Sudden cardiac death

Sudden cardiac death occurs when unexpected heart failure preceded by sudden loss of consciousness results in natural death no later than 24 hours after the onset of symptoms. When sudden cardiac death occurs immediately, there is talk of instant death.

Sudden cardiac death is the direct consequence of cardiac arrhythmias, most commonly tachycardias, ventricular flutter, and ventricular fibrillation. Cardiac arrhythmias cause an unexpected cardiorespiratory arrest that occurs after one or two minutes of loss of consciousness. Sudden cardiac death can be due to different causes. These depend mainly on the age of the patient:

  • In adults: coronary heart disease by far plays the most important role(the risk is especially high if you have already had a heart attack).
  • In young people or young adults: Hereditary factors, myocarditisarrhythmogenic dysplasia of the right ventricle, or changes in the coronary vessels are predominantly responsible for sudden cardiac death .


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  • 1 Definition
  • 2 Causes
  • 3 Symptoms
  • 4 Diagnosis
  • 5 Treatment
  • 6 Prevention
  • 7 Source


Sudden cardiac death (SCD) is, by definition, an unexpected and natural cardiac death in people with a known or unknown heart disease that begins with sudden loss of consciousness and occurs within the first 24 hours after the onset of symptoms.

Sudden cardiac death is the consequence of cardiac arrhythmia , that is, an excitation cardiac conduction disorder. The heart stops receiving regular electrical impulses that normally cause contraction of the heart muscle. As a consequence, the heart abandons its usual rhythm. The number of beats increases strongly in most cases, reaching more than 500 beats per minute.

A healthy person has between 60 and 80 beats per minute. This increased heartbeat causes ventricular fibrillation, uncoordinated contractions of the heart’s muscle fibers. Heart failure occurs, even contraction of the heart muscle is no longer possible, so the heart cannot pump blood to the circulatory system. If not treated right away, ventricular fibrillation causes collapse of the circulation in seconds (circulatory arrest). Patients lose consciousness after one or two minutes, after three to five minutes there will be permanent damage, after an average of 10 minutes brain death occurs.


Sudden cardiac death can be due to different causes that, through dangerous cardiac arrhythmia, cause circulatory failure. Cardiac arrhythmias directly responsible for sudden cardiac death are, in more than 80% of cases, very frequent cardiac arrhythmias or tachycardias: ventricular tachycardias, ventricular fluttering, and ventricular fibrillation. Only a small part have low frequency cardiac arrhythmias or bradycardias. The latter can originate, for example, if the natural pacemaker of the heart, the sinoatrial node , fails, or if the transmission of excitation from the atrium to the ventricle is interrupted so that sufficient cardiac output is not possible. If the heart stops beating, asystole occurs.

The main cause of cardiac arrhythmias, and with it sudden cardiac death or instantaneous death, is coronary heart disease . Rarely, sudden cardiac death is due to other heart conditions, such as myocarditis or valve disease. Among the risk factors that favor sudden cardiac death are the following:

  • Previous acute myocardial infarction.
  • Samples of heart failure with insufficient pumping such as shortness of breath at rest or due to exertion.
  • Cardiorespiratory arrest that has been survived.
  • Unfavorable genetic predisposition (sudden cardiac death of relatives).
  • Cardiac arrhythmias determined in advance on a Holter monitor.
  • Advanced age.

Although regular physical activity increases, as it can be verified, the health of the heart, in the case of the existence of risk factors, a sudden cardiac death can be due to a great physical effort (for example, in sports). In more than 80% of all cases, sudden cardiac death occurs during or just after extreme physical exertion.


Sudden cardiac death is characterized by clear symptoms such as the following:

  • Those affected fall or pass out and do not react to speech or painful stimuli. This sudden loss of consciousness can appear with or without previous cardiac symptoms.
  • No pulse is perceived in the carotid.
  • After a minute, at most, they stop breathing: the respiratory movement of the chestis interrupted and air does not come out of the mouth and nose .
  • The pupils dilate.
  • The skinchanges to an ash gray color , first noticeable on the nails and mucosa .
  • Without treatment instantaneous death occurs.

Sudden cardiac death often occurs without clear prior symptoms: in half of the cases it affects people without apparent heart problems. Also when there are no signs of heart disease, many people’s coronary vessels already show advanced changes from arteriosclerosis ( coronary heart disease ). When these changes first cause discomfort they can lead to dangerous cardiac arrhythmias and then sudden cardiac death. For this reason, it is important to recognize the first symptoms of a possible heart disease that can cause sudden cardiac death:

  • One of these symptoms is a feeling of tightness or pain in the chest that radiates to theleft arm or lower jaw . The discomforts typically appear after efforts and mainly in the morning.
  • Other frequent signs are shortness of breath and a general feeling of weakness. These symptoms can also occur separately and need to be diagnosed.
  • Also repeated dizziness and fainting in which you lose consciousness for seconds or minutes, do not have to, but may be the first warning signs of impending sudden cardiac death.
  • In people who have already suffered a myocardial infarction or with a known heart failure, a noticeable transient tachycardia must beespecially controlled .


Sudden cardiac death is associated with cardiorespiratory arrest, the diagnosis of which is made by typical symptoms such as sudden loss of consciousness and lack of pulse. Sudden cardiac death is an extremely dangerous emergency. If symptoms occur, immediate resuscitation will be essential.

When sudden cardiac death is imminent, an electrocardiogram is rarely available with which to diagnose the underlying cardiac arrhythmia.


If sudden cardiac death is imminent, prompt treatment is needed. Only with appropriate urgent measures can rapid death (instant death) be prevented.

In case of ventricular fibrillation, sudden cardiac death can be prevented and life-saving only with immediate defibrillation and (if necessary) with simultaneous cardiopulmonary resuscitation:

  • In case of cardiopulmonary resuscitation, a cardiac massage is performed in which strong pressure is exerted on the chest of the unconscious person so that the chest sinks at least five centimeters. This is done 30 times (at a fast pace: more than three times in two seconds). The cardiac massage is then interrupted to inflate the unconscious person twice with air. After practicing artificial respiration , heart massage is performed 30 times again and air is blown twice, and so on.
  • In defibrillation, the sudden cardiac death patient is given a strong electrical impulse with a defibrillator using electrodes on the chest. This should adjust the electrical activity of the heart again and it should beat again normally. All emergency vehicles have the defibrillators necessary for these emergency measures.

If sudden cardiac death can be prevented by these urgent measures, the treatment to be followed will depend on each individual case: if there is a disease in which there is a high risk of sudden cardiac death, this disease should be treated. Thus, in addition to drug treatment, stents may be used, the diseased cardiac arteries (dilation) may be widened, or a bypass performed.


Unfortunately, anyone can experience sudden cardiac arrest or sudden cardiac death (PCS / MSC). PCS / MSC is unpredictable and can happen to anyone, anytime, anywhere, even teens. Although previous heart disease is a frequent cause of cardiac arrest, many victims have never had a heart problem. The risk increases with age.

Without immediate treatment, only 5% -10% of people survive a PCS / MSC. However, survival rates of over 50% have been achieved in locations where public access programs for early defibrillation have been successfully implemented by installing easily accessible external automated defibrillators (AEDs). Survival rates can further increase when the person receives treatment within three minutes of cardiac arrest.


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