Sudden Cardiac Arrest (SCA)

What is Sudden Cardiac Arrest?

Cardiac arrest, also known as cardiopulmonary arrest or circulatory arrest, is a sudden stop in effective blood circulation due to the failure of the heart to contract effectively or at all. Medical personnel may refer to an unexpected cardiac arrest as a sudden cardiac arrest (SCA).

Arrested blood circulation prevents delivery of oxygen and glucose to the body. Lack of oxygen and glucose to the brain causes loss of consciousness, which then results in abnormal or absent breathing. Brain injury is likely to happen if cardiac arrest goes untreated for more than five minutes. For the best chance of survival and neurological recovery immediate treatment is important.

Response time to survival

Cardiac arrest is a medical emergency that, in certain situations, is potentially reversible if treated early. Unexpected cardiac arrest can lead to death within minutes: this is called sudden cardiac death (SCD).  The treatment for cardiac arrest is immediate defibrillation if a “shockable” rhythm is present, while cardiopulmonary resuscitation (CPR) is used to provide circulatory support and/or to induce a “shockable” rhythm.

Cardiac arrest is synonymous with clinical death.

Recognising Sudden Cardiac Arrest:

Cardiac arrest is sometimes preceded by certain symptoms such as fainting, fatigue, blackouts, dizziness, chest pain, shortness of breath, weakness, and vomiting. The arrest may also occur with no warning.

When the arrest occurs, the most obvious sign of its occurrence will be the lack of a pulse in the person experiencing it – since the heart has ceased to contract, the usual indications of its contraction such as a pulse will no longer be detectable.

Also, as a result of inadequate cerebral perfusion, the patient will quickly become unconscious and will have stopped breathing.


Certain types of prompt intervention can often reverse a cardiac arrest, but without such intervention the event will almost always lead to death.

Watch this video of a fit and healthy person collapsing from SCA: