MetroHealth Heart & Vascular Center
Abnormal Heart Rhythms
Long QT Syndrome
What is Congenital Long QT Syndrome (LQTS)?
It is a genetic disorder that can cause symptoms of fainting or sudden death regardless of age. In many patients, LQTS is detected as an abnormal electrocardiogram (ECG or EKG) where the length of the actual QT interval appears to be longer than that of a QT interval on a normal ECG.
What Causes LQTS?
• After each heartbeat, the heart recovers electrically and prepares itself for the next beat through what is known as repolarization.
• This process relies on the normal function of multiple ion channels in the heart muscle.
• Congenital LQTS is linked to mutations of certain genes that encode for these ion channels and leads to their abnormal function.
• Thus, patients with congenital LQTS have a prolonged repolarization stage, or QT interval.
• This can lead to a life-threatening heart rhythm called Torsades de Pointes and sudden cardiac death.
What are the Symptoms?
• Some patients with LQTS have no symptoms..
• Others experience episodes of dizziness, fainting (also known as syncope), and/or seizures.
• These symptoms often occur in childhood, adolescence and early adulthood.
In many cases, patients who are at risk of sudden cardiac death have a history of fainting spells. Unfortunately, sudden death can occur as the first symptom of LQTS so it is important that anyone with a family history of LQTS (or unexplained sudden death at a young age) be screened and treated appropriately.
What Triggers Symptoms in LQTS?
Some circumstances may trigger LQTS symptoms such as:
• Increased physical activity (especially swimming)
• Emotional distress (crying, anger, or anxiety)
• Sudden and loud noises.
However, some patients experinece symptoms at rest or during sleep. Certain medications may prolong the QT interval and should be avoided by patients with LQTS or a family history of LQTS symptoms.
How Do I Know if I Have LQTS?
• If you have unexplained fainting episodes or seizures, a family history of unexplained sudden death at a young age, or LQTS runs in your family, you might have LQTS.
• An ECG will often show the prolonged QT interval.
• Some patients with LQTS have a normal or borderline QT interval on an ECG performed at rest and may require additional tests for diagnosis, such as the ECG with stress test (administered on a treadmill) and/or a 24-hour Holter monitor.
Is There Treatment Available?
Treatment is available and may include
• Beta-blocker medications which substantially reduces the risk of fainting and sudden death. These medications must be taken daily.
• Patients who have experienced high-risk signs of LQTS such as cardiac arrest, or fainting in spite of beta blocker use, may be advised additional treatment such as an implantable defibrillator or pacemaker .
Medications to Avoid if You Have LQTS
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Certain medications may prolong the QT interval and should be avoided by patients with LQTS or a family history of LQTS symptoms.
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A regularly updated list of medications can be retrieved at www.qtdrugs.com.
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Talk to your doctor about any medications you are currently taking that appear on this list.
Genetic Basis of LQTS
After each heartbeat, the heart recovers electrically and prepares itself for the next beat through what is known as repolarization. This process relies on the normal function of multiple ion channels in the cells of the heart muscle. These channels are pores or tiny openings that allow for the passage of certain ions like sodium or potassium.
There are specific genes in the body that lead to the development of the ion channels. Congenital LQTS is linked to mutations of these genes and leads to their abnormal function. The electrical activity of the heart becomes disturbed and requires a longer time to recover. Thus, patients with congenital LQTS have a prolonged repolarization stage, or QT interval.
Scientific discoveries dating back to the 1990s have identified specific genes that encode the ion channels in the cells of the heart muscle. Although progress is being made, there are still many patients and families with LQTS for whom no mutation has been found. There are almost certainly other LQTS genes that have not yet been discovered.
Familial Heart Rhythm Center
Explore the the Familial Heart Rhythm Center to learn more about the genetic basis of LQTS and currently Recognized LQTS Syndromes and to contact center director Dr. Elizabeth Kaufman.
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