  Atrial fibrillation (AF) is associated with an increased risk of dementia and
cognitive decline, independent of strokes. Several mechanisms have been
proposed to explain this association, but altered cerebral blood flow dynamics
during AF has been poorly investigated: in particular, it is unknown how AF
influences hemodynamic parameters of the distal cerebral circulation, at the
arteriolar and capillary level. Two coupled lumped-parameter models (systemic
and cerebrovascular circulations, respectively) were here used to simulate
sinus rhythm (SR) and AF. For each simulation 5000 cardiac cycles were analyzed
and cerebral hemodynamic parameters were calculated. With respect to SR, AF
triggered a higher variability of the cerebral hemodynamic variables which
increases proceeding towards the distal circulation, reaching the maximum
extent at the arteriolar and capillary levels. This variability led to critical
cerebral hemodynamic events of excessive pressure or reduced blood flow: 303
hypoperfusions occurred at the arteriolar level, while 387 hypertensive events
occurred at the capillary level during AF. By contrast, neither hypoperfusions
nor hypertensive events occurred during SR. Thus, the impact of AF per se on
cerebral hemodynamics candidates as a relevant mechanism into the genesis of
AF-related cognitive impairment/dementia.
