Researchers in Oxford have employed a technique more commonly used in brain imaging to identify the tell-tale signs of the potentially fatal heart condition hypertrophic cardiomyopathy, the leading cause of sudden cardiac death in young people.
This Oxford BRC-supported study is the first time these microscopic heart muscle abnormalities have been spotted in living patients.
Hypertrophic cardiomyopathy (HCM) is the condition that caused the-then 23-year-old footballer Fabrice Muamba to collapse during a game in 2012.
One in 500 people across the world has HCM, an inherited condition in which part of the heart muscle becomes much thicker. In some people the condition can lead to complications such as heart failure and stroke, while others have no symptoms and normal life expectancy. But even patients with no symptoms are still at risk of dying suddenly.
“We often hear the sad news of a young person, such as David Frost’s son Miles, dying suddenly in the prime of life, with a post-mortem finding of hypertrophic cardiomyopathy,” said Dr Rina Ariga, clinical researcher at the Radcliffe Department of Medicine at the University of Oxford and lead author on the paper, published in the Journal of the American College of Cardiology.
When seen under a microscope, muscle fibres from the hearts of patients who have died suddenly of the condition are arranged abnormally, and don’t have the usual alignment that allows heartbeats to spread evenly across the heart’s muscle fibres.
This disarray in heart muscle fibres has until now only been detectable in a post-mortem.
Identifying this disarray would allow doctors to intervene before a sudden cardiac arrest happens, by fitting an implantable cardioverter defibrillator, a small device that kick-starts the heart into beating normally again when it detects life-threatening heart rhythms.
A team of researchers led by Prof Hugh Watkins, the Oxford BRC’s Theme Lead for Genomic Medicine, and Prof Stefan Neubauer, the BRC’s Theme Lead for Imaging, used a non-invasive technique called diffusion tensor magnetic resonance imaging to track the spread of water molecules within the heart’s muscle to check for muscle fibre disarray.
This imaging technique has been very successful in tracking the paths of nerve fibres in the brain, but it is much harder to use with an organ such as the heart, which is moving all the time.
“The problem is that the large movements of a beating heart dwarf the microscopic diffusional motion of the water molecules that we are trying to measure,” said Dr Liz Tunnicliffe, study co-author and lead magnetic resonance physicist who developed the diffusion tensor imaging technique for the study.
“Recent advances in magnetic resonance technology have now made diffusion tensor imaging of the heart feasible in humans,” she added.
Dr Ariga, who is an NHS cardiologist, said: “We minimised cardiac motion by scanning patients and healthy volunteers at the same point in each heartbeat, when the heart relaxed.”
Using their new scanning technique, the team were able to see similar heart muscle disarray patterns in their living HCM patients that previous post-mortem studies had found. Patients with the imaging ‘marker’ of disarray were also more likely to have abnormal heart rhythms.
“This is the first time that we’ve been able to assess disarray non-invasively in living patients with HCM,” said Dr Ariga. “We’re hopeful that this new scan will improve the way we identify high-risk patients, so that they can receive an implantable cardioverter defibrillator early to prevent sudden death.”
“We now need to work on making this scan shorter and faster for patients so that we can test its utility in a large multi-centre study.”
Prof Metin Avkiran, Associate Medical Director at the British Heart Foundation, which funded the study along with the BRC, said: “Every week in the UK, 12 people under the age of 35 die following sudden cardiac arrest. Many of these deaths are due to inherited heart conditions, of which HCM is the most common.”
“This exciting research opens up the possibility of using a non-invasive scan to better spot heart muscle changes in people with HCM, find those at risk of a sudden cardiac arrest and ensure they receive the best preventative care. “Although further work is needed to refine and test this scan, its potential benefit to patients with HCM is huge. This work is an excellent example of cutting-edge, research-led technology that could change the way we diagnose and treat heart and circulatory diseases.”