The Fabulously Fit vs the Fatally Flawed: the difficulties of identifying athletes at risk of sudden death

Sports and exercise have huge health, economic and psychological benefits. However data clearly demonstrates up to a four-fold increase in the incidence of sudden death in athletes. Distinguishing between normal heart adaptations and those who are at genuine risk of sudden death is an extremely fine line to tread. Dr Amanda Varnava, a cardiologist who sits on the Football Associations (FA) expert panel, explains the challenges and why it’s so important we get these distinctions right.

A difficult distinction

Exercise has marked health benefits, not just on the cardiovascular system but on someone’s mental wellbeing too. However, individuals who undertake high level, competitive sports are at a 3–4 fold increased risk of sudden cardiac death than their peers.

This apparent paradox relates to the increased risk that intense exercise can cause in an otherwise healthy individual, harbouring a concealed heart condition. This issue is further confused by the problems of trying to distinguish between normal, expected changes of the heart in response to vigorous exercise, and inherited heart conditions that may predispose someone to sudden death.

Aerobic adaptation or cause for concern

The normal heart undergoes physiological adaptations to the increased aerobic demands of exercise. These include electrical changes which manifest in the waves and intervals that can be seen on an Electrocardiogram (ECG) as well as structural changes such as mild enlargement of the ventricles and heart muscle thickening (allowing more blood to enter the heart and be pumped more strongly around the body). The difficulty lies in differentiating these benign changes, which can be expected in a keen athlete, from the more sinister structural changes caused by an inherited cardiac condition.

Explaining the overlap

An example of the issues involved in distinguishing the fabulously fit (normal athlete’s heart) from the fatally flawed (an individual with a concealed inherited heart condition) are illustrated in hypertrophic cardiomyopathy (HCM). HCM is the most common cause of sudden death in young athletes. The condition is caused by a thickening of the heart muscle due to a genetic defect. It is not uncommon, and is found in 1 in 500 of the population.

Many individuals have no symptoms, and indeed are able to perform high level sports to a professional or Olympic level without being aware of their underlying cardiac condition. Equally, all athletes can develop a degree of increased heart muscle mass in response to competitive level sports (at least 6 hours of exercise a week). The degree of benign thickening in an athlete’s heart muscle varies according to gender and ethnicity and can reach a level that overlaps with that found in patients with HCM. Whilst mild thickening in response to exercise does not represent any form of pathology or risk in a healthy heart, even mild thickening as a result of HCM may represent a significant risk, especially in an athlete whose regime places greater stress on the heart.

What’s at stake

Distinguishing between the two situations is therefore of the utmost importance in order to avoid either erroneously labelling an athlete with a heart condition that could potentially end their sports career, or missing an inherited heart condition and thus the opportunity to protect against a sudden death. Whilst the former is clearly to be avoided as far as possible, it should be noted that screening athletes and advising those with an inherited cardiac condition not to play competitive sports has been found in an Italian study to reduce sudden death by 90%.

In order to help distinguish between an athlete’s heart and an abnormal result there are now international guidelines on the ECG changes that are deemed within normal limits for an athlete, versus those considered unrelated to training and in need of further investigations.

These guidelines have reduced the “false positive” interpretation of an athlete’s ECG, thus avoiding unnecessary further investigations, whilst identifying almost all serious cardiac conditions. Alongside these guidelines, there is a growing body of literature on the ECG and structural findings in athletes that allow us, with increasing accuracy, to distinguish between the fabulously fit and the fatally flawed.

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