How new heart scans are helping understand heart failure
BHF-funded scientists are revealing the heart’s microscopic secrets to help predict and prevent heart failure. Katherine Woods finds out how.
Every time your heart beats, two billion muscle cells work together to force the walls of the heart inwards, pushing blood out of the heart and around the body.
For over 150 years, scientists have known that the cells of the heart are aligned in a spiral that goes in one direction on the outside of the heart and in another on the inside. “It’s similar to wood having a grain,” explains BHF-funded researcher Professor Dudley Pennell. “But we haven’t factored this in to our understanding of how the heart pumps, or our understanding of congenital and inherited heart conditions.”
Using cutting-edge scanning technologies, Professor Pennell and his team at Imperial College London have begun to reveal the microstructure of the heart in greater detail than was previously possible. Their aim is to find out whether the microscopic arrangement of a person’s heart cells affects their long-term heart health.
Inherited and congenital conditions
People born with certain heart defects have an increased risk of developing heart failure, but little is known about why some people do and others don’t. With a grant of nearly £1.5m from the BHF, Professor Pennell and his team hope to find out whether the heart’s microstructure can help to explain these different outcomes.
They have recently discovered that, in some people with hypertrophic or dilated cardiomyopathy (inherited conditions that cause the heart to become thickened or enlarged), the heart muscle cells are arranged chaotically.
They’ve also found unusual cell patterns in people born with a rare condition called dextrocardia, where the bottom of the heart is on the right side of the chest instead of the left. But it’s not known exactly how these cell patterns develop or how common they are in other congenital and inherited heart conditions.
A DT-CMR scan tracks the way that water molecules move in and around heart muscle cells. These scans compare a healthy heart (on the left) to the heart of someone with dextrocardia (right).
Professor Pennell’s theory is that hearts with a disordered microstructure might be more likely to suffer damage from high blood pressure or a heart attack, which could lead to heart failure further down the line.
“If this is the case, we might be able to identify people at high risk of heart failure many years in advance, and offer them treatment to reduce their blood pressure and cholesterol, or other drugs to help protect against heart failure.”
A new scanning technique
To test his theory, Professor Pennell is using a new type of heart scan called diffusion tensor cardiovascular magnetic resonance (DT-CMR). “Running a DT-CMR scan is like writing an orchestral score,” says Professor Pennell. “You need to create a complex set of instructions to tell the scanner exactly what to do.”
Until recently, this type of scan, which tracks the movement of water molecules, had only been used in research in animals, and on human hearts after death, but Professor Pennell’s team has developed the technique to study hearts in living people. “It is particularly difficult to do this in a moving heart, but by demonstrating it works routinely in patients, we’ve moved from the impossible to the possible.”
"Running a DT-CMR scan is like writing an orchestral score"
The researchers will scan the hearts of patients with congenital heart conditions and inherited diseases of the heart muscle. They will then follow their health over time, to find out whether patients with an unusual microstructure are more likely to develop heart failure.
They also want to make the scanning process easier and faster: currently patients need to be in the scanner for an hour to allow researchers to collect the necessary images and carry out complex calculations.
“If our research shows there’s a benefit to these scans, we think it could be introduced into routine care within five years,” Professor Pennell explains. “We hope that by revealing how the heart functions at a microscopic level, we can improve the way patients are treated and help them to stay healthier for longer.”
How does a DT-CMR scan work?
A diffusion tensor cardiovascular magnetic resonance (DT-CMR) scan is much more detailed than a standard magnetic resonance imaging (MRI) heart scan.
MRI detects the location of water molecules inside the body’s cells to build detailed pictures of organs and tissues. A magnetic field aligns the atomic particles inside the body’s water molecules and radio waves are then sent across the body to disrupt the position of these particles.
When the radio waves are switched off, the particles move back to their aligned position, and this movement creates signals that are detected by the scanner. Information from these signals is used to build a picture of the area being scanned.
A DT-CMR scan tracks the distinctive way that water molecules move in and around heart muscle cells, revealing their arrangement in more detail.