Long QT syndrome - Clinicals, Diagnosis, and Management

Cardiovascular

Clinicals - History

Fact Explanation
Syncope Stress induced syncope is a common symptom of long QT syndrome(LQTS) Syncope
Stress induced syncope is a common symptom of long QT syndrome(LQTS)
Cardiac arrest Can be the presenting symptom of some patients with LQTS Cardiac arrest
Can be the presenting symptom of some patients with LQTS
Palpitations Cardiac rhythm abnormalities can occur in patients with LQTS that will be perceived by patients as palpitations Palpitations
Cardiac rhythm abnormalities can occur in patients with LQTS that will be perceived by patients as palpitations
Seizures Can be the presentation in some patients with LQTS, especially those with bigenic mutations. Patients with Romano-Ward syndrome can present with syncope, seizures, and sudden death associated with QT prolongation Seizures
Can be the presentation in some patients with LQTS, especially those with bigenic mutations. Patients with Romano-Ward syndrome can present with syncope, seizures, and sudden death associated with QT prolongation
Sudden cardiac death Sudden cardiac death can occur in patients with LQTS due to torsade de pointes and ventricular fibrillation and may be the only presentation in 30-40% of patients with LQTS. Studies have shown that sudden cardiac events occur in these patients just after acute arousal events such as vigorous exercise, emotional stress, loud noise etc. Sudden cardiac death
Sudden cardiac death can occur in patients with LQTS due to torsade de pointes and ventricular fibrillation and may be the only presentation in 30-40% of patients with LQTS. Studies have shown that sudden cardiac events occur in these patients just after acute arousal events such as vigorous exercise, emotional stress, loud noise etc.
Family history of cardiac arrest in a young person Is a feature suggestive of congenital LQTS Family history of cardiac arrest in a young person
Is a feature suggestive of congenital LQTS
Family history of sudden cardiac death That occurred particularly at a young age, is an important factor found in patients with congenital LQTS Family history of sudden cardiac death
That occurred particularly at a young age, is an important factor found in patients with congenital LQTS
Congenital sensorineural deafness or having a family history of hearing deficit If this is present together with Long QT syndrome could be due to Jervell and Lange-Nielsen Syndrome Congenital sensorineural deafness or having a family history of hearing deficit
If this is present together with Long QT syndrome could be due to Jervell and Lange-Nielsen Syndrome
History of using medication such as salbutamol, amantadine, amitriptyline, macrolides, sotolol etc These drugs can prolong QT interval and it is important to exclude their use in a patient presenting with a sudden cardiac event History of using medication such as salbutamol, amantadine, amitriptyline, macrolides, sotolol etc
These drugs can prolong QT interval and it is important to exclude their use in a patient presenting with a sudden cardiac event
Patients presenting with a collection of features such as congenital heart diseases, cognitive and behavioral problems, musculoskeletal diseases, seizures, distinctive cranio-facial abnormalities and immune dysfunction May be seen in those with Timothy syndrome (Also called LQT8) Patients presenting with a collection of features such as congenital heart diseases, cognitive and behavioral problems, musculoskeletal diseases, seizures, distinctive cranio-facial abnormalities and immune dysfunction
May be seen in those with Timothy syndrome (Also called LQT8)

Clinicals - Examination

Fact Explanation
Bradycardia Seen in some patients with LQTS Bradycardia
Seen in some patients with LQTS
Arrhythmia A life-threatening tachyarrhythmia known as torsades de pointes can arise in patients with congenital LQTS Arrhythmia
A life-threatening tachyarrhythmia known as torsades de pointes can arise in patients with congenital LQTS
Hearing loss Can be found in patients with Jervell and Lange-Nielsen Syndrome Hearing loss
Can be found in patients with Jervell and Lange-Nielsen Syndrome
Syndactyly Is seen in patients with Timothy syndrome Syndactyly
Is seen in patients with Timothy syndrome
Presence of features such as short stature and scoliosis, periodic paralysis, dysmorphic features, ventricular arrhythmias Is seen in patients having Andersen-Tawil Syndrome (formerly LQT7) Presence of features such as short stature and scoliosis, periodic paralysis, dysmorphic features, ventricular arrhythmias
Is seen in patients having Andersen-Tawil Syndrome (formerly LQT7)

