Whats the fastest first aid that can be provided when you suspect a person is having a heart attack?

Call 911. There is no home treatment for a heart attack. Emergency hospital care is critical for survival and recovery. Prior to paramedic arrival an Aspirin can be chewed and swallowed. If the person has had heart problems and has Nitroglycerin they can use it as directed until the paramedics arrive. The 911 operator may give more specific instructions.
Call 911 + +. Call 911!, ask for others to help and get an aed, verify there is no pulse, if so start cpr, use the AED (the AED will determine if a shock is appropriate), if possible rotate with another rescuer every two minutes since you will deliver less effective compressions as you tire.