Slower Lower Limb Blood Pooling Increases Orthostatic Tolerance in Women with Vasovagal Syncope
2016 (English)In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 7, no 232Article in journal (Refereed) PublishedText
Background and Aim: Slower lower limb blood pooling and associated blunted sympathetic activation has been detected in healthy women prone to orthostatic syncope. Whether these findings are true also for patients with vasovagal syncope (WS) is unknown. The aim was to investigate initial blood pooling time (pooling(time), time to 50% of total blood pooling) together with hemodynamic responses and orthostatic tolerance during lower body negative pressure (LBNP) in WS and healthy controls. Methods and Results: Fourteen WS women (25.7 +/- 1.3 years) and 15 healthy women (22.8 +/- 0.8 years) were subjected to single-step and graded LBNP to pre-syncope. Lower limb blood pooling (ml 100 ml(-1)), poolingtime (s), hemodynamic responses and LBNP-tolerance were evaluated. LBNP induced comparable lower limb blood pooling in both groups (controls, 3.1 +/- 0.3; WS, 2.9 +/- 0.3 ml 100 ml(-1), P = 0.70). In controls, shorter pooling(time) correlated to higher LBNP-tolerance (r = -0.550, P amp;lt; 0.05) as well as better maintained stroke volume (r =-0.698, P amp;lt; 0.01) and cardiac output (r = -0.563, P amp;lt; 0.05). In contrast, shorter poolingtime correlated to lower LBNP-tolerance in VVS (r = 0.821, P amp;lt; 0.001) and larger decline in stroke volume (r = 0.611, P 0.05). Furthermore, in controls, shorter poolingtime correlated to baroreflex-mediated hemodynamic changes during LBNP, e.g., increased vasoconstriction (P amp;lt; 0.001). In VVS, poolingtime was not correlated with LBNP-induced baroreceptor unloading, but rather highly correlated to resting calf blood flow (P amp;lt; 0.001). Conclusions: Shorter poolingtime seems to elicit greater sympathetic activation with a concomitant higher orthostatic tolerance in healthy women. The contrasting findings in AS indicate a deteriorated vascular sympathetic control suggesting well-defined differences already in the initial responses during orthostatic stress.
Place, publisher, year, edition, pages
FRONTIERS MEDIA SA , 2016. Vol. 7, no 232
syncope; blood pooling; orthostatic intolerance; hemodynamics; baroreceptors; veins; sympathetic nervous system
IdentifiersURN: urn:nbn:se:liu:diva-130129DOI: 10.3389/fphys.2016.00232ISI: 000377761400001PubMedID: 27378941OAI: oai:DiVA.org:liu-130129DiVA: diva2:948578
Funding Agencies|Futurum-the Academy of Health Care, Jonkoping County Council; Medical Research Council of Southeast Sweden; Heart and Lung Foundation; County Council of Ostergotland2016-07-122016-07-112016-08-05