Light-Triggered Shunt Minimizes Invasive Surgeries for Heart Defects

Researchers at Drexel University have developed a shunt that expands when exposed to light. If further developed, this innovation could potentially reduce the number of open-chest surgeries required for children. The researchers will present their findings at the upcoming fall meeting of the American Chemical Society (ACS).

Watch a Headline Science YouTube Short about this research. Video Credit: The American Chemical Society.

Children born with defects affecting the lower chambers of the heart typically undergo multiple invasive surgeries early in life. The initial procedure involves implanting a plastic tube, known as a shunt, to enhance blood flow. However, as the child grows, the shunt often needs replacement to fit their changing anatomy.

After the surgeon first puts in the tube, these children often have to go through an additional two or three, maybe even four, surgeries just to implant a slightly larger tube. 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.

Christopher Rodell, Assistant Professor, Biomedical Engineering, Drexel University

These congenital heart disorders, affecting the ventricles (the heart's lower chambers), restrict blood flow to the lungs and other parts of the body. Babies born with these conditions require surgery to survive. These infants, often born undersized, can grow rapidly after their initial shunt placement.

Surgeons frequently need to perform additional open-chest surgeries to replace the shunt as the child grows. Each of these surgeries poses significant risks. For instance, of the 360 patients who underwent the initial heart reconstruction surgery, 41 required a larger shunt, and tragically, seven of these patients died as a result.

Previously, Amy Throckmorton and Kara Spiller, colleagues of Christopher Rodell at Drexel, developed an expandable shunt prototype that could eventually replace the most commonly used type of shunt. They achieved this by lining the inside of the shunt with a hydrogel, composed of a network of polymers surrounded by water, held together by connections known as crosslinks.

In their design, the hydrogel contracts, and the inside of the shunt expands as new crosslinks form, pulling the polymers together and expelling water from the hydrogel. This expansion occurred naturally, without the need for an external trigger.

To enhance the design, Throckmorton and Spiller enlisted Rodell's help in reengineering the shunt to ensure the materials were safe for clinical use and could be adapted to the needs of individual children.

Rodell developed novel polymers for a hydrogel that could create new crosslinks and expand the shunt's inner diameter when triggered. He chose to use blue light to initiate crosslinking on demand, as it is safe for living tissue and has sufficient energy to start the process.

“Light has always been one of my favorite triggers, because you can control when and where you apply it,” Rodell said.

Rodell and his team, led by doctoral student Akari Seiner, are developing a novel device that utilizes a fiber-optic catheter—a long, thin tube with a light-emitting tip. Their plan is for surgeons to insert the catheter into an artery near the armpit and then guide it into position, allowing them to activate the light-sensitive hydrogel inside the shunt without the need to open the baby's chest.

In laboratory tests, the researchers found that the shunt could be gradually expanded, with the degree of expansion controlled by the duration of light exposure. These findings suggest that once the shunt is implanted, its modifications could be tailored to meet the specific needs of each child.

The team was able to dilate the shunt by up to 40 %, increasing its diameter from 3.5 to 5 mm—nearly the size of the largest shunt ever placed in a child. They also assessed the modified shunt's potential effects on blood vessels and cells, finding no evidence of harmful reactions, such as blood clots or inflammation.

The group's next step is to test full-length shunt prototypes in a synthetic environment that simulates the human circulatory system. If these tests are successful, they plan to move on to animal model experiments.

Rodell notes that this approach could have applications beyond single-ventricle heart conditions. For instance, similar expandable tubes could be used by surgeons to replace blood vessels in children injured in auto accidents.

In these procedures, you run into the same problem: Children are not just tiny adults; they continue to grow. That is something we need to account for in biomaterials, how that graft will behave over time.

Christopher Rodell, Assistant Professor, Biomedical Engineering, Drexel University

The Hartwell Foundation funded the study.