L17 - Cardiac Channelopathies - Long & Short QT syndromes Flashcards
What does the Q-T segment of an ECG show?
Ventricular depolarisation and reploarisation.
How do short Q-T syndromes affect ventricular reoplarisation?
Ventricular repolarisation happens quicker making the Q-T interval shorter.
How do long Q-T syndromes affect ventricular reoplarisation?
Ventricular repolarisation happens quicker making the Q-T interval longer.
What are some implications of longer repolarisation?
- Triggered activity, myocytes stay depolarised for longer than they should.
- Voltage gated calcium ion channels can reactivate firing more action potentials - ectopic beat.
What can an ectopic beat lead to?
Ventricular tachychardia then ventricular fibrillation
What is reentrant excitation?
Where beat to beat variation regions end up out of sync due to temporal heterogeneity.
What can reentrant excitation cause?
Heart blocks, where come cells cannot recieve electrical activity.
Long Q-T syndrome symptoms?
- Prolonged Q-T inerval
- Syncope (fainting)
- Sudden death
How are long Q-T syndromes inherited?
In an autosomal dominant fashion.
How might some Long Q-T syndromes affect the ear?
A reduction in the secretion of K+ into the endolymph of the ear slowing down repolarisation.
What are some treatments for Long Q-T syndrome?
- Blockers - Class 2 anti-dysrythmic drugs.
- Atenolol - B1 selective antagonist.
What is short Q-T syndrome?
Reduced Q-T interval
Short Q-T syndrome symptoms
- Arrhythmias
- Palpitations
- syncope (fainting)
What could be associated with short Q-T syndromes?
- X-Linked gene mutations - as males are
more impacted. - Tall/peaked T-waves
- Gain of function in K+ channels and loss
of function in Ca2+ channels.
What are some treatments for short Q-T syndrome?
- Implant ventricular defibrilator
- Research suggests quinidine (K+ channel
blocker) may be effective.
