Cardiomyopathy

Cardiomyopathies are a group of diseases of the heart muscle (the myocardium) associated with abnormal muscle function or rhythm, and are usually associated with abnormal thickening or dilation of the heart’s ventricles. Many cardiomyopathies are influenced heavily by genetics, and some can run in the family. Some cardiomyopathies can lead to sudden death or heart failure-related disability.

Definition

Cardiomyopathies all reflect a defect in the mechanics of the heart muscle or in its electrical system responsible for rhythm. Usually there is thickening of the ventricles (hypertrophy) or an abnormal enlargement (dilatation). These changes in the heart result in difficulty pumping blood throughout the body and can lead to heart failure.

Classification

Traditionally, cardiomyopathies are grouped into three main categories, based on what is observed to happen to the heart muscle: 

• Dilated cardiomyopathies, in which the heart muscle becomes weak and the heart chambers enlarge.
• Hypertrophic cardiomyopathies (HCM), in which the heart muscle becomes thick, preventing blood from flowing from the heart.
• Restrictive cardiomyopathies, in which the heart muscle becomes abnormally stiff such that the chambers do not fill up properly.

More recently, in parallel with a better understanding of the genetic and nongenetic causes of cardiomyopathies, experts began to categorize cardiomyopathies differently: 

Primary cardiomyopathies, in which the disease mostly involves the heart muscle.

• Genetic (HCM, for example)
• Mixed (genetic and nongenetic causes)
• Acquired (cocaine, infections, drug reactions, stress, peripartum, for example)

Secondary cardiomyopathies, in which the disease involves many different organs, including the heart.

• Examples of secondary cardiomyopathies include those caused by diabetes and thyroid disorders

Symptoms

Many people with cardiomyopathy have no symptoms at first. Some individuals may experience a sudden worsening of symptoms while others may see a worsening of symptoms develop slowly overtime. The symptoms are those of heart failure. As cardiomyopathy progresses, symptoms of heart failure may become prevalent and can include: 

• Feelings of breathlessness when engaging in any activity or even when at rest
• The legs, ankles and feet may swell
• Fluid build-up in the stomach that causes bloating
• Fatigue
• Abnormal heartbeats, including fluttering, pounding or fast irregularities
• Fainting, dizzy spells or lightheadedness

Sudden cardiac death as the first sign of HCM in young athletes has lead to an increased awareness of this condition.

Causes

In many cases, the cause of cardiomyopathy is not known. In other cases, your doctor may be able to find a possible contributing factor to your cardiomyopathy. All causes of cardiomyopathy consist of primary and secondary cardiomyopathies, are too numerous to list, and and include the following: 

• Chronic rapid heart rate
• Diabetes
• Thyroid disease
• Nutritional deficiency
• Pregnancy
• Long-term alcoholism
• Drug abuse
• Abuse of some medications such as tricyclic antidepressants
• Viral infections of the heart
• Side effect of chemotherapy drugs
• Genetic conditions
• Hemochromatosis, a build-up of iron in the heart
• Amyloidosis
• Sarcoidosis
• Autoimmune disorders (lupus and rheumatoid arthritis, for example) 

The current scheme excludes coronary artery disease, valvular disease, and systemic hypertension as causes of true cardiomyopathy. That said the term “ischemic cardiomyopathy” is still in use, which can lead to some confusion. Many authorities still include long-term hypertension and atherosclerotic heart disease as causes of cardiomyopathy. 

Diagnostic Tests

In order to diagnose cardiomyopathy, your doctor will likely begin with a complete medical history and assessment of your symptoms and when they occur. If cardiomyopathy is suspected, your doctor will likely order a battery of diagnostic tests to confirm your diagnosis. These tests may include:

• X-ray of the chest to view any enlargement
• Echocardiography, which uses sound waves to produce moving images of the heart
• Electrocardiography, which evaluates the electrical workings of the heart and can identify any abnormalities in electrical impulses
• Cardiac catheterization, in which a catheter is threaded through the groin, arm or neck and into the heart to evaluate the arteries for blockage
• Myocardial biopsy, in which a sample is taken from the heart during cardiac catheterization to test for changes in cells of the heart muscle indicating cardiomyopathy
• Stress Test
• MRI of the heart
• Blood tests 

