In the United States, Sudden Cardiac Death is one of the most common causes of death. Those affected collapse, do not react and have no palpable pulse. After one minute at the latest, a respiratory arrest occurs. So what is behind it, and what can be done about it? This article will share everything you need to know about sudden cardiac death.
Sudden cardiac death – what is it?
Sudden cardiac death is when an unexpected heart failure first causes sudden unconsciousness and leads to natural death no later than 24 hours after the onset of acute symptoms. If the sudden cardiac death occurs instantaneously, it is called secondary death. If, however, first aid measures succeed in averting the impending cardiac death, the term survived sudden cardiac death is used to describe this.
Sudden cardiac death is the direct result of cardiac arrhythmia. This can be due to various causes. For adults, by far, the greatest role is played by coronary artery disease. In teenagers, younger adults or athletes, mainly hereditary factors, heart muscle inflammation or changes in the coronary arteries are responsible for sudden cardiac death.
In the United States, about 325,000 people die of sudden cardiac death every year – most frequently during or immediately after extreme physical exertion. According to statistics, Sudden Cardiac Death is one of the most frequent causes of death, ahead of cancer and stroke. Nevertheless, the general public seems to greatly underestimate sudden cardiac death compared to other causes of death.
With increasing age, Sudden Cardiac Death occurs more frequently. Men have a higher risk than women – mainly if they already have known cardiovascular disease, like coronary artery disease (CAD).
Causes of sudden cardiac death
The main cause of cardiac arrhythmias, and therefore sudden cardiac death or secondary death, are coronary artery disease; more rarely, a sudden cardiac death results from other heart diseases such as myocarditis or valvular heart disease.
The precise cause of sudden cardiac death depends primarily on the age of the person affected: Coronary heart disease plays by far the greatest role in adults. In adults, coronary heart disease plays by far the most important role.
In adults, coronary heart disease plays by far the most important role. At the same time, the risk of sudden cardiac death in adulthood is particularly high if a heart attack has already occurred due to heart disease. In teenagers and young adults, predominantly hereditary factors (congenital heart disease), heart muscle inflammation or changes in the coronary arteries are responsible for sudden cardiac death.
Sudden cardiac death during exercise
While regular exercise has been shown to promote heart health, sudden cardiac death – if risk factors are present – can also result directly from exercise or other very vigorous physical activity: In over 80 percent of all cases, sudden cardiac death occurs during or immediately after extreme physical exertion.
The onset of sudden cardiac death during sleep
Sudden cardiac death sometimes also occurs during sleep. This is most common in young people and people with diabetes. Sudden cardiac death even occurs twice as often during sleep in the latter than in non-diabetics. This is caused by hypoglycemia, which leads to cardiac arrhythmias. The sudden cardiac death during sleep is also called “dead-in-bed syndrome”.
Risk factors of sudden cardiac death
The risk factors that promote sudden cardiac death include:
- Previous heart attacks
- Signs of cardiac insufficiency with reduced pumping function, for example, shortness of breath already at rest or under stress
- Cardiovascular arrest that has already been survived once
- An unfavorable hereditary predisposition ( for example, hereditary heart diseases such as Brugada syndrome or long QT syndrome can trigger severe cardiac arrhythmias)
- Heart rhythm disturbances already detected in advance during a long-term ECG
- Old age
- Classical heart-damaging factors such as diabetes mellitus, hypertension, increased cholesterol levels (hyperlipoproteinemia, hyperlipidemia), smoking, heavy alcohol consumption, lack of exercise
How does sudden cardiac death occur?
In cardiac arrhythmia – a disorder in the conduction of the heart’s excitation – your heart no longer receives regular electrical impulses that normally cause the heart muscle to contract (or contract). Consequently, your heart gets out of its usual rhythm.
The heart beats much faster than in healthy people – sometimes more than 500 times per minute instead of the usual 60 to 80 times per minute. Finally, a cardiac arrest with circulatory arrest occurs: The heart can no longer pump blood into the circulatory system, so the circulation collapses.
In more than eight out of ten cases, the arrhythmias directly responsible for sudden cardiac death are high-frequency or even tachycardic arrhythmias:
- Ventricular tachycardias,
- Ventricular flutter and
- Ventricular fibrillation.
In only a small proportion of cases, sudden cardiac death is caused by low-frequency or bradycardic arrhythmias. The cause of the latter can be, for example, that the natural pacemaker of the heart – the sinus node – fails or that the transmission of excitation from the atria to the ventricles is disturbed. As a result, the heart can no longer work properly. If it stops beating, asystole is present.
Sudden cardiac death: Symptoms
Typically, sudden cardiac death proceeds as follows:
- Victims fall over or slump and do not respond to being spoken to or touched,
- They have no palpable pulse
- After one minute at the latest, a respiratory arrest occurs,
- The pupils are dilated
- The skin turns ash-gray (first on fingernails and mucous membranes);
- Without treatment, instantaneous death occurs.
Often, sudden cardiac death occurs without clear warning symptoms: In half of all cases, seemingly heart-healthy people are affected. Occasionally, those affected show no signs of heart disease, although the coronary vessels are already pathologically altered by arteriosclerosis.
It is, therefore, all the more important to watch out for the first signs of a possible heart disease that can cause sudden cardiac death – and use these symptoms immediately as an opportunity to dial the emergency number 112!
