could this man have had a heart attack due to the presence of drugs or alcohol in his system, combined with the fact that his heart rate was elevated by resisting arrest
Totally. He could have also died from a brain aneurysm, aliens, a very advanced case of SIDS, or a witch's curse. Or, you know, maybe he died from the whole not being able to breathe thing that was actually happening.
He does not appear to be in good physical condition. I see that his stomach looks a little distended and he sort of waddles as he took steps around the bar area.
He didn't look like he was in great shape? Only fitness buffs and marathon runners with no booze in their systems get to live though being cuffed? Tf is wrong with you.