(Science: cardiology, investigation) A recording of the electrical activity of the heart on a moving strip of paper. The electrocardiogram detects and records the electrical potential of the heart during contraction and relaxation. Typical regordings have 12 leads, which are calculated from 10 electrodes, 6 in the region of the heart and one on each limb. The ECG recording allows detection of cardiac rythm problems such as the causes of cardiac arrest, myocardial infarction and electrical conduction problems requiring pacemaker implantation. ECG interpretation is a subbtle science that can be learn on educational websites and practiced on ECG interpretation training moduleshttp://www.ecg-quiz.com.