Long QT Syndrome

Long QT disorder, also known as long QT syndrome, is a heart rhythm disease that can cause fast, chaotic heartbeats. Understanding long QT syndrome is crucial for those affected and their families. This comprehensive article will explore the cause of long QT interval, including genetic factors and certain medications. We'll also discuss the symptoms, potential complications, and available treatment options for long QT heart disease. Additionally, we'll cover when to see a doctor and steps to prevent complications related to this heart condition.

What is Long QT Syndrome?

Long QT syndrome (LQTS) is a heart rhythm disorder that impacts the electrical system controlling the heartbeat. This condition causes fast, chaotic heartbeats that can be life-threatening. The name "long QT" comes from a specific pattern seen on an electrocardiogram (ECG) test, which maps the heart's electrical activity.

In a typical heart, electrical signals move from top to bottom, telling the heart when to squeeze and beat. After each heartbeat, the system recharges to prepare for the next one. However, in long QT syndrome ECG, the heart's electrical system takes longer than usual to recover between beats. This delay is called a prolonged QT interval.

The QT interval represents the electrical activity in the heart's lower chambers (ventricles). Usually, this interval lasts about a third of each heartbeat cycle. In people with LQTS, the QT interval is longer than normal, which can upset the careful timing of the heartbeat and result in sudden, uncontrollable, fast heart rhythms.

Causes and Risk Factors of Long QT Syndrome

Long QT syndrome (LQTS) is a heart rhythm disorder that has an impact on the electrical system controlling the heartbeat. This cardiac condition can be either congenital or acquired.

• A. Congenital LQTS: This is present from birth and is caused by inherited DNA changes. The following are main types of congenital LQTS: 
  • Romano-Ward Syndrome: It is a more common type of long QT syndrome, and only one parent has long QT syndrome. Each child has a 50% chance of inheriting the abnormal gene.
  • Jervell and Lange-Nielsen Syndrome: It is more severe and also causes deafness.
  • Timothy Syndrome: It is a rare form of long QT syndrome that affects the heart and other parts of the body.
• B. Acquired LQTS: It develops later in life due to: 
  • Medicines: Certain antibiotics, antifungal medicines, diuretics, and heart rhythm medications. 
  • Health Conditions: Certain systemic conditions like hypothermia and thyroid problems.
  • Mineral Imbalance: Changes in body mineral levels, including low levels of calcium, magnesium, or potassium in the blood 
• Several factors can increase the possibility of developing long QT disease. These include:
  • Family history of the condition 
  • Being female 
  • A history of cardiac arrest
  • Severe vomiting or diarrhoea 
  • Eating disorders

Symptoms of Long QT Syndrome

The symptoms of long QT syndrome typically start during childhood or adolescence, with most people experiencing their first symptoms before the age of 40. However, the risk of symptoms tends to be highest before age 30.

Long QT syndrome (LQTS) can manifest in various ways, with some individuals experiencing no symptoms at all. This condition, known as silent LQTS, is often discovered through routine electrocardiogram (ECG) tests or genetic screening. The following are some common long QT syndrome symptoms:

• Fainting or Syncope: This is the most common symptom that can occur suddenly and is often triggered by physical or emotional stress. They may happen during exercise, when startled by loud noises, or even while sleeping. 
• Other Symptoms: 
  • Fast heartbeats
  • Seizures 
  • Cardiac arrest

Complications

Long QT disorder (LQTS) is a serious heart condition. It can cause severe medical consequences if left untreated. These include:

• Torsades de Pointes: In this condition, the heart's lower chambers beat rapidly and out of rhythm, reducing blood flow. This deficiency of blood in the brain can cause sudden fainting, often without warning. If the long QT interval persists, fainting may be followed by a full-body seizure.
• Ventricular Fibrillation: In this condition, the lower heart chambers beat so fast that the heart trembles and stops pumping blood. This can quickly cause brain damage and death if not corrected promptly with a defibrillator.
• Sudden Cardiac Death: This unexpected cessation of all heart activity has been linked to LQTS in young, otherwise healthy individuals. 

Diagnosis

• Medical History and Clinical Assessment: Cardiologists ask about symptoms, medical history, and family history of heart conditions. They also listen to the heart using a stethoscope to detect any irregularities.
• Electrocardiogram (EKG or ECG): This test records the heart's electrical signals and can reveal a prolonged QT interval, which is characteristic of the condition. 
• Holter Monitor or Event Recorder: If symptoms are infrequent, a doctor may recommend wearing this portable ECG device for extended periods. These devices can capture heart activity during daily activities and help identify irregularities.
• Exercise Stress Tests: These tests typically involve walking on a treadmill or cycling on a testing bike while the heart's activity is monitored.

