Rhythm Nation May 2015 Answer!

Rhythm Nation May 2015 Answer

Congratulations to Dr. Reza Roodsari!

This is indeed a case of digoxin toxicity. Whenever you see “regularized a-fib,” that is, regular QRS intervals in a patient with permanent atrial fibrillation, think digoxin toxicity until proven otherwise.

How does digoxin work in the cell?

Digoxin increases automaticity through increased intracellular Calcium. This occurs from direct inhibition of the Na-K pump of cardiac myocytes whereby the intracellular sodium builds up and is exchanged for extracellular calcium. There are other mechanisms that are not fully understood that lead to increased duration of calcium’s intracellular effect as well.

Digoxin also increases vagal tone which decreases AV conduction by stimulating central vagal nuclei and increasing the sensitivity of the carotid baroreceptors.

What do these effects have on the ECG?

Both effects of increased automaticity and decreased AV conduction can lead to a variety of arrhythmias. Nonspecific ECG findings of digitalis toxicity are very broad.

More specific findings of digoxin toxicity include:

-Bidirectional ventricular tachycardia

-Accelerated junctional rhythm or junctional tachycardia

-Atrial fibrillation with av-dissociation (slow ventricular response)

-Atrial tachycardia with AV block

“Digoxin Effect” (not toxicity) can include an upsloping ST segment sometimes referred to as a “Salvador Dali” mustache.

What happened to this patient?

Due to high digoxin level, this patient received digoxin immune Fab and the repeat ECG is below:

References:

Jon B. Cole and David J. Roberts. Cardiovascular Drugs. Rosen’s Emergency Medicine, Chapter 152, 1982-1993.e2

Hood, Jr. WB, Dans AL, Guyatt GH, Jaeschke R, McMurray JJV. Digitalis for treatment of heart failure in patients in sinus rhythm. Cochrane Database of Systematic Reviews 2014, Issue 4

Patel, V. et al. Digitalis Toxicity. Mescape reference. January 27, 2015.

Life in the Fast Lane. http://lifeinthefastlane.com/ecg-library/basics/digoxin-toxicity/