The heart is an organ composed of four chambers: two atria and two ventricles, located on the left and right sides.
The ventricles, which are involved in this disorder, are the largest chambers. Their function is to contract to pump blood out of the heart and into the arteries.
Cardiac arrest, also known as heart failure or circulatory arrest, is most often caused by ventricular fibrillation.
The atria and ventricles contract in response to an electrical impulse. A resting heart rate for healthy people ranges between approximately 60 and 100 beats per minute.
But in some cases, these contractions can become faster and/or disorganized. This is called arrhythmia or a heart rhythm disorder.
When they originate in the atria they are called atrial heart rhythm disorders, whereas those arising in the ventricles are called ventricular heart rhythm disorders.
Ventricular fibrillation is the most severe form of cardiac arrhythmia. It occurs when the ventricles can no longer contract in a coordinated way. The heart stops pumping blood, which ceases to circulate in the body and deprives the brain of oxygen. The person loses consciousness within seconds and, if circulation is not restored, brain damage becomes irreversible and will ultimately lead to death.
95%
Without immediate intervention, 95% of cardiac arrests are fatal.
70%
Seven out of ten sudden cardiac arrests occur with other people around, yet less than 40% of bystanders perform CPR.
80%
When CPR is performed by a bystander, 80% of people who experience sudden cardiac arrest survive.
Causes
Cardiac arrest can be caused by various factors, most of which are linked to pre-existing heart conditions. The most common cause is myocardial infarction, but more broadly, any form of heart failure or heart disease can lead to cardiac arrest.
Recognizing a heart attack
Cardiac and circulatory arrest is always followed by a loss of consciousness, usually occurring rapidly, within less than ten seconds. The lack of oxygen to the brain can cause brain damage that triggers convulsions, which should not be confused with an epileptic seizure. Similarly, oxygen deprivation usually leads to a cessation of breathing, which may be replaced by agonal breathing, characterized by slow, often loud breathing called gasps.
A person who suddenly loses consciousness and stops breathing or has abnormal breathing is very likely in cardiac arrest.
Treatment
Cardiac arrest is an absolute emergency. Treatment consists of cardiopulmonary resuscitation (CPR) combined with immediate defibrillation. The bystander response time is crucial: in 90% of cases, delays in assistance lead to death.
If you witness a cardiac arrest, you must:
1) Contact the emergency services by calling 15 (in France), and get help from people nearby;
2) Perform chest compressions: push down hard (5-6 cm deep) in the middle of the sternum, between the two breasts. Compress quickly (roughly the tempo of the Bee Gees’ hit song Stayin’ Alive) without stopping.
a. Each compression replaces a cardiac contraction.
b. Each minute without CPR increases the victim’s risk of permanent brain damage.
c. Performing CPR on someone who is not in cardiac arrest is not harmful and cannot kill them. However, not performing it will be fatal: when in doubt, begin CPR!
d. Mouth-to-mouth resuscitation is not necessary: chest compressions also help the patient to breathe.
e. CPR is tiring: take turns with others.3) Continue without stopping until the emergency services arrive. If you are not the only person present, locate and use an automated external defibrillator (AED). There are websites and applications that can help you locate one in seconds. If an AED is not available, the bystander must continue to perform chest compressions until the emergency services arrive.
3) Continue without stopping until the emergency services arrive. If you are not the only person present, locate and use an automated external defibrillator (AED). There are websites and applications that can help you locate one in seconds. If an AED is not available, the bystander must continue to perform chest compressions until the emergency services arrive.
Get first aid training
Many organizations, such as the Red Cross (Croix-Rouge) and the Civil Defense (Protection Civile) provide CPR training. This is of course the best way to prepare for the possibility of intervening during an emergency situation. Get first aid training
What is an automated external defibrillator?
An automated external defibrillator is a device that emerged in the 1990s and which the French Ministry of Health made available to the general public in 2007. The device delivers an electric shock to restore the heart’s rhythm. In France, there are over 400,000 AEDs, not including those in hospitals. There are two types. The semi-automatic, which delivers the shock when the user presses a button, and the automatic, which does not require this intervention. In both cases, AEDs are equipped with voice guidance to help the user perform chest compressions and place the electrodes. The device also performs a diagnosis to decide whether or not to deliver an electric shock. There are apps available to help locate the closest defibrillators, the most comprehensive being Stayin’ Alive.
In the long term, if the fibrillation is caused by a reversible condition, it should be treated. If not, an implantable cardioverter-defibrillator is used to continuously monitor the heart rate and deliver an electric shock to restore a normal rhythm. Medication can also be prescribed.
What is an implantable cardioverter-defibrillator?
The implantable cardioverter-defibrillator referred to in this article is a small device connected to leads that are often secured to the heart with screws. It should not be confused with an automated external defibrillator, which is used to revive victims of cardiac arrest.
Reviewed and approved by Josselin Duchateau, MD, Cardiologist at Bordeaux University Hospital (CHU)
