Alternative Names
Cardiac ion channelopathies; sudden arrhythmia death syndromes
Symptoms & Characteristics
Cardiac channelopathies are genetic diseases characterized by abnormalities in the function of ion channels on the surface of heart muscle cells. Cardiac channelopathies include long QT syndrome (LQTS), short QT syndrome, Brugada syndrome (also known as Sudden Unexpected Death Syndrome) and Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT). Romano-Ward syndrome and Jervell and Lange-Nielsen syndrome are subtypes of LQTS.
Symptoms are limited, and sometimes, include episodes of fainting. These conditions can lead to potentially lethal heart arrhythmias (disruptions of the heart's normal rhythm) and sudden cardiac death. Many patients with cardiac channelopathies have abnormal electrocardiograms (ECGs). Congenital deafness is associated with the Jervell and Lange-Nielsen syndrome subtype of LQTS.
Treatment
Beta receptor blocking medications are the first line treatment for LQTS to reduce the risk of dangerous arrhythmias. A medication that blocks the sodium ion channel is believed to prevent arrhythmias in one subtype of LQTS.
Beta blockers and one calcium channel blocker may be used to treat CPVT.
Medications have not been shown to be effective in treating short QT syndrome or Brugada syndrome.
Patients with cardiac channelopathies who are at high risk for sudden death may be treated with an implantable cardioverter-defibrillator (ICD).
If someone notices or experiences any of the signs or symptoms common to cardiac channelopathies, it is important to see a doctor.
How Common Is It?
Cardiac channelopathies are rare conditions, and the exact frequency in the population is not known.
- LQTS has been estimated to affect 1 in 5,000 people.
- Brugada syndrome has recently been recognized as more common than originally thought. This syndrome may cause sudden death in 5-10 per 10,000 people. In Asia, especially Thailand and Laos, Brugada syndrome is believed to be the most common cause of sudden death in men under age 50.
Genetics & Inheritance
The cardiac channelopathies can be caused by mutations in different genes and can have different patterns of inheritance.
LQTS can be inherited in an autosomal dominant or an autosomal recessive manner.
- At least 12 subtypes of LQTS have been classified based on which gene is involved.
Genetic testing can help identify the specific subtype. Treatment may be based on subtype and severity of symptoms. Once the gene has been identified in one family member, other family members can be identified who are at risk for developing LQTS.
Short QT syndrome appears to be inherited in an autosomal dominant pattern. Mutations have been found in some of the same genes responsible for LQTS.
Brugada syndrome is inherited in an autosomal dominant pattern. Many of the identified mutations are in a sodium channel gene, but several other genes have also been associated with this disorder. Other yet to be identified genes are also likely to cause Brugada syndrome. In some cases, certain drugs may cause a nongenetic (acquired) form of the disorder.
CPVT is inherited in an autosomal dominant or an autosomal recessive manner depending on which gene, RYR2 or CASQ2, is involved.
Genetic Testing
Clinical genetic testing for some of the cardiac channelopathies may be available through an in person genetic consultation for people who are considered at risk. Use our find a genetic professional directory to locate a trained genetic professional in your area.
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