Long QT Syndrome (LQTS) is an inherited condition affecting the heart’s electrical system. It causes a prolonged QT interval on an ECG — a measurement of the time it takes the heart’s lower chambers to recharge between beats. When this interval is too long, the heart is vulnerable to a dangerous arrhythmia called Torsades de Pointes, which can degenerate into ventricular fibrillation and cause sudden cardiac arrest.
In children, LQTS most commonly presents through symptoms triggered by exercise, sudden loud noises, or emotional stress — all of which cause a surge of adrenaline that the heart’s electrical system cannot manage safely. Fainting during sport or in response to a shock is a warning sign that should always be investigated. In some cases, the first presentation is a cardiac arrest.
There are several genetic subtypes of LQTS, and the specific subtype influences both the triggers to avoid and the treatment approach. Beta-blockers are the mainstay of treatment for most types and are very effective at reducing risk when taken consistently. Some patients also require an ICD, particularly those who have already had a cardiac arrest or who have not responded adequately to medication.
Because LQTS is inherited, first-degree relatives — parents, siblings, and children of the affected person — should all be offered cardiac screening, including an ECG. Family screening is arranged through an inherited cardiac conditions (ICC) service. Ask your child’s cardiologist for a referral if this has not already been arranged.
Some medications can dangerously prolong the QT interval and must be avoided. A list of drugs to avoid is maintained at CredibleMeds.org. Always inform any prescribing clinician, dentist, or anaesthetist of the diagnosis before any medication is prescribed or procedure carried out.