Is atrial fibrillation associated with a decrease in total brain perfusion?

Abstract

Purpose: Atrial fibrillation (AF) has been associated with cognitive impairment. We have recently shown that AF, both paroxysmal and persistent, was associated with decreased brain volume in addition to cognitive decline independent of stroke. The effect was stronger with longer duration of the arrhythmia. The reasons for this are not clear but may include repeated micro-embolism leading to brain atrophy or a decrease in cerebral blood flow. The stroke volume of the left ventricle varies from beat to beat in AF and this might conceivably lead to diminished blood flow to organs with a high metabolic demand like the brain. The purpose of this study was to examine total cerebral blood flow (tCBF) and total brain perfusion (tBP) with magnetic resonance imaging (MRI) in individuals with and without AF. Methods: A total of 2125 individuals were included. Those with mild cognitive impairment, dementia and previous history of heart failure were excluded. The participants were divided into three groups according to the presence or absence of AF on electrocardiogram at the time of the MRI or a previous history of AF. All participants underwent MRI of the brain including a phase-contrast scan at the level of the skull base for flow measurements in the internal carotid arteries and basilar artery and structural scans for deriving total brain volume. Total brain perfusion (ml/min/100 ml) was calculated by dividing tCBF (ml/min) by each individual's total brain volume (ml) and multiplying the obtained result by 100. Statistical comparisons were age and sex adjusted. Results: The mean age of the cohort was 79.2±4.4 years. In the AF group (n=100) tCBF was 475.7±124.6 ml/min, which was lower than in the group without AF (n=1953), 540.8±112.3 ml/min (p<0.0001). The tCBF of the group with a previous history of AF (n=72), 519.5±95.3 ml/min, was lower than in those without AF, although not statistically significant, but higher than in the AF group (p<0.02). This was also reflected in the tBP, which also was higher in the group without AF, 49.3 ml/100 ml/min compared to 42.5 ml/100 ml/min in the AF group (p<0.0001). Those with a previous history of AF had tBP of 47.2 ml/100 ml/min, which is closer to those without AF than those with AF (p=0.16). Conclusions: These novel findings show that patients with AF may have reduced cerebral blood flow and lower brain perfusion when compared to both those that have never been diagnosed with the arrhythmia and those with a previous history of AF. Further studies are needed to determine whether this could have implications for treatment decisions in AF.