Open heart surgical replacement of the aortic valve was previously an effective option for treating patients with heart valve disease. However, demographic changes mean that this surgery is not usually the best option anymore. The most relevant heart valve disease has now become aortic valve calcification, which is a mostly the age related stiffening of the valve leaflets, affecting more than 10% of people aged over 75.  These patients commonly suffer also from other diseases, which in turn dramatically increases the risk of mortality from open heart surgery.

Transcatheter aortic valve implantation (TAVI), allows the delivery of a specially designed collapsible artificial valve through the vascular system, avoiding the need of open-heart surgery and its associated risks. Therefore, it has recently been established as the treatment of preference for these patients, and its clinical benefits are now driving its expansion to lower risk subjects. However, this expansion demands some design improvements to enhance the safety and sustainability of the treatment.

In response to this,  Professor Gaetano Burriesci from UCL Mechanical Engineering has developed a new generation TAVI device, which overcomes the main limitations experienced with current solutions. Called the Triskele project, this work was made possible thanks to a cross-disciplinary team across various institutions and teams at UCL, the Royal Free Hospital, the St Bartholomew’s Hospital heart centre, various international partners including the Ri.MED Foundation, and some industrial partners. Funding has come from several institutions, including the Royal Society, the Department of Health, the Wellcome Trust, the Engineering and Physical Sciences Research Council (EPSRC), as well as the biomedical industry.

Designing a new heart valve

“This valve is characterised by a self-expanding wireframe made from super-elastic alloy, supporting polymeric leaflets and a sealing cuff,” explains Professor Burriesci. “The device offers major improvements compared to current products, by providing a simpler and more reliable solution at a significantly lower cost.  Moreover, it is suitable for a wider range of aortic valve diseases than current TAVI.”

One of the key improvements in the device that Professor Burriesci has designed is that it is fully retrievable and repositionable in case of procedural error. It also has enhanced anchoring and sealing properties, which makes it a suitable option to treat a larger range of pathologies compared to previous designs. In addition, the use of polymer for the leaflets can reduce calcification. This is the main cause of structural degeneration in current prosthetic valves, meaning the new valves may also result in extended durability.

The future of heart surgery

The Triskele device has undergone rigorous testing to get it ready for manufacture. This includes in vitro tests, which confirmed both the hydrodynamic performance and durability of the device met the requirements for market clearance.  In vivo preclinical tests have confirmed the excellent performance of the valve hemodynamics, and the superior leaflet tolerance. Notably, the tests confirmed the absence of calcification and observable damage.

The valve design and its delivery mechanism have been IP protected, and it has been licensed to a multinational biomedical corporation, which is organising the first-in-man trials and overseeing the access to market.

“Our research effort has resulted in a solution that has confirmed potential to improve safety, procedural simplification and reduced costs in replacing aortic valves,” Professor Burriesci says. “This could contribute to the expansion of TAVI to lower risk patients. It could also enable valve replacement in parts of the world where they are currently limited, due to the resource-intensive requirements of surgery, or the unaffordable costs of current transcatheter systems.”

The team is now planning to expand the functional concepts established in this project to a new transcatheter mitral valve. Mitral regurgitation is one of the most common mitral valve dysfunctions that leads to heart failure. Data from Europe and the United States shows this affects millions of people. As this problem becomes more likely as individuals get older, the ageing population means that a transcatheter mitral valve replacement device will become increasingly necessary in the future.

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