Geert Kleinnibbelink

Chapter 2 36 ABSTRACT Background . Acute exercise promotes transient exercise-induced cardiac fatigue (EICF), which affects the right ventricle (RV) and to a lesser extent the left ventricle (LV). Hypoxic exposure induces an additional increase in RV afterload. Therefore, exercise in hypoxia may differently affect both ventricles. The aim of this study was to investigate the acute effects of a bout of high-intensity exercise under hypoxia versus normoxia in healthy individuals on right- and left-sided cardiac function and mechanics. Methods . 21 healthy individuals (22.2±0.6 years, fourteen men) performed a 45-minute high-intensity running exercise, under hypoxia (fraction of inspired oxygen [FiO 2 ] 14.5%) and normoxia (FiO 2 20.9%) in a randomized order. Pre- and post-exercise echocardiography, at rest and during low-to-moderate intensity recumbent exercise (‘stress’), was performed to assess RV and LV cardiac function and mechanics. RV structure, function and mechanics were assessed using conventional 2D, Doppler, tissue Doppler, speckle tracking echocardiography and novel strain-area loops. Results . Indices for RV systolic function (RVFAC, TAPSE, RVS’, RV free wall strain) as well as LV function (LV ejection fraction, LV global longitudinal strain)) significantly reduced after high-intensity running exercise (p < 0.01). These exercise-induced changes were more pronounced when echocardiography was examined during stress compared to baseline. These responses in RV or LV were not altered under hypoxia (p > 0.05). Conclusion . There was no impact of hypoxia on the magnitude of EICF in the RV and LV after a bout of 45-minute high-intensity exercise. This finding suggests that any potential increase in loading conditions does not automatically exacerbate EICF in this setting.