Infants with heart defects in the lower chamber of the heart must undergo several invasive operations early on. The first operation involves implanting a plastic tube called a shunt to improve blood flow. This shunt must be replaced in growing children.
Scientists have developed a shunt that can expand using light to reduce the number of open heart surgeries in these children.
With this study, scientists hope to expand the inside of the tube with a light-emitting catheter that must be inserted into the shunt, thus eliminating the need for additional operations.
Congenital heart defects affect the heart chambers, restricting blood flow to the lungs and other parts of the body. Children with these conditions cannot survive without surgery.
Children are often born small and may gain weight after the first shunt implantation. To keep up with their growth, they may need additional surgeries to replace the shunt.
In a study of 360 patients undergoing initial cardiac reconstruction, 41 required additional operations to implant a larger shunt and seven died as a result.
Previously, scientists had developed an expandable prototype designed to replace the most common type of shunt. They coated the inside of the shunt with a unique hydrogel made of water-filled polymers connected by cross-links. As new cross-links form, they squeeze water out of the hydrogel, causing it to shrink and the inside of the shunt to expand. In their first design, the cross-links formed independently of one another, without the need for an external trigger.
Scientists have now redesigned the shunt for safer clinical use so that it can be tailored to the needs of individual children. They did this by developing new polymers for a hydrogel that forms new cross-links in response to a trigger and increases the inner diameter of the shunt.
To initiate cross-linking, the scientists decided to use blue light because this wavelength has enough energy to trigger the reaction but is harmless to living tissue.
Christopher Rodell presented the research results and said: “Light has always been one of my favorite triggers because you can control when and where you use it.”
For the new device, scientists are using a fiber-optic catheter, essentially a long, thin tube with a light-emitting tip. To activate the light-sensitive hydrogel in the shunt, surgeons plan to insert a catheter through an artery near the baby’s armpit and guide it into place. This method would eliminate the need to open the baby’s chest.
In laboratory tests, they found that the shunt gradually expanded depending on the length of time it was exposed to light. This means that once implanted, the shunt can be adjusted to each child’s needs. They increased the diameter of the shunt from 3.5 to 5 millimeters, almost reaching the size of the largest shunts used in children. They also checked how blood cells and vessels reacted to the shunt and found no signs of blood clots, inflammation, or other health problems.
Scientists plan to test full-length shunt prototypes in an artificial setup that mimics the human circulatory system. If the experiments are successful, they will move on to animal testing.
Rodell said: “This technology could be useful for more than just single-ventricular heart disease. For example, surgeons could use similar tubes to replace blood vessels in children injured in a car accident.”
“These procedures run into the same problem: children are not just small adults; they continue to grow. We have to take that into account with the biomaterials, how the transplant behaves over time.”
The researchers will present their results at the fall meeting of the American Chemical Society (ACS).
