Test for Genetic Mutations Linked to Sudden Cardiac Death

A new genetic test has been developed for cardiac channelopathies, a broad clinical category that includes long Q-T and Brugada syndromes, two causes of arrhythmia that can result in sudden cardiac death.

Called Familion, the test confirms the presence of mutations known to cause cardiac channelopathies, identifies family members who have similar mutations, and assists doctors in choosing the most appropriate course of treatment. The diagnosis of a cardiac channelopathy by an electrocardiogram (ECG) is often difficult and may be missed, leaving a patient at risk of sudden death.

The new test confirms the presence or absence of genetic mutations in five cardiac ion channel genes. Which gene is affected is important, both for clarifying the risk of death and for guiding treatment. For example, patients with a mutation in the LQT1 gene have the highest risk of having a cardiac event by the age of 40, while patients with a mutation in LQT3 have the lowest risk.

"The availability of this test will be of tremendous benefit to families and individuals who are or may be affected by one of these inherited causes of cardiac arrhythmias,” said G. Michael Vincent, M.D., professor of medicine, University of Utah (Salt Lake City, USA), and a founder of SADS (Sudden Arrhythmia Death Syndromes) Foundation.

Long Q-T syndrome (LQTS) is a condition that impairs the electrical system of the heart. Symptoms may include fainting, seizures, abnormal and very fast heartbeats, and even death. People with LQTS have a normal ECG at rest but experience abnormal responses under certain conditions. For example, these people may have an unusual response when startled, may experience emotional stress, or engage in rigorous physical activity. Brugada syndrome is very similar, but the ECG finding is different. Fainting is the most common symptom, and ventricular fibrillation can also occur.

The Familion test was developed by Genaissance Pharmaceuticals, Inc. (New Haven, CT, USA), which introduced the test at the Heart Rhythm Society's annual meeting in San Francisco (CA, USA) in May 2004.




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