"Examination of the function of the myocardium and ”cardiac fatigue” of an eventing horse" Past studies in human medicine as in equestrian endurance have already shown that after intense exercise signs of “Exercise induced cardiac fatigue” can occur. These become apparent by a reduced diastolic and partially systolic strain and velocity of the myocardium. Until now there aren’t any studies which relate to Tissue Doppler Imaging and 2D-Speckle-Tracking in eventing sports. The goal of this study was to evaluate the changed function of the myocardium of 19 eventing horses by ultrasound 30 min after cross country, 24 hours later and during the season. Therefore, the horses were examined the morning before cross country or intense stress, 30 min after and 24 hours later. During the winter break before the season all horses were examined clinically plus with ultrasound and confirmed to have a sound heart. The examinations of this study were repeated multiple times during the competition season. The horses were scanned during competing on different eventing levels. The distance of exposure to stress was 3.000 - 5.000 m. The average speed was 400 - 570 m/min. The Tissue Doppler Imaging is a technique to evaluate the maximum velocity of the myocardium during systole and diastole. The results of the PW-TDI show a reduced diastolic function of the myocardium after exercise. Because these measurements can depend on preand afterload after intense stress it can be discussed that the results of this study show a cardiac fatigue. The different function of the myocardium can also be due to changes in preand afterload. Mostly there was a sufficient recovery after 24 hours. No systolic dysfunction could be determined. Over the months the velocity of the myocardium partly increased. Since these changes have already been detected on trained athletes, the changes can imply a training effect over the season. Via 2D-Spekle-Tracking it is possible to evaluate the local function of the myocardium or rather the deformation of the myocardium. An increased contractile function and relaxation of the myocardium was detected after intense stress. The results of Strain and Strain rate showed an increase after intense stress. The advantage of this technique is the load-independence. During the season Strain and Strain rate decreased. The decrease can be explained due to increased parasympathetic nervous system and the reduced sympathetic nervous system.This could be caused by the better training status of the horses over the season. Altogether, the results of this study show a reduced velocity of the myocardium while early diastole after intense stress. There is a reduced diastolic function of the myocardium directly after intense stress which was proven by PW-TDI. Considering differences in load the reduced diastolic function must be confirmed before speaking about definite cardiac fatigue. The horses were mostly recovered the next morning. Over the season the results can imply a Training effect. Both ultrasound techniques, PW-TDI and 2D-Speckle-Tracking, seem to be suitable techniques in equine cardiology to deal with performance diagnostics of horses.weiterlesen