Everyone has heard of someone that died without any warning. Sudden cardiac death is an important cause of these types of deaths.
This unexpected death is caused by the stoppage of the heart’s main function: pump. This results in a loss of consciousness, respiratory arrest and death if resuscitation manoeuvres are not done quickly.
Victims of sudden cardiac arrest usually have no warning symptoms, although some may experience chest pain, palpitations, or dizziness.
How big is the problem?
Sudden cardiac arrest is the cause of 32,000 deaths annually in Canada.
It is the leading cause of death in Canada, ahead of the myocardial infarctions, cancer, and strokes.
Unexpected cardiac deaths account for 50% of deaths related to the heart. It affects adults between 30 and 50 years of age in a ratio of 2 men to 1 woman. Children are rarely affected (1-2 children per 100,000 annually).
In the younger population, sudden cardiac death occurs mainly while practicing team sports (1 out of 200,000 athletes).
In athletes over the age of 35, sudden cardiac deaths happen mainly during sports such as running or jogging (Marathon runner 1 out of 50,000 -Jogging 1 out of 15,000).
The risk of sudden cardiac death is 0.001% per year in teenagers and 0.1% per year after the age of 30, then gradually increases with age.
What is the difference between sudden cardiac arrest and myocardial infarction?
Sudden cardiac death is not a "heart attack". The heart is a muscle that has the function of pumping blood to the organs of the human heart.
This pump is regulated by an electrical system that causes cardiac contractions in a harmonious and regular way.
Infarction (heart attack) is caused by a blockage of one or more coronary arteries causing damage to the heart muscle.
Sudden cardiac death is caused by a malfunction of the heart's electrical system. The most common cause is an arrhythmia called ventricular fibrillation. This anomaly of the heartbeat is characterized by a very fast and disorganized rhythm of the lower portion of the heart, the ventricles. This chaotic rhythm that moves the ventricles like Jell-O is inefficient in ensuring adequate blood circulation.
The loss in blood circulation leads to a loss of irrigation of the brain causing loss of consciousness and cardiorespiratory arrest.
Death is inevitable unless resuscitation procedures are undertaken quickly.
What are the symptoms?
In more than half of the cases, no prior symptoms are felt.
Some patients may experience chest pain or a feeling of a fast heartbeat and dizziness before losing consciousness.
What are the causes?
In the vast majority of cases, sudden cardiac death is caused by a fatal arrhythmia. Again, ventricular fibrillation is the most common.
The cause of this arrhythmia can sometimes be difficult to determine.
Although coronary artery disease is the leading cause of sudden deaths, in most cases, it was not discovered or known by the victim before the event.
In the population over 40 years old, the predominant cause is coronary artery disease.
In a younger population, congenital anomalies predominate.
What are the risk factors for sudden cardiac death?
There are several factors that can increase the risk of sudden cardiac death.
2 main factors:
- History of myocardial infarction in more than 75% of cases.
- A history of atherosclerotic coronary artery disease in more than 80% of cases.
- A fraction of the normal left ventricular ejection: less than 40%
- History of heart failure (increases the risk by 8 times compared to the general population)
- History of sudden cardiac death
- Long QT syndrome
- Wolff-Parkinson-White syndrome or pre-excitation (accessory beam)
- Syncope history of undetermined origin
- Family history of syncope or sudden cardiac arrest
- Cardiac congenital abnormalities
- Dilated or hypertrophic cardiomyopathy
- Drug consumption
How is it diagnosed?
Anyone who loses consciousness, suddenly collapses and can not respond is possibly a victim.
The reanimationmanoeuvres should be started immediately and 911 must be dialled.
If an automatic external defibrillator is available, it must be used quickly.
The final diagnosis is made using an electrocardiogram or a rhythm tape that indicates cardiac arrhythmia.
Once the patient is transported to the hospital, the cause of the cardiac arrest will be identified.
What is the treatment?
Once arrived at the hospital, patients who have successfully been reanimated will usually be administered a coronary angiography to identify any blockages that may have caused the arrhythmia.
During hospitalization, the victim of a sudden cardiac death will undergo additional examinations to identify the cause of the episode and especially to prevent a new one.
Treatment will include the correction of coronary artery disease if it is present, medication and the implantation of an automatic defibrillator.
What is an implantable cardioverter defibrillator?
A defibrillator is, in some way, a "super" pacemaker. Like the latter, the implantable defibrillator is a device usually installed in the upper left chest (left subclavicular region). In addition to being able to do anything a pacemaker can do, it continuously monitors the heartbeat and can, if necessary, treat a potentially dangerous or life-threatening arrhythmia.
The future of patients who have survived sudden death, in other words, who’s resuscitation has been effective in ending the episode, is very limited.
Statistics show that 70 to 90% of cardiac arrests that occur outside a hospital are fatal. The more favourable statistic of 70% comes from the impact of automated external defibrillators available in schools and sports centers.
However, a survivor is not necessarily out of danger to a sudden death. Among the 10 to 30% of patients who survived the event, 5 to 40% will leave the hospital. Some may have no or very few neurological consequences, while others will be greatly limited.
Although there has been reanimation at the hospital or elsewhere, a survivor of a cardiac arrest carries the potential risk of neurological damage and consequences in the brain.
Lack of oxygen in the brain quickly causes damage; this anoxia causes congestion, cerebral edema, as well as the swelling that accompanies an injury.
It is precisely these consequences that can be fatal.
How to improve this prognosis
Rapid and effective resuscitation of sudden death patients can change everything positively.
Remember that the best treatment is prevention.
Awareness of the risk factors and changes in your lifestyle are always the best solutions to prevent heart problems.