NHS shares real difference between cardiac arrests and heart attacks in key alertBoth health emergencies can have very severe consequences - here is everything you should knowView 2 Images Cardiac arrests and heart attacks are often mixed up (Image: Grace Cary via Getty Images)The NHS has issued a crucial warning about the key symptoms of two severe health emergencies. ‌"Do you know the difference between a heart attack and cardiac arrest?" ‌A heart attack, also known as a myocardial infarction, occurs when the heart's blood supply is suddenly blocked. If you suspect someone is having a heart attack, you should dial 999 immediately. Regarding cardiac arrests, the NHS also said: "The person will be unconscious and not breathing, or not breathing normally.