What is long QT syndrome?
Long QT syndrome is a condition that increases risk for dangerous arrhythmias. It can lead to fainting, cardiac arrest and sudden cardiac death.
Heart muscle cells have tiny holes called ion channels, which open and close. Electrically charged sodium, calcium and potassium ions pass in and out of heart cells through these holes. This process creates electrical impulses that make the heart beat.
A person with long QT syndrome may not have enough ion channels or the channels may not function well. As a result, the heart can take longer than normal to recharge between beats. Long or prolonged QT interval is the name of the abnormal pattern displayed on an electrocardiogram.
Long QT syndrome is often inherited, meaning it runs in the family and you're born with it. It can also develop later in life. Many medications can make the condition worse, including:
- Antiarrhythmic medicines
- Antibiotics
- Antidepressants
- Antihistamines
In addition, there are non-inherited conditions that can cause changes in the potassium or sodium levels and can cause long QT syndrome. These conditions include:
- Eating disorders
- Severe diarrhea or vomiting
- Thyroid disorders
QT prolongation symptoms
The symptoms of long QT syndrome often occur when a person is active or experiences emotional or physical distress. Symptoms typically begin in childhood and may include:
- Fluttering feeling in the chest
- Fainting
- Gasping while sleeping
- Near-drowning or drowning incidents
- Sudden cardiac arrest
Some people with long QT syndrome have no symptoms at all. Asymptomatic long QT syndrome can still be dangerous and put you at increased risk of cardiac arrest. If someone in your family has long QT syndrome, it's important to undergo further testing.
Long QT syndrome diagnosis
If you have symptoms or a family history that indicates long QT syndrome, you will have tests including:
- Physical exam
- Electrocardiogram (ECG): this test records the electrical impulses in the heart and can detect any abnormal patterns, such as a long QT interval.
- Holter monitor: this is a wearable device that monitors the heart's electrical activity as you go about your daily activities.
- Genetic testing: blood tests can identify gene mutations that cause long QT syndrome.
Long QT syndrome treatment at Penn Medicine
Cardiac Arrhythmia at Penn Medicine is a nationally recognized leader in treatments for many types of arrhythmias. Every year, we implant more than a thousand devices and counsel patients on effective ways to prevent complications.
In addition, the Penn Center for Inherited Cardiovascular Disease cares for families with long QT syndrome. The center's physicians, nurses and counselors can help you understand the condition and decide who else should be tested.
Symptomatic patients that remain untreated have a high risk of arrhythmic complications, cardiac arrest and sudden cardiac death. But treatment is highly effective in preventing life-threatening abnormal heart rhythms and cardiac arrest. The most effective options are:
- Beta blockers: these medications help prevent sudden cardiac arrest.
- Implantable cardioverter defibrillator (ICD): an ICD is a small, battery-powered device that is surgically placed under the skin. It is connected to the heart and monitors your heart rate. If needed, it delivers an electrical shock to stop a dangerous arrhythmia.
- Lifestyle changes: our team can help you understand ways to avoid episodes. For example, modifying your physical activity and avoiding extreme emotions and things that could startle you.