Long QT syndrome

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Obesity, Sleep & Internal medicine
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Long QT syndrome
Synonyms	LQTS
Pronounce	N/A
Specialty	N/A
Symptoms	Syncope, seizures, sudden cardiac death
Complications	Torsades de pointes, ventricular fibrillation
Onset	Congenital or acquired
Duration	Lifelong
Types	N/A
Causes	Genetic mutations, certain medications, electrolyte imbalances
Risks	Family history, certain medications, electrolyte disturbances
Diagnosis	Electrocardiogram, genetic testing
Differential diagnosis	Ventricular tachycardia, Brugada syndrome, catecholaminergic polymorphic ventricular tachycardia
Prevention	Avoiding QT-prolonging drugs, managing electrolyte levels
Treatment	Beta blockers, implantable cardioverter-defibrillator, left cardiac sympathetic denervation
Medication	N/A
Prognosis	Variable, risk of sudden death
Frequency	1 in 2,000 people
Deaths	N/A

Long QT syndrome (LQTS) is a genetic disorder that affects the heart's electrical activity. It is characterized by a prolonged QT interval on an electrocardiogram (ECG), which can lead to arrhythmias, syncope, and sudden cardiac arrest.

Pathophysiology

Long QT syndrome is caused by mutations in genes that encode for ion channels in the heart. These ion channels are responsible for the flow of potassium, sodium, and calcium ions, which are crucial for the heart's electrical activity. The most commonly affected genes include KCNQ1, KCNH2, and SCN5A. Mutations in these genes can disrupt the normal flow of ions, leading to a prolonged QT interval.

Types

There are several types of Long QT syndrome, classified based on the specific gene mutation:

• LQT1: Caused by mutations in the KCNQ1 gene.
• LQT2: Caused by mutations in the KCNH2 gene.
• LQT3: Caused by mutations in the SCN5A gene.

Symptoms

Individuals with Long QT syndrome may experience:

• Palpitations
• Syncope
• Seizures
• Sudden cardiac arrest

Diagnosis

Diagnosis of Long QT syndrome typically involves:

• Electrocardiogram (ECG) to measure the QT interval.
• Genetic testing to identify specific mutations.
• Holter monitor to record heart activity over 24-48 hours.
• Exercise stress test to observe heart activity during physical exertion.

Treatment

Treatment options for Long QT syndrome include:

• Beta blockers to reduce the risk of arrhythmias.
• Implantable cardioverter-defibrillator (ICD) for individuals at high risk of sudden cardiac arrest.
• Lifestyle modifications such as avoiding strenuous exercise and certain medications that can prolong the QT interval.

Prognosis

With appropriate treatment and lifestyle modifications, individuals with Long QT syndrome can lead relatively normal lives. However, the risk of sudden cardiac arrest remains, particularly in untreated individuals.

See also

• Arrhythmia
• Cardiac arrest
• Electrocardiogram
• Genetic disorder
• Ion channel

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