title: The assisted bidirectional Glenn: a novel surgical approach for first-stage single-ventricle heart palliation.
abstract: BACKGROUND
  Outcomes after a modified Blalock-Taussig shunt (mBTS) in neonates with single-ventricle physiology remain unsatisfactory. However, initial palliation with a superior cavopulmonary connection, such as a bidirectional Glenn (BDG), is discouraged, owing to potential for inadequate pulmonary blood flow (PBF). We tested the feasibility of a novel surgical approach, adopting the engineering concept of an ejector pump, whereby the flow in the BDG is "assisted" by injection of a high-energy flow stream from the systemic circulation.
  
  
  METHODS
  Realistic 3-dimensional models of the neonatal mBTS and BDG circulations were created. The "assisted" bidirectional Glenn (ABG) consisted of a shunt between the right innominate artery and the superior vena cava (SVC), with a 1.5-mm clip near the SVC anastomosis to create a Venturi effect. The 3 models were coupled to a validated hydraulic circulation model, and 2 pulmonary vascular resistance (PVR) values (7 and 2.3 Wood units) were simulated.
  
  
  RESULTS
  The ABG provided the highest systemic oxygen saturation and oxygen delivery at both PVR levels. In addition to achieving higher PBF than the BDG, the ABG produced a lower single-ventricular workload than mBTS. SVC pressure was highest in the ABG model (ABG: 15; Glenn: 11; mBTS: 3 mm Hg; PVR = 7 Wood units), but at low PVR, the SVC pressure was significantly lower (ABG: 8; Glenn: 6; mBTS: <3 mm Hg).
  
  
  CONCLUSIONS
  Adopting the principle of an ejector pump, with additional flow directed into the SVC in a BDG, the ABG appears to increase PBF with a modest increase in SVC and pulmonary arterial pressure. Although multiscale modeling results demonstrate the conceptual feasibility of the ABG circulation, further technical refinement and investigations are necessary, especially in an appropriate animal model.
authors.affiliation: Mechanical and Aerospace Engineering Department, University of California, San Diego, La Jolla, Calif.
authors.forename: Mahdi
authors.initials: M
authors.lastname: Esmaily-Moghadam
authors.affiliation: Great Ormond Street Hospital for Children and University College London Institute of Cardiovascular Science, London, United Kingdom.
authors.forename: Tain-Yen
authors.initials: TY
authors.lastname: Hsia
authors.affiliation: Mechanical and Aerospace Engineering Department, University of California, San Diego, La Jolla, Calif. Electronic address: amarsden@ucsd.edu.
authors.forename: Alison L
authors.initials: AL
authors.lastname: Marsden
mesh_terms: D062186:Arterial Pressure; D058366:Blalock-Taussig Procedure; D016122:Brachiocephalic Trunk / Q000503:physiopathology / Q000601:surgery*; D003198:Computer Simulation; D005240:Feasibility Studies; D018729:Fontan Procedure / Q000009:adverse effects / Q000379:methods*; D006330:Heart Defects, Congenital / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery*; D006352:Heart Ventricles / Q000002:abnormalities / Q000503:physiopathology / Q000601:surgery*; D006439:Hemodynamics; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008955:Models, Cardiovascular; D010166:Palliative Care; D011652:Pulmonary Circulation; D016896:Treatment Outcome; D014655:Vascular Resistance; D014683:Vena Cava, Superior / Q000503:physiopathology / Q000601:surgery*; D014690:Venous Pressure; D016276:Ventricular Function