The condition is rarely observed during fetal life. Cardiomyopathy is generally classified as dilated or hypertrophic.

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INCIDENCE
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The incidence of fetal cardiomyopathy is not precisely known, but it is rare. In one study, dilated cardiomyopathy was present in approximately 2% of fetal cardiac abnormalities (Sivasankaran et al., 2005).

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Relatively recently, two large-scale population-based cohort studies of cardiomyopathy in children were published. One was performed in Australia (Nugent et al., 2003) and one involved American children in New England and the Central Southwest (Lipshultz et al., 2003). In the Australian study, the incidence of cardiomyopathy was 1.24 per 100,000. Of these, 58.6% had dilated cardiomyopathy, 25.5% had hypertrophic cardiomyopathy, 9.2% had cardiomyopathy due to noncompaction of the left ventricle, and 2.5% of cases were restrictive. There was a large familial component (19.8% of cases). Indigenous children had a 2.67-fold relative risk of having the disease compared to nonindigenous children. The American study showed a similar incidence (1.13 per 100,000) and identified a peak incidence in the first year of life. In this study, 51% of cases were due to dilated cardiomyopathy, 42% to hypertrophic, 3% to restrictive, and 4% to unspecified. The American study noted a higher incidence in black children. Both studies documented a higher incidence in males, presumably due to the X-linked conditions that are associated with cardiomyopathy, such as Duchenne, Becker, and Barth syndromes.

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SONOGRAPHIC FINDINGS
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Relatively few reports of the prenatal diagnosis of fetal cardiomyopathy exist. One of the most comprehensive encompasses a 9-year retrospective review of fetuses studied in the Fetal Cardiac Program at the Hospital for Sick Children ...

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