Impairment of vascular endothelial function and left ventricular filling -Association with the severity of apnea-induced hypoxemia during sleep

Study objectives: To investigate whether a dose-effect relationship exists between the severity of obstructive sleep apnea (OSA) and subclinical indic ators of myocardial or vascular dysfunction. Design: Cross-sectional study using correlation analysis. Participants: Twenty subjects referred to our sleep laboratory for screenin g or therapy of OSA but without regular medication and without known cardio vascular disease. Measurements: Severity of OSA was quantified by polysomnography. Moreover, nocturnal excretion of norepinephrine was determined. Left ventricular (LV) myocardial function was assessed with Doppler echocardiography. Using ultr asonographic measurements, endothelium-dependent and endothelium-independen t conduit artery dilation were measured as now-mediated and glyceryltrinitr ate-induced changes in brachial artery diameter. Results: Worsening nocturnal hypoxemia, measured as nocturnal oxygen satura tion nadir or percentage of sleep time spent in hypoxemia (< 90% hemoglobin oxygen saturation), predicted increased interventricular septum thickness (corrected for age and body mass index), prolonged isovolumetric relaxation time, decreased ratio between peak early and late mitral now velocities, a s well as reduced endothelium-dependent dilatory capacity of the brachial a rtery tall relationships corrected for cofactor age and with p < 0.05) were observed, Associations between these cardiovascular function markers and n octurnal excretion of norepinephrine followed the same trend, but relations with interventricular septum thickness and flow-mediated artery dilation m issed significance (p = 0.064 and p = 0.081, respectively). LV posterior wa ll thickness, measures of LV systolic function, early mitral now decelerati on time, and endothelium-independent artery dilation were not significantly related to the degree of nocturnal hypoxemia or norepinephrine excretion. None of the correlations with apnea-hypopnea index were statistically signi ficant, Conclusions: The severity of apnea-related hypoxemia is associated with a g radual deterioration of LV diastolic function as well as large-artery endot helial function.