long QT syndrome 16

Long QT Syndrome (LQTS) Description

Long QT syndrome (LQTS) is a rare heart condition that affects the electrical system of the heart, causing it to take longer than normal to recharge between heartbeats. This can lead to sudden uncontrollable fast heart rhythms, which can be life-threatening.

Characteristics of LQTS:

• A prolongation of the QT interval on electrocardiograms (ECGs)
• A propensity to experience syncope or cardiac arrest
• Fast and erratic heart rhythms or arrhythmias
• In some cases, fainting or fits (seizures)

Causes and Consequences:

LQTS is typically inherited and can cause serious arrhythmia and sudden cardiac death. The condition affects the heart's electrical system, leading to a prolonged QT interval on ECGs. This can result in ventricular arrhythmias, which are characterized by very fast and potentially dangerous heart rhythms.

Symptoms:

• Sudden uncontrollable fast heart rhythms
• Syncope (fainting)
• Fits (seizures) in some cases

References:

• [1] Long QT syndrome is an inherited heart problem that affects how your heart beats. In some people, this can cause fainting or fits (seizures). [4]
• [2] LQTS is typically characterized by a prolongation of the QT interval on the ECG and by the occurrence of syncope or cardiac arrest, mainly due to ventricular arrhythmias. [5]
• [3] Long QT syndrome is an electrical condition of the heart that affects the heart's rhythm. A person with long QT syndrome may experience fast, erratic heart rhythms. [6]
• [4] Long QT syndrome (LQTS) is a congenital disorder characterized by a prolongation of the QT interval on electrocardiograms (ECGs) and a propensity to experience syncope or cardiac arrest. [7]
• [5] Long QT syndrome (LQTS) is an abnormality in the heart's electrical system that may cause very fast and potentially dangerous heart rhythms or arrhythmias. [8]
• [6] Result: a ventricular arrhythmia characterized by a long QT interval, and accompanied by syncopal episodes sometimes leading to sudden death due to paroxysmal ventricular arrhythmia; this arrhythmia is associated with a prolongation of repolarization following depolarization of the cardiac ventricles. [9]

Common Signs and Symptoms of Long QT Syndrome

Long QT syndrome (LQTS) can cause a range of symptoms, which may vary from person to person. Some common signs and symptoms include:

• Fainting: This is one of the most common symptoms of LQTS, especially in response to emotional stress, exercise, or sudden changes in environment.
• Palpitations: People with LQTS may experience fast, erratic heartbeats, which can be felt as a fluttering sensation in the chest.
• Lightheadedness: Some individuals may feel dizzy or lightheaded, especially when standing up quickly or experiencing emotional stress.
• Shortness of breath: In some cases, people with LQTS may experience shortness of breath or chest pain due to abnormal heart rhythms.
• Seizures: Rarely, LQTS can cause seizures in some individuals.

Other Possible Symptoms

In addition to the above symptoms, some people with LQTS may also experience:

• Chest fluttering: A feeling of fluttering or irregular heartbeat in the chest area.
• Gasping while sleeping: Some individuals may experience gasping or difficulty breathing while asleep.
• Near-drowning or drowning incidents: In rare cases, LQTS can cause sudden cardiac arrest during swimming or other water activities.

Important Note

It's essential to note that not everyone with long QT syndrome will experience symptoms. Some people may be asymptomatic until they undergo an electrocardiogram (ECG) for another reason. If you suspect you or a family member has LQTS, it's crucial to consult a healthcare professional for proper diagnosis and treatment.

References:

• [1] Symptoms of long QT syndrome appear when the syndrome leads to Torsades de Pointes. During this arrhythmia, your heart can’t pump blood effectively. If your brain doesn’t get enough blood supply, you can faint and have a seizure.
• [2] Some people with long QT syndrome do not have any symptoms. They may only become aware of their condition after having an electrocardiogram (ECG) for another reason.
• [3] 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 symptoms.
• [4] Long QT Syndrome can cause: Fainting, especially as a result of acute emotions (such as anger or surprise), exercise, menses (menstruation), or swimming in cold water.
• [5] Long QT syndrome is characterised by a prolonged QT interval on ECG, which may be congenital or acquired. In congenital LQTS, genetic mutations affect ion channels important in myocardial repolarisation.

Diagnosing Long QT Syndrome (LQTS)

Long QT syndrome (LQTS) can be diagnosed through various tests, including:

• Electrocardiogram (EKG or ECg): This is a non-invasive test that measures the electrical activity of the heart. A healthcare professional can diagnose LQTS by measuring the QT interval on an EKG. If your QT interval is longer than 450 milliseconds, you may have long QT syndrome [4].
• Exercise ECG: In some cases, an exercise ECG may be needed to confirm the diagnosis. This test measures the heart's electrical activity while you are exercising [7].
• Genetic testing: Genetic testing can be used to identify the faulty gene causing LQTS. This test is usually performed with cardiac evaluation and can determine the status of long QT syndrome, short QT syndrome, catecholaminergic polymorphic ventricular tachycardia (CPVT), and Brugada syndrome (BrS) genes [8].
• Supine-stand test: This test may aid in the diagnosis of LQTS as patients fail to shorten their QT interval in response to postural changes. However, this test is not widely used due to its limitations [10].

