ECG is a diagnostic tool that records and measures electrical activity of the heart to show whether or not it is working normally. An ECG records the heart’s rhythm and activity on a moving strip of paper or a line on a screen. Check the heart’s electrical activity. Find the cause of unexplained chest pain or pressure. This could be caused by a heart attack, inflammation of the sac surrounding the heart (pericarditis), or angina. Find the cause of symptoms of heart disease. Symptoms include shortness of breath, dizziness, fainting, and heartbeats that are rapid and irregular (palpitations). Find out if the walls of the heart chambers are too thick. Check how well medicines are working and see if they are causing side effects that affect the heart. Check how well mechanical devices that are implanted in the heart, such as pacemakers, are working. These devices help to control the heartbeat. Check the health of the heart when other diseases or conditions are present. These include high blood pressure, high cholesterol, cigarette smoking, diabetes, and a family history of early heart disease.