title: Endothelial function in vasovagal syncope.
abstract: Vasovagal syncope (VVS) is a common form of fainting. The pathophysiology of VVS is complex and involves changes in the autonomic and vascular tone, resulting in reflex bradycardia with marked hypotension. Paradoxical peripheral vasodilation caused by endothelial dysfunction may also play a key role in inappropriate hypotension during VVS. Endothelial hyperactivity due to up regulation of nitric oxide synthase leads to profound vasodilation, much stronger than vasodilation caused by adrenergic stimulation in response to orthostatic stress alone. Studies have reported significantly higher flow-mediated dilation and higher plasma nitric oxide concentration in people with vasovagal syndrome. Patients with VVS showed decreased vasoconstrictive agent endothelin-1 levels during orthostatic stress. Coagulation and fibrinolysis activity also play important roles in endothelial function in syncopal patients. The response of the endothelium to orthostatic stress is similar to the reaction to haemorrhagic stress and is likely to be a remnant from the evolutionary adaptation of primates.
authors.affiliation: Department of Coronary Disease and Heart Failure, Syncope Unit, Institute of Cardiology, Medical College of Jagiellonian University, John Paul II Hospital, 80 Pradnicka St, 31-202 Cracow Poland.
authors.forename: Artur Z
authors.initials: AZ
authors.lastname: Pietrucha
mesh_terms: D001341:Autonomic Nervous System / Q000098:blood supply* / Q000503:physiopathology; D004727:Endothelium / Q000503:physiopathology*; D006801:Humans; D007024:Hypotension, Orthostatic / Q000503:physiopathology*; D013312:Stress, Physiological / Q000502:physiology; D019462:Syncope, Vasovagal / Q000503:physiopathology*; D014664:Vasodilation / Q000502:physiology*
keywords: coagulation and fibrinolysis; endothelium; endothelium independent dilation; flow mediated dilation; nitric oxide; profound vasoidaltion; vasovagal syncope