How is the long QT syndrome diagnosed?
The possibility of long Q-T syndrome should be considered in any patient with a past history of fainting associated with either emotion or exercise. A routine ECG (electrocardiogram) may show a long Q-T interval, but this is not always the case.
Further tests, including observation while the patient is exercising, may clarify the diagnosis. Genetic testing is sometimes available for individuals with a family history of long Q-T syndrome.
The diagnosis of the long QT syndrome can be made by electrocardiogram (ECG) in about 50% of cases. However, in about 10% of cases, the QT interval on the initial ECG looks normal and in another 40% the QT interval is not sufficiently prolonged to permit a clear-cut diagnosis. The long QT syndrome can also be detected after a person dies by a molecular genetic analysis of their tissue.
Early diagnosis is essential. Drugs called beta-blockers can help to maintain a normal heart rhythm in 90% of cases. In the remaining cases, a Pacemaker can be implanted to set the heart's rhythm or an automatic defibrillator can be put in that can detect and correct an abnormal heart rhythm.