The ECG testing is very common in health diagnose of a patient. Also, in present it is common to apply as many automated technology solutions as possible. Generally, this should insure better quality of gained diagnostic results. On the other hand, complex solutions invoke human error in procedure, which ultimately can provide inaccurate results. The influence of such errors on example of ECG testing is analyzed and compared to normal ECG test in this research, where six scenarios are deliberately forced to provide fault diagnose.