Cardiac catheter: umbrellas on their way
to the cardiac septum
© Universität Göttingen
„In principle these implants are comparable to tiny umbrellas. If you open up one of them, you can use it to fill a hole in the cardiac septum”, explains Dr. Christian Jux from the department of paediatric cardiology at the University Hospital of Göttingen, Germany. Starting from the groin the implant gets into the pumping muscle. With the help of a cardiac catheter it is brought to the hole in the heart where it is then stretched and anchored.
However, this umbrella remains in the patient’s body for a lifetime. Even though they are no longer needed after a few months because by then the body’s own tissue overgrows the implant and integrates it into the cardiac septum. The disadvantage: a chronic irritation due to the foreign matter may arise which increases the risk of thrombosis. The only way to completely avoid a rejection of the implant by the body would be to let the foreign body disappear in the long run. This is exactly what researchers from Göttingen are currently working on. “We want to replace the hitherto applied permanent materials with resorbable ones”, says Jux.
First of all they dealt with the umbrella’s cloth. So far, manufacturers of umbrella implants utilised plastics to make the cloth. They mostly used a fabric from polytetrafluoroethylene, which is a non-reactive and consistent polymer. The researchers now replaced this with a collagen material. Collagen occurs naturally in the body as a structural protein, guarantees tensile strength and is biocompatible. It can be reabsorbed by the body within two years which leaves enough time for the body’s own tissue to accumulate over the implant.
„Now we are working on a replacement for the metal components“, says Jux. Shaft and spokes of the umbrella are often made from nitinol, a corrosion-resistant nickel-titanium-alloy with shape memory. This is to be replaced with resorbable polymers, which are already being used in physicians’ daily life as surgical thread or degradable drug carriers.