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Flashcards in Cardiac channelopathies Deck (15)
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What is the result of long QT syndrome

Delayed start for the T wave - repolarization is delayed


What is the result of short QT syndrome

T wave starts early - ventricular repolarization is accelerated


What is the normal QT time gap and how does it change for long and short QT

normal = 0.36s long=0.45, short =0.34s


What is triggered activity of the myocardia

before full repolarization other depolarizations can occur reaching threshold level so another action potential is fired - this leads to an ectopic beat


What is re-entrant excitation of myocardia

Different layers of cells contain the mutation - so have more or less ion channels - leads to spatial and temporal dispersion of action potential firing - leads to excitatory wave moving in a circular path and returning to its site of origin.


What mutation is seen for LQT1,2,and 7

Loss of function in potassium channels - can't contribute to repolarization so it takes longer to occur


What mutation is seen in LQT3

Nav1.5alpha gain of function - Depolarization lasts for longer and the sodium channels take longer to close


What mutation is seen in LQT8

Ca1.2alpha - Gain of function mutation - Calcium channels remain open maintaining the plateau phase of myocardia


What mutations are seen in LQT1

High proportion of mutations in the transmembrane spanning domains


How is LQT syndrome treated

Beta blockers - class 2 antiarrhythmic drugs - atenolol - Beta1 adrenergic selective antagonist
cAMP linked receptor antagonists - cAMP dependent kinase channels linked with sodium influx - reduced sodium = reduced calcium channel opening = reduced heart rate and force of contractility


How is short QT syndrome diagnosed

In normal patients the QT would normally shorten - in short QT sufferers it stays the same


How is a short QT syndrome seen on the electrocardiogram

Short/absent ST segment
Tall/peaked T wave
QT interval is fixed


What mutation is seen for SQT1-3

Gain of function in potassium channels - open too early and increased potassium efflux causes rapid repolarization


What mutation is seen in SQT4and5

Loss of function in calcium channels - this shortens the plateau phase - repolarization can therefore occur earlier


How is short QT treated

Implant defibrillator
Quinidine - potassium channel blocker may be effective