QT syndrome Flashcards
What is Long QT syndrome (LQTS)?
An inherited condition associated with delayed repolarization of the ventricles
It may lead to ventricular tachycardia/torsade de pointes and can cause collapse/sudden death.
What are the most common variants of LQTS?
LQT1 and LQT2
Caused by defects in the alpha subunit of the slow delayed rectifier potassium channel.
What is a normal corrected QT interval for males?
Less than 430 ms
What is a normal corrected QT interval for females?
Less than 450 ms
What are some congenital causes of prolonged QT interval?
- Jervell-Lange-Nielsen syndrome
- Romano-Ward syndrome
Name some drugs that can cause prolonged QT interval.
- Amiodarone
- Sotalol
- Class 1a antiarrhythmic drugs
- Tricyclic antidepressants
- Selective serotonin reuptake inhibitors
- Methadone
- Chloroquine
- Terfenadine
- Erythromycin
- Haloperidol
- Ondansetron
What electrolyte imbalances can cause prolonged QT interval?
- Hypocalcaemia
- Hypokalaemia
- Hypomagnesaemia
What are some other causes of a prolonged QT interval?
- Acute myocardial infarction
- Myocarditis
- Hypothermia
- Subarachnoid haemorrhage
How can Long QT syndrome be detected?
May be picked up on routine ECG or following family screening
What is a characteristic feature of Long QT1?
Usually associated with exertional syncope, often swimming
What is a characteristic feature of Long QT2?
Often associated with syncope occurring following emotional stress, exercise or auditory stimuli
What is a characteristic feature of Long QT3?
Events often occur at night or at rest
What is a potential outcome of Long QT syndrome?
Sudden cardiac death
What is one management strategy for Long QT syndrome?
Avoid drugs which prolong the QT interval and other precipitants
What is another management strategy for Long QT syndrome?
Beta-blockers
What is a management option in high risk cases of Long QT syndrome?
Implantable cardioverter defibrillators
True or False: Sotalol may exacerbate long QT syndrome.
True
Fill in the blank: The usual mechanism by which drugs prolong the QT interval is blockage of _______.
potassium channels
What is terfenadine known for in relation to Long QT syndrome?
A classic cause of prolonged QT in a patient, especially if also taking P450 enzyme inhibitor
