How long does your qt interval how to be to be considered long qt syndrome ?

QTc interval: Definitions of "normal" qtc vary among being equal to or less than 0.40 s (≤400 ms), [5] 0.41s (≤410ms), [6] 0.42s (≤420ms)[7] or 0.44s (≤440ms).[8] for risk of sudden cardiac death, "borderline qtc" in males is 431-450 ms, and in females 451-470 ms. An "abnormal" qtc in males is a qtc above 450 ms, and in females, above 470 ms.[9] from wikipedia. Best wishes.

Long QT Synd. (LQTS): A normal QT interval, corrected for heart rate (QTc), is 500ms, but can rarely fall into the normal range. Medications may change QT. See heart rhythm specialist. Call 911 if pass out.

Qt: Depends on some other factors , a QTc over 470 Msec not normal but you can have long qt syndrome even with shorter numbers best to consult your doc and an eldctrophysiologist if there is suspicion