Treatment Options

Treatment of cardiomyopathy may not be necessary if there are no symptoms present. The goal of treatment of this condition is to control and suppress the symptoms. Treatment will be dependent upon the type of cardiomyopathy and the severity of symptoms. Treatment options may include: 

-Medications to manage heart failure (ACE inhibitors, ARBs, beta blockers)

-Antiarrhythmics, to help prevent arrhythmias

-Blood thinners, to prevent clots in people with dilated cardiomyopathies

-Corticosteroids in certain cases, to reduce inflammation

-Open heart surgery to repair thickening and encourage blood flow, when medications are not controlling symptoms in people with HCM

-Heart transplant for end-stage heart failure

-Non-surgical alcohol septal ablation (ASS), in which alcohol is injected through a small tube into the small artery that supplies blood to the thickened portion of the heart. The alcohol kills a select area of cells to minimize the thickened portion.

-Surgically implanted devices

• Pacemaker to control arrhythmias
• Cardiac resynchronization therapy (CRT) device to synchronize the left and right ventricles
• Left ventricular assist device (LVAD) to aid the heart in flowing blood through the body
• Implantable cardioverter-defibrillator (ICD) to sense dangerous arrhythmias and send an electric shock to the heart to correct these rhythms

Lifestyle Changes

In some cases, it may be possible to manage cardiomyopathy by taking better care of your heart and making a few changes: 

• Follow a heart-healthy diet that is low in sodium
• Maintain a healthy weight
• Lose excess weight
• Quit smoking
• Limit alcohol intake
• Avoid drug abuse
• Get an adequate amount of sleep
• Manage and reduce stress
• Exercise, after consulting your doctor and evaluating physical activity
• Manage any underlying medical conditions

Prevention

In many cases, cardiomyopathy cannot be prevented. It is important to make your doctor aware of your medical and family history and manage any underlying medical conditions that may contribute to the onset of cardiomyopathy. Screening may have a role in some cardiomyopathies. Though you may not be able to prevent cardiomyopathy, you may be able to reduce your risk of heart failure by adopting a heart-healthy lifestyle. 

Considerations

If you have been diagnosed with cardiomyopathy, it is essential to remain under a doctor’s care. If you are experiencing any new or worrisome symptoms report them to your doctor right away. New symptoms may be an indication that your condition is worsening. Be sure to follow all of your doctor’s orders and take all necessary medications, follow a heart-healthy regimen and manage any concurrent medical conditions.

Cardiomyopathy can lead to heart failure overt time. It is important to treat cardiomyopathy and be closely monitored by your doctor. If you suspect you may have cardiomyopathy or are experience any worrisome symptoms contact your doctor immediately.

Sources:

1. Maron BJ, Towbin JA, Thiene G, et al. Contemporary definitions and classification of the cardiomyopathies: an American Heart Association Scientific Statement from the Council on Clinical Cardiology, Heart Failure and Transplantation Committee; Quality of Care and Outcomes Research and Functional Genomics and Translational Biology Interdisciplinary Working Groups; and Council on Epidemiology and Prevention. Circulation. 2006;113(14):1807-1816. http://www.ncbi.nlm.nih.gov/pubmed/16567565.
2. MedlinePlus. Cardiomyopathy. http://www.nlm.nih.gov/medlineplus/ency/article/001105.htm. Accessed May 10, 2013.
3. National Heart, Lung and Blood Institute. Other names for cardiomyopathy. http://www.nhlbi.nih.gov/health/health-topics/topics/cm/names.html. Accessed May 10, 2013.
4. National Heart, Lung and Blood Institute. What is Cardiomyopathy? http://www.nhlbi.nih.gov/health/health-topics/topics/cm/. Accessed May 10, 2013.
5. Quarta G, Sado DM, Moon JC. Cardiomyopathies: focus on cardiovascular magnetic resonance. Br J Radiol. 2011;84 Spec No 3:S296-305. http://www.ncbi.nlm.nih.gov/pubmed/22723536/.
6. Sen-Chowdhry S, McKenna WJ. Sudden death from genetic and acquired cardiomyopathies. Circulation. 2012;125(12):1563-1576.

Medically reviewed by Tom Iarocci, MS, MD.

Last Updated May 17, 2013.