New brain infarcts in AF patients, despite anticoagulation, affect cognitive function
Silent brain infarcts impact on cognitive function in atrial fibrillation
Introduction and methods
In a recent cross-sectional analysis, cognitive decline in patients with AF was not only associated with clinical strokes but also with silent brain infarcts . While oral anticoagulants (OACs) are highly effective in preventing clinical stroke and have been associated with a lower risk of dementia in AF patients , prospective data on the development of brain lesions and their association with cognitive decline in AF patients treated with OACs are lacking.
Aim of the study
The authors investigated the incidence of new (overt and silent) brain lesions in AF patients and the association of new brain lesions with change in cognitive function.
In this prospective, multicenter, observational study, 1227 AF patients from the Swiss Atrial Fibrillation (Swiss-AF) cohort were enrolled, who underwent standardized brain MRI at baseline and after 2 years. Numbers of new small non-cortical infarcts (SNCIs), large non-cortical or any cortical infarcts (LNCCIs), white matter lesions, and microbleeds were quantified. Clinically silent infarcts were defined as a new SNCI/LNCCI on the second MRI scan in patients without a clinical stroke or TIA during follow-up.
The investigators assessed cognitive function at baseline and 2-year follow-up with several validated neurocognitive tests. They also calculated their own developed Swiss-AF Cognitive Construct (CoCo) score, which is composed of 17 differently weighted combined items from these individual neurocognitive tests.
The outcomes were the estimated 2-year risk of each of the lesion types, the associations between a pre-defined set of potential predictors and lesion risks, and the effect of lesions on cognitive test scores.
New brain lesions
- During 2 years of follow-up, 28 patients (2.3%) experienced a clinical stroke or TIA.
- In 68 patients, at least one new brain infarct (SNCI or LNCCI) was seen on the second MRI scan, which resulted in an estimated 2-year risk of a new brain infarct of 5.5% (95% CI: 4.4–7.0).
- New brain infarcts were silent in 58/68 patients (85.3%).
- Of these 68 patients, 60 (88.2%) were anticoagulated at baseline.
- New white matter lesions were detected in 229 patients (estimated 2-year risk: 18.7%, 95% CI: 16.6–20.9), and new microbleeds occurred in 136 patients (estimated 2-year risk: 11.4%, 95% CI: 9.7–13.3).
Predictors of new brain lesions
- Of the 9 potential predictors of new brain lesions included in multivariable models—such as arterial hypertension, DM, and OAC use at baseline—only age (odds ratio (OR) per 10-year increase: 1.89; 95% CI: 1.30–2.78; P=0.001) and history of prior stroke/TIA (OR: 1.95; 95% CI: 1.11–3.32; P=0.017) were associated with a higher risk of a new brain infarct.
- In patients with a new brain infarct, a decline across most individual cognitive test scores was observed, which was reflected in the median (IQR) change in CoCo score, which was −0.12 (−0.22 to −0.07) in patients with new brain infarcts versus 0.07 (−0.09 to 0.25) in those without brain infarcts.
- There were no differences in change in cognitive scores in patients with clinically overt and clinically silent brain infarcts.
- New white matter lesions or microbleeds were not consistently associated with cognitive decline.
Over 2 years of follow-up, 5.5% of AF patients had developed a new brain infarct, the majority of which was clinically silent and occurred in anticoagulated patients. New clinically overt and silent brain infarcts were similarly associated with cognitive decline. According to the authors, the results suggest that OAC treatment alone may not be sufficient to prevent vascular brain injury and cognitive decline in all AF patients.