Such symptoms include a feeling of tightness or pain in the chest that radiates to the left arm or lower jaw. The complaints typically occur after exertion and predominantly in the morning hours. Other frequent signs include shortness of breath and a general feeling of weakness. However, these symptoms can occur independently and are important to investigate further.
Repeated bouts of dizziness and fainting, where consciousness returns on its own within seconds and minutes, need not but can be the first alarm signs of impending sudden cardiac death. For people with a previous heart attack or known heart failure, temporary palpable palpitations should be especially noted.
Sudden cardiac death: Therapy
Sudden cardiac death is a medical emergency! Immediately call for help at the emergency number 911 and then take first aid measures yourself.
If sudden cardiac death is imminent, defibrillation is the only saving measure apart from life-prolonging immediate cardiopulmonary resuscitation (i.e. cardiac massage and, if necessary, administering breaths).
Reanimation with the defibrillator
Defibrillation involves administering a strong current or voltage pulse to the victim via electrodes on the chest using an electric shock device (the defibrillator, or defi for short): This is intended to prevent sudden cardiac death by realigning the electrical activity of the heart and thus getting it to beat normally again.
Defibrillators are available in all emergency ambulances. Some publicly accessible buildings (e.g., train stations, airports) are also now equipped with easy-to-use defibrillators so that even medical laypeople can use them in an emergency.
Cardiopulmonary resuscitation consists of cardiac massage, applying firm pressure to the unconscious person’s chest so that the chest sinks in at least five centimeters. This is done 30 times (in a rapid rhythm – i. e., more than 3 presses in 2 seconds!). Then, stop chest compressions to give 2 breaths to the unconscious person. After administering breaths, cardiac massage is performed 30 times again, followed by 2 breaths, and so on.
Quick action is vital here, as cardiovascular arrest can lead to permanent brain damage after just three to four minutes. Oxygen deprivation is fatal in 90 percent of cases without early intervention.
Therapy of the underlying disease
Should sudden cardiac death be prevented by these immediate measures, the further therapy depends on the individual case: In the case of a disease that poses an increased risk of sudden cardiac death, the underlying disease must be treated. Besides medication, stents can be used to dilate narrowed coronary arteries, or a bypass operation can be performed.
Most importantly, an implantable cardioverter-defibrillator (ICD) can be used to prevent sudden cardiac death in the event of a threatening cardiac arrhythmia in the future: What this is is a scaled-down electric shock device that you implant (implant) under your skin, much like a pacemaker.
Can one survive sudden cardiac death?
About 15 percent of people affected by sudden cardiac death currently survive in the United States – at local peaks of up to 60 percent.
In the USA, the best prognosis for successfully averting a cardiac death through first aid measures (surviving sudden cardiac death) is in areas where public access defibrillation (PAD) with publicly accessible defibrillators is used.
For example, casinos in Las Vegas do so, where security personnel have mastered resuscitation measures thanks to appropriate training, and automatic external defibrillators (AEDs) are available that are easy to operate even for medical laypersons. Some buildings in European countries that are open to the public (such as airports or train stations) are now also equipped with such defibrillators.
Sudden cardiac death: Prevention
You can largely avoid sudden cardiac death by preventing heart disease. The main strategy against sudden cardiac death is to identify an increased risk early – Even if there are no heart symptoms yet. The more classic risk factors that apply to you, the greater your risk. They include:
- Fat metabolism disorders (such as hypercholesterolemia)
- High blood pressure
- Diabetes mellitus
- Lack of physical exercise
So, those who live healthy lives and exercise moderately regularly can reduce their risk of sudden cardiac death.
Sport is not always good for the heart: it is very important to take it easy during or after infection (e.g. cold, diarrhea or flu). However, especially athletes often start training even though their infection is not yet completely cured. In doing so, they risk the infectious agents leading to an inflammation of the heart muscle (myocarditis).
This can lead to severe cardiac arrhythmias during physical exertion, resulting in sudden cardiac death. Myocarditis caused by pathogens can be prevented to a certain extent by refraining from training during and after any infectious disease or taking it easy on yourself physically.
- Besides the classic risk factors, any one of the following is sufficient to increase the likelihood of sudden cardiac death:
- Prior myocardial infarction
- Signs of cardiac insufficiency
- Surviving sudden cardiac death
- Adverse hereditary predisposition
- Known heart rhythm disturbances
Suppose you have an increased risk of sudden cardiac death. In that case, you should talk to your family doctor or a specialist in heart disease (cardiologist) about appropriate preventive measures.
For those at increased risk of sudden cardiac death, preventative measures consist primarily of treating the underlying condition – e.g., by:
- Medication (such as beta-blockers and antiarrhythmics),
- Dilatation of narrowed arteries in the heart using stents, or
- Bypass surgery.
There is no certain way to protect oneself from sudden cardiac death. Three to five out of ten people who have already experienced cardiac arrest or circulatory failure will suffer such an event again within a year. In such cases, supplementary treatment methods such as the implantable cardioverter/defibrillator (ICD) are available to make sudden cardiac death unlikely.
An implantable cardioverter/defibrillator is a miniaturized electrical shock device (defibrillator) which can be implanted in the same way as a pacemaker and can offer the greatest possible protection against sudden cardiac death in the event of a recurrence of a threatening cardiac arrhythmia.