ECG Features demonstrating the Digoxin Effect
Digoxin effect refers to the presence on the ECG of:
- Downsloping ST depression with a characteristic “Salvador Dali sagging” appearance
- Flattened, inverted, or biphasic T waves.
- Shortened QT interval.
Other Digoxin effect features
Additional ECG Features
- Mild PR interval prolongation of 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 (my personal favourite) “Salvador Dali’s moustache”!
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.
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.
NB. The presence of digoxin effect on the ECG is not a marker of digoxin toxicity. It merely indicates that the patient is taking digoxin.
- This is the classic picture of digoxin effect with the “sagging” ST segments and T waves taking on the appearance of “Salvador Dali’s moustache“.
- Sagging ST segments are most evident in the lateral leads V4-6, I and aVL.
- The sagging morphology is most evident in V6 and in the lead II rhythm strip.
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 example.
- 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.
- Sagging ST depression is clearly evident in leads I, II, III, aVF and V5-6.
- Frequent premature ventricular complexes (PVCs) suggest the possibility of digoxin toxicity.
LITFL Further Reading
- ECG Library Basics – Waves, Intervals, Segments and Clinical Interpretation
- ECG A to Z by diagnosis – ECG interpretation in clinical context
- ECG Exigency and Cardiovascular Curveball – ECG Clinical Cases
- 100 ECG Quiz – Self-assessment tool for examination practice
- ECG Reference SITES and BOOKS – the best of the rest
- Brady WJ, Truwit JD. Critical Decisions in Emergency and Acute Care Electrocardiography
- Surawicz B, Knilans T. Chou’s Electrocardiography in Clinical Practice: Adult and Pediatric
- Wagner GS. Marriott’s Practical Electrocardiography 12e
- Chan TC. ECG in Emergency Medicine and Acute Care
- Rawshani A. Clinical ECG Interpretation
- Mattu A. ECG’s for the Emergency Physician
- Hampton JR. The ECG In Practice, 6e