An electrocardiogram (EKG or ECG) is a test that checks for problems with the electrical activity of your heart. An EKG shows the heart 's electrical activity as line tracings on paper.The spikes and dips in the tracings are called waves.The heart is a muscular pump made up of four chambers.n EKG is done to: 1  Check the heart's electrical activity. 2  Find the cause of unexplained chest pain or pressure. 3  Find the cause of symptoms of heart disease. 4  Find out if the walls of the heart chambers are too thick. 5  Check how well medicines are working and see if they are causing side effects that affect the heart. 6  Check how well mechanical 7  ... Che