The electrocardiogram allows you to detect several heart conditions, including arrhythmias, a myocardial infarction, an abnormality of the atrium or heart ventricle, coronary suffering, etc. In addition, it allows you to evaluate the functioning of a pacemaker or implantable cardioverter defibrillator, in all those subjects who are carriers of devices for the normalisation of heart rhythm. Cardiologists are able to understand what the state of health of the heart is and how it works from the appearance of the electrocardiographic tracing.