Holter monitoring observes the heart functioning 24 h. It is done with fixing electrodes to the patient’s chest and with a lightweight, matchbox-size machine that saves the data and that is invisible under clothes and does not interrupt daily work. Only all water procedures should be avoided that day. In case the patient has too much hair on the chest, it will be shaved. The monitoring shows what type of arrhythmia you have, how often arrhythmia occurs and how long it lasts. With this monitoring connection between the patient’s problems and arrhythmia can be explained. It also monitors heart muscle ischemia. It is possible to clinically discover cases of stenocardia and changes in sinus tachycardia segments and also cases of asymptomatic ischemia at the same time.