Digoxin Effect

Note: The presence of digoxin effect on the ECG is not a marker of digoxin toxicity. It merely indicates that the patient is taking digoxin.

ECG Features demonstrating the Digoxin Effect

Digoxin effect refers to the presence on the ECG of:

  • Downsloping ST depression with a characteristic “reverse tick” or “Salvador Dali sagging” appearance
  • Flattened, inverted, or biphasic T waves
  • Shortened QT interval
Digoxin Effect T waves
Digoxin effect: Sagging ST segments resemble a “reverse tick”

Other Digoxin effect features
Additional ECG Features
  • Mild PR interval prolongation, up to 240 ms (due to increased vagal tone)
  • Prominent U waves
  • Peaking of the terminal portion of the T waves
  • J point depression (usually in leads with tall R waves)

QRS complex / ST segment changes

The morphology of the QRS complex / ST segment is variously described as either “slurred”, “sagging” or “scooped” and resembling either a “reverse tick”, “hockey stick” or (our personal favourite) “Salvador Dali’s moustache”!

Digoxin effect reverse tick salvador dali moustache

T-wave changes

The most common T-wave abnormality is a biphasic T wave with an initial negative deflection and terminal positive deflection. This is usually seen in leads with a dominant R wave (e.g. V4-6).

The first part of the T wave is typically continuous with the depressed ST segment. The terminal positive deflection may be peaked, or have a prominent U wave superimposed upon it.

Digoxin Effect T waves


The ECG features of digoxin effect are seen with therapeutic doses of digoxin and are due to:

  • Shortening of the atrial and ventricular refractory periods — producing a short QT interval with secondary repolarisation abnormalities affecting the ST segments, T waves and U waves
  • Increased vagal effects at the AV node — causing a prolonged PR interval

Remember, the presence of digoxin effect on the ECG is not a marker of digoxin toxicity. — it merely indicates that the patient is taking digoxin!

ECG Examples
Example 1
Digoxin effect 1

Digoxin effect:

  • This is the classic picture of digoxin effect, with “sagging” ST segments and T waves taking on the appearance of “Salvador Dali’s moustache

Example 2
Digoxin effect Atrial Fibrillation 2

Digoxin effect:

  • Sagging ST segments are most evident in the lateral leads V4-6, I and aVL

Example 3
Digoxin effect AF fibrillatory waves V1 2

Digoxin effect:

  • The sagging morphology is most evident in V6 and in the lead II rhythm strip

Example 4
Digoxin effect 4

This is a slight variation on the classic digoxin pattern:

  • There is still downsloping ST depression but it is slightly more angular, in comparison to the “sagging” ST segments from the previous examples
  • Also, there is J-point depression in V4-6, which mimics the appearance of left ventricular hypertrophy
  • The short QT interval, the “sagging” appearance in the inferior leads, and the lack of voltage criteria for LVH indicates that this is digoxin effect rather than LVH

Example 5
Digoxin effect and Digoxin toxicity

Digoxin effect:

Advanced Reading



LITFL Further Reading



Emergency Physician in Prehospital and Retrieval Medicine in Sydney, Australia. He has a passion for ECG interpretation and medical education | ECG Library |

MBBS (UWA) CCPU (RCE, Biliary, DVT, E-FAST, AAA) Adult/Paediatric Emergency Medicine Advanced Trainee in Melbourne, Australia. Special interests in diagnostic and procedural ultrasound, medical education, and ECG interpretation. Editor-in-chief of the LITFL ECG Library. Twitter: @rob_buttner

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