Key Points

• Long QT syndrome (LQTS) is a disorder of the heart's electrical activity.
• If you have LQTS, your heart is more likely to develop a sudden, uncontrollable, and dangerous heart rhythm (called an arrhythmia) in response to exercise, stress, or other conditions.
• This abnormal heart rhythm makes you prone to fainting or to sudden cardiac arrest because your heart stops beating.
• LQTS is a rare condition that's usually inherited. It's often first detected in children and young adults. LQTS also may be acquired, rather than inherited, and caused by certain medicines and disorders.
• Faulty genes that control the production of certain types of ion channels in your heart cells cause inherited long QT syndrome (LQTS). The faulty ion channels interfere with the normal flow of sodium and potassium atoms into and out of the cells during a heartbeat. The abnormal flow may disrupt the timing of the electrical activity in the heart and lead to dangerous heart rhythms.
• For many people who have LQTS, lifestyle changes and medical treatments may help prevent dangerous complications.
• If you have LQTS, you're prone to developing a sudden and dangerous arrhythmia in response to certain conditions. The signs and symptoms of arrhythmias that people with LQTS tend to have include unexplained fainting or seizures, drowning or near drowning (due to fainting while swimming), sudden cardiac arrest, and sudden death.
• To diagnose LQTS, your doctor will consider your EKG (electrocardiogram) results, your personal and family medical history, and genetic test results.
• Treatments for LQTS include lifestyle changes, medicines, implanted medical devices, and surgery to regulate your heartbeat.
• You should let the people whom you see regularly know about your condition. Ask them to immediately call emergency medical services if you faint.
• See your cardiologist regularly. He or she will adjust your treatment as needed.