Long QT Syndrome (LQTS)
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Long QT syndrome (LQTS) is a heart signaling abnormality that can lead to arrhythmias, characterized by rapid and irregular heartbeats. It is also referred to as a cardiac conduction disorder.
Some individuals are born with congenital long QT syndrome, which is caused by DNA alterations. Additionally, certain medical conditions, medications, or imbalances in minerals can lead to acquired long QT syndrome, a form of the condition that develops later in life.
Long QT syndrome can trigger seizures and sudden fainting episodes. Young people with LQTS are at a higher risk of experiencing sudden death.
Treatment for long QT syndrome typically involves medication to prevent dangerous heart rhythms and lifestyle changes. In some cases, surgery may be necessary to implant a device that regulates the heart’s rhythm.
Symptoms
There are some long QT syndrome (LQTS) sufferers who show no symptoms at all. When genetic tests or an electrocardiogram (ECG) are performed for other purposes, the condition might be found.
The most typical symptom of long QT syndrome is fainting, or syncope. Long QT syndrome may cause a fainting spell that manifests little or no warning. Some people exhibit early warning indicators of fainting, such as:
- Palpitations
- Weakness
- Blurry vision
- Lightheadedness
When the heart briefly beats erratically, it causes fainting. Exercise and emotional states such as excitement, anger, or fear can cause fainting. You could lose consciousness from things that startle you, such an alarm clock or a phone.
Some persons may experience seizures as a result of long QT syndrome. Long QT syndrome symptoms might occasionally manifest while you’re asleep.
The majority of LQTS sufferers experience their first episode by the age of 40. In cases when congenital long QT syndrome is present at birth, symptoms may manifest in the early weeks to months of life or later in childhood.
After a long QT episode, the heart usually returns to its normal beat. Sudden death will occur if the heart does not reset itself or if an external defibrillator is not utilized in time to reset the cardiac rhythm.
If you unexpectedly lose consciousness during exercise, intense emotional moments, or after trying a new medication, it’s essential to reach out to your doctor. Informing your healthcare provider about any cases of long QT syndrome in your immediate family, such as parents, siblings, or children, is vital. Family history plays a significant role in long QT syndrome.
Causes
Long QT syndrome, a cardiac rhythm disorder, is caused by alterations in the heart’s electrical recharging system, with no impact on the heart’s physical structure.
During each heartbeat, the heart propels blood throughout the body by contracting and relaxing its chambers in a synchronized manner. This coordinated activity is regulated by the cardiac electrical system, which transmits electrical impulses from the top to the bottom of the heart, instructing it to beat and contract. After each heartbeat, the system replenishes itself, preparing for the next one.
In long QT syndrome, the heart’s electrical system takes longer than usual to recharge, leading to a prolonged QT interval, which can be detected on an electrocardiogram (ECG).
Long QT syndrome is often categorized into two primary types, depending on the underlying cause.
- The disorder is known as congenital long QT syndrome if it is present from birth. Certain types of long QT syndrome are caused by DNA changes that run in families (inherited).
- It is known as acquired long QT syndrome if it results from a pharmaceutical side effect or an underlying medical issue. Long QT syndrome of this kind is typically curable if the underlying cause is found and addressed.
Causes of congenital long QT syndrome
Researchers have identified over a dozen genes associated with long QT syndrome. These genes have been found to undergo hundreds of different changes or mutations in connection to the condition.
Types of congenital long QT syndrome:
- Jervell and Lange–Nielsen syndrome (autosomal recessive form). This uncommon type of LQTS typically manifests as more severe episodes that happen very early in life. Children with this condition inherit the changed gene variations from both parents. The youngsters are deaf and have long QT syndrome from birth.
- Romano–Ward syndrome (autosomal dominant form). Those who receive only one gene variant from one parent tend to have this more frequent type.
- Ion channel abnormalities. Among these categories, LQT1, LQT2, LQT3, LQT4, and LQT5 are the most prevalent. They are categorized by researchers based on the kind of channel that produces the condition. The risk of further cardiac incidents varies among kinds.
- Timothy Syndrome. This is a rare kind of long QT syndrome that impacts not just the heart but also other areas of your body.
Causes of acquired long QT syndrome
In otherwise healthy individuals, more than 100 drugs, many of them common ones, can result in prolonged QT intervals.
Drug–induced long QT syndrome is the term used to describe a condition where a medicine results in acquired long QT syndrome (LQTS). The following medications may result in LQTS:
- Diuretics that lead to an imbalance in electrolytes (usually low potassium)
- Anti–arrhythmic medications that prolong the QT interval
- A few antibiotics, including azithromycin and erythromycin, among others
- Specific antifungal medications for the treatment of yeast infections
- Certain antiemetic drugs
- A few antipsychotic and antidepressant drugs
It is important to inform your healthcare practitioner about all of your prescriptions, even over–the–counter ones.
The following medical disorders have the potential to cause acquired long QT syndrome:
- Pheochromocytoma, a benign tumor of the adrenal gland
- Stroke or bleeding in the brain
- Hypothyroidism or decreased thyroid activity
- Hypothermia, defined as a body temperature below 95 degrees Fahrenheit (37 degrees Celsius).
