[Association between duration of digoxin use and adverse outcomes among Chinese patients with atrial fibrillation]

Objective: We aimed to explore the impact of digoxin use on outcomes in Chinese patients with atrial fibrillation (AF). Methods: We used the dataset from the Chinese Atrial Fibrillation Registry, a prospective, multicenter, hospital-based registry study. According to the inclusion and exclusion criteria, 10 472 eligible patients enrolled from August 2011 to December 2016 were included in this ancillary study. The patients were classified into three groups according to the status of digoxin use at study enrollment, patients already receiving digoxin before registry were represented as continuous group, patients initiated on digoxin for the first time were represented as newly group, and patients without digoxin prescription at enrollment were represented as control group. Patients were followed by telephone or outpatient service every 6 months. Kaplan-Meier survival analysis and Cox proportional hazards regression models were used to investigate the association of digoxin use with adverse outcomes (all-cause death, cardiovascular death and cardiovascular hospitalization). Results: In the overall study population, men accounted for 42.8%, and the average age was (66.9±11.8) years. There were 777（7.42%）patients in continuous group, 375 (3.58%) patients in newly group, and 9 320 (89.00%) patients in control group. Compared with the control group, the patients in the newly group and the continuous group were older, had faster heart rate, lower estimated glomerular filtration rate, higher proportion of persistent atrial fibrillation, heart failure, renal insufficiency, diabetes mellitus, ischemic stroke, coronary heart disease, vascular disease and bleeding history. At the same time, the patients in the newly group and the continuous group were treated more often with anticoagulants, antiplatelet drugs, ACE inhibitors or angiotensin receptor blockers, beta-receptor blockers while the proportion of antiarrhythmic drugs was lower as compared to control group (P<0.05). During a median follow-up of 36 months (interquartile range: 18-48 month), risk of all-cause mortality was significantly higher in newly group compared to control group (7.3% vs. 4.7%, P<0.05), the rates of all-cause mortality, cardiovascular death and cardiovascular hospitalization were all higher in continuous group than in control group (8.0% vs. 4.7%; 4.7% vs. 3.0%; 16.7% vs. 11.8%; P all<0.05). After adjustment for age, male, body mass index, blood pressure, heart rate, renal function, AF type, history of stroke, heart failure, diabetes, coronary artery disease and other drugs treatment, the association between newly group and adverse outcomes was not significant, however, digoxin use was associated with increased all-cause mortality (HR 1.26; 95%CI 1.04-1.56; P=0.019), cardiovascular death (HR 1.38; 95%CI 1.08-1.77, P =0.01), and cardiovascular hospitalization (HR 1.10; 95%CI 1.06-1.52, P=0.02) in continuous group. Conclusion: Continuous digoxin use is associated with a significant increase in adverse outcomes among Chinese patients with atrial fibrillation.