Abstract des Autors

Serum cardiac troponin T (TnT) measurements have been used as a very sensitive and specific method for the detection of myocardial damage. Recently some authors suggested that small areas of myocardial necrosis, symptomless and undetectable electrocardiographiycally nor by usual enzymatic indicators, can be caused by microvascular spasm, related to high catecholamine concentrations and other mechanisms, following extraordinary unremitting endurance exercises or due to the cumulative effect of several endurance events. It was this last suggestion which prompted us to use TnT measurement in order to investigate 25 top cyclists (aged 24-36; mean 29), who took part in the 77th Giro d'Italia: 22 laps in 22 consecutive days for a total of 3.740 kms, including 36 mountain passes (a total difference altitude of 25,985 m). Blood samples were obtained the day before the start of this multi-day event and once a week until the end of the competition. We measured hematocrit, TnT, creatine kinase isoenzyme MB, serum indicators of muscle damage (myoglobin, lactic dehydrogenase, totale creatine kinase) for the possible cross-reactivity between myocardial and released by skeletal muscle TnT, plasmatic and intraerythrocytic potassium and magnesium because of their role in determining myocardial injury, iron and ferritin, because they are involved in the oxidative stress. Hematocrit, iron and ferritin did not change during the race. Plasmatic and intraerythrocytic potassium and magnesium showed little variations. While serum indicators of muscle damage increased significantly in the following controls, compared with their values at the beginning of the competition, creatine kinase isoenzyme MB did not change. Finally TnT was present only in the serum of 5 athletes, in some of them repeatedly (mean+/-SD; 0.06+/-0.03 micro-g/l), but always below of the cut off values (0.1 micro-g/l), considered as indicating myocardial ischemia. We can conclude that heavy endurance exercises, repeated daily for 22 days, as in our experience, do not seem able to produce, in top athletes, permanent heart damage. Verf.-Referat