Does the effect of anticoagulation on stroke risk differ by CHA2DS2-VA score in patients with atrial fibrillation? A nationwide cohort study
L Leppiniemi, E Jalli, V Langen, J Jaakkola, K E J Airaksinen, O Halminen, J Putaala, P Mustonen, J Haukka, J Hartikainen, M Linna, M Lehto, K TeppoAbstract
Background
Oral anticoagulation (OAC) therapy for stroke prevention is the cornerstone of managing patients with atrial fibrillation (AF). Trials from the era of vitamin K antagonists (VKAs) demonstrated an impressive two-thirds reduction in stroke risk with VKA therapy in patients with high stroke risk. Recent studies indicate that patients with subclinical device-detected AF and a lower baseline stroke risk experience only a one-third reduction in stroke risk with direct oral anticoagulant (DOAC) therapy. However, it remains uncertain whether OACs reduce stroke risk equally across varying stroke risk profiles in patients with clinical AF.
Purpose
Therefore, we conducted a nationwide retrospective cohort study to evaluate whether the reduction in stroke risk associated with OAC therapy varies according to baseline stroke risk as categorized by the CHA2DS2-VA score in patients with AF.
Methods
The Finnish AntiCoagulation in Atrial Fibrillation (FinACAF) study includes all patients with AF in Finland between 2007 and 2018. Data were obtained from national registries covering all levels of care. Incidence and incidence rate ratio (IRR) of ischemic stroke were calculated for follow-up periods with and without OAC therapy, defined in a time-dependent manner.
Results
We identified 210 434 patients with new-onset AF and a CHA2DS2-VA score ≥ 1. During follow-up without OAC therapy, stroke rates increased from 0.90 (95% CI 0.83-0.97) to 7.78 (95% CI 5.53-10.63) per 100 patient years as the CHA2DS2-VA score rose from 1 to 8. Corresponding rates during OAC therapy were lower and increased more modestly, from 0.79 (95% CI 0.73-0.86) to 3.65 (95% CI 2.56-5.06) per 100 patient years. A statistically significant interaction between OAC therapy and CHA2DS2-VA score category on stroke rate was observed (p < 0.001). OAC therapy was associated with a lower stroke rate across the CHA2DS2-VA score spectrum, with the association increasing gradually from CHA2DS2-VA scores 1 to 3 and then stabilizing at approximately a 60% reduction among patients with CHA2DS2-VA ≥ 3. When comparing DOACs and VKAs to follow-up without OACs, the pattern of their association with stroke rate was similar, but point estimates for VKAs were consistently higher, suggesting a comparatively smaller reduction in stroke rate with VKAs than DOACs across the studied CHA2DS2-VA score spectrum.
Conclusions
In patients with AF, OAC therapy is associated with a lower risk of stroke across CHA2DS2-VA categories from 1 to 8, but the relative effect varies and is smaller among those with lower stroke risk scores.