Atrial fibrillation Ultra-thin sensors support the heart

Related Vendors

Helmholtz-Zentrum Hereon

Wuxi InfiMotion Technology Co., Ltd.

Atrial fibrillation can lead to the formation of dangerous blood clots in the heart. Therefore, in many patients, the part of the heart where the clots form is sealed with a graft. Special sensors check whether the grafts are also sealed.

Around 60 million people worldwide are affected by atrial fibrillation. In this form of cardiac arrhythmia, parts of the heart, the atria, no longer contract properly, but move quickly and disorderly. This significantly disrupts blood flow through the heart. Especially in the small protrusions of the left atrium, known as the left atrial appendage, the blood flows turbulently and almost chaotically. This can lead to the formation of blood clots, which can block the arteries and lead to a stroke.

Therefore, many people with atrial fibrillation receive small plugs that are implanted into their hearts - a established procedure. These so-called occluders close the heart appendage, so that no blood can flow into it. This works well for some patients. The occluders fit perfectly. This also reduces the risk of forming blood clots. However, in some patients the occluders do not seal properly. There remain small gaps between the closure and the inner heart tissue, through which blood can flow in and out. Despite the closure, blood clots can form. The surgical intervention was in vain.

Ultra-thin sensors detect a sealed occluder

A team of researchers from the Hereon Institute for Active Polymers in Teltow therefore teamed up with doctors from the Charité in Berlin a while ago to develop closures that can be inserted more precisely into the left atrial area of the heart. These are better in several ways than traditional plugs. So far, commercially available occluders are only available in standard sizes with fixed diameters. Therefore, they do not always fit perfectly. The occluders developed by the research team can be widened and closed like the aperture of a camera—and can therefore be positioned much better in the opening of the appendage.

"The advantage of our cooperation is that doctors and materials scientists are working closely together," says Teltow researcher Dr. Katarzyna Polak-Kraśna, who heads the Digital Design and Processing department. "We are working with interventional cardiologist Dr. Markus Reintaler from Charité, who has a lot of experience with such procedures." Occluders are now inserted into the heart minimally invasively via catheters—i.e. pushed through large blood vessels into the atrium.

A challenge for doctors is that they cannot really observe from the outside whether the occluder is well positioned. The position can only be corrected with imaging techniques such as X-rays or ultrasound. Small gaps between the occluder and the appendage are hardly noticeable. For this reason, the new occluders contain a second special feature. Ultra-thin sensors are mounted on their surface, which can detect whether the occluder is firmly resting on the tissue or not.

Sensor records changes in pressure or position

First, an ultra-thin fabric made of nanometer polymer fibers is produced for the occluders. To do this, a liquid polymer is passed through a nozzle, from which the fibers shoot out like the thread of a spider. These fibers are laid criss-cross over each other until a tissue is formed, which under the microscope resembles the fine fiber tangle of a Kleenex handkerchief. This process is known as electrospinning. In a second step, the sensors are integrated into the fabric. Afterward, the fabric is glued to the occluder.

The sensor integrated in the new occluders is a pressure-sensitive sensor that was developed to monitor the contact strength between the occluder and the surrounding tissue. These sensors operate on the basis of piezoelectric or capacitive principles to detect changes in pressure or position and provide real-time feedback.

Piezoelectric sensors generate an electrical charge when subjected to mechanical pressure. Embedded in the occluder, they can measure the pressure distribution on the surface of the tissue and determine whether the occluder is fitting snugly or not. Capacitive sensors measure changes in the capacity between two electrodes, which are separated by a non-conducting material. When the occluder is in contact with the tissue and pressure is exerted, the distance between the electrodes changes, leading to a measurable change in capacity.

Possible spin-off after successful test phase

After two years of work, the first prototypes have been created. The project is now being funded for a further two years with over one million euros as part of the GoBio Initial program of the German Federal Ministry of Education and Research (BMBF). This will allow the occluders to be tested on real pig hearts from next year. "This will be exciting, because it will show how well the closures work in a living, moving heart," says Katarzyna Polak-Kraśna.

Following successful initial tests in animal trials, the team is planning a spin-off that will make it possible to bring the device into clinical trials and clinics to improve patient treatment outcomes and reduce their risk of stroke. (heh)