How does repeated exercise impact your heart? Tom Crawford spoke to St George’s University of London heart specialist Sanjay Sharma. He’s the medical director for the London Marathon and also studies how the heart copies with the demands of professional sport…
Sanjay - I’ve got a very exciting job. I look after the hearts of football players, tennis players, and most individuals involved with the English Institute of Sport. Clearly, these people push themselves to their limits on a regular basis and exercise probably 10 to 15 times more than the current recommendations and, by doing so, they do develop a constellation of changes within the heart that we sometimes call the athlete's heart. Specifically this involves a 10 to 20% increase in the thickness of the heart muscle and around a 10% increase in the cavities of the heart. The heart relaxes much, much more briskly than a normal heart and contracts more avidly than a normal heart during exercise. These people, because their hearts are very, very big they have quite a slow heart rate at rest because the heart doesn’t have to do very much to pump five litres of blood round the body.
Tom - I’m glad that’s true because I’ve heard that quite a bit and I’ve always wondered whether or not it’s a myth, but as an athlete you generally do have a bigger more powerful heart?
Sanjay - Oh yes you have to. If you think about the fact that whilst we’re sitting down here we are pumping 5 litres of blood round the body. Now when someone exercises that goes up to between 25 to 30 litres of blood round the body. That’s okay if you’re running for a bus and it’s a short dash that’s going to take 20 or 30 seconds, but when you’re running for 2 or 3 hours and you’ve got to maintain that kind of cardiac output, the only way you can do that is with the heart growing in size.
Tom - In that sense the heart really is like any other muscle in your body that by training a particular muscle it grows larger and the heart is no different?
Sanjay - Absolutely. People who train intensively at least 4 hours a week develop some of the changes I’ve just been talking about, and if they stop training things go back to normal.
Chris - The extreme physical demands that sports professionals place upon themselves can have drastic consequences if their heart isn’t working properly. There have been a few recent examples of young athletes and footballers suffering sudden death as a result of an underlying heart problem; sadly these can remain undiagnosed until it is too late. Dr Amanda Varnava is a cardiologist at Hammersmith Hospital, in London...
Amanda - About 1 in 300 of the population will harbour an inherited cardiac condition or a so-called sudden death syndrome. These can be structural problems of the heart where the heart muscle thickens, or the heart enlarges, or electrical problems of the heart where the heart’s structurally normal and the electricity becomes abnormal under certain conditions, particularly under sports and exercise.
Chris - That’s quite high - 1 in 300?
Amanda - Many of these conditions and individual can live with until they’re well into their 90s and not even discover it nor, indeed, get significant symptoms. But certain individual will be at risk with our without exercise - these high risk individuals - and as a cardiologist we see the individuals that we make this diagnosis in and assess whether they’re at high risk or not and counsel them and treat them appropriately. However, an individual who harbours one of these conditions will increase their risk of sudden death by up to 3 or 4 fold by competitive sports, and that’s the issue that we’re dealing with here.
Chris - Do they come and see you or is there a sort of framework for people who are sports professionals, because there is that 1 in 300 risk, are they referred to you just for screening?
Amanda - Individuals come through various mechanisms. One, of course, is if they have symptoms, the second is if they have family history. Certain sports disciplines screen their sportsmen, particularly in football, where the FA have been leaders in this field perhaps because they do attract more money and therefore have the resources to offer. But they certainly are the standard bearers for doing and screening, and by doing a questionnaire looking at family history and symptoms. By doing an ECG and echo we’re able to tease out those footballers who harbour one of these conditions.
Chris - You made an interesting point there because you said “sportsmen,” and football has been very much something that men have participated in for a really long time. Is there very much data on sportswomen?
Amanda - There is data. Reassuringly, as a woman, we have a far less chance of sudden death even with one of these conditions. So, overall, perhaps the risk of sudden death in a female athlete is perhaps up to ten times less than it is for a male athlete - it’s markedly reduced.
Chris - Do we know why?
Amanda - I think that men adapt to exercise in different ways, both structurally and electrically. There are certain groups of men, and certain ethnicities that for various genetic reasons will be at greater risk with a given condition. It is also the case that the sudden death that occurs in females is generally perhaps for the electrical problems and less the structural problems. So there are different conditions that affect athletes, male or female, differently and their risk accordingly.
Chris - What about ethnicity as well because what we’re also seeing is when you go the Olympics people often say that this is in fact a trial of a person’s genetics isn’t it? it’s how genetically they’re set up because it’s always stereotypically can’t be beaten on the marathon, they’ve got the perfect genetic and evolutionary history for that but they’re not terribly good at swimming on the other hand so there’s certainly a strong genetic element. To what extent does ethnicity put you at risk of these disorders?
Amanda - Ethnicity plays a huge role in both the way that the heart adapts in a normal physiological way to exercise, but also according to ethnicity your risk will change, so black athletes, unfortunately, have up to 5 fold greater risk of sudden death due to these concealed conditions than their white peers. And, again, the exact reason for that is unknown - genetic variabilities and genetic risk markers are probably to play