Short answer · Medically reviewed summary · Last updated: 2026-04-07

Long QT Syndrome (LQTS) is a heart rhythm disorder that can cause fast, chaotic heartbeats, potentially leading to fainting, seizures, or sudden cardiac arrest. It is characterized by an abnormality in the heart's electrical system, specifically a delay in the "recharging" phase of the heart muscle between beats, which can be identified on an electrocardiogram (ECG). What exactly is Long QT Syndrome? Long QT Syndrome is a genetic or acquired condition that affects the heart's electrical activity.

What is Long QT Syndrome

Name: What is Long QT Syndrome
Creator: DiseaseMaps Editorial Team
Published: 2015-07-12UTC21:14:45.0000000

What is Long QT Syndrome? Plain-language, medically reviewed definition plus the lived reality told by patients.

Long QT Syndrome (LQTS) is a heart rhythm disorder that can cause fast, chaotic heartbeats, potentially leading to fainting, seizures, or sudden cardiac arrest. It is characterized by an abnormality in the heart's electrical system, specifically a delay in the "recharging" phase of the heart muscle between beats, which can be identified on an electrocardiogram (ECG).

What exactly is Long QT Syndrome?

Long QT Syndrome is a genetic or acquired condition that affects the heart's electrical activity. In a healthy heart, the electrical signal that triggers a heartbeat flows through the muscle and then resets. In patients with Long QT Syndrome, this reset process (repolarization) takes longer than normal. This delay is measured as the "QT interval" on an ECG. If the interval remains too long, it can trigger dangerous arrhythmias, most notably torsades de pointes, which may cause the heart to stop pumping effectively.

What causes Long QT Syndrome?

The condition is primarily caused by mutations in genes that encode the ion channels in heart cells, which control the flow of potassium, sodium, or calcium. There are two main ways to acquire this condition:

Congenital (Inherited): This is the most common form, often linked to Romano-Ward syndrome (autosomal dominant) or the rarer Jervell and Lange-Nielsen syndrome (autosomal recessive, which also causes deafness).

Acquired: This form occurs due to external factors, most frequently as a side effect of certain medications, severe electrolyte imbalances (like low potassium or magnesium), or specific medical conditions.

How common is Long QT Syndrome?

Long QT Syndrome is estimated to affect approximately 1 in 2,000 to 1 in 5,000 individuals worldwide. Because many people remain asymptomatic, the true prevalence may be higher. At DiseaseMaps.org, we currently have a dedicated community of 357 people with Long QT Syndrome who share their personal experiences, symptom management strategies, and insights into living with this diagnosis.

Who is typically affected by the condition?

Long QT Syndrome can affect individuals of any age, gender, or ethnic background. While symptoms often appear during childhood or adolescence, some individuals are not diagnosed until adulthood. Interestingly, gender plays a role in risk: before puberty, boys are slightly more likely to experience symptoms, whereas after puberty, the risk becomes higher in females. Geographic factors do not appear to influence the prevalence of the genetic form, though access to diagnostic ECG screening remains a global health priority.

Key differences from other heart conditions

Unlike structural heart diseases where the heart muscle is physically thickened or enlarged (such as hypertrophic cardiomyopathy), Long QT Syndrome is a "channelopathy." This means the heart is often structurally normal on an ultrasound (echocardiogram), but its electrical "wiring" is faulty. This makes the condition difficult to detect without a specialized ECG test.

Next steps

Consult a Cardiologist: If you suspect you have Long QT Syndrome, seek a referral to an electrophysiologist, a cardiologist who specializes in heart rhythm disorders.

Genetic Testing: Discuss with your doctor whether genetic testing is appropriate for you or your family members to identify specific mutations.

Review Medications: Maintain an updated list of all medications and supplements, and check them against the CredibleMeds database to ensure they are safe for people with Long QT Syndrome.

Join the Community: Connect with the 357 members at DiseaseMaps.org to share experiences and learn how others manage their treatment plans.

Medical disclaimer: This content is for informational purposes only and does not constitute professional medical advice, diagnosis, or treatment; always seek the guidance of your physician or qualified health provider with any questions regarding a medical condition.