Treatment timing and the effects of rhythm control strategy in patients with atrial fibrillation: nationwide cohort study

Abstract

Objective: To investigate whether the results of a rhythm control strategy differ according to the duration between diagnosis of atrial fibrillation and treatment initiation.

Design: Longitudinal observational cohort study.

Setting: Population based cohort from the Korean National Health Insurance Service database.

Participants: 22 635 adults with atrial fibrillation and cardiovascular conditions, newly treated with rhythm control (antiarrhythmic drugs or ablation) or rate control strategies between 28 July 2011 and 31 December 2015.

Main outcome measure: A composite outcome of death from cardiovascular causes, ischaemic stroke, admission to hospital for heart failure, or acute myocardial infarction.

Results: Of the study population, 12 200 (53.9%) were male, the median age was 70, and the median follow-up duration was 2.1 years. Among patients with early treatment for atrial fibrillation (initiated within one year since diagnosis), compared with rate control, rhythm control was associated with a lower risk of the primary composite outcome (weighted incidence rate per 100 person years 7.42 in rhythm control v 9.25 in rate control; hazard ratio 0.81, 95% confidence interval 0.71 to 0.93; P=0.002). No difference in the risk of the primary composite outcome was found between rhythm and rate control (weighted incidence rate per 100 person years 8.67 in rhythm control v 8.99 in rate control; 0.97, 0.78 to 1.20; P=0.76) in patients with late treatment for atrial fibrillation (initiated after one year since diagnosis). No significant differences in safety outcomes were found between the rhythm and rate control strategies across different treatment timings. Earlier initiation of treatment was linearly associated with more favourable cardiovascular outcomes for rhythm control compared with rate control.

Conclusions: Early initiation of rhythm control treatment was associated with a lower risk of adverse cardiovascular outcomes than rate control treatment in patients with recently diagnosed atrial fibrillation. This association was not found in patients who had had atrial fibrillation for more than one year.

Fig 1

Flow chart of enrolment and analysis of the study population, *Aged >75, had a previous transient ischaemic attack or stroke, or met two of the following criteria: age >65, female, heart failure, hypertension, diabetes mellitus, previous myocardial infarction, or chronic kidney disease

Fig 2

Initial choice of rhythm control treatments. *Catheter ablations performed within 180 days after the initial prescription of rhythm control drugs were classified as initial choices for rhythm control

Fig 3

Weighted cumulative incidence curves for the primary composite outcome in early and late treatments for atrial fibrillation. CI=confidence interval

Fig 4

Weighted cumulative incidence curves for individual components of the primary composite outcome in early and late atrial fibrillation treatments. CI=confidence interval

Fig 5

Subgroup analyses for the primary composite outcome in early treatments of atrial fibrillation. CI=confidence interval

Fig 6

Subgroup analyses for the primary composite outcome in late treatments of atrial fibrillation. CI=confidence interval

Fig 7

Benefit to harm ratios of rhythm control compared with rate control according to treatment timing. The ratios >1 indicate positive net benefit. CI=confidence interval

Fig 8

Relation between treatment timing and risk of clinical outcomes for rhythm control or rate control in the overall period and within one year after the first diagnosis of atrial fibrillation. The y axis shows hazard ratios associated with rhythm control compared with rate control. The black horizontal lines indicate a hazard ratio of 1, corresponding to an equal risk of outcomes in patients treated with rhythm and rate control. Dashed purple lines show the 95% confidence interval (CI)