Light-Activated Expanding Implant to Eliminate Open-Chest Surgeries for Shunt Replacement in Children

By HospiMedica International staff writers
Posted on 21 Aug 2024

Image: The blood shunt with an inner diameter that expands when exposed to a blue light-emitting catheter (Photo courtesy of Akari Seiner and Christopher Rodell)

Children born with congenital heart defects that impact the heart’s lower chambers often require multiple invasive surgeries early in life. The initial procedure typically involves implanting a plastic tube known as a shunt to enhance blood flow. As the child grows, this shunt frequently needs replacement to match their changing body size, leading to additional surgeries. Now, researchers have developed a shunt that can be expanded using light, marking a breakthrough that could reduce the number of open-chest surgeries these children have to undergo.

Congenital defects in the ventricles, or lower chambers of the heart, severely restrict blood flow to the lungs and body, necessitating surgical intervention for survival. Infants affected by these defects are often small at birth but can grow quickly after the initial shunt placement. To keep pace with their growth, repeated surgeries are required to implant larger shunts. Each surgery carries significant risks for the child. Previously, researchers at Drexel University (Philadelphia, PA, USA) had developed a prototype shunt that could expand by incorporating a hydrogel with polymers connected by crosslinks inside the tube. These crosslinks, when new ones formed, would expel water from the hydrogel, causing it to contract and thereby expand the shunt’s diameter. Initially, this process occurred automatically without external activation.

In their latest research, the team redesigned the shunt to use materials suitable for clinical applications and adjustable to individual needs. They engineered a new type of hydrogel that forms crosslinks in response to an external trigger, thereby increasing the diameter of the shunt. They chose blue light as the trigger because it has sufficient energy to start the reaction while being safe for living tissues. The researchers used a fiber-optic catheter with a light-emitting tip to activate the hydrogel. Surgeons can activate the light-sensitive hydrogel inside the shunt by inserting the catheter through an artery near the armpit and guiding it to the shunt, thus avoiding open-chest surgery.

Laboratory tests demonstrated that the shunt could be expanded incrementally based on the duration of light exposure, suggesting that post-implantation adjustments could be tailored to each child’s growth needs. They achieved up to a 40% dilation of the shunt, increasing its diameter from 3.5 millimeters to 5 millimeters. The team also evaluated the biocompatibility of the shunt, finding no significant risk of blood clots, inflammatory responses, or other adverse effects. Future plans include testing full-length prototypes in a synthetic model of the human circulatory system and later in animal models. The researchers believe this technology could also be adapted for other uses, such as replacing blood vessels in children who have sustained injuries.

“Our goal is to expand the inside of the tube with a light-emitting catheter that we insert inside the shunt, completely eliminating the need for additional surgeries,” said Christopher Rodell, an assistant professor of biomedical engineering at Drexel University. “Children aren’t just tiny adults; they continue to grow. That’s something we need to account for in biomaterials, how that graft will behave over time.”

Related Links:
Drexel University