Elite Soccer Players Have Big Hearts and That's Okay

Debra L. Beck

December 18, 2020

Elite American soccer players have, on average, larger, thicker, and heavier hearts than the general population, according to a new study that provides clinicians with normative echocardiogram and electrocardiogram (ECG) cutoffs to use when assessing the heart health of competitive athletes.

To provide these age- and sex-specific reference values, a team from Massachusetts General Hospital, Boston, led by Timothy W. Churchill, MD, and Aaron L. Baggish, MD, analyzed data from 122 female and 116 male soccer players from the American national teams preparing for World Cup play and undergoing FIFA-mandated preparticipation screening.

The athletes frequently exceeded normal echocardiographic ranges for left ventricular (LV) mass, volume, and wall thickness — structural cardiac parameters responsive to exercise-induced remodeling — but with none showing pathologic findings that might indicate the need to restrict their participation in the sport.

Almost one-third (30%) of female athletes and 41% of male athletes exceeded the American Society of Echocardiography's upper limit of normal for LV wall thickness, with a measure greater than12 mm seen in 12% of men and 1% of women.

The majority (51% of females and 59% of males) exceeded normal ranges for body surface area-indexed LV mass, with 77% and 68%, respectively, having LV volumes above the normal range.

Baggish stressed in an interview, however, that these data tell a story about healthy hearts, not at-risk hearts.

"These are the healthiest, highest-performing elite soccer players that we have in the United States, and this is really a look at how adaptive the heart can be, how much it can grow and change in size, shape, structure, and function in response to sport," said Baggish.

The mean age of screened athletes was 20 years (range, 15 to 40 years). The majority of the female players were White (71%), whereas the male players were more evenly divided between Black (34%), Hispanic (33%), and White (32%).

Screening was performed at US Soccer training sites by experienced clinicians affiliated with the Massachusetts General Hospital cardiovascular performance program.

Interestingly, the study debunks the idea that women, on average, have smaller chamber sizes. "When we did body size correction, the men and women actually looked pretty similar with respect to their ability to adapt to strenuous exercise," noted Baggish.

They did see, however, that women were more likely than men to have abnormal ECG findings. Male athletes showed a higher prevalence of "normal" training-related ECG findings, whereas female athletes were more likely to have abnormal ECG patterns (11.5% vs 0.0% in the male cohort), most often pathologic T-wave inversions (TWI) confined to the anterior precordial lead distribution.

"This is important because ECGs are the most common screening tool used and we wanted to alert people to the fact that these women who showed some abnormalities on ECG went on to have a total healthy-looking echo, so a false-positive ECG is something to consider," said Baggish.

This excess in anterior TWIs has been seen in previous studies and is thought to be benign, although the mechanism remains unclear. Four of the nine female athletes with abnormal ECG findings on initial evaluation had normalized on repeat testing 2 to 4 years later. Serial data were available in only a subset of athletes.

Clarity Needed After COVID

The data, published recently in JAMA Cardiology, are particularly valuable these days given concern over the effects of COVID-19 on the heart and return-to-play recommendations.

"Athletes who have had COVID are being sent for echocardiograms before they can return to play to check for COVID-induced heart disease — which is real — but what we're seeing is that there's confusion out there in terms of what is a COVID-related abnormality and what is a normal, adapted athletic heart," said Baggish.

"In this paper, we provide a dataset of normal values — generated before COVID was on anyone's radar — to let cardiologists know what's 'big good' and not 'big bad'."

More Sport-Specific Data Needed

"Although these numbers are still small, this dataset is an important step forward in our understanding of athletic adaptations," said Matthew Martinez, MD, in an email. "Many factors impact physiologic athletic changes, and the study aids in our understanding of gender- and sport-specific changes in athletes."

Martinez, who is the director of sports cardiology at Atlantic Health-Morristown Medical Center and the Gagnon Cardiovascular Institute, Morristown, New Jersey, and the chair of Sports and Exercise Cardiology Section Leadership Council for the American College of Cardiology, noted the relatively young mean age of screened athletes.

"The data represent collegiate-age athletes with some older groups mixed in, but it does not represent older established elite athlete changes," he said.

Mean age was 21 years in the female players but only 18 years in the males because the men's senior national team failed to qualify for the World Cup during the study period and was therefore not screened. The authors acknowledge the "dearth of older men in the cohort."

There is, overall, little age-, sport-, and sex-specific normative data for differentiating training-related cardiovascular adaptations from potentially pathologic phenotypes, write the authors.

It exists for men playing in the National Football League and for both sexes participating in the National Basketball Association, but most other studies have mixed the sports and focused mainly on men. That said, Baggish does not consider these data to be applicable to all elite athletes.

"Soccer is kind of in a league of its own with respect to the mixed amount of explosive or resistant and aerobic work that these athletes have to do, and also it's the most popular sport in the world, so we really wanted to focus on them," said Baggish.

Although the findings are perhaps applicable to athletes from other team sports characterized by explosive spurts of high-intensity activity — like hockey, lacrosse, and field hockey — he would not suggest they be applied to, say, long-distance runners, cyclists, or other sports that require a similar type of aerobic output.

Baggish reported no relevant conflict of interest. Martinez is league cardiologist for Major League Soccer.

JAMA Cardiol. Published online December 2, 2020. Full text

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