Schlüsselwort: horse riding

Speckle tracking, heart rate variability and blood pressure measurements in endurance horses The previous study investigated, whether and which changes of the heart rate variability, of the myocardial function via measurement with speckle tracking and in blood pressure exist due to strenuous endurance exercise during an endurance ride. The participating horses were investigated before and after the race as well as after three days after finishing the race. We compared also the measurements of the horses, who completed the race successfully and the horses, who failed to complete the race. The data were collected from 29 participating horses at three different long-distance endurance events lasting from 68 - 162 km. An echocardiography, a resting ecg and noninvasive blood pressure measurement with highdefinition oscillometry advice were performed. B-mode, M-mode and offline speckle tracking analyses in the short and long axis view were carried out. In addition, the blood pressure was measured at mandated stops between the loops. The standard echocardiographic examinations of the B-mode at the measurements after the endurance ride showed a statistically significant larger area of the left atrium at all three measurement points during the cardiac cycle compared to the values before the endurance ride. In the examination of myocardial contractility using speckle tracking echocardiography statistically significant lower values were found in the early diastolic measurements after the endurance ride, which suggest the presence of diastolic dysfunction in the sense of an “exercise-induced cardiac fatigue”. However, the systolic values after the ride were initially less clear. The comparison of the values after the endurance ride between the groups “lameness” and “metabolic” did not show a clear tendency either. After three days, a marked reduction in the systolic values of speckle tracking and a persistence or even an exceed of the diastolic values could be demonstrated. In contrast, the standard echocardiographic measurements returned to or even exceeded the baseline three days after the endurance race. Thus, it could be demonstrated that Speckle Tracking echocardiography allows a more accurate measurement of myocardial contractility after strenuous endurance exercise. Overall, the heart rate variability showed a significant decrease in the parasympathetic parameters after the endurance ride. This showed a marked influence of strenuous exercise on heart rate variability with a predominance of the sympathetic nervous system at a disadvantage of the parasympathetic nervous system. After three days, the heart rate variability also reached or exceeded the previous values measured before the endurance ride. In contrast, the blood pressure measurements showed only minor changes, with systolic blood pressure being higher before the race than afterwards. The diastolic blood pressure showed exactly the opposite effect. Overall, the results of the present study indicate the presence of a diastolic dysfunction after long-term strenuous exercise, which could be determined by standard echocardiographic measurements and Speckle Tracking echocardiography. Systolic dysfunction could only be detected after three days by using Speckle Tracking echocardiography, but not by standard echocardiographic measurements. Heart rate variability also proved to be a useful technique to detect changes due to endurance exercise. Blood pressure measurement provided only little further insight. All three methods proved to be useless to predict whether a horse would finish the endurance race successfully or retire early.