CHAPTER SUMMARY AND CENTRAL ILLUSTRATION
This chapter summarizes the pathogenesis, diagnosis, and management of dilated cardiomyopathy (DCM). The term DCM covers a wide spectrum of heart muscle disease phenotypes characterized by dilatation and systolic impairment of the left or both ventricles unexplained by abnormal loading conditions (such as hypertensive, diabetic, valvular, or congenital heart disease) or coronary artery disease sufficient to induce the observed phenotype (see Fuster and Hurst’s Central Illustration). The causes of DCM are heterogeneous; genetic in up to 50% (familial DCM), autoimmune/immune-mediated and inflammatory (usually postmyocarditic), and, less commonly, cardiotoxicity (anticancer drugs, alcohol abuse, and cirrhosis). DCM is diagnosed by clinical presentation and morphofunctional echocardiographic and magnetic resonance imaging. Tissue diagnosis is needed for inflammatory cardiomyopathies. The genetic diagnosis is based on testing of genes coding for proteins of the sarcomere, nuclear lamina, intermediate filaments, sarcolemma, sarcoplasmic reticulum and Golgi, desmosomes, and mitochondria. Familial DCM is considered when two or more family members are affected, and diagnosed by family history, clinical screening of relatives, and cascade genetic testing. Early diagnosis in relatives can be framed in the context of nondilated hypokinetic cardiomyopathy based upon the recommended major or minor criteria.
eFig 41-01 Chapter 41: Dilated Cardiomyopathy
DILATED CARDIOMYOPATHY: DEFINITION
In 2006, the American Heart Association (AHA) defined dilated forms of cardiomyopathy as “characterized by ventricular chamber enlargement and systolic dysfunction with normal left ventricular (LV) wall thickness.”1 In 2008, the European Society of Cardiology (ESC) defined dilated cardiomyopathy (DCM) as a chronic heart muscle disease characterized by “the presence of dilatation and systolic impairment of the left or both ventricles unexplained by abnormal loading conditions or coronary artery disease sufficient to cause the observed myocardial dilation and dysfunction.”2 In 2016, a position statement of the ESC working group on myocardial and pericardial diseases proposed the definition of hypokinetic nondilated cardiomyopathy (HNDC), and its implications for clinical practice to bridge the gap between recent understanding of the disease spectrum and its clinical presentation in relatives.3 The last universal definition and classification of heart failure (HF) distinguished HF from cardiomyopathy: “HF is a clinical syndrome with different etiologies and pathophysiology rather than a specific disease.” ‘Cardiomyopathy’ is a term, itself with widely differing definitions, that describes features of structural and functional heart muscle dysfunction.”4
In this chapter, DCM is intended as a disease of heart muscle defined by structural (dilation) and functional (systolic dysfunction) descriptors. DCM is proven to be familial with identifiable genetic defects in more than 50% of cases.5 Acquired disorders manifesting with the DCM phenotype, or DCM phenocopies (defined as environmentally induced phenotypes mimicking one usually produced by a specific genotype) are sporadic and are categorized as nongenetic DCM. This distinction is essential to separate heritable nonreversible DCM from acquired, nongenetic, and potentially reversible phenotypes arising from ...