Key Points

• Long QT syndrome (LQTS) is a disorder of the heart's electrical activity. It may cause you to develop a sudden, uncontrollable, and dangerous heart rhythm called an arrhythmia in response to exercise or stress.
• Arrhythmias also can develop for no known reason in people who have LQTS. Not everyone who has the disorder develops dangerous heart rhythms, but if one does occur, it may be fatal.
• 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 conditions.
• Faulty genes that control the production of certain types of ion channels in your heart cells cause inherited LQTS. The faulty ion channels interfere with the normal flow of sodium and potassium ions 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.
• If you have LQTS, you're prone to developing a sudden and dangerous arrhythmia in response to certain conditions. The signs and symptoms of LQTS-related arrhythmias include unexplained fainting or seizures, drowning or near drowning (due to fainting while swimming), sudden cardiac arrest, and sudden death.
• Some people who have LQTS have no signs or symptoms. This condition is called silent LQTS.
• To diagnose LQTS, your doctor will consider your EKG (electrocardiogram) results, your personal and family medical histories, and genetic test results.
• Treatments for LQTS include lifestyle changes, medicines, implanted medical devices, and surgery to regulate your heartbeat. Treatment isn't a cure for the condition, but it does greatly improve survival.
• If you have LQTS, you will need to take certain steps for the rest of your life to prevent an abnormal heartbeat and to ensure that you get treatment right away if one occurs.
• Avoid things that trigger an abnormal heartbeat, such as exercise or certain medicines. Let the people whom you see regularly know about your LQTS. Ask them to call 9–1–1 right away if you faint. Have a plan in place for when you develop and abnormal heartbeat.
• See your cardiologist (heart specialist) regularly. He or she will adjust your treatment as needed.