Digoxin treatment increases mortality risk in patients with newly diagnosed AF

Turakhia MP, Santangeli P, Winkelmayer WC,  et al.,
J Am Coll Cardiol. 2014;64(7):660-668. doi:10.1016/j.jacc.2014.03.060

Background

Digoxin is a commonly used rate control agent in atrial fibrillation/atrial flutter (AF, collectively). Although evidence from randomised trials is lacking, its use in AF is endorsed by clinical guidelines [1,2]. The effectiveness and safety of digoxin was shown to vary with serum digoxin concentrations in heart failure (HF) cohorts [3-5], which might mean that kidney function affects the effect of digoxin [6].
Because adequate safety data of digoxin use in AF is lacking, this study examined the association of digoxin therapy with mortality in a large cohort of patients with newly diagnosed AF, from the U.S. Department of Veterans Affairs (VA) healthcare system. 28.679 (23.4%) of the 122.465 patients in the TREAT-AF (The Retrospective Evaluation and Assessment of Therapies in AF) study cohort received digoxin during the first 90 days after initial AF diagnosis. Medication Possession Ratio (MPR) was calculated as a measure of digoxin exposure, reflecting the proportion of total outpatient days’ supply out of days after diagnosis. Mean MPR was 0.79+0.27 in patients receiving digoxin.

Main results

• Digoxin recipients had higher unadjusted mortality as compared with nonrecipients. In a multivariate Cox regression model, digoxin was associated with higher risk of death (HR: 1.26, 95%CI: 1.23-1.29, P<0.001), as well as after propensity matching (HR: 1.21, 95%CI: 1.17-1.25, P<0.001).
• When MPR was included as a time-varying covariate, the results were similar and statistically significant.
• Both in multivariate adjusted and propensity matched analyses, digoxin was associated with a significant increase in risk of death in nearly all strata of eGFR, except in dialysis patients. There was, however, no evidence of effect modification across strata of kidney dysfunction (P=0.76).
• Patients with prior MI were the only subgroup in whom there was evidence of possible effect modification in the full cohort (P(interaction)=0.002) and in the propensity matched cohort (P(interaction)=0.077).

Conclusion

This analysis of a large, retrospective cohort shows that digoxin treatment in patients with newly diagnosed AF is associated with increased mortality, irrespective of drug adherence, kidney dysfunction, HF or concomitant drug therapy. Patients with prior MI may be at higher risk. These findings are in contrast with current CV society guidelines.

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Referenties

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