WMH Behan, E Georgiades, Y Pitsiladis, N Macfarlane, J Wilson, L Kilduff & SA Ward
Department of Pathology and Centre for Exercise Science and Medicine,
Professor WMH Behan,
Department of Pathology,
Glasgow G11 6NT
Cardiovascular function and exercise intolerance in chronic fatigue syndrome
Chronic fatigue syndrome (CFS) is characterised by impaired skeletal muscle function, with consequent impairment of exercise tolerance. Little attention, however, has been given to the contribution of cardiovascular dysfunction to this impaired exercise capacity.
Seven patients with CFS (age 35 + 7 yr, SD) therefore performed cardiopulmonary exercise testing on different occasions, utilising (a) ramp-incremental cycle-ergometer exercise to the limit of tolerance and (b) moderate (i.e. below the lactate threshold) constant-load.
Subjects demonstrated resting pulmonary function that was within normal limits (FEV1/FVC = 0.78 ± 0.05). Evidence of exercise intolerance was found in the reduced peak oxygen uptake (1.48 ± 0.41 l/min, 71% predicted) on the ramp exercise test, with maximum levels of perceived leg fatigue being attained. There was a modest reduction in both peak heart rate (HR) (164 ± 31 bt/min; 89 ± 11 % pred) and oxygen pulse (8.9 ± 1.6 ml/bt; 80 ± 11 % pred). Further evidence consistent with cardiovascular dysfunction was that cardiac output (estimated by the CO2 rebreathing technique) during moderate exercise was below predicted in 4 of the 7 patients (although normal, or even high, in 2, with valid measurements not being obtained in one patient).
These results therefore, provide preliminary evidence of cardiovascular impairment during dynamic exercise in patients with CFS, as judged by the cardiac output response to moderate exercise. However, as is the case with other "markers" of functional impairment in this patient population, there was considerable heterogeneity in its degree.
Acknowledgements: This work was supported by the Barclay Trust & the Myalgic Encephalomyelitis Association.
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