  This paper describes computer models for three palliations used in treating
refractory pulmonary hypertension. These procedures effectively create an
atrial septal defect, a ventricular septal defect, or a patent ductus
arteriosus, also known as a Potts shunt. The aim in all three cases is to
generate a right-to-left shunt, allowing for either pressure or volume
unloading of the right side of the heart in the setting of right ventricular
failure, while allowing for maintenance of cardiac output. However, these
shunts are created at the expense of introducing de-oxygenated blood into the
systemic circulation, thereby lowering the systemic arterial oxygen saturation.
The models developed in this paper are based on compartmental descriptions of
human hemodynamics and oxygen transport. An important parameter included in our
models is the cross-sectional area of the surgically created defect. Numerical
simulations are performed to compare different interventions and various shunt
sizes and to assess their impact on hemodynamic variables and oxygen
saturations.
