Your doctor may suggest that you have tests such as coronary angiography or an electrophysiological study (EPS). Both these tests are performed in an X-ray laboratory that allows the body and any medical tools (such as cardiac catheter tubes or pacing wires) to be seen using an X-ray camera. You will be asked to lie down on a special moving table and will be given a local anaesthetic in your groin. The doctor will then place fine tubes, called cardiac catheters or electrodes, into blood vessels in your groin. These are gently passed through to the heart.

During coronary angiography the coronary arteries (the arteries that supply blood to the heart muscle) are injected with a dye to reveal any furring or blockages – coronary artery disease. (The ECG changes that are characteristic of Brugada syndrome or long QT syndrome (LQTS) can sometimes be caused by coronary artery disease.)

An EPS involves placing electrical leads inside the heart to analyse its electrical properties and induce arrhythmias. It may be useful in diagnosing Wolff-Parkinson-White syndrome (WPW) and progressive cardiac conduction defect (PCCD) and deciding on what treatment to give people with Brugada syndrome. If the extra pathway seen in WPW is detected at EPS it can be treated there and then by ‘burning’ it away using high frequency radio waves. This procedure is called RF ablation.

There are other tests that may be used to provoke ECG features in LQTS such as ‘cold pressor tests’. A stimulus such as placing your hands in ice-cold water can bring out the ECG features of the condition. This does not appear to increase significantly the likelihood of making a diagnosis but is still used at some centres.