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.
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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 than 12 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.
Dr. 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 Dr. Baggish.
The mean age of screened athletes was 20 years (range, 15-40 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 U.S. 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 Dr. 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 Dr. 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 2-4 years later. Serial data were available in only a subset of athletes.