Performing CPR and Using the ECG on a man experiencing Cardiac Arrest

Sudden Cardiac Arrest 101: Symptoms, Causes & What To Do

What is a cardiac arrest? Is it different from a heart attack? Learn the symptoms and causes, and how you can help in the event of a cardiac arrest.

by Elaine Francis, R.N.

A cardiac arrest happens when your heart stops pumping blood around the body. A cardiac arrest is a life-threatening medical emergency, and without immediate and effective treatment, will result in death. A cardiac arrest outside of an acute healthcare setting may be referred to as an out-of-hospital arrest (OHCA) or sudden cardiac arrest (SCA).

What is a Cardiac Arrest?

In a cardiac arrest, the heart malfunctions and stops pumping blood around the body. 

This may be caused by a purely cardiac condition — a problem with the structure of the heart — or a problem with the heart’s natural electrical conduction system which triggers and organises every heartbeat. The most common cause of a cardiac arrest is usually underlying heart diseases.

Sudden cardiac arrests have poor rates of recovery. Only around 25% of people who suffer an out-of-hospital cardiac arrest survive the arrest. 

During a cardiac arrest, brain function declines with every second that passes. Hypoxic brain injury — brain damage that occurs due to a lack of oxygen supply to the brain for a length of time — is common after a cardiac arrest. Anyone who survives an arrest has a long way to go to recover fully, and the number of people who survive and go on to leave hospital with normal neurological function is less than 3%. 

However, more education and resources mean that survival rates and outcomes are improving all the time; a bystander who can step in quickly with basic resuscitation skills more than doubles someone’s chances of surviving a cardiac arrest. In general, perfusing the organs with oxygenated blood is the key to a good outcome. 

What’s the Difference Between a Cardiac Arrest and a Heart Attack

A heart attack (also known as acute myocardial infarction or MI) is caused by a blockage or narrowing in the blood vessels that nourishes the heart muscle (myocardium) with oxygen and the nutrients it needs. This results in damaged heart muscle cells. 

Unlike a cardiac arrest, a heart attack does not necessarily mean that the heart has completely stopped working. However, a heart attack can cause cardiac arrest.

Cardiac Arrest Symptoms

A person having a cardiac arrest usually collapses suddenly, loses consciousness and has no pulse. They may completely stop breathing or make occasional gasps or wheezing sounds. There may not be any warning signs or symptoms beforehand at all.

Is it a cardiac arrest?

Some heart conditions may result in a slow heart rate with significant pauses, where an individual loses cardiac output and has no pulse for several seconds. When this occurs, the individual may pass out or feel faint. However, the difference between a pause and a cardiac arrest is whether or not the person’s heart begins to beat again spontaneously

Do note that symptoms of a heart attack or heart rhythm disturbance, such as chest pain, fainting, awareness of the heartbeat (palpitations) or sudden severe shortness of breath should be investigated as a medical emergency.

Cardiac Arrest Causes & Risk Factors

The most significant risk factor for cardiac arrest is underlying heart diseases, with the most common one being coronary artery disease

The good news is, coronary artery disease can often be prevented or managed reasonably well with simple healthy lifestyle measures. Following a good diet, getting plenty of exercise, stopping smoking and restricting alcohol intake are the most important things a person can do to reduce their risk of cardiovascular disease. 

However, some heart conditions cannot be improved by lifestyle changes, so following medical advice and having regular health screening and check-ups is essential.

Besides heart conditions, cardiac arrest can be caused by the following:

  • Poisoning – such as a drug overdose.
  • Hypothermia – severely low body temperature.
  • Losing a large amount of blood.
  • Electrocution.
  • Severe electrolyte imbalance – too high or too low levels of some of the chemicals that the heart needs to beat properly.
  • Lack of oxygen.

What to Do During a Cardiac Arrest

In recent years, campaigns to educate the general public on what to do if they witness a cardiac arrest has made a huge difference to survival rates of sudden cardiac arrests. Effective bystander CPR and an early shock from a public access defibrillator can save a life. 

The Singapore Civil Defence Force has developed the MyResponder app that alerts volunteers to cardiac arrests in their immediate location, increasing the chances of effective basic life support while an ambulance is on its way.

Life support sessions are now commonly taught in schools, community centres and workplaces, improving the chances that a trained bystander will be present at a cardiac arrest.

Resuscitation guidelines are subject to ongoing review and are regularly updated. The Singapore Resuscitation and First Aid Council can provide the most up-to-date guidelines.

The mnemonic acronym ‘DRS ABC’ is taught to prompt responders to follow effective resuscitation guidelines:

  • Danger: This means making the environment safe for the casualty and any responders – this can involve stopping traffic, checking for live electrical wires, or avoiding broken glass or vehicle parts.
  • Response: Check for a response to voice, or a firm tap or grip on the shoulders. If there’s any possibility of serious injury to the back or neck, it is important not to try and move or shake the person.
  • Shout for help: Getting immediate support and making sure that professional help is on its way is essential. If there is more than one person present, one can attend to the casualty while another calls emergency services.
  • AED: If someone else is present, they should try to find a nearby public access defibrillator. If there is only one responder present, they should only leave the casualty if there is a defibrillator in the immediate vicinity.
  • Breathing and pulse check: Looking for the rise and fall of the chest is a good way to tell whether someone is breathing. Watch for ten seconds and perform a pulse check at the same time. In an emergency, it isn’t always easy to feel if someone has a pulse. If you are unsure if someone has a pulse even after trying for ten seconds, it is better to start CPR than to delay chest compressions.
  • CPR: An unresponsive person with no signs of normal breathing needs immediate CPR.

