When being too fit can be bad for you
Atrial fibrillation (AF) is five times more common in middle-aged men who are lifelong marathon runners, long-distance rowers and cyclists, compared with individuals of the same age who don't exercise as much. Roz Lewis finds out more.
CAN you ever be too fit? It may sound unlikely, but actually you can have too much of a good thing when it comes to exercise, especially if you are tall.
And that may be particularly true when it comes to the risk of developing a common heart condition: atrial fibrillation (AF), which affects around 1.5 million people in the UK. It is a heart rhythm disorder which makes the heart beat irregularly and often abnormally fast, causing dizziness, shortness of breath and tiredness.
Left untreated, the condition can cause heart failure and stroke. It is triggered by irregular electrical impulses in the upper chambers of the heart (the atria) which disturb its rhythm.
AF gets more common with age. Risk factors include high blood pressure, heart valve problems, blocked arteries, excessive alcohol consumption and an overactive thyroid, all of which make the heart work harder.
Mild to moderate exercise will help prevent AF by reducing obesity and blood pressure.
But AF is an astonishing five times more common in middle-aged men who are lifelong marathon runners, long-distance rowers and cyclists, compared with individuals of the same age who don't exercise as much. ‘The theory is that excessive exercise causes enlargement of the atria due to the stretching of the tissues as a result of exertion,' explains Sanjay Sharma, a professor of sports cardiology and inherited cardiac diseases at St George's University Hospitals NHS Foundation Trust in London.
‘There is also emerging evidence that repetitive stretching may cause inflammation or scarring of the atria, which predisposes a patient to AF.'
As an Olympic rowing champion, Greg Searle, now 48, prided himself on his fitness.
‘After the 2012 Olympics, I retired from competitive sport but kept my fitness ticking along, playing the odd game of tennis or five-a-side football and going for a run,' explains Greg, who is now a rowing commentator and performance coach. He lives in Buckinghamshire with his wife and two children.
But a year after picking up a bronze medal at London 2012, he says: ‘I found myself struggling during spinning classes, though I didn't really think anything of it at the time.'
A few months later, in October 2013, Greg was in Italy for a triathlon and underwent a routine medical before the race.
To his surprise, the doctor told him his heart rate was ‘jumping around all over the place' and he couldn't take part.
Suspecting AF, the doctor sent Greg to hospital where he was put on blood-thinning drugs to reduce the risk of stroke.
He was flown back to the UK and within weeks had tests at St ?George's Hospital – including one in which he had to walk on a treadmill.
‘My heart rate started low, at around 80 beats per minute, then climbed as my exertion levels increased, to 110, then 140. Next it shot up to 260 beats per minute,' says Greg.
‘I knew that reading was very high, above what was healthy. It was a really sad moment for me. I knew this was the end of my career as an athlete.'
Trudie Lobban, founder and chief executive officer of Arrhythmia Alliance and the AF Association, says AF can be easily detected with a simple pulse check.
But while some people are alerted to the condition by the heart fluttering or pounding for a few seconds or minutes at a time, others have no symptoms and, as a result, ‘it can be years before it is detected', she says.
The fitter you are, the more likely you are to feel symptoms, as it brings performance levels down, says Professor Sharma.
This is because AF is associated with a 25 per cent reduction in the amount of blood the heart can pump out.
‘When people exercise intensively, instead of the heart pumping five litres of blood per minute around the body, this increases to 25 to 30 litres per minute to provide sufficient oxygen and fuel to the muscles,' he says.
‘If you have AF, this dramatic increase in output may not be achievable, causing breathlessness or exhaustion.
‘In contrast, someone who just walks briskly or jogs slowly may not need such a high increase in cardiac output and may tolerate the AF much better. Anyone who does a form of endurance exercise who gets tightness in the chest or another symptom, such as a feeling of breathlessness disproportionate to the amount of exercise; dizziness during exertion; or an unusually fast or erratic heart rate should seek medical attention.'
To be at greater risk of exercise-related AF you need to have done 21 years of intensive exercise or 1,500 hours of competitive running, cycling or triathlon, he says.
But another factor is height. ‘Taller men generate higher blood pressure during exercise, which may load the heart more and put more stress on the atria,' adds Professor Sharma.
Since an untreated irregular heart rhythm raises the risk of a stroke, diagnosis is vital.
This is because AF allows blood to pool in the atria, which can lead to blood clots that may travel to the brain.
Anticoagulant drugs such as warfarin can help with this but do not treat the underlying problem, and while antiarrhythmic drugs such as flecainide can help restore the heart's normal rhythm, they don't work for all.
Another option includes cardio-version, a controlled electric shock treatment used to bring back a normal heart rhythm.
Alternatively, those with AF could try ablation therapy, where a small patch of heart tissue causing the electrical problem is destroyed.
Greg was recommended to try cardioversion. Treatment is needed sooner rather than later, as the longer you have AF, the less likely it is that the heart will retain a normal rhythm afterwards.
The day-case procedure, carried out under light sedation at St George's in 2014, was a success. ‘My heart was back to what it was,' says Greg.
Since his diagnosis, he has cut down his sporting activities; he plays golf, cricket and does the odd run, but doesn't overdo it.
‘AF definitely runs in my family,' he says. ‘My father, who is now in his 70s, was diagnosed with it in his 40s, and two of my paternal uncles have it, too.
‘Being male, 6ft?5in and a sportsman could be another reason why I developed it.
‘However, I loved my rowing career and wouldn't have changed it for a second.'
As an ambassador for the charity Access Sport, Greg encourages young and disabled people to be active.
‘If exercise were medicine it would be considered a wonder drug,' he says.
‘I wouldn't want anyone not to consider taking up rowing because of this issue. I certainly have no regrets.'
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