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Cardiomyopathy (cont.)

Cardiomyopathy Causes

There are many causes of cardiomyopathy that can be categorized in several ways. One method of defining cardiomyopathy is based on the official definition by the American Heart Association (see below), which are broken into two categories, primary and secondary. Another method of categorizing cardiomyopathy causes are extrinsic and intrinsic (which are more commonly used when discussing the disease with patients, family, and caregivers) and are discussed later in this article.

The official definition of cardiomyopathy of the American Heart Association in 2006 is as follows:

"Cardiomyopathies are a heterogeneous group of diseases of the myocardium associated with mechanical and/or electrical dysfunction that usually (but not invariably) exhibit inappropriate ventricular hypertrophy or dilatation and are due to a variety of causes that frequently are genetic. Cardiomyopathies either are confined to the heart or are part of generalized systemic disorders, which may lead to cardiovascular death or progressive heart failure-related disability."

The definition divides heart disease into 1.) primary cardiomyopathies, those that usually affect the heart alone (primary) and 2.) secondary cardiomyopathies, those that are a result of an underlying condition affecting many areas of the body. The primary cardiomyopathies are further divided into inherited (genetic) diseases, those that are acquired, and those that are a combination of both.

Some causes are listed below of primary and secondary cardiomyopathies are listed below.

Primary cardiomyopathy

  • Genetic
    • hypertrophic cardiomyopathy
    • Ion conduction abnormalities
      • prolonged QT syndrome
      • Brugada syndrome
  • Mixed
    • dilated cardiomyopathy
    • restrictive cardiomyopathy
  • Acquired
    • inflammatory myocarditis
    • peripartum
    • physically and physiologically stress induced (tako-tsubo syndrome or "broken heart syndrome")

Secondary cardiomyopathies

As previously mentioned, another method of categorizing cardiomyopathy causes are extrinsic and intrinsic (which are more commonly used when discussing the disease with patients, family, and caregivers). Extrinsic and intrinsic causes of cardiomyopathies are discussed below.

  • Extrinsic cardiomyopathies: Extrinsic cardiomyopathies are those that are due to diseases that are not uniquely due to heart muscle cell abnormalities
  • Intrinsic cardiomyopathies: Intrinsic cardiomyopathies are due to abnormalities that originate in the heart muscle cell.

Extrinsic cardiomyopathies

Examples of extrinsic cardiomyopathies include:

  • Ischemic cardiomyopathy is a disease of heart muscle due to inadequate blood supply to heart muscle and is a common cause of cardiomyopathy. When blood vessels to heart muscle become blocked, heart muscle cells can be deprived of oxygen and fail to function normally. An example of this is aheart attack, where a complete blockage of a blood vessel causes muscle cells to die, decreases the total amount of muscle that can contract and cardiac output is compromised.
  • Poorly controlled high blood pressure (hypertension) can lead to abnormally functioning heart muscle.
  • Diabetes
  • Alcohol abuse

Intrinsic cardiomyopathies

Examples of extrinsic cardiomyopathies include:

  • Amyloidosis can infiltrate heart cells with amyloid protein.
  • Sarcoidosis can cause heart cell inflammation.
  • Viral infections may cause inflammation of heart muscle (myocarditis) with temporary or potentially permanent damage to heart muscles cells leading to a secondary cardiomyopathy.
  • Dilated cardiomyopathies occur when the heart muscle fibers are abnormally stretched when the heart chambers increase in size and volume. The stretched muscles lose their ability to contract strongly, similar to a slinky or an elastic band that has been overstretched and loses its shape and function. As the heart walls continue to stretch, they can also cause damage to the heart valves between the chambers of the heart causing blood to regurgitate or backwash, and as a result there is decreased cardiac output and heart failure. There are many causes of dilated cardiomyopathy including:
    • infection,
    • alcohol,
    • cancer therapies,
    • chemical poisonings (for example, lead and arsenic),
    • neuromuscular disorders such as muscular dystrophy, and
    • a variety of genetic diseases.
  • Hypertrophic cardiomyopathy is a genetic or familial disease where muscle in the left ventricle has a predisposition to thicken and prevent normal flow of blood out of the heart. Hypertrophic cardiomyopathy is the most common cause of sudden death in young people, such as exercising athletes.
  • Peripartum cardiomyopathy is seen late in the third trimester of pregnancy, though it can continue to be a potential cause of cardiomyopathy for five months post-partum. It is more common in obese older pregnant women who develop preeclampsia.
Medically Reviewed by a Doctor on 5/28/2014

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