Haptic feedback solutions for transcatheter aortic valve replacement procedures

Background and research impact - Aortic stenosis is a very serious valve disease associated with a high rate of death among untreated patients (50% in the first two years after symptoms appear). The disease is characterised by a narrowing of the aortic valve opening, usually induced by age-related progressive calcifications. Such a constriction implies that a reduced blood flow is pumped into the vascular system, hence, the heart rate increases potentially leading to heart failure.
Open-heart aortic valve replacement (AVR) is the most common approach to treat aortic stenosis. However, at least 30% of the patients, due to their advanced age, are classified as high-risk patients who have multiple coexisting conditions and cannot undergo the open surgical procedure. In 2002, transcatheter aortic valve replacement (TAVR) was introduced as a minimally invasive alternative to AVR. In TAVR, the native valve is replaced by a bioprosthetic valve, delivered on a catheter through either the femoral artery, which is the preferred access route, or the ventricular apex. The positive clinical outcomes allowed this technique to rapidly develop in the past fifteen years. Improved prostheses and delivery systems, as well as the increased experience of surgeons, favoured the reduction of complication rates and contributed to the evolution of TAVR from an experimental strategy to a routine intervention.
Nevertheless, TAVR is still affected by some major intra-operative complications, such as:
- neurological events, caused by dislodged calcific material from the valve (hit during valve crossing) or the vessels (hit during endovascular navigation);
- aortic regurgitation, associated with prosthetic valve malpositioning;
- renal failure, induced by the contrast agent injected for computed tomography (CT) imaging.
The first two problems are related to the poor manoeuvrability of current delivery systems and the inadequacy of site information provided to the surgeon during TAVR. In fact, for each step, from endovascular navigation to prosthetic valve deployment, the operator only relies on visual feedback from 2D CT imaging. The third problem is caused by the lack of alternative sources of feedback which limits the employment of invasive imaging modalities such as CT.
With the average life expectancy increasing, a higher number of patient will be in need of an aortic valve replacement conducted in a minimally invasive way. Obtaining and fusing multiple sensory information (such as position/orientation, flow, tactile) and supporting the deployment of the prosthetic valve by haptic feedback might decrease the occurrence of current complications and lead to a higher success rate.

Aim and objectives - The aim of this project is to develop a steerable robotic system, capable of crucial intravascularly sensing information and providing guidance to the surgeon through haptic feedback. The objectives are to:
- investigate microscale sensing technologies that could be embedded in the catheter;
- explore suitable state-of-the-art actuation methods for endovascular navigation and relevant control techniques;
- design the system, developing an haptic feedback interface;
- validate our approach through in vitro experiments.

Alignment to EPSRC's strategies - This PhD study is closely aligned with the EPSRC's research theme "Healthcare Technologies" and "Developing Future Therapies". In particular, we aim at optimising and increasing the success rates of the current TAVR procedure. Being able to guide the surgeons to accurately position prosthetic aortic valve might allow to also conduct TAVR on lower-risk patients and to develop a robotic solution.