Long QT syndrome
Long QT syndrome
Long QT syndrome (LQTS) is a heart rhythm disorder that can potentially cause fast, chaotic heartbeats. These rapid heartbeats may trigger a sudden fainting spell or seizure. In some cases, your heart may beat erratically for so long that it can cause sudden death.
You can be born with a genetic mutation that puts you at risk of long QT syndrome. In addition, certain medications and medical conditions may cause long QT syndrome.
Long QT syndrome is treatable. You may need to limit your physical activity, avoid medications known to cause prolonged Q-T intervals or take medications to prevent a chaotic heart rhythm. Some people with long QT syndrome need surgery or an implantable device.
Many people with long QT syndrome don't have any signs or symptoms. They may be aware of their condition only from results of an electrocardiogram (ECG) performed for an unrelated reason, because they have a family history of long QT syndrome or because of genetic testing results.
For people who do experience signs and symptoms of long QT syndrome, the most common long QT symptoms include:
Signs and symptoms of inherited long QT syndrome may start during the first months of life, or as late as middle age. Most people who experience signs or symptoms from long QT syndrome have their first episode by the time they reach age 40.
Rarely, signs and symptoms of long QT syndrome may occur during sleep or arousal from sleep.
When to see a doctor
Because long QT syndrome can occur in families, see your doctor to be tested for long QT syndrome if a first-degree relative (parent, sibling or child) has been diagnosed with long QT syndrome.
Your heart beats about 100,000 times a day to circulate blood throughout your body. To pump blood, your heart's chambers contract and relax. These actions are controlled by electrical impulses created in the sinus node, a group of cells in the upper right chamber of your heart. These impulses travel through your heart and cause it to beat.
After each heartbeat, your heart's electrical system recharges itself in preparation for the next heartbeat. This process is known as repolarization. In long QT syndrome, your heart muscle takes longer than normal to recharge between beats. This electrical disturbance, which often can be seen on an electrocardiogram (ECG), is called a prolonged Q-T interval.
Prolonged Q-T interval
An ECG measures electrical impulses as five distinct waves. Doctors label these five waves using the letters P, Q, R, S and T. The waves labeled Q through T show electrical activity in your heart's lower chambers.
The space between the start of the Q wave and the end of the T wave (Q-T interval) corresponds to the time it takes for your heart to contract and then refill with blood before beginning the next contraction.
By measuring the Q-T interval, doctors can tell whether it occurs in a normal amount of time. If it takes longer than normal, it's called a prolonged Q-T interval. The upper limit of a normal Q-T interval takes into account age, sex, and regularity and speed of the heart rate.
Long QT syndrome results from abnormalities in the heart's electrical recharging system. However, the heart's structure is normal. Abnormalities in your heart's electrical system may be inherited or acquired due to an underlying medical condition or a medication.
Inherited long QT syndrome
Doctors have described two forms of inherited long QT syndrome:
Additionally, scientists have been investigating a possible link between SIDS and long QT syndrome and have discovered that about 10 percent of babies with SIDS had a genetic defect or mutation for long QT syndrome.
Acquired long QT syndrome
Medications that can lengthen the Q-T interval and upset heart rhythm include certain antibiotics, antidepressants, antihistamines, diuretics, heart medications, cholesterol-lowering drugs, diabetes medications, as well as some antifungal and antipsychotic drugs.
People who develop drug-induced long QT syndrome may also have some subtle genetic defects in their hearts, making them more susceptible to disruptions in heart rhythm from taking drugs that can cause prolonged Q-T intervals.
Chambers and the valves of the heart
A normal heart has two upper and two lower chambers. The upper chambers, the right and left atria, receive incoming blood. The lower chambers, the more muscular right and left ventricles, pump blood ...
People at risk of long QT syndrome include:
Long QT syndrome often goes undiagnosed or is misdiagnosed as a seizure disorder, such as epilepsy. However, long QT syndrome may be responsible for some otherwise unexplained deaths in children and young adults. For example, an unexplained drowning of a young person may be the first clue to inherited long QT syndrome in a family.
Prolonged Q-T intervals may never cause any problems. However, physical or emotional stress may "trip up" a heart susceptible to prolonged Q-T intervals and cause the heart's rhythm to spin out of control, triggering life-threatening, irregular heart rhythms (arrhythmias) including:
Preparing for your appointment
If you develop signs and symptoms common to long QT syndrome, call your doctor. After an initial examination, it's likely that the doctor will refer you to a doctor who specializes in the diagnosis and treatment of heart conditions (cardiologist) or a heart rhythm specialist (electrophysiologist).
