Newer pacemakers have the equivalent of the "black box flight recorder" within them showing and recording activity, need to intervene in stimulus pacing etc.
and yes, you can download whats been recorded and play it back so you know what has happened.
As for the "one temperature" comment? Sorry, not the case.
Here is a listing overview of the basic tests that any and all medical products must meet:http://effectiveelectrons.com/medee.html
That is the very basics, specific applications require specific tests, and life support devices require an even more strenuous set of case by case requirements.
Consumer electronics 90% design, 10% regulatory
Medical electronics, 90% regulatory, 10% design
I have redesigned a bunch of medical products, because the original designers were clueless on regulatory issues. Had to trash what they did and start over.