On a number of occasions during first aid training I have been asked what the difference is between a heart attack and a cardiac arrest.
A heart attack (myocardial infarction or MI) is caused by a clot in the circulation that supplies the heart. This circulation can be likened to a tree (upside down)
where it’s branches and twigs stretch around the heart supplying oxygen rich blood from the aorta to the heart muscle.
It is possible to have an a heart attack where the pain is transient and not even realise the significance or potential diagnoses. This usually happens when the clot forms in one of the smaller branches of the circulation. So only a very small part of heart is affected. Often the pain is mistaken for indigestion and is true cause if discovered is through other tests any time after the event.
In the classic heart attack where the pain is heavy and crushing, the patient is pale and clammy and often feels sick and / or short of breath. Pain may also appear to moved into the jaw and left arm, however this is due to nerve pathways that were initiated during foetal development and there is nothing wrong with the arm or jaw.
The clot here is in one of the bigger branches and a greater area of the heart is affected , the majority of these cases survival and have a stent fitted, which is a mesh which supports the artery and helps prevent future heart attacks with the aid of medication. However a heart attack of this level can lead to a cardiac arrest.
The last scenario is when the clot stops in one of the larger branches this stop a large portion of the heart from working and the patient immediately has a cardiac arrest and needs to be resuscitated.
Mostly this happens later in life due to poor diet and lifestyle choices such as over eating, smoking and lack of exercise. Although some people are born with heart problems (congenital) which if not detected and treated can predispose people to heart disease and / or cardiac arrests.
There are other reasons a person may have a cardiac arrest, such as major haemorrhage, electrocution or damage to the structure or conduction system of the heart.
So essentially a heart attack is damage to the heart muscle due to lack of oxygenated blood which causes pain where as a cardiac arrest is the loss of the hearts ability to pump effectively leading to collapse.
There are many other factors that can affect this but this is a simplified explanation.
The author is a Registered Nurse who served with the RAMC, a Paramedic and Clinical Tutor with additional qualifications in Trauma and Remote Medicine. He has had a long term interest in remote medicine and is the Medical Advisor for several groups and runs courses in Outdoor First Aid, Expedition, Remote and Survival Medicine.