Potts shunt for suprasystemic pulmonary artery hypertension: decision-making and design

The human cardiovascular system consists of two large arteries: the aorta (AO), which supplies oxygenated blood to the body, and the pulmonary artery (PA), which supplies deoxygenated blood to the lungs for oxygenation. In healthy individuals, the pressure in the AO is significantly higher than the pressure in the PA. Pulmonary artery hypertension (PAH) is a disease in which the PA pressure is abnormally elevated and is classified as one of the most devastating disorders by the pulmonary artery association UK. This is evidenced by a mean survival time after diagnosis of less than 30 months in adults and less than 12 months in children.

A recently proposed treatment for severe PAH, i.e. the case when PA pressure is higher than the pressure in AO, is to create a connection, known as the Potts shunt, between the PA and the AO. Just as a connection between two pipes carrying fluids with high and low pressures will lead to a reduction of pressure in the high-pressure pipe and an increase of pressure in the low-pressure pipe, the idea is that a Potts shunt can lead to a reduction of PA pressure in severe PAH patients. This reduction in PA pressure is desirable but will also result in mixing of oxygenated and deoxygenated blood, an undesirable effect. Clinical experience has shown favourable results of this treatment in some patients and unfavourable in others, which is attributed largely to a reduction in cardiac output, the total volume of blood ejected by the heart in one cardiac cycle. This project aims to develop computational models to assess three measures of Potts shunt treatment:

1) reduction of pulmonary artery pressure,
2) mixing of oxygenated and deoxygenated blood, and
3) reduction in cardiac output.

Through the computational models, this project will assess the mechanisms behind the success/failure of Potts shunt in relation to the above measures. The end-product will be a computer model which, given a new patient, can determine if a Potts shunt is likely to succeed in the patient. Furthermore, technology to optimise the design of Potts shunt for each patient individually, such that maximal clinical benefit is achieved, will be developed.

This project, with the aim to aid clinicians in developing a palliative procedure for severe pulmonary artery hypertension, is aligned with EPSRC's theme of healthcare technologies and the two associated grand challenges of Frontiers of Physical Intervention and Optimising Treatment for achieving the goal of a healthy nation.

The societal impact of this project, not only in the UK but also internationally, will be in terms of an improved quality of life and the availability of a treatment option for patients, especially children, with severe pulmonary artery hypertension (PAH). This project will deliver a method/tool to select patients for the recently proposed Potts shunt treatment for severe PAH. It will also develop the technology to design optimal shunts, for each patient individually, so that maximal clinical benefit is achieved. The proposed development of Potts shunt technology will contribute to the creation new knowledge about PAH physiology and its treatment, thereby making an impact on both engineering and clinical understanding. Furthermore, the computational models of the heart and circulation developed in this study can be extended to other pathophysiologies and utilised in development of novel surgical and interventional strategies. This impact will be realised by presentation of the project methodology and results at two meetings of the special interest group on 'challenges in cardiovascular flow modelling' (comprising of 10 UK universities) funded by the UK Fluids network. For international dissemination, the results will be presented at the International Conference on Engineering Frontiers in Paediatric and Congenital Heart Disease, which attracts approximately equal numbers of clinical and engineering participants.

The use of computational methods for the development of novel procedures and devices will also increase the competency of UK in in-silico testing (requiring minimal, and eventually eliminating, animal testing) and over a longer period lead to improved healthcare provision. The UK has an increasing interest in such technology as evidenced by the recent approval of a computational diagnostic tool developed by the American start-up HeartFlow Inc. Therefore, the economic impact of this project will be on the advancement of indigenous in-silico testing capabilities in the UK for maintaining an internationally competitive edge.

Lastly, as a true multi-disciplinary project, with both clinicians and engineers from multiple countries involved in the project, this project will train two individuals-a post-doctoral research assistant and a PhD student-to perform excellent cardiovascular research and develop innovative solutions to challenging problems.