Here's some information to help you prepare for your appointment, and what to expect from your doctor.
What you can do
Questions to ask the doctor at your initial appointment include:
Questions to ask if you are referred to a cardiologist or electrophysiologist include:
In addition to the questions that you've prepared to ask your doctor, don't hesitate to ask questions during your appointment if you don't understand something.
What to expect from your doctor
What you can do in the meantime
A nonprofit advocacy organization called the Sudden Arrhythmia Death Syndromes (SADS) Foundation can help you prepare and understand your family history as it relates to a possible diagnosis of LQTS.
If exercise makes your symptoms worse, avoid exerting yourself physically until you've been seen by your doctor.
Tests and diagnosis
If your doctor suspects that you have long QT syndrome, you may need to have several tests to confirm the diagnosis. These include:
While some people with suspected long QT syndrome have a visibly lengthened Q-T interval on an ECG, others don't, making the condition more difficult to diagnose. Other testing may then be necessary:
Treatments and drugs
Treatment for inherited long QT syndrome can involve medications, medical devices, surgery or lifestyle changes. The goal of treatment is either to prevent the long QT heart from ever beating out of control or to prevent sudden death.
It's often possible to eliminate drug-induced long QT syndrome simply by switching medications, with your doctor's direction. Some people, however, may need additional treatment.
Your doctor may suggest treatment for long QT syndrome even if you don't experience frequent signs or symptoms of the disorder.
If you do need treatment, take the medications your doctor prescribes for long QT syndrome as directed. While medications won't cure the condition, they provide some protection against potentially fatal disruptions of your heart rhythm. You may need to take a medication such as a beta blocker indefinitely.
Medical devices and surgical procedures
Work with your doctor to balance these lifestyle recommendations against the clear, heart-healthy benefits of an active lifestyle. In some circumstances, it may be possible to stay fully active in sports, including competitive sports, after carefully reviewing the risks and benefits with your doctor.
If your symptoms are mild or don't occur very often, your doctor may recommend only lifestyle changes as treatment for your condition.
Lifestyle and home remedies
Once you've been diagnosed with long QT syndrome, several steps can help you avoid serious consequences of the illness. These steps include:
Sexual intercourse doesn't appear to increase the risk of long QT syndrome. Pregnancy and delivery aren't associated with increased risk of symptoms in women with long QT syndrome. Nonetheless, your doctor will want to monitor you closely both during your pregnancy and after if you have inherited long QT syndrome. Women with long QT syndrome, especially a form called LQT2, are at increased risk during the postpartum period and need careful monitoring.
Coping and support
Long QT syndrome can be a worrisome condition because of its serious potential outcomes. Worrying about possible fatal heart rhythms can obviously cause you and your family a lot of stress.
Families with inherited long QT syndrome may find it helpful to talk to a cardiologist with expertise in diagnosing and treating long QT syndrome, a genetics counselor, a psychiatrist or psychologist, as well as other families with the condition.
If you have inherited long QT syndrome, be careful about which medications you take. Some medications — including certain appetite suppressants, decongestants and common antibiotics, such as erythromycin — may trigger dangerous heart rhythms. Ask your doctor what you can and can't take safely. Street drugs, such as cocaine and amphetamines, pose a serious risk for people with long QT syndrome.
In addition, seek medical treatment right away for illnesses that could result in low blood-potassium levels, such as conditions that cause excessive vomiting and diarrhea. Such sicknesses could trigger an episode of long QT syndrome in people at risk. Your doctor may advise you not to take some drugs, such as diuretics, that lower blood-potassium levels.
For some people — especially older adults with long QT syndrome who haven't had signs or symptoms of the condition in decades — preventive measures may be all the treatment that's required.
Last Updated: 2012-04-20
© 1998-2015 Mayo Foundation for Medical Education and Research (MFMER). All rights reserved. A single copy of these materials may be reprinted for noncommercial personal use only. "Mayo," "Mayo Clinic," "MayoClinic.com," "Mayo Clinic Health Information," "Reliable information for a healthier life" and the triple-shield Mayo logo are trademarks of Mayo Foundation for Medical Education and Research.
Terms and conditions of use