DNA Test for Long QT Syndrome

A new DNA test helps to clarify the diagnosis of long QT syndrome (LQTS), Brugada syndrome, and related cardiac ion-channel diseases in patients.

Called Familion, the test is the first commercially available, comprehensive genetic test for a heart-rhythm disorder. Instead of waiting six to 12 weeks or more for the results of tests conducted in a research setting, doctors can now obtain results in four to six weeks. The test was developed by Genaissance Pharmaceuticals, Inc. (New Haven, CT, USA).

The diagnosis of LQTS and other channelopathies by an electrocardiogram (ECG) is often difficult and may be missed, which leaves a patient at risk for sudden cardiac death. LQTS is a condition that impairs the electrical system of the heart. Symptoms may include fainting, seizures, abnormal and very fast heartbeats, and even sudden death. Some people with LQTS have a normal ECG at rest but experience abnormal responses under certain conditions, such as emotional distress or vigorous physical activities. Most of the deaths can be prevented with early diagnosis and treatment.

By examining five cardiac ion channel genes for a mutation, Familion helps to clarify the diagnosis in patients. If a genetic mutation is detected, its type and location can help the doctor to select treatment that could include life-style modification, prescription or avoidance of specific classes of drugs, or the implantation of a defibrillator.

The patient's family members also benefit from the test because it can detect if they inherited the same mutation as the patient and may be at risk of a potentially fatal arrhythmia. Relatives often have ambiguous findings on an ECG, while the results of Familion can answer whether or not they carry the familial mutation.

"This genetic test for cardiac ion channel mutations may remove uncertainty for the patients, their families, and their physicians with respect to establishing a diagnosis, and can guide the physician in determining the best treatment option,” said Michael Ackerman, M.D., Ph.D., director of the Long QT Syndrome Clinic and Sudden Death Genomics Laboratory at the Mayo Clinic (Rochester, MN, USA).




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