Ultimately all of us will experience a cardiac arrest, it simply means the complete cessation of the normal heart contractions so that the pumping of the blood stops. 

However, the cause of this stoppage can be for numerous reasons including…

Trauma i.e. blunt strike to the chest aka commotio cordis
Drugs, both prescription and recreational
Natural end of life i.e. other organ failure, disease

…and of course cardiac ones like

Abnormal heart rhythms (arrhythmia) i.e. LQTS, Brugada
Cardiomyopathies i.e. HCM/HOCM, DCM, ARVC
Heart disease
Heart attacks (myocardial infarction)
Electrolyte imbalances i.e. Potassium, Magnesium

…and it is this last group that when they happen unexpectedly and suddenly that constitute a Sudden Cardiac Arrest and the reason behind SCA UK.

Whilst these are the known causes of a cardiac arrest, many survivors are given a diagnosis of idiopathic, which means…

“relating to or denoting any disease or condition which arises spontaneously or for which the cause is unknown.”

This diagnosis can be particuarily frustrating for the survivor and family as they are left wondering why the SCA happened and will it occur again?


The most common cause of a sudden cardiac arrest is a life threatening abnormal heart rhythm called ventricular fibrillation (VF), which is where the heart quivers rather than pumping.

If a person goes into VF, blood will cease pumping around their body, they will collapse and go unconscious.  If not treated this will usually lead to death within minutes.  The only way to save the person is to get their heart pumping again and this will usually require a defibrillator (AED).  In some rare cases an episode of VF can self terminate, such that the heart restarts without being defibrillated.  Whilst in VF, CPR should be carried out immediately to keep oxygen circulating around the body until a defibrillator can be used.

Ventricular Tachycardia can preceed VF and some ICD’s can pace (“overdrive”) the heart out of this arrythmia before deteriorating into VF.


Below are a number of videos explaining a number of types of cardiomyopathy.  If you have cardiomyopathy you may be interested in the charity supporting people with this condition – Cardiomyopathy UK

Other conditions that can cause cardiac arrest