What causes sudden cardiac arrest in a young and previously healthy person?

Sick heart. If heart is not working well and if suddenly there is a high demand this can cause an arrest.
Depends. Undiagnosed structural heart problems can (very rarely) lead to a cardiac arrest in what appears to be an otherwise healthy person. Certain illegal drugs, particularly stimulants such as cocaine, also have the potential to cause rhythm problems that can lead to cardiac arrest.

Related Questions

What can cause sudden cardiac arrest in young people?

Abnormal rythm. Cardiac arrest in young people is most commonly cause by an abnormal rhythm that originates from the pumping chamber of the heart (ventricle). Heart attacks are a rare cause for cardiac arrest in young people.

Is it possible for a completely healthy young fall victim of a sudden cardiac arrest without any reason?

Possible. It is possible, but rare. There are cases of young healthy athletes arresting while playing sports. This is usually thought to be caused by abnormal electrical conduction system of the heart.
Sudden MI. Yes. Likely due to an undiagnosed pre-existing cardiac condition.

How can unexplained sudden cardiac arrest with no known cause happen to people with healthy hearts? Is there anything that could avoid this?

Testing. Usually this can occur in certain condition when a person is involved in athletics or some strenuous activities. Only thing a person can do these days to have a check before participating in sports especially when there is a family history.
Not normal. There are some underlying issues. Electrical system, or congenital that surface with sudden cardiac arrest commonly.

How common is it for a young person suffering from sudden cardiac arrest?

Very rare. Unless some one an underlying diseases such as hypertrophic cardiomyopathy, the likelyhood of having a cardiac arrest is remote.
Unusual. Congenital anomalies hyperlipidemia diabetes cocaine are known causes.

I was wondering what are the chances of a young person suffering from sudden cardiac arrest?

SCA. Sudden cardiac arrest in a healthy young person is a very low probability event. When you hear about it in a young person, they generally have a structural heart problem or an underlying disease.

In an older person in their 80's what would be the most common cause of sudden cardiac arrest?

Coronary artery dise. Coronary artery disease is the most frequent cause of sudden death over the age of 60. Unfortunately some of these have no symptoms prior to their cardiac arrest.