ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

patient, flow conditions drive its optimum hepatic factor distribution. However shape
optimization methods help to achieve such optimum [15]. The non-intuitive interplay of
geometry and hemodynamics requires patient specific optimization of the Fontan
design. The results suggest that such optimization might be facilitated by a careful
choice of the anastomosis for the SVC-PA junction in the Glenn procedure, especially
for highly uneven pulmonary flow splits.
Figure 1: For the five patients, streamline representation of the flow at peak deceleration zoomed at
the anastomosis and the full Glenn models used for simulations. Flow splits to the right lung are
from left to right [0.6 0.5 0.6 0.8 0.7]. Lower right: example of Fontan virtual Y-design with
particles assessing hepatic factors distribution to the left and right lungs.
5. DISCUSSION
5.1 Sensitivity to input data
Since the boundary conditions are constructed based on a combination of measurements
and models, sensitivity of the results to these input data is an important validation step.
However little work has been done in this area, apart from inflow studies (on pulsatility
or velocity profiles – e.g. [16]). In [10] the location of the pressure measurement and the
downstream capacitances were varied when constructing the two pulmonary boundary
conditions of a patient-specific Glenn case, without much influence on the resulting
resistance of the pulmonary arteries and pulmonary flow waveforms, respectively. In
[12], the sensitivity of patient-specific simulations to hemodynamics input data was
systematically investigated: with only small variations of input parameters, some output
indicators (such as power loss or wall shear stress) varied non-negligibly. Efficiency
was found to be an indicator more sensitive than power loss to pressure uncertainties.
However, power loss was less sensitive to the power law relating cross-sectional area of
a branch and its mean flow rate than to flow split variation between right and left lungs.
To lower output uncertainties, more precision in the flow split acquisition would thus be
expected to be more important than to further refine the repartition of flow in the
smaller branches. The study suggested that ±10% flow split imprecision seemed
reasonable in terms of patient comparison but that the patient-specific flow split should
be used (fig.1). This sensitivity to the flow split was thus investigated when comparing