Grey zone between physiological adaptation and cardiac disease in athletes: state of knowledge and future perspectives

Athletes often exhibit a plethora of physiological changes that, on occasion, overlap with cardiac diseases that may cause sudden cardiac death (SCD). Several factors, such as age, sex and ethnicity, influence cardiac adaptation to exercise in athletes. The differential diagnosis between 'athlete's heart' and heart disease may be challenging. However, a careful and learnt interpretation of clinical findings and use of a broad diagnostic armamentarium often lead to an appropriate differential diagnosis. Sometimes, features observed in athletes falling in the grey area are isolated and of equivocal significance. These cases require ongoing surveillance, especially in very young individuals, where clinical expression of a cardiac disease may be partial, with revelation of full phenotypic manifestations at an older age. This review article focuses on the differentiation between physiological cardiac changes as a result of intense exercise and cardiac conditions at risk of SCD. We will discuss the diagnostic challenges, tackling the 'grey zone', the benefits and pitfalls of the currently available diagnostic tests and the future perspectives in this rapidly developing field.