What to know about a signal-averaged electrocardiogram

A signal-averaged ECG uses skin electrodes to record the heart's electrical activity. Computer processing aligns multiple beats and reduces background noise, allowing the clinician to examine very low-amplitude signals near the end of the electrical waveform. It is different from a routine ECG, which displays the heart rhythm and electrical pattern from a shorter recording.

The test may be considered when a clinician is assessing the risk of particular rhythm problems or interpreting symptoms alongside other findings. A result is not a diagnosis on its own and must be interpreted with your history, examination, and other tests.

Wear clothing that allows access to the chest and tell the team about medicines, implanted devices, skin sensitivity, and recent symptoms. The electrodes are placed on clean skin while you remain still and quiet. The recording is non-invasive; removing electrodes may briefly irritate sensitive skin.

Ask whether you should also have a routine Electrocardiogram, longer rhythm monitoring, or another assessment. Bring previous results if available so the clinician can compare patterns over time.

Do not wait for a planned ECG if you develop chest pressure, severe breathlessness, fainting, sudden weakness, a sustained racing or irregular heartbeat, or new confusion. Seek emergency care for symptoms that are severe, sudden, or worsening. A planned test is not a substitute for urgent assessment.

Ask why this specialised recording is being recommended, what question it is intended to answer, how the result may change your care, whether other rhythm tests are needed, and when you should expect an explanation of the findings.