No stroke risk decline in atrial fibrillation patients over the last decade

Chamberlain AM, Brown RD, Alonso A, et al.
J Am Heart Assoc. 2016;5: published online ahead of print

Background

Atrial fibrillation (AF), the most common sustained cardiac arrhythmia, is associated with a 5-fold increased risk of stroke and a 2-fold increased risk of mortality [1–4]. Since 1958, survival and the incidence of stroke due to AF have improved, however, recent data suggest that the incidence of AF has stabilised, and that mortality due to AF and stroke has not improved further [5-7].
In this study, the incidence of ischemic stroke (IS) and transient ischemic attack (TIA) between 2000 and 2010 was evaluated in 3247 patients with AF who experienced an IS/TIA and 3265 who experienced a TIA (patients who experienced an IS/TIA at the same day of incident AF were excluded).

Main results

• Over a mean follow-up of 4.6 years, 321 patients (10%) had IS, (n=221) or a transient ischemic attack (TIA, n=100). 
• The incidence rates per 100 person-years were 2.14 (95% CI: 1.91–2.38) for IS/TIA and 1.54 (95% CI: 1.35–1.75) for IS. 
• After adjustment for demographics and comorbidities, the hazard ratio (HR) of IS/TIA per year of AF diagnosis was 1.00 (95% CI: 0.96–1.04; P=0.80). 
• No temporal trend was observed when considering IS alone (HR: 1.01; 95% CI: 0.96–1.06; P=0.73). 
• There was no evidence of an improvement in survival over time among the 321 patients who developed IS/TIA (adjusted HR of death within 30 days of IS/TIA per year of AF diagnosis: 1.37; 95% CI: 0.99–1.88; P=0.06). 
• There was no evidence of a difference in the risk of haemorrhagic strokes (n=41) over time per year of AF diagnosis after adjustment (HR: 0.97; 95% CI: 0.87–1.08; P=0.57). 
• In patients diagnosed with AF from 2004 to 2010, the cumulative incidence of anticoagulation use was 40.0% (95% CI: 37.8% - 42.1%) at 30 days after diagnosis and 50.8% (95% CI: 48.5% - 53.0%) at 1 year after AF diagnosis. 

The mean proportion of “time in therapeutic range” of warfarin was 50.4%, which did not change over time (P=0.49). The incidence rates for IS/TIA and IS only were lower for those receiving anticoagulation.

• Predictors of IS and TIA were increasing age (only after adjusting for sex) and a history of IS/TIA (after adjusting for age and sex)

Conclusion

IS and TIA are frequent in patients with AF, occurring in 10% of patients after 5 years of follow-up. The occurrence of IS/TIA did not decline over the last decade, which may be associated with the underutilisation of anticoagulation. These data support the importance of AF screening and the need for treatment optimisation in these patients.

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