My wife drove me to the hospital during my first heart attack and that was a mistake.
Another reason to call 911: When you arrive at the hospital by ambulance they'll see you right away. If you arrive by private car you may have to wait, and wait, and wait...
My son had a seizure while we were in the car, so we just drove to the hospital figuring that was under five minutes rather than at least 20 to get an ambulance to us and then transport him. Moron at the front desk put him in line for triage with the people with sniffles! I got some attention for my son and then chewed out the desk person. The hospital staff got huffy so I called my son's neurologist, who chewed out the president of the hospital.