How is Long QT Syndrome diagnosed?

Cardiologists are doctors who specialize in the diagnosis and treatment of heart diseases, including long QT syndrome (LQTS). They will use an ECG and review your medical history. A genetic test may be recommended if LQTS is suspected in your family.

  • An ECG is a simple test that detects and records the heart's electrical activity. This test may reveal a long QT interval and other signs that make it more likely that you have LQTS. Often, doctors first discover a long QT interval when an ECG is done for another suspected heart problem.
  • Medical history and physical exam will tell your doctor about any symptoms of an abnormal heartbeat, including unexplained fainting, a fluttering in your chest, or loud gasping during sleep.
  • Genetic blood tests can detect some forms of inherited LQTS. If your doctor suspects that you have LQTS, he or she may recommend genetic testing. Genetic blood tests usually are suggested for family members of people who have LQTS as well. However, genetic tests can't detect about one-third of LQTS cases. So, even if you have LQTS, the tests may not show it.