Long QT Syndrome: Causes, Symptoms, and Treatment
Medically reviewed by Harsha Moole, MD, Internal Medicine. Last reviewed: October 23, 2026.
What kind of doctor treats Long QT Syndrome?
A cardiologist, a heart doctor, usually treats long QT syndrome. An electrophysiologist, a heart doctor who focuses on heart rhythm problems, may also be involved. Families with the inherited form may also talk with a genetic counselor. A direct primary care or concierge doctor can be a first stop for an evaluation and can refer you to a specialist when needed.
What is long QT syndrome?
Long QT syndrome (LQTS) is a problem with the electrical system that controls your heartbeat.
The term "long QT" refers to a problem with the pattern seen on an electrocardiogram (EKG). An EKG is a test that records the heart's electrical activity. In people with LQTS, the QT interval, a part of each heartbeat shown on the EKG, lasts longer than normal.
A long QT interval can upset the timing of the heartbeat. It can cause sudden, uncontrollable fast heart rhythms. LQTS is rare, and not everyone who has it has dangerous heart rhythms. When they do happen, they can be fatal.
Symptoms
Some people who have LQTS have no symptoms, which is called silent LQTS. Others may have heart rhythm symptoms. These may happen in specific situations, such as stress or sleep. Symptoms may include:
- Fainting, which may happen during physical or emotional stress and may include fluttering feelings in the chest before fainting.
- Noisy gasping while sleeping.
- Seizures.
The symptoms of inherited types of LQTS often start during childhood. In about 1 out of 10 people who have LQTS, cardiac arrest or sudden death is the first sign. Cardiac arrest is when the heart suddenly stops beating for no obvious reason.
Causes and who gets it
The heart's muscle cells have tiny pores called ion channels. They let charged particles flow in and out. In people who have LQTS, the ion channels may not work well, or there may be too few of them.
LQTS is often inherited, which means you are born with it and have it your whole life. You can also acquire it, which means you develop it during your lifetime. The most common inherited form is called Romano-Ward syndrome. The Romano-Ward form is usually passed down from one affected parent.
These factors can raise your risk of LQTS:
- A family history of LQTS, or of unexplained fainting, seizures, drowning, or sudden death.
- Conditions that cause low blood levels of potassium, magnesium, or calcium, such as eating disorders, thyroid disease, or serious diarrhea or vomiting.
- Medicines that affect how the heart's ion channels work, including some antibiotics, antidepressants, and antihistamines.
How doctors diagnose it
Your doctor will ask about your health, your family's health, your symptoms, and the medicines you take. You will have a physical exam and may have tests:
- Blood tests can check electrolyte levels, such as potassium, and thyroid hormone levels.
- An EKG is the most common test used to diagnose LQTS.
Your QT interval may change from time to time, so you may need several EKGs over days or weeks. You may also wear a Holter monitor, which records your heart rhythm.
Treatment
The goal of treating LQTS is to prevent abnormal heart rhythms and fainting spells. Treatment is not a cure for the disorder and may not restore a normal QT interval. However, treatment greatly lowers the risk of life-threatening problems. Treatment may include:
- Lifestyle changes: your doctor may ask you to avoid triggers such as swimming, sudden loud noises like an alarm clock, stress, and some medicines.
- Medicine: you may need beta blockers, which keep your heart from beating faster in response to physical or emotional stress.
- Surgery: you may need surgery to cut the nerves that cause dangerous heart rhythms.
- Devices: your doctor may suggest a pacemaker or a defibrillator (ICD) to help control your heart rhythm.
An NIH-supported study found that treated people with LQTS who exercised hard had no higher risk of heart events than those who exercised less. Ask your doctor how much activity is safe for you. Do not stop a prescribed medicine on your own.
When to see a doctor
Call 911 or go to the emergency room if someone faints or has a seizure. Also call for chest pain that lasts 2 minutes or more or trouble breathing. If the heart suddenly stops, which is called cardiac arrest, call 911 right away. See a doctor if you or your child has noisy gasping during sleep, or if close family members have had unexplained fainting, drowning, or sudden death.
How a direct primary care or concierge doctor fits in
A direct primary care doctor charges a flat monthly fee instead of billing insurance, while a concierge doctor usually charges more and often works alongside insurance. Such a doctor can ask about your symptoms and family history. They can check which medicines may affect the heart. They can also refer you to a heart rhythm specialist.
Common questions
Is long QT syndrome life threatening?
It can be, because a long QT interval can cause sudden fast heart rhythms that can be fatal. However, LQTS is rare, and not everyone who has it has dangerous heart rhythms. Treatment greatly lowers the risk of life-threatening problems.
Can long QT syndrome be cured?
Treatment is not a cure for long QT syndrome, but it greatly lowers the risk of life-threatening problems. LQTS is usually a lifelong condition.
Can medicines cause long QT syndrome?
Yes, some medicines can raise your risk of LQTS. These include some antibiotics, antidepressants, and antihistamines, which affect how the heart's ion channels work.
Sources
- NHLBI, NIH - Arrhythmias: Long QT Syndrome
- MedlinePlus Genetics - Romano-Ward syndrome
- NHLBI, NIH - Vigorous exercise not linked to increased risk of adverse cardiac events in long QT syndrome
Medical Disclaimer
This content is for general educational and informational purposes only and is not medical advice. It is not a substitute for professional medical advice, diagnosis, or treatment, and reading it does not create a doctor-patient relationship. Always seek the advice of your physician or another qualified health provider with any questions about a medical condition, and never disregard or delay seeking professional advice because of something you read here. If you think you may have a medical emergency, call 911 (or your local emergency number) immediately.
