EMDT_European Medical Device Technology

European Medical Device Technology, Summer 2015

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BREAKTHROUGHS 10 | Summer 2015 European Medical Device Technology emdt.co.uk British Scientists Develop Next Generation of TAVR Devices Recent developments in the field of transcatheter aortic valve implantation and replacement (TAVI or TAVR) enable the delivery of a valve substitute through the vascular system, avoiding the need for open-heart surgery and its associated risks, such as cardiac arrest. As a result, this method allows surgical-valve replace- ment for patients who were previously considered too ill or too weak to with- stand the stress of invasive treatments. Clinical experience with first-gener- ation TAVI/TAVR devices has indicated that substantial design improvements are still needed for the burgeoning technology. Common complications were the inability to extract or reposition misplaced valves, common recurrence of paravalvular leakage, and high incidence of atrio-ven- tricular blocks deriving from the excessive anchoring forces, according to Gaetano Burriesci, reader in biomedical engineer- ing at University College London. Burriesci was part of a research team that developed a transcatheter heart valve, the Triskele, designed to mitigate these limitations. "The valve is designed to be retrievable and repositionable, ensuring enhanced anchoring and seal- ing without applying excessive pressure on the annulus," Burriesci told EMDT. Moreover, contrary to first-generation solutions, anchoring does not require calcifications, expanding the potential use of the valve to a wider range of diseases. The device consists of three polymeric flexible leaflets supported and secured through a self-expanding frame. The poly- meric leaflets are not prone to dehydration during implant and are alpha-gal free, thereby reducing tissue degradation and calcification, according to Burriesci. For the leaflets, the researchers used a novel synthetic nanocomposite biostable polyurethane (POSS-PCU) that was recently developed at UCL. "This solu- tion, which is alpha-gal free, also allows reduced thickness, consistent manufac- turing, easier storage and sterilisation, and the possibility of loading the valve into the delivery system long before the operation," Burriesci explains. "More- over, the same material is used to form a sealing component, which fills the gaps between the prosthesis and the surround- ing tissues, reducing paravalvular leak- age." The supporting frame is made from a superelastic nitinol wire thermomechani- cally formed and joined at a number of points, which does not require laser-cutting processes. "After complete valve implanta- tion, if necessary, the device can safely be recollapsed and repositioned—or com- pletely removed and exchanged for an alternative solution—acting of a system threads departing from the delivery sys- tem," the researcher said. "The anchor- ing is achieved by application of axial forces, which wedge the prosthesis into place, avoiding the need for radial forces that might result into atrio-ventricular blocks." According to research company GBI, the number of TAVI/TAVR procedures performed in Europe more than quadru- pled between 2009 and 2012, increasing from 5,000 to an estimated 25,000. For the United States, the report from 2013 forecasts a rise in the procedures from 7,946 in 2012 to 59,000 in 2017, driv- ing the country's TAVI/TAVR market value from $238 million to $1.9 billion during the same period. Burriesci assumes that, because of the improved safety offered by the valve repositionability and retrievability, future procedures could be performed in cath labs; they are currently done in hybrid rooms in case the rapid insti- tution of cardiopulmonary bypass is necessary due to an incorrect implan- tation. This could lead to substantial cost-savings to the healthcare system, he notes. Moreover, Burriesci thinks that the device offers significant pricing advantage over existing solutions, as this technology is engineered from a temoset nitinol wire, avoiding the high costs of nitinol tubes, laser-cutting and the asso- ciated waste of material. As the project is still at a relatively early stage, the team is currently looking for partners to help them to archieve regula- tory approval for the technology. - Thomas Klein Triskele transcatheter heart valve developed at the University College London.

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