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Europace Advance Access published online on August 22, 2008
Europace, doi:10.1093/europace/eun217
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Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2008. For permissions please email: journals.permissions@oxfordjournals.org

Impaired arterial baroreflex function before nitrate-induced vasovagal syncope during head-up tilt test

Massimo Iacoviello* {dagger}, Pietro Guida {dagger}, Cinzia Forleo, Sandro Sorrentino, Luciana D'Alonzo and Stefano Favale

Cardiology Unit, Emergency and Organ Transplantation Department, University of Bari, Piazza Giulio Cesare 11, 70124 Bari, Italy

Aims: The aim of this study was to evaluate arterial baroreflex control of heart rate immediately before head-up tilt test (HUT)-induced vasovagal syncope (VVS).

Methods and results: We enrolled 97 otherwise healthy subjects with recurrent unexplained syncope. After 10 min of rest in supine position, they underwent a passive HUT potentiated with nitroglycerin administration after 20 min. Beat-to-beat heart rate and systolic blood pressure were continuously recorded. Sequence method was used to measure two complementary parameters reflecting arterial baroreflex control of heart rate: the baroreflex sensitivity (BRS) and the baroreflex effectiveness index (BEI). Twenty-one patients fainted before nitrate administration (HUT+) and 37 after nitrate administration (NTG+). Immediately before syncope, the NTG+ patients showed significantly lower BRS values than those observed at the end of the test in the patients without syncope (5.5 ± 2.8 vs. 7.7 ± 3.4 ms/mmHg; P = 0.004) and a significantly lower BEI (30 ± 20% vs. 53 ± 24%; P < 0.001). The HUT+ patients did not show any significant differences in BRS and BEI before syncope from the values observed during the corresponding tilt period in the other groups.

Conclusion: A significant depression in BRS and BEI occurs immediately before syncope in patients who faint after nitrate administration, thus suggesting that arterial baroreflex dysfunction plays a role in mediating nitrate-induced VVS.

Key Words: Vasovagal syncope, Tilt table test, Baroreceptor reflex

* Corresponding author. Tel: +39 080 5478622; fax: +39 080 5478796. E-mail address: massimo.iacoviello{at}cardio.uniba.it

{dagger} These two authors equally contributed to this paper.

Manuscript submitted 28 April 2008. Accepted after revision 1 August 2008.


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