From the British Heart Foundation website
“A heart attack is a sudden interruption to the blood supply to part of the heart muscle. It is likely to cause chest pain and permanent damage to the heart. The heart is still sending blood around the body and the person remains conscious and is still breathing.
A cardiac arrest occurs when the heart suddenly stops pumping blood around the body. Someone who is having a cardiac arrest will suddenly lose consciousness and will stop breathing or stop breathing normally. Unless immediately treated by CPR this always leads to death within minutes.
A person having a heart attack is at high risk of experiencing a cardiac arrest.
Both a heart attack and a cardiac arrest are life-threatening medical emergencies and require immediate medical help”
Recent statistics show that in the UK roughly 70-80% of heart attacks sufferers survive, compared to just 8% of those who experience a cardiac arrest.
A clear and concise explanation of the difference between Heart Attack and Cardiac Arrest can be seen in this video
This video shows the difference between a heart attack and a cardiac arrest in a simple non medical way.