Digoxin Significantly Increases Risk of Ventricular Fibrillation in Patients with Accessory Pathways
Yes, digoxin is potentially harmful and should never be used in patients with accessory conduction pathways who have pre-excitation on their resting ECG, as it shortens the refractory period of the accessory pathway and can precipitate ventricular fibrillation if atrial fibrillation develops. 1
Mechanism of Harm
Digoxin creates a life-threatening situation through two key mechanisms:
Shortens accessory pathway refractoriness: Digoxin directly reduces the refractory period of the accessory pathway, allowing more rapid conduction through the bypass tract 1, 2
Enables catastrophic ventricular rates: When atrial fibrillation occurs in a patient on digoxin with an accessory pathway, the shortened refractory period permits extremely rapid ventricular rates that can degenerate into ventricular fibrillation 1, 2
Unpredictable AF conversion: Even patients presenting with orthodromic AVRT (atrioventricular reentrant tachycardia) can spontaneously convert to atrial fibrillation during the episode, suddenly exposing them to this risk 1, 2
Guideline Recommendations
The ACC/AHA/HRS guidelines provide a Class III: Harm recommendation (meaning potentially harmful) for digoxin use in patients with pre-excitation: 1
Intravenous digoxin is contraindicated for acute treatment in patients with pre-excited atrial fibrillation 1
Oral digoxin is contraindicated for ongoing management in patients with AVRT or AF who have pre-excitation on their resting ECG 1
Historical context matters: Before safer alternatives became available, IV digoxin was commonly used for orthodromic AVRT, but this practice has been abandoned because digoxin puts patients at risk of ventricular fibrillation 1
FDA Drug Label Warning
The FDA label for digoxin explicitly warns about this danger: 3
After IV digoxin therapy, patients with paroxysmal atrial fibrillation or flutter and a coexisting accessory AV pathway have developed increased antegrade conduction across the accessory pathway, leading to very rapid ventricular response or ventricular fibrillation 3
Unless conduction down the accessory pathway has been blocked (pharmacologically or surgically), digoxin should not be used in such patients 3
Critical Clinical Distinction
The presence or absence of pre-excitation on the resting ECG determines safety:
Manifest accessory pathway (pre-excitation visible on ECG): Digoxin is absolutely contraindicated, both IV and oral forms 1, 2
Concealed accessory pathway (no pre-excitation on resting ECG): Oral digoxin may be reasonable for ongoing management of orthodromic AVRT in highly selected patients who are not ablation candidates, though efficacy is low 1
Safe Alternatives
For patients with accessory pathways requiring treatment:
Acute pre-excited AF (hemodynamically unstable): Synchronized cardioversion is the treatment of choice 1
Acute pre-excited AF (hemodynamically stable): IV procainamide or ibutilide are recommended 1
Definitive management: Catheter ablation of the accessory pathway is the Class I recommendation for patients with AVRT and/or pre-excited AF, with 93-95% success rates 1
Other Medications to Avoid
Several other rate-controlling agents share similar risks in pre-excited AF: 1
IV amiodarone, IV/oral beta blockers, diltiazem, and verapamil are all potentially harmful in pre-excited AF 1
These agents increase ventricular rate through drug-induced hypotension with increased catecholamines, or by blocking AV nodal conduction and preventing competitive concealed retrograde conduction into the accessory pathway 1
Common Pitfall to Avoid
Never assume a patient is safe from atrial fibrillation just because they have never had documented AF: 1, 2
Orthodromic AVRT can spontaneously degenerate into atrial fibrillation during an episode 1, 2
Even patients with intermittent anterograde conduction over the accessory pathway have been documented to have rapid conduction during AF 1
The only way to safely use digoxin in a patient with an accessory pathway is if the pathway has been definitively ablated or surgically blocked 3