I hate Digoxin

[Roy7]

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Okay, I may be totally off, and am all wrong but if someone could explain this i'd be much obliged.

Digoxin causes hyperkalemia because it blocks Na-K-atpase.
Hyperkalemia ==> spike T waves

Digoxin SE as per everywhere: Inverted T waves, ST scooping.

I dont like starting individual threads on like questions... but none of my classmates know the answer.

 

[phassett74]

So here is an answer to your question:

Digitalis can cause the EKG findings you are describing, as can digitalis "toxicity". That is, QRS is shortened, and you get the hallmark "Salvador Dali" scooping effect.

There is also digitalis "syndrome", which encompasses systemic effects.

Digitalis and K+ actually compete for spots on the ATPase, and as such cause two interesting phenomenon:

- hypokalemia is actually more dangerous with dig as it potentiates the effects of dig
- ironically, elevated K+ actually "knocks" dig off, thereby decreasing the toxicity of the agent; essentially, you could almost view it as a negative feedback, although I think that would be a bit much - lets just call it a convenient incidental safety feature

Lastly, K+ is highly regulated and buffered in the body to protect against levels outside of the serum normals. You are correct in the assertion that digitalis will increase ECF K+, but that is the cause of the scoop, nor is it to suggest that it will provoke K+ levels high enough to prompt T wave peaking. That is, dig may increase ECF K+, but increased K+ secondary to dig does not result in peaked T waves.

Hope that helps.

 

[JNP]

Dig is falling off the list anyway. It is sometimes given to control heart rate in patients with A Fib but since it can lead to arrhythmias and other toxicities, people are steering away. I would say for A Fib, docs or recommending a beta blocker or a nondihydropyridine calcium channel blocker first and only adding dig if the heart rate really needs to be controlled. If it is AFIB plus systolic heart failure, a beta blocker is better than a calcium channel blocker (with an ACE or ARB plus maybe a diuretic for symptom relief). Dig is only above an aldosterone antagonist as far as the therapy step ladder. If DIG is needed, keep levels below 1 ng/ml for heart failure and it may go a little higher if needed for AFIB (always watch for decreased renal function that can increase serum dig levels and for interactions)