Long QT syndrome (LQTS)

2021-08-02 03:45 PM

Many people with long QT syndrome do not have any signs or symptoms. They can only perceive their condition from the results of the electrocardiogram.


Long QT syndrome (LQTS) is a heart rhythm disorder that can have the potential to cause a rapid, chaotic heartbeat. A fast heartbeat can cause sudden fainting. In some cases, the heart can be erratic and can cause sudden death.

May be born with a genetic mutation that puts you at risk for long QT syndrome. In addition, certain medications and medical problems can cause long QT syndrome.
Long QT syndrome can be treated. It may be necessary to limit physical activity, avoid medications known to cause QT prolongation or take medications to prevent chaotic heart rhythms. Some people have surgery to treat long QT syndrome or need a device implanted under the skin.


Many people with long QT syndrome do not have any signs or symptoms. They may only become aware of their condition from the results of an electrocardiogram (ECG) done for an unrelated reason because they have a family history of long QT syndrome or because of the test results. genetic.

For people who experience signs and symptoms of long QT syndrome, the most common symptoms include:


This is the most common sign of long QT syndrome. In people with long QT syndrome, syncope is caused by a temporary erratic heartbeat. Fainting episodes can happen when excited, angry or scared, or during exercise. Fainting in people with long QT syndrome can happen without warning, like losing consciousness after being startled by a ringing phone.

Signs and symptoms of fainting include dizziness, fast or irregular heartbeat, weakness, and blurred vision. However, in long QT syndrome, such a warning sign before fainting is unusual.


If the heart continues to be erratic, the brain becomes increasingly deprived of oxygen. This can then cause seizures.

Sudden death

Usually, the heart rate returns to normal. If this does not happen spontaneously and defibrillation returns to a normal rhythm in time, sudden death will occur.

Signs and symptoms of inherited long QT syndrome can begin in the first months of life, or possibly late middle age. Most people who experience signs or symptoms of long QT syndrome have their first symptoms by age 40.
Rarely, signs and symptoms of long QT syndrome may occur during sleep or upon awakening.
A doctor should be consulted if there is a sudden decrease in physical activity or emotional interest or after taking a new medication.

Because long QT syndrome can run in families, see your doctor be screened for long QT syndrome if a close relative (parent, sibling, or child) has been diagnosed with long QT syndrome.


The heart beats about 100,000 times a day to circulate blood throughout the body. To pump blood, the heart chambers contract and relax. These actions are controlled by electrical impulses generated in the sinus node, a group of cells in the heart's right upper chamber. These impulses pass through the heart and cause it to contract.

After each heartbeat, the heart with its electrical system prepares for the next heartbeat. This process is called repolarization. In long QT syndrome, the heart muscle takes longer than usual to load between beats. This electrical disturbance, which can often be seen on an electrocardiogram (ECG), is known as a prolonged QT interval.

QT interval prolongation

Electrocardiogram (ECG, also called EKG). Pole plates with wires attached to the skin and pulses are displayed on the screen or printed on paper.

The ECG pulse consists of five distinct waves. Doctors evaluate five waves using the letters P, Q, R, S, and T. The Q to T waves shows electrical activity in the lower chambers of the heart.

The distance between the start of the Q wave and the end of the T wave (the QT interval) corresponds to the time it takes for the heart to contract and then refill before it begins to contract.

By measuring the QT interval, doctors can tell how long it is. If it lasts longer than normal, it is called a prolonged QT interval. The limits of the normal QT interval will take into account age, sex, regularity, and rate of heart rate.

Long QT syndrome results from abnormalities in the heart's electrical system. However, the structure of the heart is normal. Abnormalities in the heart's electrical system can be inherited, acquired, or due to an underlying medical problem or medication.

Inherited long QT syndrome

To date, at least 12 genes associated with long QT syndrome have been discovered and hundreds of mutations in these genes have been identified. Mutations in the three genes account for about 70 to 75 percent of long QT syndrome and cause forms called LQT1, LQT2, and LQT3.

Doctors have described two inherited forms of long QT syndrome:

Romano syndrome. This form usually occurs in single heirs who have only one genetic variant from their parents.

Lange-Nielsen and Jervell syndrome. Signs and symptoms of this form often precede and are rarely more severe in the syndrome. Romano. Seen in babies born deaf and with long QT syndrome because they inherit the genetic variant from their parents.

In addition, scientists have studied the possible link between SIDS and long QT syndrome and have found that about 10 percent of infants with SIDS have a genetic defect or mutation in long QT syndrome.

Drug-induced long QT syndrome

More than 50 drugs, many of which are common, can prolong the QT interval in healthy people and cause a long QT syndrome known as drug-induced long QT syndrome.

Medications that can prolong the QT interval and cause cardiac arrhythmias to include certain antibiotics, antidepressants, antihistamines, diuretics, cardiovascular medications such as cholesterol-lowering drugs, diabetes medications, as well as certain medications. antifungal and antipsychotic drugs.

