23-51: Digoxin Effect, Toxicity

Maite A. Huis in ‘t Veld; Amal Mattu; R. Jason Thurman

ECG Findings

ST segment shortening and depression leading to a “scooped” appearance.
QT interval shortening.
PR interval prolongation.
Decreased T-wave amplitude.
Premature ventricular complexes are the most common dysrhythmia.
Bradydysrhythmias, heart block, especially with findings consistent with increased automaticity (atrial tachycardia with block, atrial fibrillation with slow ventricular response, accelerated junctional rhythms).
Bidirectional VT may rarely be seen (see Fig. 17.99).

Pearls

ECG changes associated with digoxin can be seen from therapeutic or toxic levels.
ST-segment changes may be exaggerated by myocardial disease or tachycardia.
An acute overdose of a digoxin is usually associated with hyperkalemia, which may increase the height of the T wave.
Avoid calcium for treatment of hyperkalemia in the setting of digoxin toxicity as this may potentiate adverse effects of digoxin.

FIGURE 23.52A

Digoxin Effect with Evidence of Toxicity. (ECG contributor: James V. Ritchie, MD.)

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FIGURE 23.52B

The “sagging” appearance of the ST segment (arrow) is characteristic of digoxin therapy and is not a sign of toxicity. However, this patient also has a sign of chronic digoxin toxicity. Atrial fibrillation is present, but the R-to-R interval has become regular. Digoxin toxicity has produced a total AV block but has also excited the AV node, producing a relatively accelerated junctional escape rate.