Learn About Your Heart...
Made Simple

By Nicolas Shammas, MD

A new, comprehensive sourcebook for
heart and vascular disease patients

Cardiovascular Health Topics

Statistics about Heart and Blood Vessel Diseases in the United States
Structure and Function of the Heart and Blood Vessels
Diseases of the Blood Vessels of the Heart
Surgical Therapies for the Cardiovascular Patient
Peripheral Vascular Disease
Diseases of the Blood Vessels of the Head and Neck
Strokes: How to Survive Them and How to Prevent Them
Valvular Heart Disease
Heart Rhythms: How to Recognize Them and Treat Them
Congestive Heart Failure
11. Understanding Cardiomyopathy, or Weak Heart Muscle
12. Children and Heart Disease
13. Diseases of the Pericardium
14. Systemic Illnesses, Infections and Drugs that Affect the Heart
15. Erectile Dysfunction: a Vascular Disease
16. Cardiovascular Disease Prevention
17. Heart Healthy Nutritional Tips
18. Cardiac Rehabilitation
19. Medications for Cardiovascular Disorders
20. Heart Tests You Need to Know
21. Learn What to Do in a Medical Emergency
22. How to Choose Your Doctor and Hospital
23. Medical Research and How You Can Get Involved
24. Taking the Next Step — A Few Community Resources to Help You Live More Healthfully
25. How Much Did You Learn from This Book: Take a Simple Test


Peter J. Sharis, MD

What is cardiomyopathy ("weak heart muscle"), and how is it classified?

The cardiomyopathies are a group of diseases in which the primary feature is direct involvement and weakening of the heart muscle (myocardium only). Cardiomyopathies are increasing in incidence and are a significant cause of death. Dilated cardiomyopathy, the most common type of cardiomyopathy, is reported to occur in 5 to 8 people per 100,000 population per year.

Cardiomyopathies occur more frequently in blacks than whites and more commonly in men than women. Factors that are associated with increased death rates in cardiomyopathy patients include the following:

  • Weak heart function (left ventricular ejection fraction < 35%)

  • Aging (age greater than 55 years)

  • Reduced functional capacity

  • Electrical abnormalities

  • Low blood sodium level (hyponatremia)

  • Worsening kidney function.

Cardiomyopathy can be classified as primary, which is heart muscle disease of unknown cause, or secondary, which is heart muscle disease due to specific causes (such as narrowing of the heart arteries [coronary artery disease], heart valve disease, high blood pressure).

The World Health Organization (WHO) classifies cardiomyopathy into 3 major groups:

  • Dilated

  • Hypertrophic

  • Restrictive.

What are the features and causes of dilated cardiomyopathy (DCM)?

Dilated cardiomyopathy (DCM) is typically characterized by significant enlargement of the 2 pumping chambers of the heart—the left ventricle (which pumps blood to the body) and the right ventricle (which pumps blood to the lungs). As a result of the chamber enlargement, there is some degree of reduction in the pumping power of the ventricle (reduced ejection fraction).

While there are many causes of DCM (nearly 80 specific diseases have been associated with DCM), a clear cause is often not identified in many individuals, and these cases are described as idiopathic. Alcohol abuse is a common cause of DCM, as long-term ingestion leads to cardiac cell (myocyte) damage with subsequent heart dysfunction. Many patients can see significant improvement if they stop drinking. Cocaine abuse can lead to DCM in some individuals; in 1 large study, more than 10% of cocaine users had at least mild left ventricular dysfunction.

Infectious causes can also lead to DCM. Viral infections can attack the heart muscle and lead to significant cardiac dysfunction; in many cases, the damage can be irreversible and severe. In young adults, severe viral-related DCM is the top reason to be "listed" for heart transplantation. Human immunodeficiency virus (HIV), the cause of AIDS, can also lead to DCM in a minority of causes. Vitamin deficiencies (such as thiamine) can lead to DCM, though such cases occur more commonly in Third World countries.

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