An ECG (electrocardiogram) records the electrical activity of your heart at rest. It provides information about your heart rate and rhythm, and shows if there is enlargement of the heart due to high blood pressure (hypertension) or evidence of a previous heart attack (myocardial infarction). However, it does not show whether you have asymptomatic blockages in your heart arteries or predict your risk of a future heart attack. The resting ECG is different from a stress or exercise ECG or cardiac imaging test.