The RELF system is a small, portable 3-lead ECG monitor. The system is linked to a software application that tests the ECG signals against a person's own normal values and, if necessary, alerts the person in question in the event of an acute coronary artery blockage. The aim of this project is to set up a multi-center clinical study that: (1) validates the R-ELF method in outpatient home situations as well as during planned acute coronary occlusion, (2) aims for broader clinical validation through predetermined to include subgroups of patients in preparation for CE test conditions and (3) aims for broader clinical acceptance by including centers from multiple countries. Further business development by attracting external expertise in the cardiovascular field.