You may be asked to have this test if your doctor suspects Brugada syndrome. While you are having an ECG test you will be given an injection of ajmaline or flecainide (antiarrhythmic drugs). The test may show changes on the ECG that are typical of one of the channelopathies.
A fine plastic tube is inserted into a vein at the front of your elbow. The drug is injected over a short period of time (5-10 minutes) and you will be monitored for 20 minutes or a few hours afterwards, depending on the drug used. There is, however, a risk in 1 in 200 Brugada syndrome carriers or their immediate blood relatives of causing a potentially life-threatening arrhythmia during the injection. The test is therefore always performed with appropriate facilities to protect patients from this risk. Ajmaline is preferable as it lasts a shorter period of time in the circulation.
Recently slow adrenaline (epinephrine) injections have been given in a similar way to try and improve the diagnosis of certain forms of long QT syndrome by uncovering longer QT intervals. The same approach has been used for catecholaminergic polymorphic ventricular tachycardia (CPVT) where the test attempts to reveal specific forms of ventricular arrhythmia. The place of these tests over and above more usual tests such as an exercise ECG is unclear.
Adenosine (another short-acting chemical) is given under the same circumstances if Wolff-Parkinson-White syndrome (WPW) is considered a possible diagnosis.