Sympathetic cardiovascular control during orthostatic stress and isometric exercise in adolescent chronic fatigue syndrome
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The chronic fatigue syndrome (CFS) has been shown to be associated with orthostatic intolerance and cardiovascular dysregulation. We investigated the cardiovascular responses to combined orthostatic stress and isometric exercise in adolescents with CFS. We included a consecutive sample of 15 adolescents 12–18 years old with CFS diagnosed according to a thorough and standardized set of investigations, and a volunteer sample of 56 healthy control subjects of equal sex and age distribution. Heart rate, systolic, mean and diastolic blood pressure, stroke index, and total peripheral resistance index were non-invasively recorded during lower body negative pressure (LBNP) combined with two consecutive periods of handgrip. In addition, we measured baseline plasma catecholamines, and recorded symptoms. At rest, CFS patients had higher heart rate, diastolic blood pressure, plasma norepinephrine (P < 0.01), mean blood pressure and plasma epinephrine (P < 0.05) than controls. During LBNP, CFS patients had a greater increase in heart rate, diastolic blood pressure, mean blood pressure (P < 0.05) and total peripheral resistance index (n.s.) than controls. During handgrip, CFS patients had a smaller increase in heart rate, diastolic blood pressure (P < 0.05), mean blood pressure and total peripheral resistance index (n.s.) than controls. Our results indicate that adolescents with CFS have increased sympathetic activity at rest with exaggerated cardiovascular response to orthostatic stress, but attenuated cardiovascular response when performing isometric exercise during orthostatic stress. This suggests that CFS might be causally related to sympathetic dysfunction.
KeywordsSympathetic nervous system Adolescents Chronic fatigue syndrome Hemodynamics Catecholamines
We thank Kristin Godang, Department of Endocrinology, Rikshospitalet-Radiumhospitalet Medical Centre, Oslo, Norway for performing the catecholamine assays; Elisabeth Getz, Department of Pediatrics, Rikshospitalet-Radiumhospitalet Medical Centre, Oslo, Norway and Torun Flatebø, Department of Physiology, University of Oslo, Norway, for technical assistance during the experiments; and Helene Gjone, Rikshospitalet-Radiumhospitalet Medical Centre, Oslo, Norway, for clinical assessment of the CFS patients.
Financial support: Vegard Bruun Wyller has received a grant from the University of Oslo.
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