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  #1  
Old 11-25-2013
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EKG Hypokalemia and Torsades !

Hypokalemia is a risk factor for Torsade de pointes , where as hyperkalemia is not !

Has anyone come across the CONCEPT behind these electrolyte changes causing this type of arrythmia ??

Memorizing them simply just doesn't work
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Old 11-25-2013
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Torsades is always due to prolongation of QT, therefore drugs that prolong QT can cause torsades.

Electrolite imbalances like hypokalemia, hypocalcemia, prolong QT interval, the hyper shorten QT, therefore since it slows the QT interval = torsades

Last edited by Ianmrz; 11-25-2013 at 10:20 PM.
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Old 11-25-2013
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qt prolong is the cause of torsades, but other things such as left heart failure and hypokalemia are great risks that lean towards torsades


A little Background on K+
Normal condition: K+ repolarizes are cell memb -->resting state right after an action potential has passed

Hypokalemia Condition: If our K+ decreases in the extracellular department, then hyperpolarization (more neg.) occurs affecting our resting memb potential.So in this situation we would need a greater stimulus in order for depolarization to occur so we can generate an action potential


Hypokalemia---> Torsades?

I mentioned Hypokalemia leads to hyperpolarization: so in the heart, this will affect the myocytes' resting memb potential. The more NEGATIVE memb potentials cause arrhythmias because our Sodium channel is inactive---> this is what leads to an action potential. Furthermore: our decreased extracelluar K+ inhibits the IKf potass. current----> delayed ventric depolarization
this delay is key in reentrant arrhthymias.
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Old 11-25-2013
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hope that helps a bit
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Old 11-26-2013
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Quote:
Originally Posted by betablocker_22 View Post
qt prolong is the cause of torsades, but other things such as left heart failure and hypokalemia are great risks that lean towards torsades


A little Background on K+
Normal condition: K+ repolarizes are cell memb -->resting state right after an action potential has passed

Hypokalemia Condition: If our K+ decreases in the extracellular department, then hyperpolarization (more neg.) occurs affecting our resting memb potential.So in this situation we would need a greater stimulus in order for depolarization to occur so we can generate an action potential


Hypokalemia---> Torsades?

I mentioned Hypokalemia leads to hyperpolarization: so in the heart, this will affect the myocytes' resting memb potential. The more NEGATIVE memb potentials cause arrhythmias because our Sodium channel is inactive---> this is what leads to an action potential. Furthermore: our decreased extracelluar K+ inhibits the IKf potass. current----> delayed ventric depolarization
this delay is key in reentrant arrhthymias.

Good one but medical students don't like action potential topics.
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Old 11-28-2013
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Quote:
Originally Posted by betablocker_22 View Post
qt prolong is the cause of torsades, but other things such as left heart failure and hypokalemia are great risks that lean towards torsades


A little Background on K+
Normal condition: K+ repolarizes are cell memb -->resting state right after an action potential has passed

Hypokalemia Condition: If our K+ decreases in the extracellular department, then hyperpolarization (more neg.) occurs affecting our resting memb potential.So in this situation we would need a greater stimulus in order for depolarization to occur so we can generate an action potential


Hypokalemia---> Torsades?

I mentioned Hypokalemia leads to hyperpolarization: so in the heart, this will affect the myocytes' resting memb potential. The more NEGATIVE memb potentials cause arrhythmias because our Sodium channel is inactive---> this is what leads to an action potential. Furthermore: our decreased extracelluar K+ inhibits the IKf potass. current----> delayed ventric depolarization
this delay is key in reentrant arrhthymias.

Thank you for taking the time to reply !
However, i am a bit confused.
The more negative membrane potential (hyperpolarized) should make the cell more stable , shouldn't it ?
And shouldn't the Na channels be in the RESTING mode if the cell is hyperpolarized ?
aghhh .. it is getting all messy
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Old 11-28-2013
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Plus the reason why I don't understand why hyperkalemia isn't causing torsades is :

Hyperkalemia generally decreases the conc gradient of K+ flow thus reduce the efflux of K+ .. this causes the K+ ions to stay in the cell which prolongs phase 3 / hyperpolarization phase which corresponds to longer QT interval thus should cause torsades .. HOWEVER for anyone reading this, it was only my personal thinking .. haven't read this reasoning anywhere and was wondering why it won't work this way too ?!

Any one here with a decent answer please
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Old 11-28-2013
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Quote:
Originally Posted by hope007 View Post
Plus the reason why I don't understand why hyperkalemia isn't causing torsades is :

Hyperkalemia generally decreases the conc gradient of K+ flow thus reduce the efflux of K+ .. this causes the K+ ions to stay in the cell which prolongs phase 3 / hyperpolarization phase which corresponds to longer QT interval thus should cause torsades .. HOWEVER for anyone reading this, it was only my personal thinking .. haven't read this reasoning anywhere and was wondering why it won't work this way too ?!

Any one here with a decent answer please
yeah that part is really confusing me as well, and i havent gotten a clear answer about it.
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Old 10-20-2016
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Quote:
Originally Posted by hope007 View Post
Hypokalemia is a risk factor for Torsade de pointes , where as hyperkalemia is not !

Has anyone come across the CONCEPT behind these electrolyte changes causing this type of arrythmia ??

Memorizing them simply just doesn't work
hypokalemia means low K+ outside cell as compared to cardiomyocytes. Looking at phase 3 myocardial action potential, which is characterized by massive K+ effux due to opening of voltage gated slow K+ channels(rapid repolarization). When there is low K+ outside cell, more K+ efflux will happen to balance this, which will prolong phase 3, causing prolong QT interval. This effect is quite similar to Class 1A antiarrhythmic which also causes torsades.

pls correct me if i am wrong!
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Cardiovascular-, EKGs-, Electrolytes-, Physiology-

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