Heart electrocardiogram: what should you know?

An ECG creates a tracing from electrodes placed on the skin. A clinician reviews the timing and shape of the signals, looking for clues about rhythm disturbances, changes in how the heart is activated, or patterns that may fit reduced blood flow. The tracing is one part of an assessment, not a stand-alone explanation for every symptom. Angina, atrial fibrillation, and heart failure can require different combinations of history, examination, and testing.

A resting ECG is recorded while you lie still. If symptoms are occasional, a longer monitor may be considered because a short appointment can capture only one moment.

Wear practical clothing and tell the clinician about medicines, implanted devices, skin irritation, or symptoms such as palpitations and dizziness. Avoid moving or talking during the recording so the tracing is easier to interpret. Keep a note of what you felt, when it happened, and whether activity or rest changed it. Your GP consultation can help determine whether an ECG is the right first test and what should happen next.

Call emergency services for new chest pressure, severe breathing difficulty, collapse, sudden weakness, or a fast or irregular heartbeat with faintness. Do not delay urgent care while arranging an ECG or waiting to discuss an old result. A normal-looking tracing cannot explain away serious or worsening symptoms.

What question is this ECG intended to answer? Does my tracing need comparison with an earlier one? If symptoms were absent during the test, would longer monitoring be useful?