long QT syndrome 9

Long QT Syndrome (LQTS) Description

Long QT syndrome (LQTS) is a heart rhythm disorder that affects the electrical system of the heart, causing it to take longer than normal to recharge between beats. This can lead to potentially life-threatening arrhythmias.

• Characteristics: The condition is characterized by a prolongation of the QT interval on electrocardiograms (ECGs), which measures the time it takes for the heart's ventricles to recharge between beats.
• Symptoms: People with LQTS may experience fast, erratic heart rhythms, fainting or fits (seizures).
• Causes: The condition is typically inherited and can be caused by genetic mutations that affect the heart's electrical system.

Key Points

• Long QT syndrome affects the heart's electrical system, causing it to take longer than normal to recharge between beats.
• The condition is characterized by a prolongation of the QT interval on ECGs.
• LQTS can lead to potentially life-threatening arrhythmias and sudden cardiac death.
• The condition is typically inherited and can be caused by genetic mutations.

References

• [9] - The characteristic signs are QT interval prolongation and T wave abnormalities. The QT shows reduced penetrance and variable expression, and diagnosis may be challenging due to the variability of symptoms.
• [11] - If you have LQTS, your heart takes longer than usual to recharge between beats, which is because the channels are not letting the ions in or out of your cells properly.

Symptoms of Long QT Syndrome

A person with long QT syndrome may experience fast, erratic heartbeats when exercising, or at times of emotional excitement. This may cause fainting, seizures, and other cardiac-related issues.

• Fainting: Also known as syncope, fainting is a common symptom of long QT syndrome, especially during physical activity or emotional stress.
• Seizures: Some people with long QT syndrome may experience seizures due to the abnormal heart rhythms.
• Erratic heartbeat: A person with long QT syndrome may feel their heart beating irregularly, which can be alarming and even lead to fainting.

These symptoms are often triggered by physical activity, emotional stress, or other factors that affect the heart's electrical system. It's essential for individuals with a family history of long QT syndrome or those who experience these symptoms to consult a doctor for proper diagnosis and treatment.

References:

• [9] A person with long QT syndrome may experience fast, erratic heartbeats when exercising, or at times of emotional excitement. This may cause fainting, seizures ...
• [13] Signs and symptoms of Long QT Syndrome. LQTS can cause: Fainting, especially as a result of acute emotions (such as anger or surprise), exercise, menses (menstruation), or swimming in cold water ...

Diagnostic Tests for Long QT Syndrome

To diagnose long QT syndrome (LQTS), several diagnostic tests can be performed.

• Electrocardiogram (ECG or EKG): This test records your heart's rhythm and is usually the first step in diagnosing LQTS. An ECG can detect abnormal heart rhythms, including those associated with LQTS [5].
• Cardiac MRI: A cardiac MRI uses radio waves to produce detailed images of your heart, which can help diagnose LQTS [2].
• Genetic testing: Next-generation sequencing can be used to detect single nucleotide and copy number variants in 10 genes associated with LQTS [9].

The Schwartz-score is a diagnostic criteria for long QT syndrome (LQTS), which defines definite LQTS as an LQTS score ≥3.5 points, indicating an intermediate probability of LQTS [7].

Beta Blockers as First-Line Treatment

The cornerstone of drug treatment for long QT syndrome (LQTS) is beta blockers, which are considered the first-line treatment for most patients with inherited LQTS [5]. Beta blockers, such as propranolol or nadolol, help control heart rhythm and prevent life-threatening arrhythmias [4].

Other Medications

In addition to beta blockers, other medications may be prescribed to manage symptoms of LQTS. These include:

• Potassium and/or spironolactone to regulate electrolyte levels
• Mexiletine to stabilize the heart rhythm
• Antibiotics, such as erythromycin or trimethoprim/sulfamethoxazole, to treat infections that can trigger abnormal heart rhythms [6]

Treatment Goals

The primary goal of drug treatment for LQTS is to prevent life-threatening arrhythmias and sudden cardiac death. Beta blockers are effective in achieving this goal by reducing the risk of arrhythmic events [5].

References:

[4] Most people with inherited long QT syndrome will need treatment with medicines. Beta blockers, such as propranolol or nadolol, may be prescribed to help control heart rhythm.

[5] As indicated, the cornerstone of management of LQTS patients is ß-blocker therapy (figure 5). The non-selective ß-blockers nadolol and propranolol have been shown to be effective in preventing arrhythmic events.

[6] Erythromycin (E-Mycin, EES, EryPed, PCE) may be prescribed for lung, ear, and throat infections.

Other causes of acquired Long QT Syndrome (LQTS)

According to [9], other causes of acquired LQTS include:

• Electrolyte abnormalities
• Eating disorders
• Coronary artery disease
• Bradyarrhythmias

These conditions can lead to a prolongation of the QT interval on the electrocardiogram (ECG), similar to congenital LQTS. It's essential to consider these differential diagnoses when evaluating patients with suspected LQTS.

In particular, electrolyte disturbances such as hyperkalaemia, hypocalcaemia, hypoglycaemia, hypokalaemia, and hypomagnesemia can cause QT prolongation [3]. Additionally, conditions like Brugada syndrome and Short QT syndrome should also be considered in the differential diagnosis of LQTS [6].

It's crucial to note that acquired LQTS can have a similar presentation to congenital LQTS, making it essential to investigate and rule out these other causes before making a definitive diagnosis.