New expandable heart valve offers hope for young children with heart defects

Researchers at the University of California, Irvine have successfully performed preclinical laboratory testing of a replacement heart valve intended for toddlers and young children with congenital cardiac defects, a key step toward obtaining approval for human use. The results of their study were published recently in Journal of the American Heart Association.

The management of patients with congenital heart disease who require surgical pulmonary valve replacement typically occurs between the ages of 2 and 10. To be eligible for a minimally invasive transcatheter pulmonary valve procedure, patients currently must weigh at least 45 pounds. For children to receive minimally invasive treatment, they must be large enough so that their veins can accommodate the size of a crimped replacement valve. The Iris Valve designed and developed by the UC Irvine team can be implanted in children weighing as little as 17 to 22 pounds and gradually expanded to an adult diameter as they grow.

Research and development of the Iris Valve has been supported by the Eunice Kennedy Shriver National Institute of Child Health and Human Development; the National Heart, Lung, and Blood Institute; and the National Science Foundation.

This funding has enabled benchtop fracture testing, which demonstrated the valve's ability to be crimped down to a 3-millimeter diameter for transcatheter delivery and subsequently enlarged to 20 millimeters without damage, as well as six-month animal studies that confirmed successful device integration within the pulmonary valve annulus, showing valve integrity and a favorable tissue response.

We are pleased to see the Iris Valve performing as we expected in laboratory bench tests and as implants in Yucatan mini pigs, a crucial measure of the device's feasibility. This work represents the result of longstanding collaboration between our team at UC Irvine and Dr. Michael Recto at Children's Hospital of Orange County built over several years of joint research and development."

Arash Kheradvar, lead author, UC Irvine professor of biomedical engineering

Congenital heart defects affect about 1 percent of children born in the United States and Europe, with over 1 million cases in the U.S. alone. These conditions often necessitate surgical interventions early in life, with additional procedures required to address a leaky pulmonary valve and prevent right ventricular failure as children grow.

The Iris Valve can be implanted via a minimally invasive catheter through the patient's femoral vein. The Kheradvar group employed origami folding techniques to compress the device into a 12-French transcatheter system, reducing its diameter to no more than 3 millimeters. Over time, the valve can be balloon-expanded up to its full 20-millimeter diameter.

This implantation method, along with the ability to begin treatment earlier in very young patients, helps mitigate the risk of complications from delayed care and reduces the need for multiple surgeries in this vulnerable population.

"Once the Iris Valve comes to fruition, it will save hundreds of children at least one operation – if not two – throughout the course of their lives," said Recto, an interventional pediatric cardiologist at CHOC who's also a clinical professor of pediatrics at UC Irvine. "It will save them from having to undergo surgical pulmonary valve placement, as the Iris Valve is delivered via a small catheter in the vein and can be serially dilated to an adult diameter and also facilitate the future placement of larger transcatheter pulmonary valves – with sizes greater than 20 millimeters, like the Melody, Harmony and Sapien devices – if needed."

Kheradvar said that the next phase of preclinical testing of the Iris Valve is funded by the Brett Boyer Foundation, which is committed to supporting research into treatments for congenital heart disease.

"We are actively engaged with the U.S. Food and Drug Administration to define and carry out the required experiments and documentation for first-in-human authorization of the Iris Valve," Kheradvar said. "Our team is urgently advancing the Iris Valve through preclinical studies to enable its clearance for first-in-human use. This is a critical step toward providing toddlers – who currently have no viable minimally invasive treatment until they reach the 45-pound threshold – with a much-needed option."

First co-author Nnaoma Agwu, a biomedical engineering Ph.D. candidate at UC Irvine, said: "The development of the Iris Valve required a strong and knowledgeable team that understood the clinical and mechanical design requirements. This accomplishment would not have been possible without the collaboration of talented clinicians, veterinarians and engineers. With this milestone reached, we are rigorously advancing the Iris Valve's development, setting our sights on human clinical trials."

Joining Kheradvar, Recto and Agwu as co-authors of the article in Journal of the American Heart Association were Daryl Chau, a recent UC Irvine master's graduate; Gregory Kelley and Tanya Burney, both research specialists at UC Irvine, with Burney also affiliated with the Beckman Laser Institute; Ekaterina Perminov, a clinical veterinarian with UC Irvine's University Laboratory Animal Resources; and Christopher Alcantara, a radiology technician at CHOC.