Sudden cardiac death refers to the unexpected stopping of the heart. This is also called cardiac arrest.
Cardiac arrest is not always fatal if the person receives medical attention within minutes. About one in five people who experience cardiac arrest survive.
Sudden cardiac death can occur in people who have a diagnosed heart condition or those that never show symptoms and are undiagnosed. Sudden cardiac death occurs in roughly one out of every 200,000 to 300,000 children.
What causes sudden cardiac death?
About half of the cases occur in older people who develop clogged heart arteries over time. The other half occur in people with either:
- congenital heart disease, especially involving electrical instability in the heart (arrhythmias)
- acquired diseases that result in an enlarged heart, such as cardiomyopathy
For instance, in patients with hypertrophic cardiomyopathy, the risk of sudden cardiac death is 2% per year. Often when you hear of young athletes suddenly dying with no prior symptoms, they have undiagnosed cardiomyopathy due to an underlying heart condition or abnormal electrical patterns in the heart. Pulmonary hypertension and Eisenmenger syndrome are also strongly associated with sudden cardiac death. It is also considered to be a late complication after surgery to correct a heart defect.
About one-third of the cases of sudden cardiac death have a genetic component. This involves conditions like hypertrophic cardiomyopathy, certain tachycardias, Marfan syndrome, and long QT syndrome. If there is a family history of sudden death, genetic screening may be possible in order to identify family members at risk who may not be showing symptoms.
Cardiac arrest is not always fatal
Cardiac arrest is not always fatal. It all depends on how quickly a child can get life-saving medical attention — specifically a machine called an automated external defibrillator — in order to reverse the cardiac arrest, or "jumpstart" the heart. This is known as "converting" an abnormal fibrillation to a normal heartbeat. Medical attention is needed within minutes of an arrest.
About 20% of patients who experience cardiac arrest do survive. They need to be closely examined, usually through cardiac catheterization and electrophysiology tests, to determine the source of the problem and prevent a recurrence. This is especially important since people who have experienced cardiac arrest are at increased risk of experiencing it again. Treatment, depending on the type of problem, may then involve structural correction of the heart through surgery, radiofrequency catheter ablation, drugs, implantable cardiac defibrillators, or heart transplant.
What can be done to prevent sudden cardiac death?
Early detection of the risk of sudden cardiac death is key to preventing it. This is challenging since in many cases, there are no symptoms and it occurs in seemingly healthy adults. Early detection would involve a complete physical examination and review of the family medical history and any symptoms that might have been experienced. Key symptoms include dizziness, fainting, or chest pains after vigorous exercise, shortness of breath, and palpitations. An echocardiogram, and sometimes an electrocardiogram, can also help identify a problem.
Researchers are also having some success at identifying gene mutations that may predispose individuals to sudden cardiac death. It may be possible to test for these mutations and take measures to protect these individuals.