Pioneering artificial heart valve grows inside the body

Artificial heart valve that GROWS inside the body ‘could stop children with deadly defects needing multiple risky surgeries’

• The prosthetic has been hailed as a huge step forward in medical care
• Tested in young lambs, the valve expanded with the growth of their own hearts
• Human trials are expected to go ahead within two years, US researchers said 
• It could spell the end of repeated surgeries for children with replacement valves
• Their artificial valves do not grow with their own heart, and have to be swapped 

A pioneering heart valve replacement that grows at the same rate as the organ does could transform lives of children with defects, scientists say.

The prosthetic could remove the need for patients to have multiple risky heart surgeries during childhood and provide a longer-lasting fix for weak hearts. 

Its inventors say it could ‘transform the field’ if it is proved totally safe and they hope it can be tested in humans within two years. 

Replacement heart valves are used when a person’s natural valve is diseased or damaged, stopping the heart from working as it should.

Children with congenital heart disease are forced to endure repeated open-heart surgeries during their life to swap the replacement valve with a larger version as their body grows.

But the new valve, created by Boston Children’s Hospital, is intended to provide a more permanent solution. 

It has been tested on lambs and worked safely and effectively for at least 10 weeks.

A pioneering heart valve replacement that grows as the same rate as the organ does could transform lives of children with defects. It safely worked in growing young lambs as they grew in their first weeks of life (pictured, the valve expanding to different lengths in sheep)

A pioneering heart valve replacement that grows as the same rate as the organ does could transform lives of children with defects. Scientists at Boston Children’s Hospital used a computer to model how the valve would expand to deal with the stress of increasing blood flow as a child gets older

More than 1.35million children worldwide are born with a congenital heart disorder every year.

In the UK, one in every 180 babies have potentially deadly problems with their hearts, according to the British Heart Foundation.  

These defects account for three to five per cent of all deaths in children under five years of age.

Heart valve replacement surgery is an operation to repair one or more of the heart’s four valves.

If these are damaged by disease or age it can reduce how well the vital organ pumps blood around the body.

Valves – where the main arteries and veins connect to the heart – can become less efficient if they do not open or close properly, obstructing the flow of blood or leaking as the heart pumps.

A valve replacement op is one in which the damaged valve is replaced with either an artificial part or one from an animal or human donor.

During the op the chest is sliced open, the heart stopped and blood pumped with a bypass machine, then the heart valve is replaced and the chest closed back up and the heart restarted.

Patients will usually spend a week in hospital and may take up to three months to fully recover.

The survival rate of an aortic valve replacement – a common type – is between 97 and 99 per cent, according to the NHS.

Risk depends on the patient’s age and general health but it can cause endocarditis, a heart infection. Blood clots and stroke are also possible complications

WHAT TYPE OF REPLACEMENT VALVES ARE AVAILABLE? 

Mechanical valves are made of metal. They can lead to blood clots which can be fatal if they cause a heart attack or stroke.

Because the body can tell that a mechanical valve is not made of natural tissue, blood is more likely to clot on the surface of the valve. 

The hard surface can also tear blood cells as they pass through the valve, causing clots to form. 

Tissue valves may be recommended to patients over 70 or those who do not want to take blood thinning medication.

Tissue valves from an animal are strong and flexible. The advantage of tissue valves is that a patient does not need life-long blood thinning medication like mechanical valves do. 

They can last 10-20 years, but are considered to wear out quicker than a mechanical/artificial valve. 

Sources: British Heart Foundation and NHS  

The number of operations performed for congenital heart disease increased by around 60 per cent between 2000 and 2010.

It’s thought that most cases occur when something affects the heart’s development during the first six weeks of pregnancy. Maternal diabetes, alcohol and flu are some risk factors.  

More severe heart defects usually require surgery, of which there are many kinds. A prosthetic valve replacement can give children the best chance of life without symptoms such as shortness of breath, fatigue and chest pain.

Valve replacements are made of either metal – which comes with the risk of blood clots – or animal tissue.  

Animal heart valves can last 10-20 years, but are thought to wear out quicker than a mechanical valve. 

A fake heart valve will not grow as the child grows and will need to be replaced again. For this reason, it is delayed for as long as possible to reduce the number of repeat surgeries.

The valves are put inside the body by opening the chest and cutting the breastbone to reach the heart – which has four valves in total – in a complex procedure.  

Around two per cent of patients die from an aortic valve replacement, according to The British Heart Foundation, which is much smaller than the risk of leaving severe aortic valve problems untreated.  

To provide a more permanent solution that reduces surgical burden, Dr Sophie Hofferberth and colleagues created a heart valve that draws inspiration from valves in human veins. 

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.

The valves expand and contract to handle large changes in blood flow volume which would be expected as the child gets older. 

In a new study, published in Science Transitional Medicine, the artificial valve safely worked in seven growing young lambs for a period of up to 10 weeks, without causing injury or inflammation. 

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

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 valve could also benefit adults with heart valve defects. 

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 initiation of a clinical study within one to two years.

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