Neurohormonal Response to Head-Up Tilt and Its Role in Vasovagal Syncope

Neuropeptides and peptide hormones in syncope and orthostatic intolerance

“…Vasopressin was among the first NPs (or 'peptide hormones') to be evaluated as a potential contributor to VVS pathophysiology [8,15,16]. All studies agree that at the time of tilt-table induced reflex syncope VP levels are elevated.…”

“…All studies agree that at the time of tilt-table induced reflex syncope VP levels are elevated. By way of example, Jardine et al [8] observed a statistically significant VP increase 5 min before symptoms, with an even greater excess occurring at the time of syncope. However, in other reports an increase in VP levels occurred during upright tilt in both subjects who eventually develop syncope and those who do not faint [15].…”

“…In this regard, changes in circulatory catecholamines have tended to be of greatest interest given the apparent association of VVS with anxiety or stress states [8][9][10][11][12][13][14]. However, the potential role of NPs has also attracted attention; specifically, BNP [8], vasopressin (VP) [8,15,16], atrial natriuretic peptide (ANP) [8,17], adrenomedullin (ADM) [17][18][19], galanin (GAL) [19,20], and endothelin-1 (ET-1) [17,[21][22][23]. A summary of the primary physiologic effects of these NPs is shown in Table 2.…”

“…Jardine et al [8] hypothesized that VPs direct pressor effect may be overcome by an indirect effect enhancing arterial and ventricular mechanoreceptor activity; however, other reports suggest that carotid baroreceptor activity is down-regulated by VP. Clearly, further study of VP-baroreceptor interaction is needed.…”

“…Jardine et al [8] examined BNP and ANP levels during head-up tilt testing in control subjects and individuals who developed reflex syncope. BNP did not differ appreciably in the two patient groups and consequently is not likely to play a pathophysiological role.…”