Sudden death in young people — Heart problems often blamed

Heart problems and sudden death (sudden cardiac death) in young people: A Mayo Clinic specialist discusses how this rare and tragic event can occur.

Michael Ackerman, M.D.

A young, seemingly healthy teenager collapses on a playing field and dies. News of these unexpected and sudden deaths saddens and alarms parents, who wonder if their child may be at risk of sudden death.

Fortunately, sudden death in young people, often due to hidden heart defects or overlooked heart abnormalities, is rare. Millions of elementary, high-school and college athletes compete every year without incident. Still, when sudden death in young people is due to a heart abnormality — sometimes referred to as sudden cardiac arrest (SCA) or sudden cardiac death (SCD) — it's often triggered by physical activity, such as during a sporting event.

Doctors are learning more about sudden death risk factors, including genetic reasons and other causes. Michael Ackerman, M.D., is a Mayo Clinic physician and researcher who specializes in caring for young people at high risk of sudden cardiac death. He's director of Mayo Clinic's Long QT Syndrome Clinic, as well as head of Mayo Clinic's Windland Smith Rice Sudden Death Genomics Laboratory. He answers some common questions about sudden death in young people.

How common is sudden cardiac death in young people?

There are about 300,000 sudden cardiac deaths each year in the United States alone, but the vast majority of those deaths are in the elderly. Of those sudden cardiac deaths, about 1 percent to 2 percent occur in young people. So you're looking at perhaps 3,000 to 6,000 such deaths annually. I should add that when we say "young people," we don't just mean teenagers. Typically, our definition of young is anyone under age 35.

What can cause sudden cardiac death in young people?

The causes of sudden death in young people vary. About two-thirds of the time, a coroner discovers during an autopsy that the death was due to a heart abnormality. The remaining one-third of deaths are sometimes referred to as sudden unexplained death, because a cause could not be pinpointed. In these cases, we usually suspect a genetic disorder, and we may need to do further genetic testing to confirm such suspicions that it's heart-related. However, what all sudden cardiac deaths have in common is the final common pathway that leads to death.

For a variety of reasons, something — such as a structural heart defect — causes the heart to degenerate into a chaotic and abnormal electrical rhythm and the heart beats 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 and is 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 to the heart. The arteries can become compressed during exercise and not provide proper blood flow to the heart.
Long QT syndrome (LQTS). This disorder can be inherited. It occurs when the heart's electrical system malfunctions. On an electrocardiogram, the letter Q marks the point where an electrical impulse signals the heart's ventricles to contract (depolarization). The letter T marks the point where the cells of your ventricles are electrically recharging for the next heartbeat (repolarization). When the space between the start of the Q wave and end of the T wave is prolonged, this indicates that the electrical recovery phase is sluggish, inefficient, and/or disorganized. Young people with QT prolongation have an increased risk of sudden death.

There are many other causes of sudden cardiac death in young people. Like the previous examples, they usually affect the structure of the heart or heart's electrical system.

There's another rare cause of sudden cardiac death that can occur in anyone, though it's usually heard about in young people who play sports. 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. Its medical name is commotio cordis. The blow to the chest can trigger ventricular fibrillation if the blow strikes at exactly the wrong time in the heart's electrical cycle.

Are there symptoms or red flags parents, coaches and others should be on the lookout for that signal a young person is at high risk of sudden cardiac death?

Many times these deaths occur with no advance warning. However, there are two big red flags. The first is sudden and unexplained fainting (syncope) that occurs during physical exertion. In addition to these fainting spells, seizures can also occur. For example, if someone passes out mid-stride while running in a race, that's a warning sign.

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 if there are deaths like this in your family, it should prompt you to pay close attention and perhaps talk with your doctor about screening options.

Once in a while physical symptoms such as exercise-induced shortness of breath or chest pain can occur, but these are less common and it's also hard to tell them apart from more common conditions such as asthma.

Can sudden death in young people be prevented?

Yes, it often can. If we're able to identify someone as being at high risk of sudden death, there are preventive options. For example, we can prescribe medications such as beta blockers that affect a person's heart rate. 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 a precisely calibrated electrical shock(s) to restore a normal heart rhythm.

Who should be screened for sudden death risk factors?

There's debate about whether we should establish better screening methods in the United States to detect those at high risk of sudden death. Some other countries, such as Italy and Japan, screen young people with the use of an electrocardiogram (ECG, or EKG), which records the electrical signals present in your heart. However, some are concerned that this type of screening is expensive and turns up a lot of what we call false-positives — tests that look suspicious, but turn out normal. I think we should be screening all young people to detect heart problems, but at the moment we haven't figured out the best way to do that.

However, there's no debate about what to do if someone has risk factors. For example, if someone in your family has died young from sudden cardiac death, it's essential that an autopsy be done on that person to determine the cause of death. In addition, all first-degree relatives of the deceased must be evaluated carefully — that means parents, siblings and children.

When sudden death in young people occurs, it often seems to happen in athletes. Does physical exertion increase the risk?

Yes. For many of these deaths, the trigger is often related to exercise. It's like fuel and a match.

If you're at risk, should you avoid sports and other physical activity?

It depends on your type of sudden cardiac death risk factors. For some disorders, such as hypertrophic cardiomyopathy, we recommend you avoid most sports. Talk to your doctor about what sort of behaviors you should avoid.