Performing CPR

Mouth-to-mouth resuscitation, or ‘rescue breaths’ are now considered optional in most circumstances, and basic life support training now teaches both CPR with mouth-to-mouth and hands-only CPR. 

Without specialist training and equipment, it is reasonable to feel unwilling to perform mouth-to-mouth. Giving continuous chest compressions while waiting for an AED or healthcare professionals to arrive is acceptable. Cardiac arrests and chest compressions sometimes cause regurgitation of stomach contents or sputum, and the situation and the possibility of risk to the responder should be considered. After all, giving rescue breaths to a close family member is a very different proposition for giving mouth-to-mouth to a stranger who is unwell.

If giving CPR with mouth-to-mouth, a cycle of 30 chest compressions then two rescue breaths should continue until professional help or an AED arrives. If you have an AED, follow the defibrillator’s voice prompts. Should a professional arrive, he or she should guide the resuscitation cycles. 

In hands-only CPR, chest compressions should be continuous. Effective chest compressions should push hard and fast – at a rate of around 100-120 compressions per minute. Compressions should be given to about one-third of the depth of the chest — about 4-6cm for an adult — and allow for full recoil. 

To give chest compressions, elbows should be locked and the responder should be positioned over the casualty so that they can push straight down with sufficient force and without tiring too easily. Delivering effective chest compressions is hard work. If there is more than one person present, they should alternate when required — tired people do not give effective CPR.

Cardiac Arrest Diagnosis

A cardiac arrest is diagnosed when someone loses cardiac output (i.e. they are unconscious, have no pulse, and do not regain spontaneous circulation). The heart of individuals experiencing a cardiac arrest will not start to beat again without medical treatment.

The type of arrest is often described by the type of heart rhythm found when a heart monitor is attached to the patient. This simply describes the type of electrical activity still present in the heart muscle, but can have some bearing on the type of treatment that could help and the likely outcome.

Cardiac Arrest Treatment

The main function of our heart is to pump oxygenated blood around the body. Without an adequate oxygen supply, the tissues of the body start to die. 

The brain is immediately affected by a cardiac arrest and the only way to continue to perfuse the brain is by ensuring that blood continues to flow through the body even when the heart isn’t pumping. This is why it’s important to start effective cardiopulmonary resuscitation (CPR) immediately.

As a First Responder

CPR should only be started after assessing the immediate risk to the responder.

While chest compressions can continue to get blood to the organs, they are not enough to get a person’s heart to start beating again, even when performed expertly. The sooner the chest compressions can start the better, but the first thing to do in the event of a cardiac arrest is to make sure more help is on its way. Calling 995 for an ambulance or flagging down a passer-by and getting them to call is the essential first step.

Public Access Automated External Defibrillators (AEDs or PADs) are increasingly available in public areas and can be used by anybody to deliver a life-saving shock that might restart the heart. AEDs are designed to be easy-to-use even without any practise or experience. They use diagrams and voice prompts to talk a bystander through the process of attaching and using the device safely. They assess the heart rhythm and will only deliver a shock in situations where it might work — they will not shock someone with a normal heart rhythm.

Basic resuscitation courses are widely available, teaching skills that save lives.

Medical Treatment for Cardiac Arrest

When a paramedic and medical team respond to a cardiac arrest, their priority is to stabilise the patient and determine and (where possible) treat the cause of the cardiac arrest. There are a number of causes for a cardiac arrest — some are reversible and some are not. Some causes can be immediately treated while others may require more complex medical or surgical intervention.

How Do I Prevent a Cardiac Arrest?

It is not always possible to anticipate a cardiac arrest. In many cases, problems with the heart or other systems do not manifest any symptoms until the arrest actually happens. However, there are certain steps that we can take to reduce our risk of cardiovascular diseases that contribute to the majority of sudden cardiac arrests.

A healthy heart begins with being aware of individual risk factors for cardiovascular disease and making the lifestyle choices that keep us healthy. We can start with a good diet, plenty of exercises, stopping smoking and reducing the amount of alcohol we drink. Being aware of blood pressure, cholesterol levels and other risk factors can also help us make the right choices. Undeniably, understanding our health is the first step towards improving it.

If you know that you have an underlying health condition that puts you at a higher risk of cardiac arrest, it is important that the people around you are aware of this and that they know what to do in the event of a cardiac arrest. Some medications can also make dangerous heart rhythm disturbances more likely. If you have any concerns about your health or any questions about your medication, a general practitioner (GP) can help.

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About the Writer
Elaine Francis, R.N.
Elaine Francis is a registered nurse with 17 years’ experience in healthcare. She turned to writing to follow her passion for realistic medical communication. She loves translating medical jargon into accessible language for the people who need to understand it most. When she’s not writing or working on a busy cardiology unit, she spends her time telling her children to hurry up.
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