In the case of a heart attack, people are really helpless , the rate of heart is beating improperly and are not usually about 10 seconds to react before they lose consciousness.
Namely, the cough can provide a great help. Namely, they should cough vigorously and continuously as you need to cough out some discharge and you should breathe deeply.
Deep breaths will help to intake more oxygen and coughing cause pressure on the heart and circulation and maintain a normal heart rhythm.
Inhalation and cough must be repeated every two seconds continuously until some help to you by a professional doctor or ambulance is given.
If you already feel some improvement, wait a while and then stop coughing. Thus, people who had just experienced a heart attack can get some time to go to the hospital and avoid serious consequences.