People who develop long QT syndrome with medication may also have certain genetic defects in their hearts, making them more susceptible to drug-induced heart rhythm disruptions and possibly prolonged QT intervals.

Risk factors

People at risk for long QT syndrome include:

Children, adolescents, and young adults with unexplained syncope, sudden death, other recent unexplained accidents, unexplained seizures, or a history of cardiac arrest

Family members of children, adolescents, and young adults with unexplained syncope, sudden death, other recent unexplained accidents, unexplained seizures, or a history of cardiac arrest

Relatives of people with known long QT syndrome.

People taking medications are known to cause QT prolongation.

Long QT syndrome is often undiagnosed or misdiagnosed as a disorder, such as epilepsy. However, researchers believe that long QT syndrome may be responsible for some unexplained deaths in children and young adults. For example, the sudden unexplained death of a young person may be the first clue to inherited long QT syndrome in the family.

People with low levels of magnesium, potassium, or calcium in their blood, such as those with anorexia nervosa and eating disorders, may be more prone to QT prolongation. Potassium, magnesium, and calcium are all important minerals for the health of the heart's electrical system.


Prolonging the QT interval can never cause any problems. However, physical or emotional stress can "trigger" a sensitive heart with a prolonged QT interval and cause the heart's rhythm to go out of control, causing life-threatening, irregular heartbeats (arrhythmias). span) includes:

Top twist

This arrhythmia is characterized by rapid heartbeats, causing the waves on the ECG monitor to twist. When this happens, less blood is pumped out of the heart. Less blood then reaches the brain.

If torsades de pointes are short, lasting less than a minute, the heart may then correct itself, and regain consciousness on its own. However, if torsades de pointes persist, it can lead to a life-threatening arrhythmia called ventricular fibrillation.

Ventricular fibrillation

This condition causes the ventricles to beat too fast, vibrate, and no longer pump blood. Unless resuscitated to a normal rhythm with a device called a defibrillator, ventricular fibrillation can lead to brain damage and death. It is thought that long QT syndrome may explain some of the sudden deaths in previously healthy young people.

Tests and diagnostics

If your doctor suspects long QT syndrome, several tests may be needed to confirm the diagnosis. These include:

Electrocardiogram (ECG)

This test is a noninvasive, pre-recorded probe that monitors the waves of electrical impulses in the heart. Transmit the waves to a computer screen or printout for the doctor to see. You can experiment while at rest or during exercise by running on a treadmill or riding a bike.

Holter ECG monitoring

This test, also known as a Holter monitor, is used to monitor abnormal heart rhythms during normal activities for a continuous 24-hour period. During the test, electrodes attached to the chest were connected to a portable recorder attached to the belt or by a shoulder strap. The recorded information can then be analyzed to check for abnormal heart rhythms, such as a prolonged QT interval.

Event electrocardiogram recording

This is similar to an electrocardiogram, except that it may be necessary to wear a portable ECG recorder daily or weekly that records heart rhythms when abnormal.

While some people with long QT syndrome have a prolonged QT interval on a suspected electrocardiogram, making the condition more difficult to diagnose. Subsequent tests may be necessary:

Stress test with medication

An electrocardiogram is done while taking a medication that stimulates the heart in a similar way to exercise. It is given through a vein in the arm and may include epinephrine (adrenaline). Adrenaline is a substance that the body releases in response to stress. During stress testing, doctors monitor the effects of adrenaline. This test can show what is called masked long QT syndrome, a normal QT interval at rest, although the syndrome is still present. In some people with long QT syndrome, fainting spells are triggered by unexpected levels of adrenaline in the body, such as experienced during a stressful or sad workout.

Electroencephalogram (EEG)

This test will be used for syncope that has a neurological cause, such as a seizure disorder. Procedure to measure the electrical activity of the brain. Small electrodes attached to the head receive electrical impulses from the brain and send them to EEG machines that record brain waves.

Genetic testing

Genetic testing for long QT syndrome is available. Genetic testing for long QT syndrome has the potential to find a genetic cause for about three out of four cases of long QT syndrome. Therefore, it is possible to be negative on genetic testing but still have long QT syndrome. If the genetic cause of long QT syndrome is discovered through positive genetic testing, then family members can be tested to prove definitively inheriting the same gene mutation.

A second opinion may be sought if your doctor diagnoses long QT syndrome. Treatment for long QT syndrome can be life-changing, such as avoiding strenuous exercise, medication, or surgery. In addition, evidence suggests that misdiagnosis associated with this condition is not uncommon, including the diagnosis of long QT syndrome when it is not present.

Treatments and drugs

Treatment of hereditary long QT syndrome may involve medications, medical devices, surgery, or lifestyle changes. The goal of treatment is to prevent long QT from getting out of control or to prevent sudden death.

It is often possible to rule out the drug causing the long QT syndrome simply by changing the medication prescribed by your doctor. Some people, however, may need additional treatment.


Medications used to treat long QT syndrome include:

Beta-blockers. Examples of these drugs include nadolol (Corgard) and propranolol (Inderal). These drugs slow the heart rate and make QT prolongation less likely to be associated with dangerous rhythms. This drug makes long QT syndrome less responsive to adrenaline during times of fear, stress, or exertion.

