Sudden Cardiac Arrest

Sudden cardiac arrest is a medical emergency in which the heart abruptly stops pumping blood effectively, most often because its electrical system malfunctions and causes the lower heart chambers to quiver chaotically instead of beating in a coordinated rhythm. When this happens, blood stops flowing to the brain and other vital organs, and a child becomes unconscious and unresponsive within seconds. Without immediate treatment to restore a normal heart rhythm, sudden cardiac arrest is fatal within minutes.

While the term is sometimes used interchangeably with sudden cardiac death, cardiac arrest describes the event itself — the sudden stopping of effective heart function — and survival is possible when it is recognized immediately and treated with cardiopulmonary resuscitation (CPR) and, when available, an automated external defibrillator (AED). Sudden cardiac arrest in children and adolescents is rare, but because it can occur in a child with no prior diagnosis and often with little or no warning, awareness of its causes, warning signs, and emergency response is an essential part of pediatric heart care.

In more than half of pediatric sudden cardiac arrest cases, the event occurs with no preceding warning at all. When warning signs are present, however, they are important to recognize, because they may reflect an underlying heart condition that increases the risk of a future event:

• Fainting or near-fainting, particularly if it occurs during or immediately after physical activity rather than from a benign cause such as standing up too quickly
• Chest pain or unusual chest discomfort
• Shortness of breath that is out of proportion to the level of activity
• Heart palpitations, described as a racing, fluttering, or pounding sensation in the chest
• Unexplained seizure-like activity, especially occurring around exertion

Because children and teenagers may feel embarrassed or may not recognize these sensations as medically significant, they often do not report them to a parent or coach, which is one reason these warning signs are frequently missed before an event occurs. Any of these symptoms, especially when they occur during exercise, warrants prompt medical evaluation rather than being dismissed as minor.

In children, sudden cardiac arrest is most often caused by an underlying, sometimes previously undiagnosed, heart condition rather than the coronary artery blockages that typically cause cardiac arrest in adults:

• Structural conditions — such as hypertrophic cardiomyopathy, in which the heart muscle becomes abnormally thickened, and certain congenital heart defects that can disrupt normal heart function and predispose to dangerous rhythm disturbances
  
  
• Inherited electrical disorders — including long QT syndrome and other conditions that affect the heart's electrical signaling, which can trigger sudden arrhythmias even in a heart that otherwise appears structurally normal
  
  
• Blunt chest trauma — a forceful blow to the chest during sports, which can disrupt the heart's rhythm at a vulnerable point in its electrical cycle
  
  
• Electrolyte imbalances, infections, or medication reactions — less commonly, severe electrolyte imbalances, certain infections affecting the heart muscle, or reactions to specific medications or substances can also precipitate an arrest

In a meaningful proportion of cases, a thorough evaluation after the event, including genetic testing, is needed to identify the underlying cause.

• A personal history of a diagnosed heart condition, particularly one already known to be associated with dangerous arrhythmias, is the most significant risk factor and is a primary reason children with such diagnoses are followed closely by a pediatric cardiologist
  
  
• A family history of sudden cardiac arrest, sudden unexplained death at a young age, or a known inherited heart rhythm disorder substantially raises risk for other family members, since many of the underlying conditions are genetic and can be silently present in relatives who have never been evaluated
  
  
• A prior episode of unexplained fainting, especially during exercise, is a warning sign that should prompt cardiac evaluation, since it may reflect an undiagnosed electrical or structural heart condition
  
  
• Participation in competitive sports does not itself cause sudden cardiac arrest, but the physical exertion involved can act as a trigger in a child who has an underlying, previously unrecognized heart condition, which is why sports physicals are an important opportunity for screening

Sudden cardiac arrest cannot be entirely prevented, but several measures meaningfully reduce the risk and improve the chances of survival if an event does occur:

• Ensure regular checkups and a thorough sports physical before participation in athletics, so a physician has the opportunity to ask about family history and listen for signs of an underlying heart condition
  
  
• Seek prompt medical evaluation of any exercise-related fainting, chest pain, or palpitations, allowing conditions that increase arrest risk to be identified and managed before a life-threatening event occurs
  
  
• Discuss genetic counseling and screening for other family members if there is a history of sudden cardiac death, inherited arrhythmia, or cardiomyopathy in the family
  
  
• Support community-level preparedness, since a substantial number of events still occur with no warning at all — widespread availability of automated external defibrillators at schools and sports venues, combined with training for parents, coaches, and caregivers in recognizing an arrest and performing CPR, meaningfully improves survival when prevention is not possible