The electrocardiogram (ECG ) is a diagnostic test that involves the registry, with special tools ( electrocardiograph ) of the normal electrical activity of the heart and having a pathology. Also, is one of the most important knowledge and valuation of most of the technical heart disease. Also, electrocardiography provides an invaluable aid to the diagnosis of growth of different heart chambers ( atria and ventricles ). In many cases, the diagnosis of a congenital heart disease known from graphic layout of this characteristic. In fact, the ECG provides important data for the valuation of more than 80 % of heart disease.