Heart and Vascular
Long QT Syndrome
Get expert care for long QT syndrome from the leading heart providers in the Sacramento area.
Medically reviewed by M. Bilal Munir, M.D. on Aug. 13, 2025.
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Long QT syndrome (LQTS) is a condition that affects the electrical activity that controls your heartbeat.
If you are diagnosed with LQTS, our specialists will create a personalized treatment plan. We’ll work with you to prevent arrhythmias and reduce your risk of life-threatening complications.
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What is Long QT Syndrome?
LQTS is commonly found during an electrocardiogram (EKG or ECG) test. An EKG displays your heart’s electrical activity on a graph. Each heartbeat is made up of three different electrical waves on the graph. The waves are named: P, QRS and T.
The electrical activity that occurs between the QRS and T waves takes place in the lower chambers (ventricles) of your heart. This is called the QT interval. It makes up one-third of each heartbeat cycle.
In LQTS, the QT interval lasts longer than normal. This can result in sudden, fast heart rhythms, which are dangerous. Abnormal heart rhythms are called arrhythmias.
Long QT Symptoms
You may have “quiet LQTS” and never experience symptoms. Or, you may experience symptoms that are similar to other types of heart conditions.
Common Symptoms
Talk to your physician if you experience any of these LQTS symptoms:
- Change in heart rate or rhythm
- Fluttering feeling in the chest
- Gasping for air while sleeping
- Lightheadedness
Emergency Symptoms
These symptoms require immediate emergency care:
- Chest pain or pressure
- Fainting
- Fainting while swimming or in water
- Seizure
Causes of Long QT Syndrome
Long QT syndrome is a rare condition that tends to be inherited, meaning it runs in families. Less commonly, it can also be caused by certain medications or underlying health conditions.
Health Conditions
Certain health conditions can cause low blood levels of magnesium, potassium, or sodium and are linked to LQTS.
These can include:
- Eating disorders, such as anorexia and bulimia
- Excessive diarrhea or vomiting
- Malnutrition
- Thyroid conditions, especially hyperthyroidism
Medications
Some medications are known to contribute to LQTS, including:
- Antibiotics
- Antidepressant and antipsychotic drugs
- Antihistamines
- Diuretics
LQTS is also sometimes associated with medications that treat:
- Arrhythmias
- Diabetes
- High cholesterol
Genetics
Researchers have identified over 15 changes in genes (genetic mutations) that can cause LQTS.
Intense Events
Being startled or feeling an intense emotion can trigger a short episode of LQTS.
Long QT Syndrome Risk Factors
Heart Conditions
If you have another heart condition, like cardiomyopathy or a congenital heart defect, you have a higher risk of developing LQTS.
Biological sex
Women are more likely to have LQTS than men.
Family History
If other people in your family have had LQTS, you are more likely to have it.
Diagnosis and Testing for Long QT Syndrome
Long QT syndrome can be a life-threatening condition, so it’s important to talk to your physician if you have a family history of heart-related deaths.
To diagnose LQTS, your physician will ask about your medical history and do a physical exam. They may also recommend tests, including:
- Blood tests, which check the levels of magnesium, potassium, sodium and thyroid hormone in your body
- Electrocardiogram (EKG), which measures the electrical activity of your heart and QT intervals
- Exercise stress test, which measures how well your body and heart handle physical activity
Treatments for Long QT Syndrome
Our treatment options can help with symptoms you are experiencing and reduce your risk of life-threatening complications. We may recommend one or more of the following treatments:
Implantable Cardioverter Defibrillator (ICD)
An ICD is a tiny device implanted under the skin of your chest. It is connected to your heart through a tiny wire. The ICD delivers short electric shocks to reset your heart rhythm when it detects an abnormal rhythm.
Medications
Sometimes we prescribe medications like beta blockers to help prevent your heart rate from speeding up. We may also change your current medications if they’re causing LQTS.
If your electrolytes are low, infusions of potassium or magnesium through an IV can help.
Preventing Complications of Long QT Syndrome
You can take steps to avoid serious complications of LQTS, like cardiac arrest.
These include:
- Avoiding loud, startling noises
- Keeping exercise moderate and avoiding overly strenuous activities
- Eating a healthy diet that includes optimal amounts of minerals like potassium and magnesium
- Using stress-reduction techniques like meditation
Treatments
How serious is Long QT Syndrome?
1 in 10People with LQTS experience sudden death
How many people does it affect?
1 in 2KPeople in the U.S. have LQTS
Sources: National Heart, Lung, and Blood Institute: Long QT Syndrome
SADS Foundation: Long QT Syndrome
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