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Key Points

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  • Disease summary:

    • Dilated cardiomyopathy (DCM) is characterized by left ventricular (LV) enlargement and systolic dysfunction.

    • The prevalence of DCM is 1 in 2700, however, this is undoubtedly an underestimate.

    • Histologic findings include myocyte hypertrophy, myocyte loss, and interstitial fibrosis.

    • Approximately 35% of DCM cases are deemed idiopathic dilated cardiomyopathy (IDC) after detectable causes have been excluded (Fig. 24-1).

    • 20% to 50% of IDC may be found in one or more family members, and if so, is termed familial dilated cardiomyopathy (FDC). Of these cases, approximately 20% to 25% have identifiable genetic mutations correlating with disease phenotype.

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  • Hereditary basis:

    • A majority of heritable DCM is nonsyndromic disease isolated to the heart and can be divided into two subsets:

      • FDC, as defined above.

      • IDC with a known genetic mutation but no known familial penetrance. Because of the availability of genetic testing, some patients with IDC are sent for testing and have positive results.

    • Less commonly, heritable DCM can occur as part of a genetic syndrome; causes from autosomal and X-linked genes are shown (Table 24-1).

    • Differential diagnosis:

      • Differential includes all detectable causes of dilated cardiomyopathy: ischemic, congenital, primary valvular, toxin-induced, metabolic abnormalities, and infectious (Fig. 24-1).

      Table Graphic Jump Location
      Table 24-1Syndromic Dilated Cardiomyopathy

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Diagnostic Criteria and Clinical Characteristics

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Diagnostic Criteria, DCM

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  • Fractional shortening less than 25% (>2 SD) and/or ejection fraction less than 45% (>2 SD)

  • LV enlargement

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Diagnostic Criteria Compatible With IDC

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  • DCM with no evidence of a detectable cause (Fig. 24-1).

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Figure 24-1

Diagnostic Algorithm for Dilated Cardiomyopathy (DCM).

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