Older male endurance athletes may be at higher risk of abnormal heart rhythms, according to a study led by the University of Leeds.
The study, funded by the British Heart Foundation and published in the journal Circulation: Cardiovascular Imaging, suggests that male endurance athletes who have spent decades training and competing are more likely to have scarring in their hearts than non-athletes.
We can all benefit from being more active, and this study is an important step towards helping people take part in sport as safely as possible.
Athletes with scarring were over 4.5 times more likely to experience an abnormal heart rhythm episode – which is linked with an increased risk of sudden cardiac arrest – compared to those without scarring, the findings suggest.
Dr Peter Swoboda, Associate Professor in Cardiology and Consultant Cardiologist in the School of Medicine at the University of Leeds, led the study. He said: "In our study, the athletes who experienced dangerous heart rhythms often had symptoms first. I'd encourage anyone who experiences blackouts, dizziness, chest pain or breathlessness, whether during sport or at rest, to speak to their doctor and get it checked out.
"These results shouldn't put people off regular exercise. Our study focused on a very select group, and not all the athletes involved were found to have scarring in their hearts. We can all benefit from being more active, and this study is an important step towards helping people take part in sport as safely as possible."
Investigating heart health
Scarring is seen in many heart conditions, and in recent years studies have shown that some lifelong endurance athletes – particularly older men – have scarring in their hearts. It's thought this could be caused by their levels of exercise, as during endurance sports like long-distance running and cycling, the heart has to work even harder to pump blood.
But, as these athletes often don't have any other symptoms of heart problems, doctors were not previously certain what this meant for their health.
The new study involved 106 healthy male endurance athletes, aged over 50, without symptoms or a diagnosis of cardiovascular disease. Everyone involved was a competitive cyclist or triathlete, who had been exercising for 10 or more hours every week for at least 15 years. Many still competed at a local, national or international level.
At the beginning of the study, all participants had an MRI scan of their hearts to look for any scarring, and an implantable loop recorder fitted to record their heart rhythm.
Scans showed that 50 of the athletes (47%) had scarring in their hearts, most commonly in the bottom of their left ventricle – the main pumping chamber. Athletes with scarring were on average slightly older (61.8 years compared with 57.0 years).
This was more than four times higher than in a group of non-athletes, matched for age and sex, who took part in up to three hours of exercise per week. Only 11% of this group (three of 27) had signs of scarring in their hearts.
During the two-year study, more than a fifth of the endurance athletes (23 of 106) had at least one episode of ventricular tachycardia – an abnormally fast heartbeat where the heart's main pumping chambers, the ventricles, contract too quickly and don't pump blood around the body effectively, that can lead to cardiac arrest. Of these, most (78%) had evidence of scarring in their hearts on MRI scans.
Three athletes had one or more episodes of sustained ventricular tachycardia (lasting longer than 30 seconds) which in certain circumstances can be life threatening. All three were previously found to have scarring in their hearts.
Ongoing research is expanding this study into female endurance athletes, to investigate whether they also experience scarring and an increased risk of abnormal heart rhythms.
"It might well have saved my life" - Brian's story
Brian Cookson OBE was one of the 106 men involved in the trial. The 74-year-old grandad from Whalley, Lancashire has dedicated his life to cycling, both as a competitor and as President of British Cycling and Union Cycliste Internationale – cycling's world governing body.
On retirement, Brian began training and competing more regularly. Then in May 2024, Brian was training at Manchester Velodrome when he started feeling unwell.
"I was pushing it a little bit on the track, but not absolutely full gas, as we say in cycling," Brian says. "I came off and looked at my sports watch which read 'new heart rate record – 238bpm' and I thought 'oh, that's not good'. And it wasn't going down."
It took around 15 minutes for Brian's heart rate to return to normal. Soon afterwards, he contacted the team leading the study about what had happened.
As part of the trial, Brian had been fitted with an implantable loop recorder, a small device about half the size of a biro pen placed under the skin of his chest to record his heart rhythm. That meant that every heartbeat he had – including at the velodrome – was recorded, so the researchers were able to see exactly what had happened for themselves.
"The next day, I got a call. They said, 'Stop riding your bike, don't do anything more strenuous than walking until we can get you in here because we think you need an ICD [implantable cardioverter defibrillator].'"
Brian had had an episode of ventricular tachycardia and in August, he was fitted with an ICD - a small device which will shock the heart if it goes into an abnormal rhythm.
Heart problems can affect anyone so I would say to others like me, don't take your health for granted. If you get the opportunity for a health check, take it and if you have any symptoms, rest and get them checked out.
Brian is cycling again but has agreed with his doctors that he won't push himself as hard. "I keep a closer eye on my heart rate now and if I'm getting to 150bpm I'll start backing off," he says. "We've all agreed that I can't be breathing through my ears anymore, as we'd say in cycling.
"I'm so grateful to have been part of this study. It might well have saved my life," Brian reflects. "Without it, I might have carried on pushing myself until something more serious happened.
"I don't think people should be put off by this – if I could go back to when I first got into cycling, I wouldn't do anything differently. I still have all the health benefits that a lifetime of staying active brings. Heart problems can affect anyone so I would say to others like me, don't take your health for granted. If you get the opportunity for a health check, take it and if you have any symptoms, rest and get them checked out.
"Everyone can benefit from exercise, and taking part in competitive sport is fun. We've been able to take action to manage my condition, and I'm still cycling regularly. The way I put it is, maybe it's time I started acting just a little bit more like I'm 70-something, rather than like I'm 20-something. One thing's for sure – I won't be stopping cycling any time soon!"
Dr Sonya Babu-Narayan, Clinical Director at the British Heart Foundation and consultant cardiologist, said: "There's no doubt that exercise is good for our hearts. It helps to reduce blood pressure and cholesterol, manage our weight, and it boosts our mental health. But in some veteran male athletes, this early research suggests that intense exercise over many years may have affected their heart health.
"More research in veteran endurance athletes – both in men and women – will be needed to identify the small number of people who have the kind of heart scarring, together with other risk factors, that mean their life could be saved by having an implantable defibrillator."
The VENTOUX study (VENTricular arrhythmia and cardiac fibrOsis in endUrance eXperienced athletes) is named after Mont Ventoux, one of the most famous mountain climbs cycled in the Tour de France. This year, the professional cyclists will race to its summit on 22 July 2025.
This research is supported by the National Institute for Health and Care Research (NIHR) Leeds Biomedical Research Centre and Leeds Clinical Research Facility.
