What is sudden cardiac arrest?

Sudden cardiac arrest (SCA) occurs when the heart suddenly and unexpectedly stops beating. It is caused by the immediate loss of electrical heart function, usually from an irregular and rapid quivering of the ventricles (called ventricular fibrillation).

Sometimes, these abnormal heart rhythms go away on their own, but most of the time they can worsen into a dangerous rhythm called ventricular fibrillation (cardiac arrest in which the heart is quivering) or asystole (cardiac arrest in which the heart stops beating). Early emergency treatment with cardiopulmonary resuscitation (CPR) or an automated external defibrillator (AED) can help restart a stopped heart and allow the return of a normal heartbeat to help prevent sudden cardiac death (SCD).

Although SCA is rare in children, it can affect anyone, even those who are physically fit. Each year, SCA claims the lives of over 2,000 children and adolescents in the United States and accounts for approximately 3-5% of all deaths in children ages 5 to 19 years. SCA is also responsible for 10-15% of sudden unexpected infant deaths.

Risk factors for sudden cardiac arrest

Sudden cardiac arrest (SCA) happens more often in boys than girls and is most common in children ages 10 to 19. However, SCA can happen in children of any age, even babies. 

Risk factors include:

• Two-thirds of the deaths caused by SCA in children occur during exercise or activity. SCA is the leading cause of death in young athletes, accounting for 75% of all athlete-related deaths.
• Known congenital heart disease or structural heart abnormalities.
• Known abnormal heart rhythms associated with congenital heart disease. These most often include irregular beats in the ventricles or atria, especially after surgery or if the heart is weak.
• Known abnormal heart rhythms that are very rapid, even with a normal heart. For example, rapid ventricular tachycardia or atrial fibrillation with a rapid ventricular response.
• Undiagnosed cardiac conditions, especially those known to be associated with sudden cardiac arrest.
• Exposure to drugs, medications, toxins and infectious agents, including cocaine, inhalants, recreational or club drugs, and some prescription medications.
• Sudden blow to the chest directly over the heart (called commotio cordis).
• A family history of:
  • Known heart abnormalities
  • Sudden death before 50
  • Conditions known to cause SCA, such as long QT syndrome, Brugada syndrome, catecholaminergic polymorphic ventricular tachycardia (CPVT), hypertrophic cardiomyopathy (HCM), arrhythmogenic right ventricular cardiomyopathy (ARVC) or other familial cardiomyopathies
  • Unexplained fainting or seizures

If you have a family history of any of these conditions, immediate family members should be tested for conditions that can be inherited or linked to a genetic mutation. This can help identify a condition early and possibly prevent SCA or SCD.

Causes of sudden cardiac arrest

SCA is usually caused by ventricular fibrillation (VF), an abnormality in the heart's electrical system. VF makes the heart quiver instead of pumping, so no blood reaches the body or brain. VF is not the same as a heart attack. A heart attack happens when a coronary artery is blocked, which damages the heart muscle. Sometimes, a heart attack can lead to sudden cardiac arrest.

SCA may also be associated with a sudden stop of all electrical activity in the heart (also called asystole). It can also be associated with pulseless electrical activity (PEA), which is when the heart shows electrical signals but doesn’t contract or pump blood.

The most common causes of SCA in children are:

• Structural cardiac abnormalities (congenital heart diseases and heart surgeries, problems with the coronary arteries, or Marfan syndrome)
• Abnormalities of the electrical system of the heart (also known as primary electrical diseases), such as long QT syndrome and Wolff-Parkinson-White syndrome
• Abnormalities of the heart muscle structure or function, such as hypertrophic cardiomyopathy (HCM), arrhythmogenic right ventricular cardiomyopathy (ARVC), or dilated cardiomyopathies
• Acquired heart disease (inflammation or infection in the heart, called myocarditis)
• Arrhythmias, including atrial flutter/atrial fibrillation, ventricular tachycardia (VT), ventricular fibrillation, sinus node dysfunction, and complete heart block
• Atherosclerotic coronary disease (in children who have had a heart transplant or rare cholesterol problems)
• Commotio cordis (caused by a blow to the chest)
• Drug-induced SCA

Often, the cause of SCA isn’t known until after it happens. In many cases, these conditions are inherited, but family members don’t know about their family history.

Symptoms of sudden cardiac arrest

In 30-50% of SCA/SDA cases, there are warning signs and symptoms that have been ignored or misunderstood.

If your child experiences any of the warning signs or symptoms of SCA, make an immediate appointment with your pediatrician or take your child to the emergency department.

Warning signs and symptoms may include:

• Unexplained fainting (syncope) or near fainting, especially during or just after activity
• Repeated episodes of unexplained fainting (syncope)
• History of recurrent fainting or unusual seizures or seizure-like activity, especially during or just after activity
• Dizziness or lightheadedness
• Excessive fatigue or unexplained shortness of breath with exercise
• Recent viral infection with chest pain or change in exercise tolerance
• Prior evaluation or treatment for a cardiac condition, particularly if the condition is known to be associated with SCA 

In more than half of sudden cardiac arrest cases in children, death happens with no warning. Many young people don’t know their risk factors and may not tell adults when they have symptoms. They might feel scared, embarrassed, or not realize that what they’re feeling could be a serious problem. Educating parents, children and teenagers about the symptoms and risk factors of SCA is one way to help prevent it.