Abstract
For babies born with hypoplastic left heart syndrome, several open-heart surgeries are required. During Stage I, a Norwood procedure is performed to construct an appropriate circulation to both the systemic and the pulmonary arteries. The pulmonary arteries receive flow from the systemic circulation, often using a Blalock–Taussig (BT) shunt between the innominate artery and the right pulmonary artery. This procedure causes significantly disturbed flow in the pulmonary arteries. In this study, we use computational hemodynamic simulations to demonstrate its capacity for examining the properties of the flow through and near the BT shunt. Initially, we construct a computational model which produces blood flow and pressure measurements matching the clinical magnetic resonance imaging (MRI) and catheterization data. Achieving this required us to determine the level of BT shunt occlusion; because the occlusion is below the MRI resolution, this information is difficult to recover without the aid of computational simulations. We determined that the shunt had undergone an effective diameter reduction of 22% since the time of surgery. Using the resulting geometric model, we show that we can computationally reproduce the clinical data. We, then, replace the BT shunt with a hypothetical alternative shunt design with a flare at the distal end. Investigation of the impact of the shunt design reveals that the flare can increase pulmonary pressure by as much as 7% and flow by as much as 9% in the main pulmonary branches, which may be beneficial to the pulmonary circulation.
Highlights
Each year in the United States, 1 out of every 4,344 babies are born with hypoplastic left heart syndrome (HLHS) [1]
In spite of the refinements, there remain several shortcomings, such as the inability to adapt to the growing child, a high incidence of stenosis developing at the site of the pulmonary artery anastomosis, and even complete shunt occlusion
If stenosis develops at the pulmonary artery anastomosis, this markedly alters the amount and velocity of blood flow delivered to the pulmonary circulation, leading to adverse hemodynamics and propensity for developing progressive stenosis, all of which can add to morbidity and mortality
Summary
Each year in the United States, 1 out of every 4,344 babies are born with hypoplastic left heart syndrome (HLHS) [1]. Even in the best cases, the Norwood procedure can have several complications, including low cardiac output, arrhythmias, respiratory insufficiency, and stenosis of the pulmonary arteries or aorta [2]. These complications can be affected by the function of the shunt. We utilized our in-house geometric modeling, closed-loop circulatory design, and Navier–Stokes computational hemodynamics simulation package [5,6,7] These tools allow us to develop highly customizable lumped parameter model circuits that can capture complex facets of the patient’s presentation, including aortic atresia and mitral stenosis, as well as a large atrial septal defect and evidence of bilateral aortopulmonary collateralization with discrete collaterals to the right lung. We use the model to consider an alternative, flared design for the BT shunt
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