Investigations - Diagnosis

Fact Explanation
Electrocardiography(ECG) The most helpful ECG finding is prolongation of QT interval for more than 0.46 seconds. In addition there can be other changes such as torsade de pointes, T wave alternans, notched T wave in three leads etc Electrocardiography(ECG)
The most helpful ECG finding is prolongation of QT interval for more than 0.46 seconds. In addition there can be other changes such as torsade de pointes, T wave alternans, notched T wave in three leads etc
Genetic Testing The common mutations related to the long QT syndrome are in three genetic loci termed KCNQ1 (LQT1), KCNH2 (LQT2) and SCN5A (LQT3). LQT1 and LQT2 are potassium channel genes and LQT3 is a sodium channel gene. Some studies has shown that LQT1 mutations to be the least hazardous. LQT2 and LQT3 mutations were associated with a relatively high risk of cardiac events. These can be identified by genetic testing Genetic Testing
The common mutations related to the long QT syndrome are in three genetic loci termed KCNQ1 (LQT1), KCNH2 (LQT2) and SCN5A (LQT3). LQT1 and LQT2 are potassium channel genes and LQT3 is a sodium channel gene. Some studies has shown that LQT1 mutations to be the least hazardous. LQT2 and LQT3 mutations were associated with a relatively high risk of cardiac events. These can be identified by genetic testing
Serum Electrolytes Serum levels of potassium, calcium and magnesium are done in patients who present with QT prolongation to eliminate secondary reasons for repolarization abnormalities, as hypocalcemia, hypokalemia or hypomagnesia can precipitate similar arrythmias Serum Electrolytes
Serum levels of potassium, calcium and magnesium are done in patients who present with QT prolongation to eliminate secondary reasons for repolarization abnormalities, as hypocalcemia, hypokalemia or hypomagnesia can precipitate similar arrythmias
Echocardiography This is done to exclude the presence of any structural abnormality in the heart which can trigger arrhythmia Echocardiography
This is done to exclude the presence of any structural abnormality in the heart which can trigger arrhythmia

Management - Supportive

Fact Explanation
Avoid competitive sports Strenuous activities, vigorous exercise, swimming etc can trigger sudden cardiac events in patients with long QT syndrome. Therefore they are advised to avoid competitive sports and stressful activities Avoid competitive sports
Strenuous activities, vigorous exercise, swimming etc can trigger sudden cardiac events in patients with long QT syndrome. Therefore they are advised to avoid competitive sports and stressful activities
Avoid drugs that prolong QT interval Certain medication such as some antihistamines, macrolides, antifungal agents, psychotrophic agents etc. (see above) should be avoided in these patients as they prolong QT interval and worsen their disease Avoid drugs that prolong QT interval
Certain medication such as some antihistamines, macrolides, antifungal agents, psychotrophic agents etc. (see above) should be avoided in these patients as they prolong QT interval and worsen their disease

Management - Specific

Fact Explanation
Beta-blockers Beta-blockers are effective in preventing cardiac events in a majority of patients but some continue to develop cardiac events despite treatment Beta-blockers
Beta-blockers are effective in preventing cardiac events in a majority of patients but some continue to develop cardiac events despite treatment
Pacemakers Implanted cardiac pacemakers can eliminate arrhythmogenic bradycardias, decrease irregularities in heart-rate and diminish the risk of torsade de pointes ventricular tachycardia. Can be used in combination with beta blockade Pacemakers
Implanted cardiac pacemakers can eliminate arrhythmogenic bradycardias, decrease irregularities in heart-rate and diminish the risk of torsade de pointes ventricular tachycardia. Can be used in combination with beta blockade
Implantable Cardioverter-Defibrillators(ICD) These are designed to detect and treat life-threatening arrhythmias, and have been proven to be highly effective in preventing sudden cardiac death (SCD), particularly in individuals who have a strong family history of SCD. Implantable Cardioverter-Defibrillators(ICD)
These are designed to detect and treat life-threatening arrhythmias, and have been proven to be highly effective in preventing sudden cardiac death (SCD), particularly in individuals who have a strong family history of SCD.
Left cardiac sympathetic denervation Done for high-risk patients with long QT syndrome, who experience recurrent cardiac events despite maximal therapy on beta-blockers.

The procedure decreases the risk of cardiac events but does not completely eliminate their occurrence.

Therefore, it is limited to very high risk patients without adequate response to implantable devices or beta-blockers
Left cardiac sympathetic denervation
Done for high-risk patients with long QT syndrome, who experience recurrent cardiac events despite maximal therapy on beta-blockers.

The procedure decreases the risk of cardiac events but does not completely eliminate their occurrence.

Therefore, it is limited to very high risk patients without adequate response to implantable devices or beta-blockers

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