Geert Kleinnibbelink

Exercise-Induced Cardiac Function under Hypoxia 2 45 repeated measurements were performed to test the acute effects of a bout of 45-minutes high-intensity exercise on cardiac function and mechanics (Exercise), and whether this effect was influenced when echocardiography was performed at rest or during stress (Exercise*Stress). Furthermore, linear mixedmodels were used to test the effect of hypoxia versus normoxia (Hypoxia) and the effect of rest versus stress echocardiography (Stress) on cardiac structure and function. To examine our primary objective, linear mixed models analysis was used to examine whether hypoxia impacted the effect of exercise on cardiac function (Exercise*Hypoxia), and how this was affected by testing condition rest versus stress (Exercise*Hypoxia*Stress). For all tests, we assumed statistical significance at p < 0.05. RESULTS Both the right and left heart had normal geometry and all structural measurements were within normal ranges ( Table 2 ). There were no abnormal 12-lead ECG findings. Exercise characteristics. HR during exercise was matched between exercise under hypoxia and normoxia (172±1 bpm, 173±2 bpm respectively, p=0.23). Body mass loss (hypoxia -410±70g vs . normoxia -410±43g p=0.99) and water intake (hypoxia 373±60ml vs . normoxia 336±44ml, p=0.24) during exercise did not differ between testing sessions. Mean distance covered during exercise was significantly higher in normoxia (6,655±351m) compared to hypoxia (5,797±308m, p < 0.001), whilst there was no significant difference in subjective ratings of perceived exertion (RPE normoxia 12.5±0.3, RPE hypoxia 13.3±0.3; p=0.07). SpO 2 during exercise was significantly lower in hypoxia (82±0.8) compared to normoxia (95±0.4). Right ventricular structure, function and mechanics All RV structural, functional and mechanicals indices pre- and post- 45-minute high- intensity running exercise are displayed in Table 2 . Indices of RV systolic function (RVFAC, TAPSE, RVS’, RV freewall strain ( Figure3A )) significantly reduced following 45-minute high- intensity exercise (Exercise: p < 0.01). The decline in indices of RV function and mechanics after exercise were not different between rest and stress echocardiography, except for a more pronounced reduction in RV free wall strain during stress (Exercise*Stress: p=0.01, Table 2 , Figure 3A )). Related to the strain-area loop, following 45-minute high-intensity