Case Study: Predicting recurrence of heart disease based on vessel shape and flow

Atherosclerosis is when a fatty substance like cholesterol is taken into the blood vessels. This causes vessels to become swollen and narrower, meaning the blood flow through it becomes reduced. If atherosclerosis happens to blood vessels feeding the heart, the heart does not receive enough oxygen and nutrients. As a result, the heart either dies or stops working, and usually presents as angina or a heart attack.

These patients are usually treated with a stent, which helps to widen the vessels to improve blood flow. Around 100,000 people in the UK have this kind of stent treatment every year. Yet approximately 10% of these patients suffer from the narrowing of blood vessels again, even after the stent treatment. Little is known about why certain patients have this recurrence of heart disease.

In response to this, Professor Ryo Torii undertook a research project to look more closely at the vessels around the heart, to identify signs that could indicate an increased risk of the recurrence of heart disease. To do the research, Professor Torii and his team collaborated with a number of medical doctors from St Bartholomew’s Hospital in London, as well as other hospitals. He also worked with other researchers with an interest in the topic in countries across the UK and the world, including Australia, Germany, Ireland, Italy, the Netherlands and the United States.

A closer look at blood vessels

“This study set out to predict the probability of a patient having this recurring disease based on the shape of the vessel, and also a computer simulation that we use to see how the flow is going through the standard section,” explains Professor Torii. “We suspect that those patients who experience some difficulties years after having the stent put in have some particular type of flow.”

Professor Torii and his team used computer simulations to try to identify where future problems might lie. They measured the flow acting on the vessel wall of the heart using colour maps. This helped them to spot where the blood flow is low, which can help to predict whether this might worsen in the future. Doctors will be able to use this information to know which patients need to be kept under closer review, and treat them earlier, instead of reacting to issues after they arise.

Until now, doctors have used various scanning devices to see cross sections of a patient’s body. These images mostly show shapes that indicate disease, but they cannot offer the level of detail needed to understand the trajectory or urgency of the disease. “I'm trying to add more information to this data, like how blood flows,” says Professor Torii. “That's useful for diagnostic decisions. We also calculate the pressure in blood vessels, to help doctors decide how urgently they need to administer treatment for a particular patient.”

Findings of clinical significance

The research that has taken place so far has clinical significance, in the sense that it shows the possibility of being able to predict the patients who will have a problem again at some point after a stent has been implanted. “That’s a potential impact for 10,000 patients a year in the UK alone,” Professor Torii says.

Portrait of Professor Ryo Torii of UCL Mechanical Engineering

Next, the team needs to run larger scale testing, which will include making use of data from a big clinical trial. “We have the technology established and I have developed some software that is actually being used by technicians,” Professor Torii explains. “It’s not being used for clinical decision making yet, as we will apply our approach to a large dataset first. We can then more confidently say that this technology helps patients, and is useful in predicting how the disease is progressing.”

As well as this research, Professor Torii and his team are doing ventricularisation device studies, which focuses on a machine that helps patients with weakened hearts get sufficient blood flow. At the moment, there is no consensus on how the device should best be used, and little is known about what impact the continuous flow – rather than the natural pulsing of the heart – has on patients. The team is simulating different approaches on computerised virtual patients to see what impact different modes of operation on the device have.

Professor Torii also notes how trust and collaboration between the medical and engineering communities is growing. The team worked on a paper that was published in the European Heart Journal, and Professor Torii estimates that at least a third of the authors were engineers. “Previously, we would never have been published in such a big medical paper in Europe,” he says. “But the medical community is becoming more open to the engineering approach.”