  Cardiac disease and clinical intervention may both lead to an increased risk
for thrombosis events due to modified blood flow in the heart, and thereby a
change in the mechanical stimuli of blood cells passing through the chambers of
the heart. Specifically, the degree of platelet activation is influenced by the
level and type of mechanical stresses in the blood flow. Here we analyze the
blood flow in the left ventricle of the heart through a computational model
constructed from patient-specific data. The blood flow in the ventricle is
modeled by the Navier-Stokes equations, and the flow through the mitral valve
by a parameterized model which represents the projected opening of the valve. A
finite element method is used to solve the equations, from which a simulation
of the velocity and pressure of the blood flow is constructed. A triple
decomposition of the velocity gradient tensor is then used to distinguish
between rigid body rotational flow, irrotational straining flow, and shear
flow. The triple decomposition enables the separation of three fundamentally
different flow structures, each generating a distinct type of mechanical
stimulus on the blood cells in the flow. We compare the results to simulations
where a mitral valve clip intervention is modelled, which leads to a
significant modification of the ventricular flow. It was found that the shear
in the simulation cases treated with clips increased more compared to the
untreated case than the rotation and strain did. A decrease in valve opening
area of 64 % in one of the cases led to a 90 % increase in rotation and strain,
but a 150 % increase in shear. The computational analysis suggests a process
for patient-specific simulation of clinical interventions in the heart with a
detailed analysis of the resulting blood flow, which could support clinical
risk assessment with respect to platelet activation and thrombosis events.
