Cerebral Structure and Function in Stroke-free Patients with Atrial Fibrillation

OBJECTIVES

Atrial fibrillation (AF) is associated with high risk of dementia and brain atrophy in stroke-free patients, but the mechanisms underlying this association remain unclear. We aimed to examine the brain volume and connectivity of paramount cognitive brain networks in stroke-free patients with AF without dementia.

MATERIALS AND METHODS

Twenty-six stroke-free patients with AF and 26 age and sex-matched subjects without AF were submitted to a 3-tesla brain structural and functional MRI. An extensive clinical evaluation excluded stroke, dementia, low cardiac output, carotid stenosis and metabolic diseases without optimal therapy. We used CHA₂DS₂-VASc score to classify the cardiovascular risk factor burden and a broad neuropsychological battery to assess the cognitive performance. Voxel based morphometry analysis of. structural MRI defined whole-brain gray and white matter volumes. Finally, we used eco-plannar MRI images to compare the differences of functional connectivity of 7 large-scale resting-state networks between AF patients and controls.

RESULTS

Taking into account the history of hypertension and heart failure, AF was associated to volume decrease of the right basal frontal lobe and right inferior cerebellum. Decreased connectivity of the ventral Default Mode Network (vDMN) was observed in the AF group. No disruption of connectivity was observed in the executive, visuospatial and salience networks.

CONCLUSION

Individuals with AF without stroke or dementia have subtle reduction of gray and white matter, restricted to frontal areas and cerebellum. These patients show decreased vDMN connectivity, without other large-scale brain network disruption.

Circulating Levels of Biomarkers of Cerebral Injury in Patients with Atrial Fibrillation

Atrial fibrillation (AF) is a source of altered brain perfusion and ischemia, potentially leading to cerebral injury and blood brain barrier (BBB) disruption, which may result in the permeation of neurospecific molecules into the bloodstream. We retrospectively analyzed circulating levels of biomarkers of cerebral injury: Astrocyte-specific glial acidic fibrillary protein (GFAP), calcium-binding protein B (S100 b), stress response marker growth differential factor 15 (GDF15), and microtubule associated Tau protein, in patients with AF and non-AF controls. A total of 196 AF cases and 47 non-AF controls were enrolled in this study all without previous clinical stroke or cerebral injury. Plasma samples were obtained from the Intermountain INSPIRE biobank registry. AF status was determined at the time of the sample draw using clinical diagnosis. Assessment of circulating biomarkers was conducted with EIA. Multivariate linear modeling, using natural log, and square root transformation of the biomarkers, was done adjusting for (1) CHA₂DS₂-VASc and anticoagulation, and (2) age, gender, coronary artery disease and anticoagulation. Circulating Tau, GDF15, and GFAP were elevated in AF cases. After multivariate adjustment, GFAP and Tau remained significantly elevated in the AF, whereas the signal for GDF15 was confounded by age. In conclusion, circulating biomarkers of neuronal and glial injury Tau and GFAP are elevated in patients with AF that are consistent with subclinical cerebral injury and disruption of the BBB, which can predispose these patients to the development of cognitive dysfunction and/or dementia later in life.