EE 4thyr Projects 2015/2016
Project Title:	Carbon nanotube-polymer sensor for in-vivo hemodynamic monitoring in patients with heart failure
Supervisor:	Prof Richard Jackman		Submitted on: Thursday 19th February 2015

Heart failure is a chronic condition affecting at least 1 in 100 people in the UK. Heart failure is more deadly than many cancers, whereby 40% of the patients die within one year of diagnosis - a survival rate worse than breast, prostate or bladder cancer. (www.heartstats.uk) Left heart failure is by far the most common cause whereby excess intravascular fluid increases the pulmonary capillary pressure. Once the pulmonary capillary pressure exceeds approx. 20-25mmHg, fluid will leak into the alveolar space – where gas exchange occurs – which results in increasing shortness of breath that is the main symptom triggering hospital admissions.

Unfortunately, shortness of breath occurs rather late in the course of impending heart failure. However, elevated cardiac filling pressures were found to precede clinical signs of pulmonary congestion by several days or even weeks. Patients with decompensated heart failure require hospital admission and intravenous diuretic therapy. Repeat hospitalisations in patients with heart failure impose a huge burden on the healthcare system. In the US, more than half of the direct cost of heart failure are related to the in-hospital treatment. Early detection of fluid accumulation and initiation of treatment is expected to prevent hospitalisations for decompensated heart failure and result in massive cost savings.

To this end, home monitoring devices have been developed which obtain non-invasive or invasive pressure measurements. Hemodynamic monitoring with an implantable pressure sensor in the right heart showed a non-significant reduction of hospitalisations. Conversely, a significant reduction in hospitalisations (-39%) was found when a pressure sensor was implanted further downstream in a pulmonary artery to obtain end-diastolic pulmonary artery pressure (a surrogate of pulmonary capillary pressure) for guiding medical treatment.

However, a drawback of the latter study is the implantation of a large device in a proximal pulmonary artery which entails the risk of thrombo-embolism. Moreover, the measurement of end-diastolic pulmonary artery pressure only loosely correlates with pulmonary capillary pressure and depends on various factors. Ultimately, pulmonary capillary pressure determines whether or not fluid accumulates in the lung. Therefore, better outcomes may be expected when using direct measurement of capillary pulmonary pressure. So far, capillary wedge pressure can only be measured during invasive right heart catheterization. Continuous monitoring of pulmonary capillary pressure would help to optimize fluid balance in patients with heart failure and hence improve quality of life and reduce hospitalisations for decompenstated heart failure.

This PhD programme addresses the urgent need for improved continuous hemodynamic monitoring and will provide for the first time continuous, non-invasive pulmonary capillary pressure measurements. The devised pressure sensor will be injected at the time of right heart catheterization into the pulmonary artery. The blood flow will carry the sensor downstream in the pulmonary circulation where it will be wedged in a pre-capillary arteriole. This will ensure for continuous capillary wedge pressure measurement.

The sensor will consist of a pressure-sensitive polymer consisting of carbon-nanotubes. Changes in ambient pressure will lead to changes of electrical conductivity of the polymer that may be read-out via a radiofrequency tag. The sensor will allow for external, non-invasive measurement of pulmonary capillary pressure.

Project Partners:
Heart Hospital, Department of Cardiology, UCLH
Department of Physics, Polytechnic of Turin, Italy