Open AccessAn Increased Endothelial‐Independent Vasodilation Is the Hallmark of the Neurally Mediated Syncope
Author(s) -
Santini Luca,
Capria Ambrogio,
Brusca Valentina,
Violo Arianna,
Smurra Francesca,
Scarfò Iside,
Forleo Giovanni B.,
Papavasileiou Lida P.,
Borzi Mauro,
Romeo Francesco
Publication year - 2012
Publication title -
clinical cardiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.263
H-Index - 72
eISSN - 1932-8737
pISSN - 0160-9289
DOI - 10.1002/clc.20990
Subject(s) - medicine , vasodilation , bradycardia , cardiology , fainting , pathophysiology , anesthesia , vasovagal syncope , syncope (phonology) , tilt table test , peripheral , endothelial dysfunction , heart rate , blood pressure
Background: The neurally mediated syncope (NMS) is sustained by complex cardiac and vascular reflexes, acting on and amplified by central autonomic loops, resulting in bradycardia and hypotension. Hypothesis: Our aim was to assess whether the pathophysiology of NMS is also related to an abnormal peripheral vasoreactivity. Methods: We evaluated by ultrasound the flow‐mediated vasodilation (FMD) and the nitrate‐mediated dilation (NMD) in 17 patients with NMS, induced by drug‐free tilt test in 6 subjects and by nitrate‐potentiated tilt test in the other 11 cases; the syncope was classified as vasodepressive (VD) in 8 cases, cardioinhibitory (CI) in 7, and mixed in 2. Results: The FMD was not different from controls (10.2 ± 4.5 vs 11.4 ± 3.9, P = ns), with normal recovery times; the NMD was greater in fainting subjects than in controls (26.7 ± 7.3 vs 19.0 ± 3.6, P < 0.05), with higher values in VD than in CI syncope (31.1 ± 7.0 vs 23.1 ± 5.0, P = ns); compared to controls, subjects with NMS showed normal recovery times after FMD but longer recovery times after nitrate administration (13.0 ± 5.6 vs 6.3 ± 0.7 minutes, P < 0.05). Conclusions: The evaluation of endothelial function supports evidence that NMS is characterized by a marked and sustained endothelial‐independent vasodilation, in the presence of a normal FMD; vascular hyperreactivity in response to nitrate administration is particularly overt in vasodepressive syncope and can explain the high rate of responses to nitrate administration during tilt test. © 2011 Wiley Periodicals, Inc. The authors have no funding, financial relationships, or conflicts of interest to disclose.