24: Dilated Cardiomyopathy

Key Points

• 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.

• 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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    Table 24-1 Syndromic Dilated Cardiomyopathy

    Syndrome	Gene Symbol	Gene Product	Inheritance Patterna	Additional Clinical Features
    Emery-Dreifuss muscular dystrophy types 2 and 3 (EDMD2 and EDMD3), limb girdle muscular dystrophy (LGMD1B)	LMNA	Lamin A/C	EMD 2: AD EMD3: AR LGMD1B: AD	Joint contractures (more severe in EDMD), arrhythmias, childhood muscle weakness (shoulder or hip girdle in LGMD1B)
    Hemochromatosis	HFE	Hereditary hemochromatosis	AR	Cirrhosis, diabetes, hypermelanotic pigmentation, increased serum iron and ferritin
    Laing distal myopathy	MYH7	Beta-myosin heavy chain	AD	Childhood-onset weakness of ankles and great toes, then finger extensors. Neck flexors and facial weakness
    Duchenne muscular dystrophy (DMD), Becker muscular dystrophy (BMD)	DMD	Dystrophin	XL	DMD: males: elevated CK, childhood muscle weakness, wheelchair bound by age 12, DCM after age 18; BMD: elevated CK, skeletal muscle weakness in 20s or lager; females can be affected with milder phenotype or DCM alone
    Barth syndrome	TAZ/G4.5	Tafazzin	XL	Growth retardation, intermittent lactic academia, granulocytopenia, recurrent infections

    ^aAD, autosomal dominant; AR, autosomal recessive; XL, X-linked; CK, creatine kinase.

    Adapted from Hershberger RE, Cowan J, Morales A, Siegfried JD. Progress with genetic cardiomyopathies: screening, counseling, and testing in dilated, hypertrophic, and arrhythmogenic right ventricular dysplasia/cardiomyopathy. Circ Heart Fail. 2009;2:253-261.

Diagnostic Criteria and Clinical Characteristics

Diagnostic Criteria, DCM

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

• LV enlargement

Diagnostic Criteria Compatible With IDC

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