Conventional treatment of Hypoplastic Left Heart Syndrome (HLHS), the Norwood operation, establishes univentricular circulation through a series of highly invasive reconstructive procedures. The relatively new Hybrid Norwood (HN) operation involves a less invasive strategy that avoids a cardiopulmonary bypass (heart-lung machine), deliberate cardiac arrest and circulatory arrest of the patient in the neonatal period . We present multiscale model of the entire circulatory system developed utilizing an electrical lumped parameter model (LP) for the peripheral or distal circulation coupled with a 3D Computational Fluid Dynamics (CFD) model to understand the local hemodynamics .
3D models of six HN anatomic variants were developed— with/without 90% and 70% distal preductal arch stenosis and with/without a 4mm reverse – BT shunt (RBTS). A lumped parameter model (LPM) of the circulation was coupled to a local 3D computational fluid dynamics (CFD) model. The outputs from the LPM provided waveform boundary conditions (BCs) for the CFD model.
A 90% distal arch stenosis reduced pressure and net flow-rate through the coronary and carotid arteries by 30%. Addition of the RBTS completely restored pressure and flow rate to baseline in these vessels. Zones of flow stagnation, flow reversal, and recirculation in the presence of stenosis were rendered more orderly by addition of the RBTS. In the absence of stenosis, presence of the shunt resulted in extensive zones of disturbed flow within the RBTS and arch .
The multiscale model developed in this study shows its promising potential as a predictive tool for surgeons. Detailed local hemodynamics derived from the model provide an insight of the effects of severe stenosis and RBTS implantation.
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