Other diagnostic criteria

The Schwartz-score can be used to diagnose definite LQTS, which is defined by an LQTS score ≥3.5 points [9]. Additionally, a corrected QT interval of greater than 450–500 milliseconds on an EKG can also confirm the diagnosis, although clinical findings and genetic testing may be needed for confirmation [14].

References

• [4] August 20, 2024 - This is a life-threatening arrhythmia that can lead to sudden death. Healthcare providers can diagnose long QT syndrome during a routine electrocardiogram (EKG). To make a diagnosis, they measure the QT interval on the EKG.
• [7] August 8, 2021 - Anyone diagnosed with congenital ... can be tested. Acquired long QT syndrome is the result of conditions, medications or events that prolong the QT interval.
• [8] Performed with cardiac evaluation, genetic testing may be used to determine the status of long QT syndrome (LQTS), short QT syndrome (SQTS), catecholaminergic polymorphic ventricular tachycardia (CPVT), and Brugada syndrome (BrS) genes from blood, saliva, or tissue specimens, including postmortem ...
• [9] by AAM Wilde · 2022 · Cited by 143 — Diagnostic criteria for long QT syndrome (LQTS) (the 'Schwartz-score'). Definite LQTS is defined by an LQTS score ≥3.5 points, intermediate probability of LQTS ...
• [10] Background: Long QT syndrome (LQTS) is a sudden death predisposing condition characterized by ECG-derived prolongation of the QT interval.
• [14] 1 month ago - LQTS can be diagnosed using an electrocardiogram (EKG) if a corrected QT interval of greater than 450–500 milliseconds is found, but clinical findings, other EKG features, and genetic testing may confirm the diagnosis with shorter QT intervals.

Beta Blockers as First-Line Treatment

The cornerstone of management for patients with Long QT Syndrome (LQTS) is beta-blocker therapy [5]. Beta blockers, such as propranolol or nadolol, are commonly prescribed to help control heart rhythm and prevent life-threatening arrhythmias [4].

• Non-selective beta blockers: Nadolol and propranolol have been widely used for LQTS patients due to their effectiveness in preventing abnormal heart rhythms [5].
• Lifestyle modifications: In addition to medication, lifestyle changes such as avoiding strenuous exercise can also help manage the condition [6].

Other Pharmacologic Therapies

While beta blockers are the primary treatment, other pharmacologic therapies may be considered for patients who do not respond to or cannot tolerate beta blockers. These include:

• Potassium and/or spironolactone: To regulate potassium levels and prevent arrhythmias
• Mexiletine: An anti-arrhythmic medication that can help stabilize heart rhythm

Surgical Options

In some cases, surgical options may be considered to manage LQTS. These include:

• Left cardiac sympathetic denervation (LCSD): A procedure that involves removing or disrupting the nerves that control the left side of the heart
• Implantable cardioverter-defibrillator (ICD): A device that can detect and correct abnormal heart rhythms

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 widely used for LQTS patients due to their effectiveness in preventing abnormal heart rhythms.

[6] Treatment for long QT syndrome includes lifestyle changes and medicines to prevent dangerous heartbeats. Sometimes a medical device or surgical procedure may be necessary.

Differential Diagnoses for Long QT Syndrome

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

• Brugada syndrome: A genetic disorder characterized by abnormal electrocardiogram (ECG) patterns and an increased risk of sudden cardiac death.
• Cardiac death: Sudden cardiac death can be a manifestation of various underlying conditions, including coronary artery anomalies, hypertrophic cardiomyopathy, and other heart-related disorders.
• Coronary artery anomalies: Abnormalities in the coronary arteries can lead to reduced blood flow to the heart muscle, potentially causing arrhythmias and sudden cardiac death.
• Drug-induced QT prolongation: Certain medications, such as antibiotics and antipsychotics, can cause QT interval prolongation, which may mimic LQTS symptoms.
• Hypertrophic cardiomyopathy: A genetic disorder characterized by thickening of the heart muscle, which can lead to arrhythmias and sudden cardiac death.

Other Conditions to Consider

In addition to these differential diagnoses, other conditions that may present with similar symptoms to LQTS include:

• Short QT syndrome: A rare genetic disorder characterized by a shortened QT interval on ECG.
• Epilepsy: Seizures can sometimes be mistaken for arrhythmias or other cardiac-related symptoms.

Prenatal Diagnosis

In some cases, prenatal diagnosis may be considered when one of the parents has LQTS. This involves testing the fetus for genetic mutations associated with LQTS to determine if they are at risk of developing the condition.

References:

• [4] Electrolyte disturbances such as hyperkalaemia, hypocalcaemia, hypoglycaemia, hypokalaemia, and hypomagnesemia can cause QT prolongation.
• [7] Other conditions to consider in the differential diagnosis of long QT syndrome include Brugada syndrome. Short QT syndrome.
• [9] Differential diagnosis must be made with epilepsy, catecholaminergic ...
• [12] Long QT syndrome (LQTS) is an inherited primary arrhythmia syndrome that may present with malignant arrhythmia and, rarely, risk of sudden death.