Not to be confused with other types of electrography or with echocardiography. Electrocardiography (ECG or EKG) is the process of recording the electrical activity of the heart over a period of time using electrodes placed on the skin.
Addiction is defined as a chronic, relapsing brain disease that is characterized by compulsive drug seeking and use, despite harmful consequences. It is considered a brain disease because drugs change the brain; they change its structure and how it works.
1 Brain changes that occur over time with drug use challenge an addicted personâs self-control and interfere with their ability to resist intense urges to take drugs. This is why drug addiction is also a relapsing disease.  Relapse is the return to drug use after an attempt to stop.