  There has recently been growing evidence that atrial fibrillation (AF), the
most common cardiac arrhythmia, is independently associated with the risk of
dementia. This represents a very recent frontier with high social impact for
the number of individuals involved and for the expected increase in AF
incidence in the next 40 years. Although a number of potential haemodynamic
processes, such as microembolisms, altered cerebral blood flow, hypoperfusion
and microbleeds, arise as connecting links between the two pathologies, the
causal mechanisms are far from clear. An in silico approach is proposed that
combines in sequence two lumped-parameter schemes, for the cardiovascular
system and the cerebral circulation. The systemic arterial pressure is obtained
from the cardiovascular system and used as the input for the cerebral
circulation, with the aim of studying the role of AF on the cerebral
haemodynamics with respect to normal sinus rhythm (NSR), over a 5000 beat
recording. In particular, the alteration of the haemodynamic (pressure and
flowrate) patterns in the microcirculation during AF is analysed by means of
different statistical tools, from correlation coefficients to autocorrelation
functions, crossing times, extreme values analysis and multivariate linear
regression models. A remarkable signal alteration, such as a reduction in
signal correlation (NSR, about 3 s; AF, less than 1 s) and increased
probability (up to three to four times higher in AF than in NSR) of extreme
value events, emerges for the peripheral brain circulation. The described
scenario offers a number of plausible cause-effect mechanisms that might
explain the occurrence of critical events and the haemodynamic links relating
to AF and dementia.

Fluid Dynamics;Medical Physics;Tissues and Organs