• Scientists develop a new type of heart valve that expands as the organ grows.
  • Trials in lambs remained functional for 10 weeks without causing injury or major inflammation.
  • Device could reduce the number of open-heart surgeries during childhood required to replace valves as the heart grows.

Scientists have created a heart valve replacement that can be expanded over time as the organ grows. They say it is a big step towards a major goal in heart valve prosthetics.

In a new study, the artificial valve safely worked in growing young lambs for a period of up to 10 weeks.

Researchers say that although studies with longer follow-up times are needed to further validate the design, the device could offer a superior alternative to traditional, fixed-diameter heart valve prostheses.

The nature of this means that children with congenital heart disease require repeated open-heart surgeries during childhood to replace the valve with a larger version.

However, scientists say the new device created at Boston Children’s Hospital could allow children to keep the same prosthetic valve until adulthood.

Revolutionary new valve could save children from repeated open-heart surgery © Sophie C Hofferberth/Boston Children’s Hospital
© Sophie C Hofferberth/Boston Children’s Hospital

Published in Science Translational Medicine, they suggest it could also benefit adults with heart valve defects.

More than 1.35 million children worldwide are born with a congenital heart disorder each year, resulting in an annual expense of around $6bn.

Of these disorders, most that involve heart valves are treated with prosthetic replacements.

To provide a more permanent solution that reduces surgical burden, Sophie Hofferberth and colleagues created a heart valve that draws inspiration from valves in human veins, which can expand and contract to handle large changes in blood flow volume.

It is composed of two synthetic leaflets attached to a stent and can be manually expanded with a balloon catheter to accommodate larger volumes of blood moving through the heart.

When implanted into four lambs and four adult sheep, the prosthetic valves showed good performance without impeding blood flow.

A separate test in seven other lambs found the valves remained functional for 10 weeks without causing injury or major inflammation.

The scientists caution that longer-term animal studies should assess the valve’s durability and effects on the heart, as well as the structural integrity of the expandable leaflet design.

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Dr Pedro del Nido, chairman of cardiovascular surgery at Boston Children’s Hospital and senior author on the paper, said: “We hope to bring this new device into clinical testing fairly rapidly.

“If our pre-clinical results hold up in human testing, this could transform the field.”

Dr Hofferberth said: “A shortcoming of many existing devices is the presence of flow disruptions that lead to blood clot formation and early valve deterioration.

“Our design achieves a favourable flow profile that seems to facilitate effective valve washout and minimise flow stagnation, which is likely to be an important determinant of long-term device durability.”


The team believes their data support the initiation of a clinical study within one to two years.

Reader Q&A: Why is the heart slightly to the left in the chest?

Asked by: Adam King, Huddersfield

The heart is located fairly centrally beneath the breastbone, but it does protrude towards the left. This is because the heart’s bottom-left chamber (the ‘left ventricle’) is responsible for pumping oxygenated blood around the whole body, so it needs to be stronger and larger than the right ventricle, which only pumps blood to the lungs.

It’s this left ventricle that you can feel beating in your chest. One in 10,000 people actually have a mirror-image heart which points towards the right – a condition known as ‘dextrocardia’.

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Alexander McNamaraOnline Editor, BBC Science Focus

Alexander is the former Online Editor at BBC Science Focus.