title: The effect of modified Blalock-Taussig shunt size and coarctation severity on coronary perfusion after the Norwood operation.
abstract: BACKGROUND
  The size of the modified Blalock-Taussig shunt and the additional presence of aortic coarctation can affect the hemodynamics of the Norwood physiology. Multiscale modeling was used to gather insight into the effects of these variables, in particular on coronary perfusion.
  
  
  METHODS
  A model was reconstructed from cardiac magnetic resonance imaging data of a representative patient, and then simplified with computer-aided design software. Changes were systematically imposed to the semi-idealized three-dimensional model, resulting in a family of nine models (3-, 3.5-, and 4-mm shunt diameter; 0%, 60%, and 90% coarctation severity). Each model was coupled to a lumped parameter network representing the remainder of the circulation to run multiscale simulations. Simulations were repeated including the effect of preserved cerebral perfusion.
  
  
  RESULTS
  The concomitant presence of a large shunt and tight coarctation was detrimental in terms of coronary perfusion (13.4% maximal reduction, 1.07 versus 0.927 mL/s) and oxygen delivery (29% maximum reduction, 422 versus 300 mL·min(-1)·m(-2)). A variation in the ratio of pulmonary to systemic blood flow from 0.9 to 1.6 also indicated a "stealing" phenomenon to the detriment of the coronary circulation. A difference could be further appreciated in the computational ventricular pressure-volume loops, with augmented systolic pressures and decreased stroke volumes for tighter coarctation. Accounting for constant cerebral perfusion did not produce substantially different results.
  
  
  CONCLUSIONS
  Multiscale simulations performed in a parametric fashion revealed a reduction in coronary perfusion in the presence of a large modified Blalock-Taussig shunt and severe coarctation in Norwood patients.
authors.affiliation: Laboratory of Biological Structure Mechanics, Politecnico di Milano, Milan, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Corsini
authors.affiliation: Centre for Cardiovascular Imaging, UCL Institute of Cardiovascular Science, and Great Ormond Street Hospital for Children, NHS Foundation Trust, London, United Kingdom. Electronic address: g.biglino@ucl.ac.uk.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Biglino
authors.affiliation: Centre for Cardiovascular Imaging, UCL Institute of Cardiovascular Science, and Great Ormond Street Hospital for Children, NHS Foundation Trust, London, United Kingdom.
authors.forename: Silvia
authors.initials: S
authors.lastname: Schievano
authors.affiliation: Centre for Cardiovascular Imaging, UCL Institute of Cardiovascular Science, and Great Ormond Street Hospital for Children, NHS Foundation Trust, London, United Kingdom.
authors.forename: Tain-Yen
authors.initials: TY
authors.lastname: Hsia
authors.affiliation: Laboratory of Biological Structure Mechanics, Politecnico di Milano, Milan, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Migliavacca
authors.affiliation: Laboratory of Biological Structure Mechanics, Politecnico di Milano, Milan, Italy.
authors.forename: Giancarlo
authors.initials: G
authors.lastname: Pennati
authors.affiliation: Centre for Cardiovascular Imaging, UCL Institute of Cardiovascular Science, and Great Ormond Street Hospital for Children, NHS Foundation Trust, London, United Kingdom.
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Taylor
mesh_terms: D001017:Aortic Coarctation / Q000503:physiopathology; D058366:Blalock-Taussig Procedure / Q000379:methods*; D003326:Coronary Circulation; D006801:Humans; D021621:Imaging, Three-Dimensional; D008955:Models, Cardiovascular; D058327:Norwood Procedures; D012720:Severity of Illness Index