Question

5. Write an essay explaining how potassium chloride stops the heart.

I understand that the potassium chloride will disrupt the electrical signaling of potassium and sodium ions which maintain the heartbeat, but I need to know more of the mechanism of the process with how it does so. If you could explain. Thank you.

Answer 1

Potassium chloride is used as a lethal injection. High doses of KCl lead to a state of hyperkalemia and in the heart it leads to cardioplegia.

Now you must know that normally, there is a greater concentration of Na ions outside the cells and more K+ inside the cell. When K+ increases on the outside, this disturbs the ionic gradient. Since the K+ gradient dramatically increases, the membrane becomes depolarised.

There is also decrease in the availability of Na+ fast channels and overall excitability and conduction velocity.

So the end result is that there is cardiac failure. The heart fails during diastole. Basically electrical heterogeneity of any kind is dangerous for the heart. But K+ and Na+ being the chief ionic contributors of membrane potential cause a greater effect.

I have attached some ECGs to help you understand this even more. As you can see, the T waves are very prominent but the P waves are almost negligible.

I hope this makes things clear.