Equations to help mend broken hearts

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What does mathematics have to offer heart disease patients?

It turns out that the answer is quite a lot. Mathematics researchers have developed a model to optimise the design of heart stents.

Working alongside biomedical engineers and scientists, together with the NHS and Industry, the team from the universities of Strathclyde and Glasgow have used their model to design a new cardiac drug-releasing stent that they hope will improve the treatment of coronary heart disease in the future.

Working with the NHS

Coronary heart disease is the leading cause of death globally. In the United Kingdom, it accounts for just under one-in-five of all deaths and costs the NHS more than £3.5billion in treatment costs annually. It is a narrowing of one or more of the blood vessels that supply blood to the heart, which if left untreated can lead to a heart attack.

To prevent this, the majority of patients are now treated by permanent insertion of a tiny metal mesh tube, known as a stent, which re-opens the vessel and restores blood flow. The most advanced stents are now coated with a drug, which releases slowly into the vessel wall to improve outcomes.

The clinicians who treat this condition day in day out are clear that there are tremendous opportunities to further improve on the design of these drug-eluting stents, such that they perform even better and in a wider number of patients than is currently possible.

The EPSRC funded research team (EP/J007242/1), drawn from Strathclyde and Glasgow, have been working closely with NHS colleagues to do just that.

Working with industry

A key element of modern stent performance is the drug release profile – releasing too much drug too fast will result in toxicity; releasing it too slowly or in small amounts may result in no therapeutic effect. Optimising this aspect of stent performance currently relies on empirical approaches. As a result the development of new devices by industry is a slow and costly process, which ultimately inhibits effective innovation in this important area.

The team has been working to address this gap by developing a series of mathematical and computational models that can be used to understand the performance limitations of existing stent drug release profiles, thus helping inform the design of optimised future devices.

Working with an industry partner in the United Kingdom specialising in polymer coatings, the team have now used their model to design and produce a prototype drug-eluting stent with optimised release kinetics.

Developing better treatments now…

The optimised device is now undergoing the first stage of pre-clinical trials.

By using a new type of polymer, allied to the application of mathematical modelling to optimise the drug release kinetics, it is hoped that the prototype stent will produce better results than existing devices. Ultimately, such performance improvements are targeted at reducing the number of repeat procedures and extending the use of stents to many patients who are currently treated by a more invasive coronary artery bypass graft procedure.

As well as representing an important improvement in the treatment for coronary heart disease sufferers, this would also help reduce the overall cost of treating this condition.

…and in the future

An important feature of the models that have been developed is that they can be easily applied to optimise the design of a wide number of different stent types, from traditional polymer coated devices, to polymer-free drug and fully bioresorbable versions.

By applying their models as a complement to the empirical methods currently used, the team hope to make the whole stent design process more efficient for industry, ultimately leading to more rapid development of a wider range of stents in the future.

Importantly, the modelling techniques can also be applied to the optimisation of drug release from other implantable devices, which are becoming an increasingly important aspect of medical technology in the 21st Century.