What are cardiac arrhythmias?
Cardiac arrhythmias are disturbances in the heart's natural rhythm. These disturbances are caused by disruptions in the normal conduction of electrical signals within the heart. For various reasons, electrical signals may be detoured, slowed, or blocked while traveling through certain parts of the heart. This can cause the heart's natural rhythm to speed up or slow down, affecting the flow of blood to the body's internal organs. There are many different types of arrhythmias.

What Causes Arrhythmias?
There are many known causes of arrhythmias, including scars in the heart muscle from a previous myocardial infarction (heart attack), lack of blood to the heart muscle from atherosclerosis, abnormalities in the electrical conduction system, or extra electrical connections within the heart. Other known causes include abnormalities in the heart's muscle or electrical system and the effects of certain medications.

The underlying mechanisms of certain arrhythmias remain unresolved. For example, inherited disorders can contribute to the onset of arrhythmias in several ways. First, single gene mutations may be directly responsible for the abnormality that causes the arrhythmia, such as in Long QT Syndrome. Second, inherited structural abnormalities may cause arrhythmias, such as in familial Hypertrophic Cardiomyopathy or familial mitral valve prolapse. Finally, certain inherited disorders may lead to premature coronary artery disease or cardiomyopathy, which may cause arrhythmias.

What are some common symptoms of arrhythmias?
Depending on the type of arrhythmia, the symptoms will vary. Some arrhythmias may be brief, lasting only a few moments, and others may be longer, causing sustained episodes. Arrhythmias may cause the heart to pump less effectively and may cause dizziness, chest discomfort, shortness of breath, or loss of consciousness. While many arrhythmias are not life-threatening, the most dangerous types can lead to sudden cardiac death. Although the severity of the symptoms is usually related to the seriousness of the arrhythmia, there are situations in which symptoms have not occurred but the potential for serious arrhythmias still exists.

What is being done to study arrhythmias?
Significant breakthroughs have occurred in the past several years that have greatly increased the understanding of the genetic basis of certain forms of sudden cardiac death. These breakthroughs form the foundation on which new testing techniques and treatments are being made available.

Inherited rhythm disorders, such as Long QT Syndrome, Hypertrophic Cardiomyopathy and Brugada Syndrome, are known as autosomal dominant genetic variations, which means that the child of a person with the gene for one of those disorders has a 50:50 chance of inheriting the same genetic mutation.

Talk to your doctor regarding the feasibility of genetic testing for inherited rhythm disorders. At this time, commercially available genetic tests exist for Long QT Syndrome and Brugada Syndrome (visit www.familion.com), and Hypertrophic Cardiomyopathy (visit www.hpcgg.org).

Where can I learn more about arrhythmias?
The best person to talk to is a board-certified cardiologist or electrophysiologist. These specialists can evaluate symptoms and family histories and make recommendations based on their findings. You can also obtain additional information about arrhythmias by visiting the C.A.R.E. Foundation website at www.longqt.org or by calling C.A.R.E. at 800-404-9500.