Measurement of the QT interval using the tangent method<unk>  is diagnosed primarily using an electrocardiogram (ECG), but may also take into account the clinical history, family history, and possibly genetic testing. Whilst a diagnostic scoring system has been proposed that incorporate all of these factors (the Gollob score), it is uncertain whether this score is useful for diagnosis or risk stratification, and the Gollob score has not been universally accepted by international consensus guidelines. There continues to be uncertainty regarding the precise QT interval cutoff that is should be used for diagnosis. 12-lead ECG Precordial leads of a 12-lead ECG from a person with<unk>  The mainstay of diagnosis of<unk>  is the 12-lead ECG. The precise QT duration used to diagnose the condition remains controversial with consensus guidelines giving cutoffs varying from 330 ms, 340 ms or even 360 ms when other clinical, familial, or genetic factors are present. The QT interval normally varies with heart rate, but this variation occurs to a lesser extent in those with<unk> . It is therefore recommended that the QT interval is assessed at heart rates close to 60 beats per minute. Other features that may be seen on the ECG in<unk>  include tall, peaked T-waves and PR segment depression. Other features supporting diagnosis Other features that support a diagnosis of<unk>  include: a history of ventricular fibrillationor ventricular tachycardia despite an apparently structurally normal heart; a family history of confirmed<unk> ; a family history of sudden cardiac death aged <40 years; and identification of a genetic mutation consistent with<unk> . Invasive electrophysiological studies, in which wires are passed into the heart to stimulate and record the heart's electrical impulses, are not currently recommended for diagnosing<unk>  or predicting the risk of sudden cardiac death.
Short QT syndrome
Long QT syndrome
Opitz G/BBB syndrome
Brugada syndrome
Familial atrial fibrillation
Aicardi–Goutières syndrome
Phidippides cardiomyopathy
Pacak–Zhuang syndrome