SUDDEN DEATH: everything you need to know…
SUDDEN DEATH: everything you need to know…


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What is sudden death?
Sudden cardiac death (SCD) is an unexpected death due to cardiac causes that occurs in a short time period (generally within 1 hour of symptom onset) in a person with known or unknown cardiac disease. Though SCD is a tragic situation at any age, when it affects a youth, it has, understandably, a greater media impact.

Is sudden death frequent?
Sudden death is not rare, affecting, in the general population, about 100 individuals per 100 thousand inhabitants per year. Applying this data to Portugal, about ten thousand of sudden deaths occur per year in our country. However, and in opposition to the usual belief, sudden death is much less frequent among the youth (1/100 thousand per year below 30 years of age) than in older ages; it sometimes affects elite athletes leading to intensive media coverage, and that’s the reason why it is currently thought that it is predominant in younger age groups.

What are the causes of sudden death?
In the majority of cases sudden death is caused by heart disease (more than 90% of cases) but in a small percentage it results from diseases of other organs such as the lungs or the central nervous system. Another important concept is that the causes of sudden death vary with age: thus, over the age of 35, the main cause is, by far, coronary artery disease, while below this age group the causes are multiple, predominantly hereditary heart diseases.

Why is the correct diagnosis of the cause of sudden death important?
A key aspect in preventing sudden cardiac death consists in the establishment of the correct diagnosis of the disease that led to it, since the detection, in a family member, of a hereditary disease potentially causing sudden cardiac death requires the screening of this pathology in other family members. Thus, in cases of sudden death in the context of a hereditary heart disease, the remaining family members should be promptly examined and, if the disease is detected in any of them, they must be submitted to appropriate prevention. That is why we say that the correct diagnosis of the cause of sudden death cause is a must, with obvious clinical and preventive implications – it saves lives. And that’s why we also say that sudden death is almost never the end, but the beginning of the story…

How does sudden death happen?
Three factors play a role in the origin of SCD: organic heart disease, precipitating factor and fatal arrhythmia. The association between the heart disease that affects the patient (substrate) and the precipitating factor of the fatal event (trigger), such as intensive physical exercise or emotional stress, creates the conditions for the occurrence of a very serious type of cardiac arrhythmia – ventricular fibrillation – which leads to death within seconds or minutes.

What is the relation between physical exercise and sudden death?
As mentioned, exercise alone does not cause sudden death, but can act as a precipitant (trigger) in susceptible individuals (patients with cardiac disease).

Can sudden death occur during rest/sleep?
Yes, not only it is possible, but it is also not uncommon. In fact, there is a peak in the incidence of sudden death during the night and in the early hours of the morning.
Our central nervous system (specifically a small but important gland called pituitary), “wakes up early, well before the rest of the body” producing and releasing into the bloodstream certain substances (neuro-hormonal substances) that stimulate the production of specific hormones (such as cortisol and adrenaline), that prepare us to face another new day.
However, in individuals with structural heart disease, these substances, increasing blood pressure and heart rate, can act as precipitants of malignant cardiac arrhythmias that lead to sudden death.
This is the reason why the number of sudden cardiac deaths, strokes, myocardial infarctions and hypertensive crises (“blood pressure rises”) occur in the early morning, in times of supposedly greater rest of the body.

What are the peculiarities of sudden death in adults and the elderly?
As stated above, it is in these age groups that sudden death occurs most frequently, usually as a consequence of atherosclerosis in the coronary arteries (coronary artery disease) leading to acute myocardial infarction and SCD.

And what are the characteristics of sudden death in young people and competitive athletes under the age of 35?
Fortunately they are rare situations but also, as already stated, they have a major impact on the media as they often strike young patients, sometimes well-known sports figures.
Its main causes are hereditary diseases of the heart muscle (myocardium) – cardiomyopathies – the most frequent being hypertrophic cardiomyopathy and arrhythmogenic right ventricular cardiomyopathy and coronary artery anomalies (congenital or acquired).
Other causes (responsible for many autopsies initially considered inconclusive) are the use of illicit substances (doping), as well as another inherited heart diseases – ionic channels diseases or “channelopathies” – that only cause abnormalities at a molecular level, with changes in the concentration of certain ions (sodium, potassium, calcium…) in the heart.

Can we prevent sudden death? Is it possible to intervene effectively when it occurs?
Yes, sudden death can be prevented and this is currently a major research area in medicine.
On the other hand, timely and proper cardiopulmonary resuscitation manoeuvres may prevent a fatal outcome.

Is it “worth it” to prevent sudden cardiac death?
Obviously yes, and a good example of it is the figure below, which refers to the annual rate of sudden death in Italian athletes between the years of 1980 (when this country started a national program for the prevention of sudden death) and 2000 (20 years after the implementation of this project). It is clear (continuous line) that the incidence of SCD decreased from about 4/100 thousand (in 1980) to about 0.5/100 thousand per year (in 2000), clearly showing that prevention “is worth it”.

How to prevent sudden death?
The prevention of sudden death is based on two major issues: primary prevention and secondary prevention. In primary prevention, preventive actions are focused on individuals at risk but without any prior episode of cardiac arrest, while in secondary prevention preventive actions are focused on patients who have been “resuscitated” from sudden death.

How is the prevention of sudden death performed?
Prevention of sudden death is performed acting on each of the three above-mentioned factors that are in their origin, heart disease, arrhythmia and precipitant factors.
Regarding the presence of heart disease there’s a need to prevent its occurrence and to treat it (if it is already present). Regarding the precipitant, the correct preventive attitude is to avoid it ( for instance, disqualifying for competitive sports subjects suffering from diseases in which physical exercise is known to be a precipitant for sudden death). Regarding arrhythmia, the prevention is their treatment, either with drugs (anti-arrhythmics) or abolishing the cardiac electrical circuits that are their source (radio-frequency ablation), or by the implantation of electrical devices (implantable cardioverter defibrillators and pacemakers).


1. Sudden death is not uncommon, affecting more frequently adults and older people (despite having a greater media impact in young people).

2. In the majority of cases it results from heart diseases.

3. In patients older than 35 years of age, the main cause is coronary artery disease.

4. In individuals under the age of 35, causes may vary, but hereditary heart disease (cardiomyopathies and channelopathies) stand as the main causes.

5. Sudden death results from the interaction between heart disease and a precipitant that causes a fatal cardiac arrhythmia.

6. Exercise alone does not cause sudden death, but may be a precipitant. However, many sudden deaths occur at rest.

7. In the case of hereditary heart disease, the correct diagnosis of the cause of death is essential for screening family members and preventing sudden death in these individuals: THE CORRECT DIAGNOSIS OF THE SCD CAUSING DISEASE HAS AN IMPACT ON THE PREVENTION OF SUDDEN DEATH!

8. Often SUDDEN DEATH IS NOT THE END, BUT THE BEGINNING OF THE STORY: despite the LOSS of a life, it can lead to the prevention of its occurrence in relatives!!!

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