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This chapter describes the phenotypic and clinical characteristics of the primary and secondary dilated cardiomyopathies (DCMs), the most common causes of the clinical syndrome of chronic heart failure.1 Heart failure is an enormously important clinical problem, which, if not contained or solved, may ultimately overwhelm health care resources.2 The clinical syndrome of heart failure is a complex process during which the primary pathophysiology is quickly obscured by a variety of superimposed secondary adaptive, maladaptive, and counterregulatory processes (see also Chap. 26). Heart failure is best understood and approached from the vantage point of myocardial failure, most commonly associated with a dilated cardiomyopathy (DCM) phenotype.3 As an indication of their importance, the cardiomyopathies have recently been reclassified by an expert consensus panel under the auspices of the American Heart Association (AHA)4 (see also Chap. 31).

Importance of Heart Failure

Because of its high prevalence (1%-1.5% of the adult population) and high morbidity, including frequent hospitalizations, the clinical syndrome of heart failure is among the most costly medical problems in the United States.2 Despite improvements in the treatment of heart failure introduced in the past 20 years, including the general availability of cardiac transplantation and better medical treatment, clinical outcome after the onset of symptoms has not changed substantially. The mortality remains high (median survival of 1.7 years for men and 3.2 years for women), the natural history progressive, the cost excessive, and disability and morbidity among the highest of any disease or disease syndrome.1,2,5

Relationship of Myocardial Failure and Dilated Cardiomyopathies to the Clinical Syndrome of Heart Failure

Most cases of heart failure are caused by heart muscle disease (cardiomyopathy). Within the classification of cardiomyopathies (Table 32–1),4,6 the most common cause of the clinical syndrome of heart failure is a secondary (ischemic, valvular, hypertensive, and so on) or a primary (genetic, nongenetic, acquired) DCM, defined as a ventricular chamber exhibiting increased diastolic and systolic volumes and a low (<45%) ejection fraction.7 The natural history of the clinical syndrome of heart failure depends on the course of myocardial failure because (1) the most powerful single predictor of outcome is the degree of left ventricular (LV) dysfunction as assessed by the LV ejection fraction8; (2) treatment that improves intrinsic ventricular function improves the natural history of heart failure3,9; and (3) treatment that ultimately worsens intrinsic function, such as many types of positive inotropic agents, is associated with an adverse effect on outcome.9

TABLE 32–1. The Classification of the Cardiomyopathies

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