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Dr. Alessandro Giardini
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Watching your child collapse and lose consciousness is one of the most frightening experiences a parent can go through. Whether it happened at school, on the sports field, or simply standing up too quickly at home, the memory tends to linger long after your child has recovered and is back to normal. The reassuring news is that fainting (or syncope, as doctors call it) is extremely common in children and teenagers, and the majority of cases have a straightforward, benign explanation. Understanding what causes it, what to look out for, and when a specialist opinion is needed can make an enormous difference to how families cope.This page has been written by Dr. Alessandro Giardini to help parents and young people navigate the subject clearly and confidently, drawing on current clinical evidence and the kind of questions that come up most frequently in the paediatric cardiology clinic.
Syncope is the medical term for a temporary loss of consciousness caused by a brief reduction in blood flow to the brain. It comes on suddenly, causes the person to go limp and fall if they are not supported, and typically resolves within seconds to a minute or two. Recovery is usually rapid and complete, though many children feel tired, pale, or slightly nauseous afterwards.It is important to understand that syncope is not the same as a seizure, a stroke, or a prolonged blackout. True syncope is brief, self-limiting, and leaves no lasting effects. That said, any episode of loss of consciousness in a child deserves proper evaluation, not because it is likely to be serious, but because a careful assessment allows the right reassurance to be given, and ensures the rare cases that do need treatment are not missed.Fainting is remarkably prevalent in young people. Around 15 to 20 per cent of children and adolescents will experience at least one episode before the end of their teenage years, and the peak age is around 15, particularly in girls. In fact, for most teenagers a faint is a one-off event that never recurs.
By far the most common cause of fainting in children and teenagers is what doctors call vasovagal syncope, also known as neurally mediated syncope or, simply, the common faint. It accounts for between 60 and 80 per cent of all syncope in the paediatric age group.
What happens in a vasovagal faint is that the body’s autonomic nervous system (the part that controls heart rate and blood pressure automatically) overreacts to a trigger. Blood pools in the legs, blood pressure drops, heart rate slows, and momentarily the brain does not receive enough blood to maintain consciousness. The whole process is self-correcting: once the child is horizontal, blood flow to the brain is restored and they wake up.
Common triggers include prolonged standing (in queues, assemblies, or hot classrooms), getting up too quickly, heat, dehydration, hunger, pain, emotional distress, or the sight of blood or needles. In adolescent girls, fainting can also be associated with growth spurts, menstrual cycles, and periods of rapid weight change.The classic sequence is well recognised: the child notices they feel light-headed, nauseated, or hot; their vision may tunnel or go grey; they may look pale and sweaty. Then they faint. This warning phase, called the prodrome, is an important feature and, when present, is reassuring that the faint is benign in nature.
A related group of conditions involves difficulty maintaining blood pressure and heart rate when moving from lying or sitting to standing. The most discussed of these in teenagers is Postural Orthostatic Tachycardia Syndrome, or POTS. This is a condition where the heart rate rises abnormally on standing, causing dizziness, fatigue, brain fog, and sometimes fainting. POTS is more common in adolescent girls and can be associated with periods of rapid growth, prolonged periods of rest following illness, and occasionally anxiety.POTS is not dangerous, but it can significantly affect quality of life, and it is very much manageable with the right approach. Increased fluid and salt intake, graded exercise, and in some cases medication can make a substantial difference.
Some children faint in very specific circumstances like during coughing, breath-holding, hair-brushing, urination, or swallowing. These situational faints follow the same basic mechanism as vasovagal syncope and are generally benign, though they can be alarming to witness.
A small but important minority of fainting episodes in children have a cardiac cause. These are the cases that a paediatric cardiologist is specifically trained to identify. Cardiac syncope occurs when the heart’s output suddenly drops either because of an abnormal heart rhythm (arrhythmia), a structural problem such as hypertrophic cardiomyopathy or a congenital heart defect, or occasionally an abnormality of the heart’s electrical conduction system such as Long QT Syndrome or Wolff-Parkinson-White Syndrome.
The features that raise concern for a cardiac cause include syncope that happens during exercise rather than after it, syncope with no warning at all (so-called “drop attacks”), associated chest pain or palpitations before the episode, a personal or family history of sudden cardiac death at a young age, or an abnormal examination or ECG. When any of these features are present, prompt specialist evaluation is essential.
Dr. Giardini sees children across a wide range of inherited cardiac conditions including hypertrophic cardiomyopathy and channelopathies such as Long QT Syndrome where syncope may be the first presenting symptom, and where accurate diagnosis is critical.
Most faints do not need emergency treatment, but the following features should always prompt rapid medical evaluation:Syncope that occurs during physical exercise — not after it — is the most important red flag. Fainting during exertion can indicate a serious underlying heart condition and must be investigated without delay.
Other features that should prompt urgent assessment include: loss of consciousness with no prodromal warning at all; associated chest pain or racing heartbeat; a seizure occurring at the same time or shortly after the episode; more than two or three unexplained episodes; a family history of sudden unexplained death in a young relative; or any known heart condition in the child.If your child collapses and does not regain consciousness quickly, or if they are unresponsive and not breathing normally, call 999 immediately.