The spectrum of symptoms and QT intervals in carriers of the gene for the long-QT syndrome

Article Abstract:

Measuring the QTc interval, or heart rate, may not be an effective method for diagnosing individuals with long-QT syndrome, but genetic markers for the long-QT gene may aid diagnosis. The long-QT syndrome is a genetic disorder that is characterized by recurrent fainting and sudden death from ventricular arrhythmia. Of 199 individuals from families with the long-QT syndrome, 83 were carriers of the long-QT gene and 116 were not. Among the individuals who were carriers of the long-QT gene, 52 (63%) had experienced at least one fainting episode and four (5%) had nearly died from ventricular arrhythmia. The QTc interval of carrier of the long-QT gene was often longer than that of non-carriers, but the QTc interval of 63% of the family members overlapped. Twenty-two individuals (11%) were misdiagnosed with long-QT syndrome or failed to be diagnosed based on the length of their QTc interval.

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Molecular genetics and ventricular arrhythmias

Article Abstract:

Long-QT syndrome is a genetic disorder characterized by recurrent fainting and sudden death from ventricular arrhythmia. It was first described in 1957 in four siblings who were born deaf, experienced recurrent fainting episodes and had a prolonged QTc interval, or heart rate, on an electrocardiogram. Three of these children later died suddenly. Since 1957, approximately 400 families with long-QT syndrome have been documented. Understanding inheritance of a long-QT syndrome is aided by identifying symptoms or abnormalities associated with the disease. Patients with long-QT syndrome usually have a prolonged QTc interval, but the QTc interval may be difficult to measure accurately in many patients. A genetic marker for the long-QT gene was identified in 1991. Individuals with this marker do not necessarily have a prolonged QT interval.

Editorial

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Molecular basis of the long-QT syndrome associated with deafness

Article Abstract:

The Jervell and Lange-Nielsen syndrome appears to result from two defective copies of a gene that produces a protein involved in ion channels in the heart. This syndrome is characterized by an arrhythmia called long-QT syndrome and deafness. A baby was born with this syndrome and when her mother died of cardiac arrest, researchers studied the rest of the family. Fourteen family members had long QT syndrome but had no hearing difficulties. All had one defective copy of the gene. Only the baby had long QT syndrome and deafness and she had two copies of the defective gene.

Analysis, Deafness, Familial diseases

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