Heart attack vs cardiac arrest: what the difference is and what to do

A heart attack is a circulation problem: an artery supplying the heart is blocked, usually by a blood clot, and part of the heart muscle is starved of blood. A cardiac arrest is an electrical problem: the heart suddenly stops pumping effectively, usually because of a dangerous abnormal rhythm, and no blood reaches the brain or body.

A person having a heart attack is typically awake and has symptoms, although the NHS also lists passing out and not responding normally as a reason to call 999. A person in cardiac arrest is unconscious and not breathing normally. The distinction matters because the response differs: a heart attack needs an ambulance and hospital treatment to reopen the artery, while a cardiac arrest needs chest compressions and a shock from a defibrillator within minutes, because the brain and body are without blood flow.

The NHS lists chest pain that may feel like crushing or squeezing and may spread to the arm, neck and jaw, shortness of breath, feeling or being sick, a feeling like indigestion, sweating, and pale, blue or grey skin. It says to call 999 if you have chest pain that feels tight or like squeezing, or that spreads to your arms, neck or jaw, if you have severe difficulty breathing, or if someone has passed out and is not responding normally. The BHF notes symptoms are different for different people and you may not have all of them.

While waiting for help, the NHS says to sit and rest in a comfortable position, take aspirin 300mg if you have it (not if you have an aspirin allergy), use a GTN spray if you have angina, and keep checking that the person is responding and breathing. If they stop responding and stop breathing, start CPR. Do not drive yourself to A&E.

The BHF says that someone in cardiac arrest collapses suddenly and will be unconscious, unresponsive and not breathing or not breathing normally, and may make gasping noises. It usually happens without warning. Without immediate treatment the person will die. The BHF says to call 999 and start CPR if you see someone having a cardiac arrest, follow the instructions of the 999 operator, and ask someone to fetch a defibrillator.

The defibrillator gives a controlled electric shock to try to get the heart beating normally again. The BHF stresses that starting CPR immediately keeps blood and oxygen moving to the brain and around the body, and that if the heart rhythm is non-shockable, CPR continues. Causes include abnormal heart rhythms, cardiomyopathies, inherited heart conditions, heart failure, a heart attack, severe blood loss, a sudden drop in oxygen, electrocution and drug overdose.

After a heart attack, the NHS says tests include an ECG and blood tests, then possibly an echocardiogram or coronary angiogram. Treatment may include medicines to treat the blockage, angioplasty with a stent, or bypass surgery, followed by long-term medicines such as antiplatelets and statins and referral to cardiac rehabilitation. For some people recovery takes several weeks with little impact, for others months or years.

After a cardiac arrest, the BHF says people are looked after in a coronary care or intensive care unit and may be kept asleep to allow recovery. Doctors work out what caused it and may recommend medicines, an implantable cardioverter defibrillator or ablation. A lack of oxygen to the brain can sometimes have long-term effects, such as memory problems, tiredness and speech difficulties, and many people have no memory of the event.