Dysautonomia among patients with fibromyalgia: a noninvasive assessment

Fibromyalgia (FM) is a prevalent and poorly understood disorder associated with a significant amount of disability. Some clinical characteristics are common to both FM and vasovagal syncope (which is caused by dysautonomia). We assessed the response of patients with FM to a head up tilt table test (HUT). We also examined sympathovagal balance by assessing heart rate variability (HRV).

We studied 17 women with FM and 14 female control subjects. After baseline functional assessments, they underwent a 3 stage HUT (with isoproterenol). HRV was assessed over a 24 h period and also before and during HUT. Quality of life was assessed using the Medical Outcomes Study SF-36 Short Form Health Survey.

HUT was positive in 64.7% of the patients with FM compared with 21.3% of controls (p = 0.016). FM patients had less HRV, as measured by either time domain or frequency domain analysis. The FM group had a different response to HUT than controls. Quality of life was significantly lower in patients with FM compared to controls (p < or = 0.001 in all domains).

Patients with FM have abnormal responses to 2 tests of autonomic nervous system function. Further research is needed to determine if dysautonomia plays a role in the pathogenesis of FM or is a result of FM.