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Alterations to heart wall thickness seen in sports participants: Influence of ethnicity

In a previous blog we discussed how enlarged them main pump chamber of the heart (the 'left ventricle', LV) can be seen to be enlarged and the pump function of the heart (called the 'ejection fraction', EF) can be mildly reduced as a result of physiological adaptation certain sports (mainly endurance sports). In addition to these changes in left ventricular diameter and ejection fraction, studies have demonstrated physiological changes in athletes left ventricular wall thickness (LVWT).

These changes in adult wall thickness can be affected by gender and ethnicity. Whilst large cohort studies have shown that athletes exhibit 15-20% increase in septal and posterior wall thickness when compared to healthy controls, in only a minority of athletes the wall thickness may exceed the conventionally accepted normal limit of 12mm, entering an overlap zone that can be seen in patients with a morphological pathological process called hypertrophic cardiomyopathy (HCM). In two large European studies 1.5%-1.7% of athletes had LVWT of >12mm with a maximum LVWT of 16mm. Athletes with LVWT >12mm are almost exclusively male. It is very rare for white female athletes to demonstrate LVWT >11mm as a response to physiological adaptation to exercise.

Studies have shown that black male athletes have a greater mean maximal wall thickness than white athletes (11.3mm vs. 10mm) with a greater proportion of black athletes than white athletes having a LVWT >12mm (18% black male athletes vs. 4% white male athletes) and >15mm (3% black male athletes vs. 0% white male athletes). It is rare to have physiological hypertrophy causing LVWT >16mm irrespective of ethnicity.

A similar finding of increased LVWT is seen in black female athletes when compared to white female athletes. Studies have demonstrated LVWT > 11mm in 3% of black female athletes vs. none of white female athletes (with no female athlete exceeding a LVWT of 13mm).

Similar to adults, adolescent athletes demonstrate a degree of adaptation to exercise. In a study of predominantly white adolescent athletes (range 14-18 years, 98% white), athletes had greater absolute LVWT compared to sedentary controls (9.5±1.7 mm vs. 8.4±1.4 mm; p<0.0001). All female athletes had a LVWT ≤11mm and only 0.4% of male athletes had an absolute LVWT >12mm, maximum 14mm. In a study of adolescents of different ethnicities, 5.5% of 14-16 year old black athletes exhibited a LVWT >12mm compared to none of the white athletes with recorded LVWT of up to 15mm.

In summary, left ventricular wall thickness is usually within normal limits but can be increased in a minority of athletes. This scenario is seen more commonly seen in males rather than females and in black athletes. It is important that if heart wall thickness is increased that individuals are fully assessed by a physician with experience in sports cardiology in order to try to differentiate whether this is due to physiological adaption or a pathological process.

I drew the flow chart below which helps to identify ways to distinguish whether heart wall thickening is due to a physiological process or pathological adaptation. This was part of a journal publication for which I was lead author, published last year in Current Treatment Options In Cardiovascular Medicine entitled 'Left Ventricular Hypertrophy In Athletes: Differentiating Physiology From Pathology'.

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