Safety of digoxin in nonagenarian patients with atrial fibrillation: lessons from the Spanish Multicenter Registry

BACKGROUND: The association between digoxin and mortality is an unclear issue. In older patients with atrial fibrillation (AF), where use of digoxin is frequent, the evidence of its safety is scarce. Our aim is to assess the safety of digoxin in nonagenarian patients with AF. METHODS: We evaluated data from 795 nonagenarian patients with non-valvular AF from the Spanish Multicenter Registry. We analyzed the relationship between digoxin and all-cause mortality with the Cox proportional-hazards model. RESULTS: Follow-up was 27.7 ± 18.3 months. Mean age was 92.5 ± 3.8 years, and 71% of nonagenarian patients were female. Digoxin was not associated with increased risk of mortality [adjusted hazard ratio (aHR) = 1.16, 95% CI: 0.96−1.41,P = 0.130]. However, we found a significant increase in mortality in the subgroup with estimated glomerular filtration rate (eGFR) < 30 mL/min per 1.73 m (2) (aHR = 2.01, 95% CI: 1.13−3.57,P = 0.018), but not in the other subgroups of eGFR (30−59 mL/min per 1.73 m(2) and ≥ 60 mL/min per 1.73 m(2)). When exploring the risk of mortality according to sex, male subgroup was associated with an increase in mortality (aHR = 1.48, 95% CI: 1.02−2.14,P = 0.041). This was not observed in females subgroup (aHR = 1.03, 95% CI: 0.81−1.29,P = 0.829). Based on the presence or absence of heart failure, we did not find significant differences (aHR = 1.20, 95% CI: 0.87−1.65,P = 0.268 vs. aHR = 1.15, 95% CI: 0.90−1.47,P = 0.273, respectively). CONCLUSIONS: In our large registry of nonagenarian patients with AF, we did not find an association between digoxin and mortality in the total sample. However, in the subgroup analyses, we found an increase in mortality with the use of digoxin in men and in patients with an eGFR < 30 mL/min per 1.73 m (2).