As I typed my new post I felt I'd leave out the dismal success rate of CPR. Four of the five hikers on Club hikes did not survive, despite CPR, administered for one hour in one case. But if a person is having a SURVIVABLE cardiac infarc the aspirin could be a livesaver in thinning the blood enough to get enough past a mild blockage to reduce muscle damage.
In fact the aspirin may just prevent the pending complete blockage. It is a recommended treatment in wilderness settings where paramedics and their equipment and meds are distant, as is rapid evacuation.
The bottom line is do whatever you can to help the patient - and then pray a lot as you assist them.
"There are no comfortable backpacks. Some are just less uncomfortable than others."