ECG Features of Digoxin Toxicity
The classic digoxin toxic dysrhythmia combines:
- Supraventricular tachycardia (due to increased automaticity)
- Slow ventricular response (due to decreased AV conduction)
Other common dysrhythmias associated with digoxin toxicity include:
- Frequent PVCs (the most common abnormality), including ventricular bigeminy and trigeminy
- Sinus bradycardia
- Slow Atrial Fibrillation
- Any type of AV block (1st degree, 2nd degree & 3rd degree)
- Regularised AF = AF with complete heart block and a junctional or ventricular escape rhythm
- Ventricular tachycardia, including polymorphic and bidirectional VT
Digoxin can cause a multitude of dysrhythmias due to:
- Increased automaticity (increased intracellular calcium)
- Decreased AV conduction (increased vagal effects at the AV node)
Clinical features of Digoxin Toxicity
- GIT: Nausea, vomiting, anorexia, diarrhoea
- Visual: Blurred vision, yellow/green discolouration, haloes
- CVS: Palpitations, syncope, dyspnoea
- CNS: Confusion, dizziness, delirium, fatigue
- Sinus rhythm with frequent PVCs in a pattern of ventricular bigeminy
Paroxysmal atrial tachycardia with block
- Atrial tachycardia with high-grade AV block and PVCs
- Coarse atrial fibrillation with 3rd degree AV block and a junctional escape rhythm.
- Another example of regularised AF.
“Paroxysmal” atrial tachycardia with block and frequent PVCs
- This is a classic ECG of digoxin toxicity showing atrial tachycardia (P waves at 150 bpm), high-grade 2nd degree AV block (A:V ratio of 4:1) with frequent premature ventricular complexes.
Atrial flutter with AV block
- Atrial flutter with a slow ventricular rate due to digoxin toxicity.
Bidirectional Ventricular Tachycardia (VT)
- Example of Bidirectional VT.
- There is a broad complex tachycardia with a frontal-plane axis that alternates by 180 degrees with each successive beat.
- Wiesbauer F, Kühn P. ECG Yellow Belt online course: Become an ECG expert. Medmastery
- Wiesbauer F, Kühn P. ECG Blue Belt online course: Learn to diagnose any rhythm problem. Medmastery
- Rawshani A. Clinical ECG Interpretation ECG Waves
- Smith SW. Dr Smith’s ECG blog.
- Mattu A, Tabas JA, Brady WJ. Electrocardiography in Emergency, Acute, and Critical Care. 2e, 2019
- Brady WJ, Lipinski MJ et al. Electrocardiogram in Clinical Medicine. 1e, 2020
- Straus DG, Schocken DD. Marriott’s Practical Electrocardiography 13e, 2021
- Hampton J. The ECG Made Practical 7e, 2019
- Grauer K. ECG Pocket Brain (Expanded) 6e, 2014
- Brady WJ, Truwit JD. Critical Decisions in Emergency and Acute Care Electrocardiography 1e, 2009
- Surawicz B, Knilans T. Chou’s Electrocardiography in Clinical Practice: Adult and Pediatric 6e, 2008
- Mattu A, Brady W. ECG’s for the Emergency Physician Part I 1e, 2003 and Part II
- Chan TC. ECG in Emergency Medicine and Acute Care 1e, 2004
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