In a laboratory at Aarhus University, researchers have conducted extensive experiments with artificial heart valves. With small high-pressure balloons, they have demonstrated that it is possible to fracture the valves without damaging the surrounding healthy tissue.

This is good news for patients who have had an artificial heart valve implanted in the past 30-40 years. Today, more than 200,000 artificial heart valves are implanted worldwide every year, and this figure will increase further in line with changes in demographics due to a growing population of elderly people.

Unfortunately, many of the artificial heart valves have a limited useful life, and researchers are therefore expecting a significant growth in the number of patients who will have to undergo re-operation.

"Many patients are walking around with a valve that needs to be replaced due to the changes that occur over time.  Our goal has been to describe an effective, safe and straightforward method that makes it possible to insert a new valve without re-operation," says Peter Johansen, associate professor at Aarhus University.

Surgical technique suitable for small heart valves
The new method allows physicians to carry out catheter-based insertion of heart valves through a small hole in the groin as an alternative to open heart surgery, and this can benefit patients with small hearts in particular, he explains:

"If the degraded artificial heart valve is too small, there’s not enough space to insert the new heart valve with a catheter. To create space, we fracture the rigid structures in the degraded heart valve with a high-pressure balloon," he says.

Peter Johansen has worked closely with Jens Erik Nielsen-Kudsk, a senior hospital physician at Aarhus University Hospital on developing the new method.

The results have been published in the journal EuroIntervention

Technically, replacement of the heart valve takes place by physicians inserting a catheter with a high-pressure balloon into an artery in the groin and all the way up to the heart and the defective valve. Here, they dilate the balloon until it fractures the rigid structures in the degraded implant.

This provides a more flexible area for the new implant, which can be inserted in the same manner and thereby without open surgery.

Alternative to surgery
It may sound simple. But it is not. Fracturing the defective heart valve without damaging the surrounding tissue requires a very high level of accuracy," explains Peter Johansen:

"Obviously, we have to be able to control the pressure very accurately and have detailed insight into the fracture mechanisms of the various types of valves on the market, and how a  fracture affects the tissue surrounding the relevant the implant."

 The majority of the artificial heart valves (approximately 75%) that are implanted are made of tissue from animals, and this provides the most natural blood flow and the lowest possible risk of blood clotting. Unfortunately, this is also the fastest degrading type of biological implant.

So far, physicians have therefore had to assess the benefits of the biological implant against the disadvantages of one or more surgical operations throughout life. But with this new method, physicians have much better opportunities to retreat patients with biological valves.  

"The first results are promising. We’ve established a new method as an alternative to surgical re-operation with a minimum of complications - also for patients with small heart valves," says Peter Johansen.

The researchers are now working to examine how different forms of hardening of the arteries  locally around the heart valve may affect the pressure that the physicians need to fracture the valves. 

Clinical world premiere in Denmark
In close collaboration with clinical researchers from the Department of Cardiothoracic Surgery and the Department of Cardiology at Aarhus University Hospital, Peter Johansen has carried out extensive in vitro experiments with systematic pressure loads on various types of artificial heart valves.

“We’ve managed to create an experimental setup that can provide us with a clinical guideline for what it takes to fracture various types of heart valves, and now we have detailed knowledge of how they behave when they fracture," says Peter Johansen.  

The video below shows a test fracture of one of the most common artificial heart valves. The researchers gradually increase the pressure in the balloon, while they transilluminate the heart valve and film it all with a high-speed camera.

The camera records in high resolution at 200 frames per second and thus photographs movement in the structure of the heart valve when it fractures.  

The researchers' engineering experiment is so convincing that physicians at Aarhus University Hospital, the first in the world to have embraced the new method for treating patients, have already taken the clinical guidelines into use. 

Contact

Peter Johansen, Associate Professor, Aarhus University