A picture of the electrical activity of the heart as sensed by an ICD or pacemaker implanted in the heart. (This is different from an Electrocardiogram which senses the heart's electrical activity from the surface of the skin.)

(EGM): a picture of the electrical activity of the heart as sensed from within the heart. This is different from an ECG, which is a picture of your heart's electrical activity sensed from the surface of your skin.

A picture of the electrical activity of the heart as detected from within the heart. An EGM is different from an ECG, which is a picture of the heart's electrical activity detected from the surface of the skin.