Hi Nemel, Our QTc algorithm is based on Bazetts formula, I.e. QT interval(in ms)/square-root of RR interval (in secs). This formula leads to most people having higher QTc values at rest than during exercise, so that is expected:).

Medical literature states that 440 – 500 is a spectrum where QTc MAY be significantly prolonged but needs contextual interpretation with symptoms and genetic factors. The best way to identify this is with a 12 lead ECG, on advice from your clinician. But please note that the Frontier X is not a diagnostic device, so this information is not meant to be medical advice.