Heart & Stroke Conditions Explained


Cardiac arrest

A cardiac arrest is an emergency. It means there has been a sudden loss of function of the heart causing it to stop pumping blood all around the body.

It can occur in a person with or without heart disease. This happens due to an abrupt disturbance in the heart’s rhythm which results in the heart not beating or beating too little to keep the person alive.

The rhythm disturbances are of different types.

  • Ventricular fibrillation (VF) is where there is very erratic electrical activity but the heart does not pump blood so there is no heart beat.
  • Asystole is where there is no electrical activity and therefore no heart beat. A flat-line is seen on the monitor.
  • Complete heart block is where the heart rate is too slow to keep a person alive for long.

In each case, it occurs suddenly or very shortly after the onset of symptoms. Without treatment, the outcome is usually fatal.

The heart has an inbuilt electrical system, which makes it work. When this is interrupted, the heart cannot pump enough blood around the body and sudden cardiac death results.


Cardiac arrest

Without a supply of blood pumped by the heart the brain can’t function, the victim faints and death follows within minutes without treatment.

Usually, there are no early warning signs. Within seconds the person collapses, is not breathing or may be only gasping. This can occur in a person with or without heart disease and may occur after a heart attack.


Cardiac arrest

The problem occurs due to an abrupt or sudden disturbance in the heart’s rhythm which results in the heart not beating or beating too little to keep a person alive. This life threatening arrhythmia or abnormal heart rhythm is called ventricular fibrillation (VF).

  • Coronary heart disease is an underlying cause of VF and the most common cause of sudden cardiac death. Therefore sudden cardiac death may occur after a heart attack or after an episode where there is reduced blood flow to the heart. Between a third and a half of patients who get a heart attack suffer sudden cardiac death. Heart attacks can also cause scarring of the heart muscle leading to abnormal heart rhythm problems.
  • Heart muscle conditions such as cardiomyopathy may also cause cardiac arrest.
  • In some people, an underlying inherited heart rhythm problem may lead to the electrical disturbance ventricular fibrillation. These include Long QT Syndrome and Brugada Syndrome.
  • In some individuals with normal hearts, cardiac arrest can occur with certain drugs, both legal and illicit, with lack of oxygen, with chemical disturbances in the blood stream or following a chest injury.


Cardiac arrest

You can do a lot to prevent heart disease (coronary heart disease) and reduce your risk of having a heart attack. As this is the most common cause of sudden cardiac arrest it is the best way of preventing an adverse event.

If you have heart disease or any condition which increases your risk, you will likely need to take medications and carefully manage your condition to help to reduce your risks.

For some people with a known high risk – like heart attack or an inherited arrhythmia (e.g. LQTS) – your doctor may prescribe medications to steady your heart rhythm or recommend an implantable cardioverter defibrillator (ICD).


Cardiac arrest

With cardiac arrest a person collapses suddenly, has no pulse, is not breathing and is unresponsive.



Cardiac arrest

If treated quickly with an electric shock, delivered by an automated external defibrillator (AED), normal heart rhythm can often be restored. In addition, the best chance of survival is someone nearby knowing how to do CPR (the survival rate decreases by 10% for every minute nothing is done).

If CPR and defibrillation are delivered early on, there is a good chance of successfully resuscitating the person. There are some instances when these life-saving measures are delivered too late and although the heart returns to its normal rhythm, the brain may be severely damaged.

In individuals who have been successfully resuscitated it is important to investigate thoroughly and provide the necessary treatment to avoid further episodes of sudden cardiac death. Sometimes the situation is due to a drug overdose and avoidance is all that is necessary.

In the majority of cases, the problem is related to narrowed coronary arteries (heart disease). In this situation, it may be necessary to perform a procedure to either open up the narrowed vessel (angioplasty and stenting) or to bypass the narrowed arteries (coronary artery bypass surgery (CABG)).

In some circumstances, this is not sufficient to prevent the problem or there is another cause of the sudden cardiac death. In these situations, an implantable cardioverter defibrillator is usually inserted.

Support for you

Cardiac arrest

The Irish Heart Foundation offers a range of free support services to those affected by heart disease or stroke that can greatly improve their quality of life. These include support groups, physical exercise classes, therapy sessions and more.

For more information on these supports, see our Patient Supports page.

If you have any questions about heart disease or stroke, you can also call the Irish Heart Foundation’s Nurse Support on (01) 668 5001 to speak to a nurse specialist who will answer your questions, and give you guidance and reassurance.

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