Artem85:
the whole ECG
I'm not a doctor and I don't know what that means. Do you?
All I know from having and seeing ECG readings is that it involves having multiple electrodes stuck in multiple paces which seem to need a lot of care to find, and the set of places that have sensors attached do not always seem to be the same. Then some sort of analysis is done to compare and consolidate the readings from all of these sensors to determine various health indicators. It's not just a glorified voltmeter.