The technique that would most likely be used to check for advanced atherosclerosis in a coronary artery is Electrocardiogram (ECG) and/or Echocardiogram. ECG records electrical signals as they travel through your heart, while the echocardiogram produces images of the heart. In some cases also Holter monitoring may be recommended. It is type of ECG, in which the patient wears a portable monitor for 24 hours as you go about your normal activities.