An ECG is a painless, routine test that measures the electrical impulses produced by the heart. Patients are asked to undress from the waist up and wear a patient gown. Lying down, the patient is then connected to 12 lead wires, which transmit the information from the heart to the ECG machine. You will be asked to lie quietly for a few minutes until the ECG machine captures the data and prints out a reading (“tracing”) of your heart’s electrical activity.