Step I Hyperkalemia

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Hey guys, Im having a hard time understanding how hyperkalemia causes a taller T wave. could any one explain this thanks

 

[Fuzuli]

"The effects of changes in serum potassium on cardiac action potential duration, pacemaker rate, and arrhythmias can appear somewhat paradoxical if changes are predicted based solely on a consideration of changes in the potassium electrochemical gradient. In the heart, however, changes in serum potassium concentration have the additional effect of altering potassium conductance (increased extracellular potassium increases potassium conductance) independent of simple changes in electrochemical driving force, and this effect often predominates. As a result, the actual observed effects of hyperkalemia include reduced action potential duration, slowed conduction, decreased pacemaker rate, and decreased pacemaker arrhythmogenesis."

"Agents Used in Cardiac Arrhythmias", Katzung's Basic & Clinical Pharmacology, 11th edition.

So, hyperkalemia increases K+ efflux out of the cell (despite the decreased electrochemical gradient), which shortens the repolarization duration. This is manifested as a tall and thin T wave on EKG.

 

[jaguar1]

I thought repolarization is K= channel opening during phase 3 which causes EFFLUX of K+ = out of the cell, making it more negative-Hence, repolarizing!!!

Do you mean, increase in K+ through slow leak channels into the cell is causing the tall T wave?

Sorry-Getting some clarification for myself as well.

 

[Paseo Del Norte]

Hey guys, Im having a hard time understanding how hyperkalemia causes a taller T wave. could any one explain this thanks

I have no idea what Step I considers correct; however, as I understand, you actually increase the slope of phase three with hyperkalaemia. This leads to a decrease in the repolarisation time and may contribute to the classic T wave changes. However, I have seen many patients who were rather hyperkalaemic and had no ECG changes that I could appreciate.