Performance of TAVI valves

30,000 measurement points
on a single heart valve

The researchers spray paint the heart valve with the equivalent of more than 30,000 dots or measuring points. The camera captures the movement of the leaflets with 2,000 images per second. For each image the system recognises the pattern of the dots and uses this to calculate the strain in the tissue. The method has been used many years in the automotive industry where it is used to test the robustness of materials, but it is new in a biomedical context.

A method to measure strain in cardiac structures with an unprecedented high level of detail is attracting international attention.

What happens when a prosthetic heart valve is implanted in a patient? What impact does it have on the hemodynamic and the biomechanical conditions? Will it affect the work load of the heart and how?

After many years of development, researchers have found a new method to measure the strain in cardiac structures with an extremely high level of detail. Combined with hemodynamic measures of pressure and flow this enables an acute assessment of the overall load conditions of the cardiac structures under investigation. Potentially, this may provide means of estimating the durability of different types of heart valve prostheses.

Cameras measure heart beats in 3D
Based on high-end high-speed cameras, it is possible to perform 3D analysis of heart valves during the entire heart cycle in the laboratory and, with advanced data processing of the images, the strain on the leaflets of the aortic valve can be measured along with motion pattern analysis. Soon new equipment will even provide visualisation of the flow through and around the heart valve.

And this is something that is attracting attention far beyond the borders of Denmark because this type of measuring tension in the heart was previously carried out using much fewer measuring points.

How surgery affects force balance and blood flow
As a contribution to the already very thorough testing of artificial heart valves, the researchers use the model and system to carry out even more detailed measurements of the valve leaflet stress and strain during various load conditions.

“This can be used to compare the stresses in the native valves to the stresses in the prosthetic valves. Increased stress may indicate a reduced expected life span,” says Associate Professor Johansen.

In the long term, the method used by the researchers – and what takes place in the new interdisciplinary cardiovascular laboratory at Aarhus University – may have a significant impact on developments of prosthetic devices and surgical procedures.

“When you know exactly how an implant or cardiac surgical procedure affects the natural force balance and blood flow of the heart, you have an indication of how the work load of the heart may be altered. Moreover, knowing the exposed stress and strain on an implant may tell you if there is a risk of reduced durability. As many implants and surgical techniques are continuously improved, it takes years of experience from now before you can document any late clinical complications and the durability of implants,” says Associate Professor Johansen.