Long QT Syndrome (LQTS)

Overview

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.