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

impedances were maintained within physiological ranges [Muthurangu et al, 2004;
Pennati et al, 2001] in all the simulations. For every patient different simulations were
run changing the value of total PVRs, in order to get a complete scenario of
possibilities. Finally, one value of PVR was chosen for each patient according to the
following decisions: (i) pressures obtained from the simulations had to be within a
physiological range; (ii) in case reasonable pressures were obtained with more than one
PVR value, the simulation with the lowest PVR was considered, taking into account that
no patient was pulmonary hypertensive. In this way the mismatch of the PVR between
the two branches was identified for each patient.
3.6 Multi-domain simulations
The chosen impedances were later used as boundary conditions to run a multi-domain
simulation [Migliavacca et al, 2006; Pennati et al, 2011] replacing the non-linear
resistances RR1 and RR2 with the reconstructed 3D model of the pulmonary branches.
Patient’s MPA flow was imposed as input in the 3D model, and RPA and LPA flows
were used for validation.
4. RESULTS
Fig. 3 Scheme of the multi-domain simulation.
The LPN accurately reproduced the fluid dynamics behavior of the 3D models, thus
helping in the tuning of the boundary conditions for the multi-domain simulation saving
computational time. As expected, with the increase of the total PVR, the contribution of
the asymmetric geometry for an asymmetric flow-split between RPA and LPA become
smaller since the distal resistances overcome the local resistances. The multi-domain
simulation flow outcomes matched the patients’ data, showing an asymmetrical PVR
distribution only in the Stenotic group. Figure 4 and table 1 report the example of one
patient (Stenotic group) whose right impedance (Zr) had to be set double the left
impedance (Zl) to obtain the patient’s flow split. Peak velocities were measured at
systole in the pulmonary stenosis where present (fig. 4 right).
Tab. 1 – Flow-split between LPA and RPA as percentage of MPA from MR, in the case of equal Zr and Zl
and in case of Zr being twice Zl
% of Q MPA MR Z r:Z l = 1:1 Z r:Z l = 2:1
Q LPA 55.5 16.7 54.4
Q RPA 44.5 83.3 45.6