Treatment for Long QT Syndrome

Treatment for long QT disorder aims to prevent irregular heartbeats and sudden cardiac death, including: 

• Lifestyle Changes: These are often the first step in managing long QT syndrome. These may include avoiding triggers that could cause irregular heartbeats, such as certain physical activities or emotional stress.
• Medicines: Beta-blockers are commonly prescribed to slow the heart rate and reduce the chances of a long QT episode. In some cases, mexiletine (heart rhythm medicine) may be used alongside a beta blocker to help shorten the QT interval and lower the risk of fainting, seizure, or sudden cardiac death.
• Discontinuation of Drug: For acquired long QT syndrome caused by medications, stopping the offending drug may be sufficient to treat the disorder. 
• Surgery: An implantable cardioverter-defibrillator (ICD) can be placed under the skin near the clavicle (collarbone) to monitor heart rhythm and deliver shocks if needed. Left cardiac sympathetic denervation (LCSD) surgery is another option for those who don't respond well to beta blockers. This procedure removes specific nerves along the left side of the spine to help lower the risk of sudden cardiac death.

When to See a Doctor

Make an appointment with your doctor if: 

• If you have pounding, fast, or irregular heartbeats
• Family history of sudden cardiac death
• History of fainting episodes (syncope)
• For individuals diagnosed with long QT syndrome, regular check-ups are essential. 
• If you have an implanted device to manage your condition, annual visits are necessary to ensure it's functioning correctly.
• Children with long QT syndrome may need more frequent check-ups. They should see a provider more than once yearly to adjust medication dosages based on weight.

Prevention

While congenital long QT syndrome cannot be prevented, there are steps to manage the condition and reduce the risk of complications, such as:

• Lifestyle Changes: If you have long QT syndrome, it's crucial to avoid strenuous exercise, water sports, and sudden loud noises 
• Medication: Always inform your doctor about your condition before taking new medicines or supplements. 
• Diet: Increase your intake of potassium-rich foods like bananas, vegetables, and pulses. 
• Avoid caffeine-containing drinks and high-energy beverages as they can increase heart rate and worsen symptoms.

Conclusion

While long QT syndrome can be life-threatening, proper diagnosis and treatment can significantly decrease the risk of complications. Regular check-ups, lifestyle changes, and medication management play key roles in controlling the disorder. By staying informed and working closely with doctors, individuals with long QT syndrome can lead full and active lives while minimising their risk of sudden cardiac events.

FAQs

1. What age is long QT diagnosed?

Long QT syndrome can be diagnosed at any age, but symptoms often start during childhood or adolescence. Most people experience their first symptoms before the age of 40. 

2. How to fix long QT syndrome?

While long QT syndrome cannot be 'fixed' in the traditional manner, it can be managed effectively. Options include lifestyle changes, medications like beta blockers, and, in some cases, medical implantation devices or surgery. 

3. What is the life expectancy of someone with long QT syndrome?

With proper management, many people with long QT syndrome can lead normal, active lives. 

4. Does long QT show on ECG?

Yes, long QT syndrome typically shows on an ECG. The test reveals a prolonged QT interval, representing the time it takes for the heart's electrical system to recharge between beats. However, because the QT interval can change over time, multiple ECGs or a 24-hour ECG monitor may be needed to diagnose the condition accurately.

5. Can long QT be temporary?

While congenital long QT syndrome is a lifelong condition, acquired long QT syndrome can be temporary. Certain medications or medical conditions can cause acquired long QT. Stopping the causative drug and treating the underlying systemic conditions can cure long QT conditions.

6. What is the difference between short and long QT syndrome?

In long QT syndrome, the QT interval is prolonged, taking longer than normal for the heart to recharge between beats. In contrast, short QT syndrome is characterised by an abnormally short QT interval. Both conditions can lead to dangerous heart rhythms, but they have different causes and treatments.

7. Can anxiety cause long QT?

While anxiety itself doesn't cause long QT syndrome, it can potentially trigger symptoms in people who already have the condition. 

Dr. Chanakya Kishore Kammaripalli

MBBS, MD, DM (Cardiology) (AIIMS)
CARE Medical Center, Tolichowki, Hyderabad, CARE Hospitals, HITEC City, Hyderabad

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