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J Thorac Cardiovasc Surg 2008;136:312-320
© 2008 The American Association for Thoracic Surgery
Surgery for Congenital Heart Disease |
a Section of Cardiac Surgery, the University of Michigan School of Medicine, Ann Arbor, Mich
b Laboratory of Biological Structure Mechanics, Department of Structural Engineering, Politecnico di Milano, Milan, Italy
c International Congenital Cardiac Center and Cardiothoracic Unit, Great Ormond Street Hospital for Children NHS Trust, London, United Kingdom
Received for publication March 1, 2007; revisions received March 23, 2007; accepted for publication April 9, 2007. * Address for reprints: Edward L. Bove MD, F 7830 Mott Children's Hospital, 1500 East Medical Center Dr, University of Michigan, Ann Arbor, MI 48109-0223. (Email: elbove{at}umich.edu).
Objective: Stage one reconstruction (Norwood operation) for hypoplastic left heart syndrome can be performed with either a modified Blalock–Taussig shunt or a right ventricle–pulmonary artery shunt. Both methods have certain inherent characteristics. It is postulated that mathematic modeling could help elucidate these differences.
Methods: Three-dimensional computer models of the Blalock–Taussig shunt and right ventricle–pulmonary artery shunt modifications of the Norwood operation were developed by using the finite volume method. Conduits of 3, 3.5, and 4 mm were used in the Blalock–Taussig shunt model, whereas conduits of 4, 5, and 6 mm were used in the right ventricle–pulmonary artery shunt model. The hydraulic nets (lumped resistances, compliances, inertances, and elastances) were identical in the 2 models. A multiscale approach was adopted to couple the 3-dimensional models with the circulation net. Computer simulations were compared with postoperative catheterization data.
Results: Good correlation was found between predicted and observed data. For the right ventricle–pulmonary artery shunt modification, there was higher aortic diastolic pressure, decreased pulmonary artery pressure, lower Qp/Qs ratio, and higher coronary perfusion pressure. Mathematic modeling predicted minimal regurgitant flow in the right ventricle–pulmonary artery shunt model, which correlated with postoperative Doppler measurements. The right ventricle–pulmonary artery shunt demonstrated lower stroke work and a higher mechanical efficiency (stroke work/total mechanical energy).
Conclusions: The close correlation between predicted and observed data supports the use of mathematic modeling in the design and assessment of surgical procedures. The potentially damaging effects of a systemic ventriculotomy in the right ventricle–pulmonary artery shunt modification of the Norwood operation have not been analyzed.
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