Sudden death in young people is rare, but those at risk can take precautions. Find out more about the risk factors, causes and treatments.

By Mayo Clinic Staff

Sudden death in people under age 35, often due to hidden heart defects or overlooked heart abnormalities, is rare. When these sudden deaths do occur, it's often during physical activity, such as participating in a sporting event.

Millions of elementary, high school and college athletes compete every year without incident. Fortunately, if you or your child is at risk of sudden death, there are screening tests for heart defects and precautions you can take.

Nearly 360,000 sudden cardiac arrests occur outside of hospitals each year in the United States alone. Of those sudden cardiac arrests, very few occur in young people, and only some of those young people die of sudden cardiac arrest. Most deaths due to sudden cardiac arrest are in older adults.

The causes of sudden cardiac death in young people vary. About two-thirds of the time, death is due to a heart abnormality.

For a variety of reasons, something causes the heart to beat out of control. This abnormal heart rhythm is known as ventricular fibrillation.

Some specific causes of sudden cardiac death in young people include:

  • Hypertrophic cardiomyopathy (HCM). This is a disease in which the heart muscle (myocardium) becomes abnormally thick, making it harder for the heart to pump blood.

    Hypertrophic cardiomyopathy, while usually not fatal in most people, is the most common cause of heart-related sudden death in people under 30. It's the most common cause of sudden death in athletes. HCM often goes undetected.

  • Coronary artery abnormalities. Sometimes people are born with heart arteries (coronary arteries) that are connected abnormally. The arteries can become compressed during exercise and may not provide proper blood flow to the heart.
  • Long QT syndrome. Long QT syndrome is an inherited heart rhythm disorder that can cause fast, chaotic heartbeats. The rapid heartbeats, caused by changes in the part of your heart that causes it to beat, may lead to fainting. These irregular heartbeats can be life-threatening.

    In some cases, your heart's rhythm may be so erratic that it can cause sudden death. Young people with long QT syndrome have an increased risk of sudden death.

Other causes of sudden cardiac death in young people include structural abnormalities of the heart, such as unrecognized congenital heart disease and heart muscle abnormalities.

Other causes include inflammation of the heart muscle, which can be caused by viruses and other illnesses. In addition to long QT syndrome, other abnormalities of the heart's electrical system, such as Brugada syndrome, can cause sudden death.

Another rare cause of sudden cardiac death that can occur in anyone, though it's usually heard about in young people who play sports, is called commotio cordis. It occurs as the result of a blunt blow to the chest, such as being hit by a baseball or hockey puck, at just the right time. The blow to the chest can trigger ventricular fibrillation if the blow strikes at exactly the wrong time in the heart's electrical cycle.

Many times these deaths occur with no warning, but symptoms to watch for include:

  • Unexplained fainting (syncope). Sudden and unexplained fainting that occurs during physical activity could be a sign that there's a problem with your heart.
  • Family history of sudden cardiac death. The other major warning sign is a family history of unexplained deaths before the age of 50. This obviously isn't a physical symptom like fainting, but deaths like this in your family should prompt you to pay close attention and perhaps talk with your doctor about screening options.

Shortness of breath or chest pain may also be a sign that you're at risk of sudden cardiac death, but these aren't common and may be a sign of other health problems in young people, such as asthma.

It sometimes can. If you're at high risk of sudden cardiac death, your doctor will usually suggest that you avoid competitive sports. Depending on your underlying condition, medical or surgical treatments may be recommended to reduce your risk of sudden death.

Another option for some, such as those with hypertrophic cardiomyopathy, is an implantable cardioverter-defibrillator (ICD). This is a pager-sized device implanted in your chest like a pacemaker. An ICD continuously monitors your heartbeat. If a life-threatening arrhythmia occurs, the ICD delivers electrical shocks to restore a normal heart rhythm.

There's debate in the medical community about screening young athletes to attempt to identify those at high risk of sudden death.

Some countries such as Italy screen young people with the use of an electrocardiogram (ECG or EKG), which records the electrical signals present in the heart. However, this type of screening sometimes leads to false-positive results — indications that an abnormality or disease is present when in fact it is not — which can cause unnecessary worry and additional tests.

It's not clear that sudden cardiac death can be prevented by the types of routine physical exams that are often necessary to be cleared to play competitive sports.

There are some things you can do if you're worried about your risk factors. For example, if someone in your family dies young, it's important that an autopsy be done to determine the cause of death. If the autopsy shows that a heart condition caused the death, screening of family members may be necessary.

For example, if the autopsy showed hypertrophic cardiomyopathy, it's recommended that all first-degree relatives of the deceased be checked for this condition, including parents, siblings and children. Repeat screening of family members is recommended over time, even if the first evaluation of their heart was normal.

If you're at risk of sudden cardiac death, talk to your doctor about your physical activity level. Whether you can participate in exercise or sports depends on your condition.

For some disorders, such as hypertrophic cardiomyopathy, it's often recommended that you avoid most competitive sports, but this doesn't mean that you will need to avoid exercise altogether. Talk to your doctor about what sort of activities and behaviors you should avoid.

Apr. 14, 2014