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Cardiomyopathy overview

Published: June 19, 2009. Updated: July 29, 2009

Cardiomyopathy is the deterioration of the cardiac muscle of the heart wall. Cardiomyopathies can generally be categorized into two groups: ischemic cardiomyopathy and nonischemic cardiomyopathy.

Causes

Ischemic cardiomyopathy is weakness in the muscle of the heart due to coronary artery disease. Individuals with ischemic cardiomyopathy typically have a history of myocardial infarction (heart attack).

Nonischemic cardiomyopathy is weakness in the muscle of the heart that is not due to coronary artery disease. To make a diagnosis of nonischemic cardiomyopathy, significant coronary artery disease should be ruled out. The term nonischemic cardiomyopathy does not describe the etiology of weakened heart muscle. The nonischemic cardiomyopathies are a mixed-bag of disease states, each with their own causes.

Nonischemic cardiomyopathy has a number of causes including drug and alcohol toxicity, certain infections, and various genetic and idiopathic (i.e. unknown) causes.

There are four main types of nonischemic cardiomyopathy:

  • Dilated cardiomyopathy (DCM)
  • Hypertrophic cardiomyopathy (HCM or HOCM)
  • Restrictive cardiomyopathy (RCM)

Cardiomyopathy can lead to heart failure as the pumping efficiency of the heart is diminished. People with cardiomyopathy are often at risk of arrhythmia and/or sudden cardiac death.

Dilated cardiomyopathy (DCM) is the commonest form of cardiomyopathy, and one of the leading indications for heart transplantation. In DCM the heart (especially the left ventricle) is enlarged and weakened. Approximately 40% of cases are familial, but the genetics are poorly understood compared with HCM. Patients receiving anthracycline therapy (e.g. doxorubicin) are at risk of developing dilated CM if they receive more than a total cummulative dose during their life-time.

Hypertrophic cardiomyopathy (HCM) is a genetic disorder caused by various mutations in genes encoding sarcomeric proteins. In HCM the heart muscle is thickened, which can obstruct blood flow and prevent the heart from functioning properly.

Restrictive cardiomyopathy (RCM) is the least common cardiomyopathy. The walls of the ventricles are stiff, but may not be thickened, and resist the normal filling of the heart with blood.


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