Short QT syndrome (SQTS) is a rare genetic disorder that affects your heart. In SQTS, the length of time between your heart contracting, relaxing and contracting again is irregularly low. Some people who have SQTS feel faint or dizzy. Others have no symptoms. See your healthcare provider if you have any signs of SQTS.
Short QT syndrome (SQTS) is an extremely rare genetic disorder that causes an irregular heart rhythm. In SQTS, your heart muscle doesn’t take as long as usual to recover between beats. The part of your heartbeat called the QT interval is irregularly short.
SQTS can cause arrhythmias in which you may feel dizziness, fainting or heart palpitations. They may even cause cardiac arrest (your heart stops) and sudden cardiac death, in severe cases. If you have signs of SQTS, it’s essential to see a healthcare provider for treatment.
Healthcare providers measure heartbeats on an electrocardiogram (ECG). This test evaluates your heart’s electrical signals. On the ECG, specific voltage waves — called P, Q, R, S and T — mark each heartbeat.
When blood flows through your heart, it moves from your top right heart chamber (atrium) to your bottom right heart chamber (ventricle). Blood flows because electrical signals tell your atria and ventricles to squeeze (contract) and relax.
The P, Q, R, S and T waves on the ECG represent:
The time between the start of the QRS complex and the end of the T wave is the QT interval. Usually, the QT interval is between 0.35 and 0.45 seconds. In SQTS, the QT interval is below 0.34 seconds.
Short QT syndrome is an irregularly short QT interval, typically under 0.34 seconds. Long QT syndrome is an irregularly long QT interval, typically over 0.45 seconds.
Short QT syndrome is an extremely rare disease. Experts don’t know exactly how many people have short QT syndrome.
Some researchers have noticed that many people show SQTS symptoms during their first year of life, with symptoms peaking again later in adulthood.
SQTS is genetic. You may inherit it from one of your parents. Or you may have a gene change (mutation) that happens for no known reason.
About 4 in 5 people with SQTS have atrial fibrillation (AFib). Atrial fibrillation is an irregular heart rhythm where the electrical signals in your heart’s top chambers (atria) don’t fire properly. Other symptoms include heart palpitations (in almost 1 in 3 people), dizziness and fainting or syncope (in about 1 in 4 people).
For some people (around 2 in 5), the first sign of SQTS unfortunately is cardiac arrest or sudden cardiac death, an unexpected stoppage of heart function due to ventricular fibrillation or ventricular tachycardia, both dangerous arrhythmias of the bottom chambers (ventricles) of the heart.
Doctors may diagnose short QT syndrome if you have an ECG that shows a QT interval of less than 0.34 seconds. They may also consider whether you have SQTS if you have a QT interval between 0.34 and 0.36 seconds, plus other symptoms of SQTS.
To diagnose SQTS, your provider may use:
A cardiologist (heart doctor) treats short QT syndrome. Your cardiologist may recommend:
There’s no way to prevent SQTS. Because it’s genetic, you can’t control whether you get it.
If you have SQTS, it’s important to see a cardiologist (heart doctor) regularly. A cardiologist monitors your heart health. They can help you reduce your risk of severe SQTS complications, such as sudden cardiac death.
Short QT syndrome prognosis can vary. In some people, SQTS leads to sudden cardiac death. Estimates suggest that people with short QT syndrome have a 40% chance of experiencing sudden cardiac death by age 40, with the highest amount of risk between ages 0 to 1 and 20 to 40 years old. If SQTS occurs between the ages of newborn to 1 year old, providers might call it sudden infant death syndrome (SIDS).
However, most people who have short QT intervals (less than 360 milliseconds) on their ECG do NOT necessarily have short QT syndrome and are not at risk of sudden cardiac death. In addition, some people with short QT syndrome never experience symptoms and have a typical life expectancy. Because short QT syndrome is rare, experts are still researching how short QT syndrome affects life expectancy.
Your healthcare provider can give you treatment options to help you manage the condition and lower your risk of complications.
You may also want to ask your healthcare provider:
A note from Cleveland Clinic
Short QT syndrome is a rare genetic disorder characterized by a short QT interval. The QT interval is the time it takes for your heart ventricles to contract, relax and start again. If you have an irregularly low QT interval, you may feel dizzy, faint or have heart palpitations. Short QT syndrome is a serious condition that can lead to cardiac arrest and death. If you have any signs of SQTS, see your healthcare provider for diagnosis and treatment.
Last reviewed by a Cleveland Clinic medical professional on 06/13/2022.
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