American Hartstein, who was hand-picked by the late Professor Sid Watkins to replace him as the sport's chief doctor last decade, lost his job at the end of last season when FIA president Jean Todt chose not to renew his contract.
"I think my dismissal was partly for personal reasons," he is quoted by Speed Week.
"Some people just didn't like my ways.
"The decision was made before the (2012) Bahrain grand prix, because I wanted to set up a central emergency number; and I was proposing it not only for Bahrain," said Hartstein.
"Someone said it was a good idea and that they spoke with the president (Todt) about it. Half an hour later, the president was running towards me, ranting 'Bahrain is not a war zone!'
"I think that was the decisive factor for my release."