Is digoxin (digitalis glycoside) indicated in patients with bradycardia (heart rate less than 60 beats per minute)?

Digoxin Should Not Be Given to Patients with Bradycardia (Heart Rate Less Than 60 BPM)

Digoxin is contraindicated in patients with bradycardia (heart rate less than 60 beats per minute) due to the risk of worsening bradyarrhythmias and potential cardiac complications. 1

Rationale and Evidence

• Digoxin has negative chronotropic effects that can further slow heart rate in patients who already have bradycardia, potentially leading to dangerous bradyarrhythmias 1
• Guidelines specifically state that digoxin should not be administered to patients who have significant sinus or atrioventricular block, unless the block has been treated with a permanent pacemaker 1, 2
• Digoxin has a narrow therapeutic margin with potentially life-threatening cardiac adverse effects, making it particularly risky in patients with pre-existing bradycardia 3

Physiological Considerations

• Digoxin works by:

  • Increasing vagal tone, which slows conduction through the AV node 1
  • Prolonging the effective refractory period of the AV node 1
  • These mechanisms can exacerbate existing bradycardia and potentially lead to complete heart block 1

• Bradycardia is often an early warning sign of digoxin toxicity, making administration to patients who already have bradycardia particularly dangerous 3, 4

Alternative Approaches for Different Clinical Scenarios

For Atrial Fibrillation with Bradycardia:

• Digoxin is primarily used for rate control in atrial fibrillation, but is inappropriate when the ventricular rate is already slow 1
• European Society of Cardiology guidelines suggest optimal heart rates between 60-100 beats/min for AF patients, noting that lower ventricular rates <70 beats/min may be associated with worse outcomes 1
• For AF patients with slow ventricular response, consider addressing underlying causes rather than adding rate-controlling medications 1

For Heart Failure with Bradycardia:

• While digoxin is useful in heart failure management, it should not be initiated in patients with bradycardia 1
• For heart failure patients with bradycardia, consider:
  • Evaluating for and discontinuing medications that may be contributing to bradycardia 1
  • Assessing for electrolyte abnormalities, particularly hyperkalemia 1
  • Considering temporary or permanent pacing if bradycardia is symptomatic and persistent 5

Management of Patients Already on Digoxin Who Develop Bradycardia

• If bradycardia develops in a patient taking digoxin:
  • Consider immediate discontinuation of digoxin 6
  • Monitor cardiac rhythm closely 3, 4
  • Check serum digoxin levels to assess for toxicity (levels >2 ng/mL often associated with toxicity) 1, 2
  • Evaluate for contributing factors such as hypokalemia, hypomagnesemia, or hypothyroidism 2
  • Consider temporary cardiac pacing for symptomatic bradycardia (which has been shown to be safe in cases of accidental digoxin overdose) 5

Important Considerations and Precautions

• Digoxin has numerous drug interactions that can increase its serum concentration and risk of toxicity, including with amiodarone, verapamil, and macrolides 3
• Renal impairment significantly increases the risk of digoxin toxicity and bradycardia 3
• Elderly patients are at higher risk for digoxin toxicity and should receive lower doses if digoxin is indicated 2
• Concomitant use of other medications that slow heart rate (beta-blockers, non-dihydropyridine calcium channel blockers) can potentiate bradycardia when combined with digoxin 1

Summary

Digoxin should not be administered to patients with bradycardia (heart rate <60 bpm) due to its negative chronotropic effects and the risk of worsening bradyarrhythmias. Alternative approaches should be considered based on the underlying condition, and patients already on digoxin who develop bradycardia should be closely monitored with consideration for drug discontinuation.