Endothelial dysfunction in ME/CFS patients.

Abstract

OBJECTIVE: A few earlier studies have found impaired endothelial function in patients with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS). The  present study investigated large-vessel and small-vessel endothelial function in  patients with ME/CFS. STUDY DESIGN: The study was a substudy of the RituxME  trial, a national, multicenter, randomized, double-blind, placebo-controlled  phase III study on the effect of rituximab vs. placebo in ME/CFS patients in  Norway. Flow-mediated dilation (FMD) and post-occlusive reactive hyperemia (PORH)  was measured at baseline and after 18 months of treatment in 39 patients and  compared with healthy controls. Other outcome measures were symptom severity and  various physical function measures. RESULTS: ME/CFS patients had markedly reduced  FMD compared to healthy controls at baseline (5.1% vs. 8.2%, p< 0.0001, adjusted  for arterial diameter and sex), and significantly lower microvascular regulation  measured by PORH than healthy controls (1354 PU vs. 2208 PU, p = 0.002). There  were no differences between the treatment and placebo groups in symptom changes  or vascular measures. As a group, the ME/CSF patients experienced a slight, but  significant improvement in clinical symptoms after 18 months. PORH, but not FMD,  was similarly improved (1360 to 1834 PU, p = 0.028). There was no significant  correlation between FMD and PORH. There were non-significant tendencies towards  associations between symptom severity/physical function measures and lower FMD  and PORH, and a significant correlation between PORH and steps per 24 hours at  baseline. CONCLUSIONS: ME/CFS patients had reduced macro- and microvascular  endothelial function, indicating that vascular homeostasis may play a role in the  clinical presentation of this disease.