Orthostatic intolerance (OI) syndromes are frequent and share symptoms like dizziness and orthostatic syncope. Their pathophysiology however seems to be different. The aim of our work was to evaluate autonomic and hemodynamic behaviour in patients with familial amyloidotic polyneuropathy and neurally mediated syncope in supine position and after acute orthostatic passive stress. We studied 12 patients with autonomic failure (group A), 12 patients with neurally mediated syncope (group B) and 16 aged matched normal controls (group C), in supine position and during the first 10 min of head-up tilt test (HUTT). Beat-by-beat blood pressure and heart rate were continuously monitored and digitised at 500 Hz. The baroreceptor alfa-index gain (vagal reflex-BRG), high frequency of RR variability (HFRR, vagal tonus) and low frequency of systolic arterial pressure variability (LFSAP, sympathetic tone) were calculated. Catecholamines, plasma brain (BNP) and atrial natriuretic (ANP) peptides were also measured. Hemodynamic data were derived and calculated by the non-invasive modelflow method. During supine position, cardiac output (CO) and stroke volume (SV) were similar in all groups. Mean arterial pressure (MAP) and BNP were higher in group A. Noradrenaline (NOR), BRG, HFRR and LFSAP were extremely low in this group. BRG and adrenaline (ADR) were higher in group B than in controls. Within the first 10 min of HUTT, there was a huge drop of CO, SV and MAP in group A, maintenance of very low levels of neurohormones and lack of autonomic function. HR, LFSAP and ADR had a higher rise at HUTT in group B compared with controls (p < 0.01) but a significant decrease of BRG was noted (p < 0.05). ANP or BNP did not change with tilt in any group. Different orthostatic intolerance syndromes may show important hormonal, autonomic and hemodynamic differences during supine rest and enhanced after passive orthostatism.

Autonomic failure, Familial amyloidotic polyneuropathy, Neurally-mediated syncope, Orthostatic intolerance
dx.doi.org/10.1016/j.ijcard.2006.03.052, hdl.handle.net/1765/69458
International Journal of Cardiology
Department of Internal Medicine

Freitas, J, Santos, R, Azevedo, E, de Carvalho, M, Boomsma, F, van den Meiracker, A.H, … Abreu-Lima, C. (2007). Hemodynamic, autonomic and neurohormonal behaviour of familial amyloidotic polyneuropathy and neurally mediated syncope patients during supine and orthostatic stress. International Journal of Cardiology, 116(2), 242–248. doi:10.1016/j.ijcard.2006.03.052