Are triathletes at risk of myocardial fibrosis? New evidence has shown triathletes may be at increased risk of myocardial fibrosis (MF); a nasty condition where scarred or fibrotic tissue replaces heart muscle cells. A recent study out of Germany looked at 55 men and 30 women and found a clear link between MF and male triathletes.
While the study has limitations, it did make us wonder about how triathlon can adversely affect the heart.
Why you should care about myocardial fibrosis
‘Myocardial fibrosis (MF) is a common phenomenon in the late stages of diverse cardiac diseases and is a predictive factor for sudden cardiac death,’ says an article by Freek et al in 2016.
So in other words, MF can kill you. But how?
Myocardial fibrosis can cause arrhythmia; a sometimes fatal abnormal heartbeat pattern. Whether the arrhythmia has caused your heart to beat too fast, too slow, too irregularly or too early; if you suffer from arrhythmia, you’re in trouble.
How does this study say triathlon causes myocardial fibrosis?
During high intensity, endurance events, systolic blood pressure increases. This increase may result in a greater myocardial mass, which may put an athlete at a higher risk of myocarditis; inflammation of the heart muscle.
If the heart becomes inflamed due to exercise often enough, it is believed it can lead to the heart replacing muscle with fibrotic tissue that isn’t as spongy, responsive or powerful as normal heart tissue known as myocardial fibrosis.
How did they prove myocardial fibrosis?
The study used a contrast and examined it under MRI. Evidence of myocardial fibrosis was apparent in the left ventricle — the heart’s main pumping chamber — in 10 of 55 of the men, or 18 percent, but in none of the women.
Why don’t the women have myocardial fibrosis?
“Comparison of the sport’s history showed that females had a tendency to complete shorter distances compared to male triathletes. This supports the concept that blood pressure and race distances could have an impact on the formation of myocardial fibrosis,” said study leader Dr Starekova.
Sorry Dr, but we all know this isn’t true for female Ironman competitors who compete and train over massive distances. This seems to point to the fact the scientists really don’t know why more men were at risk than women.
Has myocardial fibrosis caused death in endurance athletes before?
Yes. One study showed the results of a post-mortem cardiac exam performed on a marathon runner who died suddenly. It found his death was caused by enlargement of his left ventricle and myocardial fibrosis. In this case, it was a series of fatal arrhythmias or irregular heartbeats that caused the sudden death of the athlete.
“Life-long, repetitive bouts of arduous physical activity resulted in the fibrous replacement of the myocardium, causing a pathological substrate for the propagation of fatal arrhythmias,” was the official summary.
In other words? The marathon runner’s heart had become stiffer, which lead to an irregular heartbeat that caused death.
Another study looked at the hearts of 51 healthy male Ironman athletes to see if any changes occurred. They found:
- Those who trained at higher volumes had larger left ventricles
- Those with significantly larger left ventricles (chambers of the heart) also had greater blood pressure at an aerobic or anaerobic threshold.
They recommended these athletes (who experienced higher blood pressure) should undertake interventions to prevent stiffening of the heart or MF.
Does triathlon definitely cause myocardial fibrosis?
No. The study only looked at 85 subjects which is definitely not enough to make solid conclusions, especially considering contrasting evidence.
A number of studies have disputed the link between triathlon and MF. Leschik and Spelsberg said, “The idea of exercise-induced cardiac disease was suggested by Heidbüchel and LaGerche but the data are controversial.”
In some athletes, studies have found left ventricular hypertrophy and myocardial fibrosis which causes arrhythmia, but in many others, these abnormalities were absent.
Should you be worried about your heart?
Despite all studies concluding further research is needed, we do know a few things:
- Triathlon can cause changes in your heart and CAN cause MF
- Triathlon can lead to cardiac arrest in men > 60 years old
- Risk probability in ambitious triathletes >35 years old is high, so cardiac testing may be important
- Those most at risk of developing cardiac changes (men training at large volumes) should be identified early through testing
- Triathletes experience significant peaks in blood pressure and changes to their left ventricles are recommended to undertake a prevention program
- Ideal training dosages that prevent cardiac changes from occurring is not yet known, but there may be a tipping point of systolic blood pressure that leads to MF
While the new study out of Germany does have some compelling evidence, the study group was small, and there is no cause for alarm. The recommendations that young pros should be screened may be of value though and could be something handy to remember for coaches of young, keen athletes.