HEDS patients showed overactivity of sympathetic nervous system (part of autonomic nervous system) at risk. Conversely, when presented with a trigger that should activate the sympathetic nervous system, they show a lower response than they should. In response to Valsalva maneuvers, their blood pressure dropped more than it should. In tilt table testing, the diastolic blood pressure increases less than it should. Hypermobility was associated with worsened dysautonomic symptoms. POTS is the most common subtype of dysautonomia found in HEDS patients.
Dysfunction of sympathetic nervous system is common in HEDS. Laxity of connective tissue and use of medications that affect blood vessels aggrevate dysautonomia. Autonomic dysfunction in HEDS patients is associated with poor disease prognosis, decreased quality of life, unstable blood pressure, increased risk of cardiac disease and death as a result of it, particularly under anesthesia.
Deconditioning has a complicated relationship to orthostatic intolerance and dysautonomia. Deconditioning lowers blood volume and alters response to adrenalin, contributing to orthostatic symptoms.
However, a study on the relationship between HEDS and dysautonomia found that decreased physical activity was not linked to worsened orthostatic symptoms. As a result, it is thought that deconditioning in this group is probably not the primary cause of orthostatic intolerance, but a secondary contributor.
de Wandele I, et al. Dysautonomia and its underlying mechanisms in the hypermobility type of Ehlers-Danlos syndrome. Seminars in Arthritis and Rheumatism 2014, 44: 93-100.
de Wandele I, et al. Autonomic symptom burden in the hypermobility type of Ehlers-Danlos syndrome: A comparative study with two other EDS types, fibromyalgia, and healthy controls. Seminars in Arthritis and Rheumatism 2014, 44: 353-361.
Wallman D, et al. Ehlers-Danlos Syndrome and Postural Tachycardia Syndrome: A relationship study. Journal of Neurological Sciences 2014, 340: 99-102.