Sudden cardiac death in young people is a rare but alarming occurrence. Doctors define sudden cardiac death as a death resulting from a heart-related issue that occurs within 1 hour of symptoms starting.

In many cases, the underlying heart issues are unknown, making sudden cardiac death even more traumatic for loved ones.

In most cases, sudden cardiac death in young people — that is, people under 35 years — is due to a genetic or congenital condition, which doctors may or may not have diagnosed before death.

This article looks at some of the most common causes of sudden cardiac death in people under 35. It lists the potential symptoms to be aware of and explains how to prevent fatal complications from underlying heart diseases.

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Sudden cardiac death is rare in young people, which makes estimating its frequency challenging. Researchers most often study sudden cardiac death in young athletes, as it is the most common cause of sudden death in this population.

A 2014 review estimated that among athletes ages 9–40 years, sudden cardiac death occurred in 1 out of every 40,000–80,000 people. Sudden cardiac death is more common among elite athletes, occurring in about 1 out of every 8,253 people per year.

The authors of the review note that among athletes, the groups most at risk include:

  • males
  • Black athletes
  • basketball players

In the general population, estimates suggest that the rate of sudden cardiac death among people aged 18 years or younger, but excluding infants, is between less than 1 and 4 deaths per 100,000 people annually.

In young people, sudden cardiac death is most often genetic or congenital in nature. Acquired forms of heart disease that lead to sudden cardiac death are rare but possible.

These conditions affect the heart’s structure or rhythm, which places strain on the heart muscles and affects blood flow.

One of the most common causes of sudden cardiac death in young people is hypertrophic cardiomyopathy (HCM). HCM is a genetic heart condition that affects up to 1 in 167 people.

In HCM, the muscles of the left ventricle become thickened and enlarged, which can result in a reduced left ventricle volume and impaired activity of the aortic valve. These effects can make it more difficult for the heart to pump blood to the rest of the body, place strain on the heart and lungs, and disrupt typical heart rhythms.

In most cases, HCM is benign, and many people may not even experience symptoms. In some cases, though, heart complications can develop. Sudden cardiac death may occur in around 1 in 3,000 people with HCM per year.

Other forms of congenital or genetic forms of cardiomyopathy can also cause sudden cardiac death but are less common. They include:

  • arrhythmogenic right ventricular cardiomyopathy (ARVC)
  • dilated cardiomyopathy
  • left ventricular noncompaction cardiomyopathy

Acquired coronary artery disease is the most common cause of sudden cardiac death in older adults. Although it is rare in young people, congenital conditions that affect the coronary arteries — the blood vessels that supply blood to the heart — can also cause sudden cardiac death in this population.

Other possible causes of sudden cardiac death in young people include, but are not limited to:

  • congenital valvular anomalies, such as mitral valve prolapse
  • structural abnormalities in the aorta
  • inherited or acquired forms of arrhythmia, such as long QT syndrome
  • ion channelopathies

The most reliable predictor of potential risk for sudden cardiac death is a previous episode of sudden cardiac arrest, which means the heart suddenly stops beating. If sudden cardiac arrest occurs in young people, doctors may put an implantable cardioverter defibrillator (ICD) in place right away to help prevent further episodes.

However, without a previous history of cardiac arrest, predicting sudden cardiac death can be difficult. Often, people are unaware of the underlying cause of disease and may not have symptoms.

The most common symptoms before sudden cardiac death are often associated with abnormal heart rhythms. These typically include:

  • a fast, heavy, or fluttering heartbeat, known as palpitations
  • chest pain, especially with activity
  • fainting
  • seizure

People at risk of other forms of heart disease should be aware of additional symptoms associated with those conditions, including:

  • shortness of breath, especially with activity
  • dizziness or lightheadedness
  • excessive tiredness
  • swelling in the lower part of the body

If a young person experiences symptoms consistent with potential heart disease, they should undergo an evaluation by a healthcare professional. They may wish to consider limiting strenuous activity until they receive the results of diagnostic tests.

In most cases, with early intervention and proactive management, it is possible to prevent sudden cardiac death. However, this relies on people being aware of any underlying heart abnormalities, or risks for heart abnormalities, and receiving appropriate treatment.

Treatment to prevent sudden cardiac death is dependent on the type of underlying disease and may involve medication, surgery, lifestyle changes, or a combination of these interventions.

In people at high risk of sudden cardiac death, research has shown the implantation of an implantable cardioverter/defibrillator (ICD) as a primary form of prevention can disrupt potentially life threatening episodes of arrhythmia by up to 49-fold.

Doctors may also advise young people with genetic or congenital heart abnormalities that put them at increased risk of sudden cardiac death to adopt a heart-healthy lifestyle. This may include a heart-healthy diet, smoking cessation, and light physical activity. They will generally discourage intensive physical activity, although this depends on individual risk factors.

The wide publicizing of sudden cardiac death, particularly in young athletes, means there is increasing interest in proactively screening all young athletes for heart conditions that may increase their risk of fatal complications.

The American Heart Association (AHA) currently recommends screening for cardiac abnormalities that may increase the likelihood of sudden cardiac death in people with high risk conditions. Examples include people with:

  • a family history of sudden cardiac death
  • evidence of left ventricular hypertrophy
  • a history of unexplained fainting
  • arrhythmias

There is still debate regarding whether people with heart abnormalities should avoid physical activity. Among people with HCM, one of the leading causes of sudden cardiac death, most cases are benign. Therefore, limiting physical activity in all cases may be unnecessary.

A personalized approach to physical activity may be more appropriate. Doctors can make recommendations on a case-by-case basis depending on the underlying risk of fatal complications and the ability to prevent these events.

Doctors may recommend that individuals at increased risk should avoid strenuous activities if treating the underlying heart abnormality is not possible.

While there is no definitive recommendation, experts generally consider moderate-intensity physical activity to be safe for people with heart abnormalities and believe it may help maintain overall heart health.

Sudden cardiac death in young people is rare but often alarming and traumatic. Although these tragedies may seem unpredictable and unavoidable, proactive screening and care can help prevent sudden cardiac death in many people with underlying heart abnormalities.

If a young person is experiencing any symptoms of cardiac dysfunction, especially during physical activity, they should consult a doctor right away to assess their heart health.