[Heart enlargement in an athlete--a diagnostic challenge].

Endurance training can result in an enlargement of the heart. These athlete's hearts are rarer than generally assumed. Pathological causes, resulting in an eccentric hypertrophy, have to be considered. We report on a 32 year old athlete performing approximately 10 hours of endurance training weekly. He consulted a physician because of a drop in performance. The eccentric left ventricular hypertrophy, diagnosed by means of echocardiography, was not interpreted as a solely physiological cardiac adaptation because the ejection fraction did not increase during exercise (stress-echocardiography), the left ventricular diastolic function (maximum E/A-ratio) was impaired at rest, and the ergometric performance was reduced in comparison to the heart size. The invasive diagnostics including myocardial biopsy demonstrate histologically a focal fibrosis as the result of former myocarditis. The fibrosis was possibly involved in the genesis of the eccentric hypertrophy based on structural dilatation through a preferably mesenchymal lesion. It remains open whether the long-term endurance training had forced the dilatation. This case demonstrates that pathological causes must be excluded if in athletes an enlarged heart does not concur together with a clearly increased ergometric performance. Stress-echocardiography and endomyocardial biopsy can considerably contribute to the differential diagnosis between physiological and pathological cardiac hypertrophy.