Scientists say a new scan technique could identify people at risk of collapsing and dying suddenly from a hidden heart condition. Normally, in people with hypertrophic cardiomyopathy, signs of structural changes in the heart can only be picked up after death.
But University of Oxford researchers used microscopic imaging to spot the same patterns in living patients.
The condition is the top cause of sudden cardiac death in young people.
It is a common, inherited condition, affecting one in 500 people in the UK, which can be fatal in small numbers of people.
Footballer Fabrice Muamba had a near-fatal cardiac arrest during a match while David Frost’s son Miles died suddenly while jogging aged 31, for example.
Yet many of those with hypertrophic cardiomyopathy, or HCM, have few or no warning symptoms – and some are able to lead perfectly normal lives.
The research team focused on detecting those at risk of sudden death, by looking for abnormal fibre patterns in the heart which could lead to potentially deadly heart rhythms.
This is thought to affect around 1% of people with the condition.
They can then have a small device implanted in their heart to kick-start it into beating again when an abnormal heart rhythm is detected.
Dr Rina Ariga, study author and cardiologist at University of Oxford, said: “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.”
She added: “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.”
Currently, calculating a patient’s risk is based on the thickness of their heart wall, their family history, plus any unexplained collapses and abnormal heart rhythms.
The difference with the Oxford researchers’ approach is that they used MRI scans to look at detailed images of the structure of the heart muscle to check for “muscle fibre disarray”.
This suggests that heartbeats are not allowed to spread evenly across the heart’s muscle fibres.
The study, published in the Journal of the American College of Cardiology, scanned 50 patients with HCM and 30 healthy volunteers and were able to see “disarray” in living patients with the heart condition that had previously only been found in patients after sudden cardiac death.
These patients were also more likely to have abnormal heart rhythms.
The technique, called diffusion tensor magnetic resonance imaging, is normally used on the brain – but advances mean it can now be used on the heart.
Dr Steven Cox, chief executive of charity Cardiac Risk in the Young, said: “It is fantastic to think in the future these clinical findings could be identified in patients living with HCM and used to help in their routine diagnostic and treatments pathways.”
Dr Cox said the key to identifying those at risk in the general population was through cardiac screening “using the cost effective and non-invasive ECG [electrocardiogram] test”.
This is available to book for under 35s via the charity’s Test My Heart website.
Prof Metin Avkiran, associate medical director at the British Heart Foundation, which helped to fund the research, said: “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.”
Hypertrophic cardiomyopathy (HCM) is very common and can affect people of any age. It affects men and women equally. It is a common cause of sudden cardiac arrest in young people, including young athletes.
Hypertrophic cardiomyopathy occurs if heart muscle cells enlarge and cause the walls of the ventricles (usually the left ventricle) to thicken. The ventricle size often remains normal,but the thickening may block blood flow out of the ventricle. If this happens, the condition is called obstructive hypertrophic cardiomyopathy.
Sometimes the septum, the wall that divides the left and right sides of the heart, thickens and bulges into the left ventricle. This can block blood flow out of the left ventricle. Then the ventricle must work hard to pump blood. Symptoms can include chest pain, dizziness, shortness of breath, or fainting.
Hypertrophic cardiomyopathy also can affect the heart’s mitral valve, causing blood to leak backward through the valve. Sometimes, the thickened heart muscle doesn’t block blood flow out of the left ventricle. This is referred to as non-obstructive hypertrophic cardiomyopathy. The entire ventricle may thicken, or the thickening may happen only at the bottom of the heart. The right ventricle also may be affected.
In both obstructive and non-obstructive HCM, the thickened muscle makes the inside of the left ventricle smaller, so it holds less blood. The walls of the ventricle may stiffen, and as a result, the ventricle is less able to relax and fill with blood.
This can raise blood pressure in the ventricles and the blood vessels of the lungs. Changes also occur to the cells in the damaged heart muscle, which may disrupt the heart’s electrical signals and lead to arrhythmias.
Some people who have HCM have no signs or symptoms, and the disease doesn’t affect their lives. Others have severe symptoms and complications. They may have shortness of breath, serious arrhythmias or an inability to exercise.
It is rare, but some people with hypertrophic cardiomyopathy can have sudden cardiac arrest during very vigorous physical activity. The physical activity can trigger dangerous arrhythmias. Ask your doctor what types and amounts of physical activity are safe for you.
Other Names for Hypertrophic Cardiomyopathy
Asymmetric septal hypertrophy
Familial hypertrophic cardiomyopathy
Hypertrophic nonobstructive cardiomyopathy
Hypertrophic obstructive cardiomyopathy
Idiopathic hypertrophic subaortic stenosis (IHSS)
What causes hypertrophic cardiomyopathy?
Hypertrophic cardiomyopathy usually is inherited. It’s caused by a change in some of the genes in heart muscle proteins. HCM also can develop over time because of high blood pressure or aging. Diseases such as diabetes or thyroid disease can cause hypertrophic cardiomyopathy.
Other Types of Cardiomyopathy:
Arrhythmogenic Right Ventricular Dysplasia
Image: Fabrice Muamba collapsed while playing for Bolton Wanderers in 2012