The long-QT syndrome is an inherited disorder affecting electrical conduction in the heart. Patients with the long-QT syndrome have a high risk of suffering sudden death due to a cardiac rhythm disturbance. The gene responsible for the chromosome 7-linked long-QT syndrome has been characterized. The gene, designated HERG, encodes a subunit of a potassium transport channel. Activity of the potassium transport channel can be modulated by altering the concentration of potassium in plasma. Preliminary data suggest that impaired function of the potassium transport channel may be improved by the administration of potassium with a reduction in the risk for cardiac rhythm disturbances. Because the long-QT syndrome has a high incidence of lethality in children, and because none of the current therapies are dramatically useful, the investigators are searching for a more specific and effective therapy. Their objectives are to determine if potassium levels can be safely and reliably maintained at slightly higher than normal values. If potassium levels can be maintained at higher than normal values, the effect of this will be determined on cardiac electrical activity as measured by electrocardiography. A pilot study performed on adults in the GCRC yielded data suggesting that elevations of plasma potassium could be sustained by the administration of oral potassium and spironolactone, and cardiac electrical properties were made more normal in patients with the long-QT syndrome.
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