Mexiletine. For people with LQT3 long QT syndrome, taking this drug in combination with propranolol may help shorten the QT interval and fight arrhythmias.

Kali. Potassium is a mineral in the body that, from the diet, is important for the health of the heart's electrical system. Supplemental potassium can improve the heart's electrical system and may be helpful for people with long QT syndrome.

Fish oil. Supplementing with heart-healthy fish oil (omega-3 fatty acids) can help stabilize irregular heart rhythms.

Your doctor may recommend treatment for long QT syndrome even if you don't regularly experience signs or symptoms.

If treatment is needed, take the medication your doctor prescribes for long QT syndrome as directed. While the drug can't cure it, it does offer some protection against potentially serious disruptions to the heart's rhythm. You may need to take a medication such as a beta-blocker indefinitely.

Medical devices and surgical procedures

Your doctor may consider two other treatments for:

A pacemaker or implantable cardioverter-defibrillator (ICD). These devices, implanted under the skin of the chest, can prevent potentially fatal arrhythmias. The ICD continuously monitors the heart rate and will deliver electrical shocks to restore a normal heart rhythm when needed.

Cardiac sympathetic neurosurgery. During this procedure, specific nerves in the chest are surgically removed. Nerves are part of the body's sympathetic nervous system, which controls the body's automatic functions, including heart rate. Cardiac sympathectomy significantly reduces the risk of sudden death.

This surgery is usually reserved for people who are at high risk of sudden death, who cannot tolerate medication or have fainting despite medication, and who have an ICD implanted. Surgery can significantly reduce the frequency of ICD shocks.

Lifestyle change

In addition to medication or surgery, your doctor may recommend certain lifestyle changes to reduce the risk of long QT episodes associated with fainting syndrome. This may include avoiding stress or exercise, reducing loud noises, startling noises, and staying away from situations that might make you happy or angry.

Work with your doctor to balance the lifestyle recommendations with the clear heart health benefits of an active lifestyle. In some cases, a full range of sports activities, including competitive sports, may be possible, after carefully reviewing the risks and benefits with your doctor.

If symptoms are mild or infrequent, your doctor may recommend lifestyle changes.

Lifestyle and remedies

Once long QT syndrome has been diagnosed, a few steps can help avoid the serious consequences of the disease. These steps include:

No need to effort

It is not necessary to give up sports if you have long QT syndrome. The doctor may authorize recreational activities as long as someone is present during the activity. In general, people with long QT syndrome should never swim alone.

Strenuous exercise can be dangerous and is not recommended for some people with long QT syndrome. However, other people who may have a low risk of complications can continue to exercise strenuously or compete in sports. Discuss this with your doctor carefully.

Know the symptoms

Be fully aware of the symptoms that can signal an irregular heart rhythm and reduced blood flow to the brain. Remember, syncope from long QT syndrome is one of the most important warning signs for the future, associated with long QT which can be even more dangerous, even deadly.

Notice to others

Make your family, friends, teachers, neighbors, and anyone else who are in regular contact know about heart disease. Wear a medical alert code number to notify the healthcare professional.

Also, have a plan in case of a cardiac emergency event. Urging family members to learn cardiopulmonary resuscitation (CPR) so they can provide immediate resuscitation efforts if it becomes necessary. In some cases, an automatic external defibrillator (AED) may be appropriate.

Control surprising events as much as possible

Lower the doorbell volume if possible, and turn off your phone or cell phone at night.

Pregnancy does not increase the risk of long QT syndrome

Pregnancy and delivery are not associated with an increased risk of symptoms in women with long QT syndrome. However, doctors want to closely monitor both during pregnancy and after birth for inherited long QT syndrome. Women with long QT syndrome, especially the LQT2 pattern, are at high risk in the postpartum period and need careful monitoring.

Coping and supporting

Long QT syndrome can be a worrisome condition because of its potentially serious outcomes. Worrying about a potentially fatal heart rate can obviously stress you and your family a lot.

Families with inherited long QT syndrome may find it helpful to talk to a cardiologist with expertise in the diagnosis and treatment of long QT syndrome, a genetic counselor, psychiatrist or psychologist. psychologists, as well as other families with similar conditions.


If you have inherited long QT syndrome, be careful about what medications you take. Certain medications, including certain appetite suppressants, decongestants, and common antibiotics, such as erythromycin, can cause dangerous heart rhythms. Ask your doctor what you can and can't safely do. Drugs, such as cocaine and stimulants, pose serious risks for people with long QT syndrome.

Also, seek immediate medical treatment for conditions that can lead to low blood potassium levels, such as excessive vomiting and diarrhea. This disease can trigger long QT syndrome in people at risk. Your doctor may advise against taking certain medications, such as diuretics, which lower blood potassium levels.

For some people, especially older adults with long QT syndrome who have had no signs or symptoms of the condition for decades, all possible precautions are necessary.