long QT syndrome 2

Long QT Syndrome Type 2 (LQT2) Description

Long QT syndrome type 2 (LQT2) is a life-threatening disorder of cardiac electrophysiology caused by loss-of-function mutations in the KCNH2 gene [1]. This condition can lead to sudden cardiac death as a result of QT prolongation and T-wave abnormalities on the electrocardiogram (ECG) [4].

The classic ECG appearance of LQT2 includes lower-amplitude T waves in the limb leads, which is a characteristic feature of this syndrome [1]. The most common symptom of long QT syndrome, including LQT2, is fainting, also called syncope, which can happen with little to no warning [3].

Individuals with LQT2 may experience other symptoms such as palpitations (a fluttering in the chest), seizure-like activity caused by lack of blood flow to the brain, and sudden cardiac death [8]. The risk of cardiac events is higher in mutation carriers than unaffected family members, even in the absence of QTc prolongation [6][9].

Current treatment for LQT2 relies on symptom management largely through the use of β-adrenergic blockade, but no mechanism-based therapies exist yet [5].

Symptoms of Long QT Syndrome

Long QT syndrome can cause a range of symptoms, including:

• Sudden fainting: This is one of the most common symptoms of LQTS, especially in young people. [1]
• Seizures: In some cases, LQTS can cause seizures, which can be life-threatening. [2]
• Chest fluttering (palpitations): People with LQTS may experience a fluttering or irregular heartbeat. [3]
• Shortness of breath or chest pain: These symptoms can occur due to the abnormal heart rhythm caused by LQTS. [4]
• Lightheadedness that comes and goes: This symptom is often experienced by people with LQTS, especially when they are under stress or experiencing strong emotions. [5]

In some cases, long QT syndrome can also cause more severe symptoms, including:

• Fainting (syncope): This can occur suddenly, without warning, and can be caused by a range of triggers, such as stress, exercise, or sudden noises. [6]
• Gasping while sleeping: Some people with LQTS may experience gasping or other abnormal breathing patterns while they are asleep. [7]

It's worth noting that not everyone who has long QT syndrome will experience all of these symptoms, and some people may only experience mild symptoms. However, if you are experiencing any of these symptoms, it's essential to seek medical attention immediately.

Diagnostic Tests for Long QT Syndrome 2

Long QT syndrome 2 (LQTS2) is a genetic disorder that affects the heart's electrical system, leading to abnormal heart rhythms. Diagnostic tests are essential to confirm the diagnosis and rule out other conditions. Here are some of the diagnostic tests used to diagnose LQTS2:

• Electrocardiogram (ECG): An ECG is the most common test used to diagnose LQTS2. It records the electrical signals in the heart and shows how fast or slow the heart is beating [10]. A PCP can help you get specialist referrals, order diagnostic tests, and coordinate providers as you build a healthcare team [11].
• Exercise ECG: An exercise ECG may be needed to confirm the diagnosis. This test records the heart's electrical activity during physical activity [7].
• Genetic testing: Genetic testing may be needed to identify the faulty gene causing LQTS2. This can involve next-generation sequencing to detect single nucleotide and copy number variants in 10 genes associated with LQTS [9].

Other Diagnostic Tests

In addition to these tests, other diagnostic criteria are used to confirm the diagnosis of LQTS2. These include:

• Schwartz score: The Schwartz score is a diagnostic criterion for LQTS2, which takes into account various factors such as the QT interval, heart rate, and other clinical features [3].
• Clinical characteristics: Clinical characteristics such as syncope, seizures, or sudden cardiac death may also be used to diagnose LQTS2 [14].

Importance of Diagnostic Tests

Diagnostic tests are crucial in diagnosing LQTS2 and ruling out other conditions. A timely diagnosis can help prevent complications and improve patient outcomes.

References:

[3] Context 3 [7] Context 7 [9] Context 9 [10] Context 10 [11] Context 11 [14] Context 14

Medications for Long QT Syndrome Type 2

Long QT syndrome type 2 (LQTS2) is a life-threatening disorder that requires careful management to prevent sudden cardiac death. While there is no cure, medications play a crucial role in managing the condition.

• Beta-blockers: Beta-blockers are the cornerstone of treatment for LQTS2. They help control heart rate and reduce the risk of abnormal heart rhythms. Nadolol and propranolol are commonly prescribed beta-blockers for this condition [8][9].
• Mexiletine: Mexiletine, a Class Ib anti-arrhythmic medication, has been shown to shorten the QT interval in patients with potassium channel-mediated type 2 long QT syndrome [3].
• Other medications: In some cases, other medications may be prescribed to manage symptoms and prevent sudden death. However, these should only be used under the guidance of a healthcare professional.

It's essential to note that while medications can help manage LQTS2, they do not provide a cure. A comprehensive treatment plan that includes lifestyle modifications, regular monitoring, and emergency preparedness is crucial for preventing sudden cardiac death.

References:

[3] Bos JM, et al. Mexiletine shortens the QT interval in patients with potassium channel-mediated type 2 long QT syndrome. Circulation. 2019; doi:10.1161/CIRCEP. [8] by AAM Wilde · 2022 · Cited by 143 — 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 ... [9] Although there is no cure for LQTS, we can treat the disorder to prevent fainting and dangerous arrhythmias. We work with you to customize a treatment plan that ...

Differential Diagnosis of Long QT Syndrome

Long QT syndrome (LQTS) can be challenging to diagnose, and it's essential to consider other conditions that may present with similar symptoms. Here are some differential diagnoses for LQTS:

• Epilepsy: Seizures can sometimes mimic the symptoms of LQTS, such as syncope or cardiac arrest.
• Catecholaminergic polymorphic ventricular tachycardia (CPVT): This is a rare heart condition that can cause abnormal heart rhythms, similar to those seen in LQTS.
• Brugada syndrome: A genetic disorder that affects the heart's electrical system, leading to abnormal heart rhythms and sudden cardiac death.
• Short QT syndrome: A rare genetic disorder characterized by a short QT interval on an electrocardiogram (ECG), which can lead to abnormal heart rhythms.

Key Points

• Differential diagnosis is crucial in LQTS cases to rule out other conditions that may present with similar symptoms.
• Epilepsy, CPVT, Brugada syndrome, and Short QT syndrome are some of the differential diagnoses for LQTS.
• A thorough medical history, physical examination, and ECG analysis are essential in making an accurate diagnosis.

References

• [5] Prenatal diagnosis should be considered when one of the parents has LQTS.
• [8] Other conditions to consider in the differential diagnosis of long QT syndrome include Brugada syndrome and Short QT syndrome.
• [14] Differential Diagnosis Management Genetic Counseling Resources Molecular Genetics References Chapter...