Rate control and digoxin

Nikolaidou and Channer’s editorial suggests that no single definition of ideal control of heart rate in chronic atrial fibrillation (AF) exists,¹ but current recommendations are between 60 and 90 beats/min at rest and between 90 and 180 beats/min during moderate exercise.² However, no controlled clinical trials have validated these target rates for preventing all-cause cardiovascular morbidity or mortality, and the best method for assessing rate control is unclear.³ Adequate rate control may encompass more than preventing fast ventricular rates.² The editorial also confuses rate control of AF per se and the use of digoxin for comorbidities such as heart failure.¹ Their overview of AF rate control (with no critical appraisal of published studies) mixes studies of digoxin monotherapy and combination therapy of digoxin and β blockers. We do agree though that differences in methodology and outcomes make direct comparisons difficult.

The NICE guidelines have clear recommendations on rate control.^{2 4} We recommend β blockers or rate limiting calcium antagonists as initial monotherapy in all patients. We do not exclude digoxin, although it is probably less good overall as monotherapy but useful in sedentary patients. If monotherapy fails, we recommend combined β blockers or rate limiting calcium antagonists and digoxin to control heart rate during normal activities, and rate limiting calcium antagonists and digoxin during both normal activities and exercise.

A Clinical Evidence review on chronic AF came to similar conclusions² and another recommends intravenous rate limiting calcium antagonists or β blockers for urgent rate control.⁵

The NICE guidelines do not contraindicate digoxin, but the limited evidence suggests that β blockers and rate limiting calcium antagonists are better for rate control per se. Digoxin may be useful for comorbidities (such as heart failure) but combination therapy is often used.