Excerpt from Cardiomyopathy, Dilated

Synonyms, Key Words, and Related Terms: myocardiopathy, disease of the myocardium, heart disease, low cardiac output, cardiac failure, heart failure, congestive heart disease, CHD, congestive heart failure, CHF

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Background: Cardiomyopathy is a broad term that includes subacute or chronic disorders of the myocardium. It is also used to refer to a group of systemic diseases and processes that are toxic to or alter the myocardium. Cardiomyopathies are divided into 3 types (ie, dilated, hypertrophic, restrictive). Of these, dilated cardiomyopathy is the most common. Dilated cardiomyopathy represents a large subset of congestive heart failure (CHF) cases. These cases are differentiated logistically, but not necessarily physiologically, from those due to ischemic and hypertensive heart disease. For the purposes of this text, dilated cardiomyopathy will refer to the subset of congestive heart disease with systolic dysfunction not due to hypertension or ischemic heart disease.

Pathophysiology: The definition of dilated cardiomyopathy is complex and rests in its pathophysiology. Apoptosis, or programmed cell death, has been reported in clinical and experimental dilated cardiomyopathy, which is characterized by depressed systolic function or systolic pump failure, cardiomegaly, and ventricular dilatation. Reduced left ventricular contractile force leads to decreased cardiac output, resulting in increased residual volumes in end-systole and end-diastole.

Low cardiac output causes upregulation of the sympathetic nervous system and the renin-angiotensin axis, causing a release of vasopressin and atrial natriuretic peptide. Stimulation of these hormonal tracts results in volume expansion, which induces vasoconstriction and thus further decreases cardiac output. Treatment for this disorder attempts to break down this vicious cycle.

Frequency:

In the US: The incidence of CHF, which is largely dilated cardiomyopathy, is 400,000 cases per year. This disease afflicts 2-3 million people in the United States.

Mortality/Morbidity: The Framingham study found that 5 years after the initial presentation of CHF, 42% of women and 62% of men had died. Long-term survival was found to be inversely proportional to the severity of disease on initial diagnosis.

Hyponatremia at the time of presentation was found to be a marker of increased stimulation of the renin-angiotensin axis and of worsening of the disease course and prognosis.

Age: The elderly represent a large subsection of the population with this disease, and among them, it is the most common discharge diagnosis. Between 3% and 5% of the elderly have CHF.