Long QT syndrome

What is the basis for a normal action potential in pacemaker cells and normal myocardial cells?
Myocardial cells phase 0 is from rapid entry of sodium channel.Transient phase 1 is due transient outwars potassium current. Phase 2 is due to calcium entry being balanced by potassium exit. Phase 3 is from unbalanced potassium exit.Phase 4 is repolarization phase with mostly Na+K+ ATPase being active and some potassium channel being open with little movement due to compensating electrochemical forces as per Nernst equation.

Pacemaker cells have very small element of Phase 0 sodium activity and is mostly calcium lead.


Why is the T wave not opposite of QRS? and why?

Subendocardial M cells have a longer Action potential when compared with epicardial myocytes. so though they depolarize first, they do not repolarize first.


What is the defect in LQTS?

There are many defects but 3 account for most. Ks accounts for LQTS1, Kr accounts for LQTS2, INa accounts for LQT3


How do the mutations affect the channel function?

Either they interfere with the functioning of normal subdivision or is a production defect by reduced number

What are the T wave patterns in LQTS?

Broad based T in LQTS1, Notched T in LQTS 2 , Tall and Notched in LQTS 3


When do you call the QT as prolonged?
When it is > 430 in makes and > 450 in females .



Patient is dead do you still need to make a diagnosis?

Ofcourse you have the family waiting to die!


What do you ask in family history?
Not just for SCD but for others like deafness/Seizures


What are the other causes of LQTS?
Many drugs  and electrolyte imbalances

What about genetic testing?

Can check for the ones you know but a negative doesnot exclude in the presence of other criteria

How is sex going to affect the presentation?
Estrogens block K channels, so prolong APD and hence QT. So prior to puberty males are likely to die more and vice versa afterwards

How about pregnancy?
Increases the risk and the increased risk remains till 6 months postpartum

Is the degree of QT prolongation important?

Yes the longer the QT the more likely for Torsades

What activities precipitate Torsades?

LQT1 - Physical exp swimming
LQT2- sudeen loud noise alarm clock
LQT3-no arousal needed

Does the type of mutation matter?
Yes it does - depending on which domain is affected the pore part/ the cytoplasmic domain or extracellular

dominant negative versus haploinsufficiency

What are the treatments that can be used?
Beta blocker,LCDS,AICD

Once AICD is it a done deal?
Still have to use beta blocker and also avoid major physical activities

Is AICD cost effective in LQTS?
It is at least 10-20 times cheaper per life saved when compared with CHF

What is electrical storm?
> 2 shocks in < 24 hours

Why does mexileten or lidocaine make sense?
How does a prolonged QT lead PVT?
Where do the antiarrhytmics act?What are the subtyeps in 1?
What are the other congenital syndromes that we need to remember for sudden death?
Are the capacitators already charged ready to go in AICD?
Does the AICD always need to shock to terminate VT? and how can it do it?
How does hypokalemia cause PVT IN long QT?
what is the problem with bazett's ? undercorrects at tachy and over corrects at brady.