Patient-Specific Multi-Scale Model Analysis of Hemodynamics Following the Hybrid Norwood Procedure for Hypoplastic Left Heart Syndrome: Effects of Reverse Blalock–Taussig Shunt Diameter
- 68 Downloads
The hybrid Norwood (HN) is a relatively new first stage palliative procedure for neonates with hypoplastic left heart syndrome, in which a sustainable uni-ventricular circulation is established in a less invasive manner than with the standard Norwood procedure. A computational multiscale model of the circulation following the HN procedure was used to obtain detailed hemodynamics. Implementation of a reverse-BT shunt (RBTS), a synthetic bypass from the main pulmonary to the innominate artery placed to counteract aortic arch stenosis, and its effects on local and global hemodynamics were studied.
A post-op patient-derived anatomy of the HN procedure was utilized with varying degrees of distal arch obstruction, or stenosis, (nominal and 90% lumenal area reduction) and varying RBTS diameters (3.0, 3.5, 4.0 mm). A closed lumped parameter model (LPM) for the proximal and peripheral circulations was coupled to a 3D computational fluid dynamics (CFD) model in order to obtain converged flow fields for analysis.
CFD analyses of patient-derived anatomic configurations demonstrated consistent trends of vascular bed perfusion, vorticity, oscillatory shear index and wall shear stress levels. In the models with severe stenosis, implementation of the RBTS resulted in a restoration of arterial perfusion to near-nominal levels regardless of the shunt diameter. Shunt flow velocity, vorticity, and overall wall shear stress levels decreased with increasing shunt diameter, while shunt flow and systemic oxygen delivery increased with increased shunt diameter. In the absence of distal arch stenosis, large (4.0 mm) grafts may risk thrombosis due to low velocities and flow patterns.
Among the three graft sizes, the best option seems to be the 3.5 mm RBTS which provides a more organized flow similar to that of the 3.0 mm configuration with lower levels of wall shear stress. As such, in the setting of this study and for comparable HN physiologies our results suggest that: (1) the 4.0 mm shunt is a generous shunt diameter choice that may be problematic particularly when implemented prophylactically in the absence of stenosis, and (2) the 3.5 mm shunt may be a more suitable alternative since it exhibits more favorable hemodynamics at lower levels of wall shear stress.
KeywordsHLHS Hybrid Norwood Reverse Blalock–Taussig shunt Stenosis CFD LPM
Andres Ceballos received funding from the NIH NRSA predoctoral fellowship. Alain J. Kassab has received funding from the Orlando Health Foundation and from the American Heart Association under Grant No. 11GRNT7940011. William M. DeCampli has received funding from the American Heart Association under Grant No. 11GRNT7940011.
CONFLICT OF INTEREST
Ray Prather declares that he has no conflict of interest. Eduardo Divo declares that he has no conflict of interest.
- 6.Bove, E. L., F. Migliavacca, M. R. de Leval, R. Balossino, G. Pennati, T. R. Lloyd, et al. Use of mathematic modeling to compare and predict hemodynamic effects of the modified Blalock–Taussig and right ventricle–pulmonary artery shunts for hypoplastic left heart syndrome. J. Thorac. Cardiovasc. Surg. 136:312–320, 2008.CrossRefGoogle Scholar
- 9.Ceballos, A. A coupled CFD-lumped parameter model of the human circulation: elucidating the hemodynamics of the hybrid Norwood palliative treatment and effects of the reverse blalock-taussig shunt placement and diameter. PhD Dissertation, University of Cental Florida, 2015.Google Scholar
- 11.Ceballos, A., Divo, E., I. Argueta-Morales, C. Calderone, A. Kassab, and W. Decampli. A Multi-Scale CFD Analysis of the Hybrid Norwood Palliative Treatment for Hypoplastic Left Heart Syndrome: effect of the reverse Blalock-Taussig shunt diameter. ASME Paper IMECE 2013-66856, Proceedings of the 2013 International Congress and Exposition IMECE 2013, November 15–21, San Diego, California, USA.Google Scholar
- 14.Esmaily, M., B. Murtuza, T. Hsia, and A. Marsden. Simulations reveal adverse hemodynamics in patients with multiple systemic to pulmonary shunts. ASME J. Biomech. Eng. 137(3):031001-1–031001-12, 2015.Google Scholar
- 20.Kroll, M. H., J. D. Hellums, L. V. McIntire, A. I. Schafer, and J. L. Moake. Platelets and shear stress. Blood 88:1525, 1996.Google Scholar
- 26.Migliavacca, F., G. Pennati, G. Dubini, R. Fumero, R. Pietrabissa, G. Urcelay, et al. Modeling of the Norwood circulation: effects of shunt size, vascular resistances, and heart rate. Am. J. Physiol. 280:H2076–H2086, 2001.Google Scholar
- 31.Waite, L. Applied Biofluid Mechanics. New York: McGraw Hill Professional, 2007.Google Scholar