Tunable Blood Shunt for Neonates With Complex Congenital Heart Defects

Abstract

Despite advancements in procedures and patient care, mortality rates for neonatal recipients of the Norwood procedure, a palliation for single ventricle congenital malformations, remain high due to the use of a fixed-diameter blood shunt. In this study, a new geometrically tunable blood shunt was investigated to address limitations of the current treatment paradigm (e.g., Modified Blalock-Taussig Shunt) by allowing for controlled modulation of blood flow through the shunt to accommodate physiological changes due to the patient’s growth. First, mathematical and computational cardiovascular models were established to investigate the hemodynamic requirements of growing neonatal patients with shunts and to inform design criteria for shunt diameter changes. Then, two stages of prototyping were performed to design, build and test responsive hydrogel systems that facilitate tuning of the shunt diameter by adjusting the hydrogel’s degree of crosslinking. We examined two mechanisms to drive crosslinking: infusion of chemical crosslinking agents and near-UV photoinitiation. The growth model showed that 15–18% increases in shunt diameter were required to accommodate growing patients’ increasing blood flow; similarly, the computational models demonstrated that blood flow magnitudes were in agreement with previous reports. These target levels of diameter increases were achieved experimentally with model hydrogel systems. We also verified that the photocrosslinkable hydrogel, composed of methacrylated dextran, was contact-nonhemolytic. These results demonstrate proof-of-concept feasibility and reflect the first steps in the development of this novel blood shunt. A tunable shunt design offers a new methodology to rebalance blood flow in this vulnerable patient population during growth and development.

Narrative review of single ventricle: where are we after 40 years?

“…Over the last years, relatively simple tasks of building biomaterials to use as patch or conduit during surgery for congenital heart defects has now evolved to bioengineering products to use in place of prosthetic materials and repair of damaged or missing myocardium (318)(319)(320)(321). Until recently, it was unthinkable to use biomaterials to construct the systemic-to-pulmonary shunt with tunable properties to control and modulate blood flow through the shunt, thus accommodating to physiological changes as the patient grows (322). Thanks to modern technologies, now these bioengineered shunts represent a new methodology to accommodate the need for increasing pulmonary blood flow in this vulnerable patient population (322).…”

“…Until recently, it was unthinkable to use biomaterials to construct the systemic-to-pulmonary shunt with tunable properties to control and modulate blood flow through the shunt, thus accommodating to physiological changes as the patient grows ( 322 ). Thanks to modern technologies, now these bioengineered shunts represent a new methodology to accommodate the need for increasing pulmonary blood flow in this vulnerable patient population ( 322 ).…”