In vitro study of the Norwood palliation: a patient-specific mock circulatory system

The aim of this study was to build a mock circulatory system replicating in vitro the hemodynamics following the Norwood procedure and testing patient-specific anatomies focusing on the effect of aortic coarctation. Three anatomies were reconstructed from magnetic resonance images and rapid prototyped with transparent rigid resin. The models presented varying degrees of coarctation (none, moderate, and severe). A Blalock-Taussing (BT) shunt was modeled in all phantoms, which were inserted into a mock circulation. The single ventricle was simulated using a Berlin Heart driven with a PC-controlled piston. Resistive and compliant elements were implemented, creating a lumped parameter network. Pressure was measured at three locations: the transverse aortic arch, just after the aortic isthmus, and further downstream in the thoracic aorta. Volume distribution was derived from the instantaneous flow measurements at three outlets: upper body, lower body, and BT shunt. The combination of three-dimensional (3D) detailed anatomy and lumped parameter network effectively renders the circuit a multiscale in vitro model that successfully reproduces physiologic pressure signals. The pressure results highlight the larger pressure drop caused by coarctation and show the effect of pressure recovery. Results also suggest a reduction of flow to the lower body with increasing severity of coarctation, to the advantage of upper body and pulmonary circulation.