Long QT Syndrome: Symptoms, Causes, Treatment

The QT interval is measured on an ECG and interpreted with heart rate and clinical context. A smartwatch value or automated report alone cannot establish diagnosis or risk.

Related reading: Brugada syndrome as a different condition.

There may be no symptoms, or palpitations, fainting and seizure-like episodes. Exercise, sudden surprise or sleep can trigger events depending on subtype; triggers are not universal.

Inherited changes may affect cardiac ion channels. Certain medicines can prolong QT, particularly with low potassium or magnesium; acquired and inherited forms require different assessment.

Family history, QT-prolonging medicines and electrolyte disturbances matter. Cause, ECG measurements and previous fainting or cardiac arrest help establish event risk.

Evaluation uses ECGs, medication and electrolyte review and family history, sometimes monitoring, exercise testing or genetics. A single normal ECG does not exclude every inherited case.

Acquired causes are corrected medically; beta blockers commonly treat inherited forms. Defibrillators or other procedures are considered selectively. Never stop a prescribed medicine without clinical advice.

Torsades de pointes ventricular tachycardia or cardiac arrest may occur. Diagnosis, treatment and trigger precautions reduce risk; absent symptoms do not eliminate it.

Check every new medicine or supplement for safety. Manage dehydration and electrolyte loss with guidance, agree exercise limits with a specialist, avoid swimming alone and discuss family testing.