Fibromyalgia is a common but poorly understood problem characterized by widespread pain and chronic fatigue. Because chronic fatigue has been associated with neurally mediated hypotension, we examined the prevalence of abnormal responses to upright tilt table testing in 20 patients with fibromyalgia and 20 healthy controls.
Each subject completed a symptom questionnaire and underwent a three stage upright tilt table test (stage 1:45 minutes at 70 degrees tilt; stage 2, 15 minutes at 70 degrees tilt with isoproterenol 1-2 micrograms/min; stage 3, 10 minutes at 70 degrees tilt with isoproterenol 3-4 micrograms/min). An abnormal response to upright tilt was defined by syncope or presyncope in association with a drop in systolic blood pressure of at least 25 mm Hg and no associated increase in heart rate.
During stage 1 of upright tilt, 12 of 20 fibromyalgia patients (60%), but no controls had an abnormal drop in blood pressure (P < 0.001). Among those with fibromyalgia, all 18 who tolerated upright tilt for more than 10 minutes reported worsening or provocation of their typical widespread fibromyalgia pain during stage 1. In contrast, controls were asymptomatic (P < 0.001).
These results identify a strong association between fibromyalgia and neurally mediated hypotension. Further studies will be needed to determine whether the autonomic response to upright stress plays a primary role in the pathophysiology of pain and other symptoms in fibromyalgia.