- Hypomagnesemia or decreased magnesium level
- Hypokalemia or decreased potassium level
- Hypocalcemia or decreased calcium level
Risk factors
The likelihood of long QT syndrome developing may be raised by the following factors:
- Taking drugs that are known to result in prolonged QT intervals
- As a woman taking medication for her heart condition
- A previous cardiac arrest
- Being affected by long QT syndrome in a parent, sibling, or child
- Prolonged diarrhea or vomiting, which throws off electrolyte balance
- Anorexia nervosa and other eating disorders that result in electrolyte abnormalities
If you have long QT syndrome and are considering pregnancy, it’s crucial to notify your healthcare provider. Your doctor will closely monitor you during your pregnancy to proactively prevent situations that might trigger a long QT syndrome episode.
Diagnosis
A doctor will examine you physically and inquire about your symptoms, medical history, and family history in order to identify long QT syndrome. The doctor listens to your heart with a stethoscope. Tests to examine the heart’s rhythm can be performed if your physician believes you have an irregular heartbeat.
Tests
Testing is done to confirm the diagnosis of long QT syndrome or to look for other disorders that could cause irregular heartbeats or interfere with the heart’s rhythm.
Electrocardiogram (ECG or EKG)
The most used test for long QT syndrome diagnosis is this one. The electrical signals in the heart are recorded by a simple and painless examination called an ECG. Electrodes, or sensors, are attached to the chest and sometimes affixed to the arms or legs during an ECG. The length and timing of each electrical phase of a heartbeat are measured by an ECG. The signals appear on a connected printer or computer monitor as waves.
- An ECG uses the letters P, Q, R, S, and T to identify the five waves that make up the heart’s electrical signals.
- The electrical activity in the ventricles, the bottom chambers of the heart, is displayed by waves Q through T.
- The interval between the beginning of the Q wave and the conclusion of the T wave is known as the QT interval. The time it takes for the heart to contract and fill up with blood before it begins to beat again is known as the interval. A prolonged QT interval occurs when the interval takes longer than usual.
Your age, gender, and unique heart rate all affect the optimal QT interval.
Long QT symptoms can not show up on a typical ECG if they are not frequent. Remote ECG monitoring might be advised if this occurs. There are numerous varieties.
- Holter monitor. This portable ECG gadget can be suggested by your doctor so you can keep an eye on your heart rate at home. To track the heart’s activity during daily activities, it is worn for at least one day.
- Event monitor. You can use this portable ECG gadget for up to 30 days, or until you have symptoms or an arrhythmia. Usually, you click a button when the symptoms appear. Certain devices initiate automatic recording upon detection of an arrhythmia, or abnormal heartbeat.
Some personal electronics, such smartwatches, can monitor an ECG. Find out from your healthcare provider if you have this as a choice.
Exercise stress test
This kind of test usually entails riding a stationary bike or walking on a treadmill while having an ECG taken. Exercise tests are useful in determining the heart’s response to physical exertion. You might be prescribed a medicine that stimulates the heart similarly to exercise if you are unable to exercise.
Genetic testing
To confirm the diagnosis, a genetic test for long QT syndrome is available.
Your doctor can advise testing additional family members to see if they shared the same gene if the results of your genetic test reveal that you have long QT syndrome.
It’s critical to realize that not all inherited cases of long QT syndrome may be identified by genetic testing. Families should consult a genetic counselor both prior to and following testing.
Treatment
Long QT syndrome (LQTS) can be managed through various approaches, including medication, surgical procedures, and lifestyle adjustments.
The primary goal of LQTS treatment is to prevent irregular heartbeats and sudden death. Your doctor will tailor the best treatment plan for you, taking into account your specific LQTS type and symptoms. Even if your symptoms are infrequent, therapy may still be necessary.
For drug–induced long QT syndrome, discontinuing the medication or substance responsible for the symptoms may be the only necessary treatment. Your doctor will guide you on how to do this safely.
In cases of other types of acquired long QT syndrome, addressing the underlying illness is crucial. Treatment options vary, but magnesium or intravenous fluids to correct electrolyte imbalances may be used.
Medications
Long QT syndrome cannot be cured, however medications can help prevent potentially fatal heart rhythm abnormalities.
The following drugs may be used to treat long QT syndrome:
- Beta blockers. Most patients with long QT syndrome receive standard therapy with these medications. They reduce the heart rate and lower the risk of prolonged QT events. Propranolol and nadolol are two examples of beta blockers used to treat long QT syndrome.
- Mexiletine. Combining this heart rhythm medication with a beta blocker may help decrease the QT interval and lower the chance of passing out, having a seizure, or fainting.
Take prescriptions exactly as directed.
Surgery or other procedures
Some patients with long QT syndrome may require surgery or other medical interventions to help regulate their heartbeat. The following procedures and treatments for LQTS may be performed:
- Left Cardiac Sympathetic Denervation (LCSD) surgery. Surgery to correct long QT syndrome and persistent arrhythmias is often only advised for patients who are intolerant to beta blockers or cannot take them. While it doesn’t treat long QT syndrome, it does lessen the chance of unexpected death. Surgeons extract particular nerves along the left side of the spine in the chest during this treatment. The sympathetic nervous system of the body, which includes these nerves, aids in regulating the heart’s rhythm.
- Implantable Cardioverter–Defibrillator (ICD). Similar to a pacemaker, an ICD is a battery–operated device that is implanted beneath the skin close to the collarbone. The heart rhythm is continuously monitored by the ICD. The gadget shocks the heart to restore its usual rhythm if it notices an irregular heartbeat. It can halt an arrhythmia that might be fatal.
Those who have long QT syndrome typically do not require an ICD. For some athletes, nevertheless, an ICD might be advised in order to resume competitive sports. It is important to give serious thought to the decision to implant an ICD, particularly in children. ICD implantation is a significant operation that carries a risk of improper shocks and other issues.
