Background Several studies have shown that autonomic dysfunction plays an important role in the fibromyalgia syndrome (FMS).^1–3 Recent studies have used the active standing test to assess the cardiovascular autonomic control responses to the orthostatic stimulus in several disorders, including FMS.⁴ However, there are few studies correlating symptoms and clinical factors with cardiovascular autonomic dysfunction.

Objectives To assess the relationship between the impact of fibromyalgia on quality of life and cardiac autonomic control response to the active standing test.

Methods Ten women (47.9±7.3 years old) with clinical diagnosis of FMS took part in the study. Diagnosis followed the criteria established by the American College of Rheumatology.⁵ All participants answered the fibromyalgia impact questionnaire (FIQ)⁶ and underwent the recording of RR intervals (RRi) using a transmitter belt. The RRi were recorded for 15 min in resting supine position and during 15 min in an orthostatic position reached by active standing. The cardiac autonomic control was assessed by indices computed via spectral analysis of RRi in low frequency (LF, 0.04–0.15 Hz) and high frequency bands (HF, 0.15–0.4 Hz). To quantify the magnitude of cardiac autonomic response to the orthostatic stimulus, the delta between values obtained in supine and standing positions was calculated for all variables. Changes induced by the orthostatic stimulus were evaluated by Wilcoxon test. Spearman's coefficient was used to assess the association between the delta of the HRV indices and the FIQ scores. α =5%.

Results There were no significant differences between the supine and standing positions in any of the spectral indices. Positive correlation was found between FIQ scores and HF (n.u.) (r =0.67; p=0.03). Negative correlations were observed between the FIQ scores and LF (n.u.) index (r = -0.67; p=0.03, Figure 1B) and LF/HF ratio (r = -0.73; p=0.016, Figure 1C).

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Conclusions The results showed that the larger the magnitude of the cardiac autonomic adjustments to the gravitational stimulus, the smaller the impact of FMS on quality of life.

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5. Wolfe F, Smythe HA, Yunus MB, et al. Fibromyalgia. Rheum Dis Clin North Am. 1990;16:681–698.

6. Marques AP, Santos AMB, Assumpção A, Matsutani LA, Lage LV, Pereira CAB. Validation of the Brazilian version of the Fibromyalgia Impact Questionnaire (FIQ). Braz J Rheumatol. 2006;46:24–31.

Acknowledgement This study was supported São Paulo Research Foundation (FAPESP), grants #2011/22122–5 and #2015/08445–7.

Disclosure of Interest None declared