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Clin. Cardiol. 23, 820–824 (2000)

Endothelial Function and Peripheral Vasomotion in the Brachial Artery in Neurally Mediated Syncope

Bonpei Takase, M.D., FACC, Takashi Akima, M.D., Akimi Uehata, M.D.,† Syuichi Katushika, M.D.,† Kazusige Isojima, M.D.,† Kimio Satomura, M.D., Fumitaka Ohsuzu, M.D., FACC, Akira Kurita, M.D., FACC*

National Defense Medical College, Internal Medicine-1, *Research Center, and †Self Defense Forces Central Hospital, Internal Medicine, Saitama, Japan

Summary

Background: Paradoxical peripheral vasodilation is one of the suspected mechanisms of neurally mediated syncope. Parasympathetic stimulation following sympathetic activation during orthostatic stress mainly contributes to this vasodilation.

Hypothesis: Since endothelial function modulates peripheral vascular tone, this study aimed to determine whether endothelial function and inappropriate peripheral vasomotion has a significant role in the pathogenesis of neurally mediat-ed syncope.

Methods: To investigate whether endothelial function is augmented or whether abnormal peripheral vasomotion exits, flow-mediated dilation (FMD, endothelium-dependent vasodilation) and sublingual glyceryl trinitrate-induced dilation (0.3 mg, GTN-D, endothelium-independent vasodilation) were measured in the brachial artery in 16 patients with neurally mediated syncope, aged 33 ± 10 years, by using high-resolution ultrasound. All patients underwent positive head-up tilt testing. These measures were compared with those in 16 control subjects matched with the patients by age, gender, and coronary risk factors. For FMD, percent diameter changes were obtained from baseline to hyperemic conditions (1 min after 5 min occlusion of the forearm artery). There were five smokers in both the patient and the control groups, but there was no structural heart disease in either group.

Results: Baseline brachial artery diameters were comparable (3.8 ± 0.6 vs. 3.8 ± 0.7 mm, NS). Flow-mediated dilation in patients with neurally mediated syncope had a normal value of 9.8 ± 5.0% despite the inclusion of five smokers. Flow-mediated dilation and GTN-D in patients with neurally mediated syncope were significantly greater than those in controls (9.0 ± 5.0 vs. 3.0 ± 3.5%, p<0.05; 18.4 ± 5.5 vs. 14.1 ± 4.4%, p<0.05).

Conclusions: Augmented endothelial function and/or abnormal peripheral vasomotion in peripheral arteries are important in patients with neurally mediated syncope in selected populations.

Key words: endothelial function, peripheral vasomotion, neurally mediated syncope

This study was presented in part at the abstract session of the 19th annual meetings of North American Society of Pacing and Electrophysiology held in San Diego in 1998.

Address for reprints:
Bonpei Takase, M.D., FACC
National Defense Medical College, Internal Medicine-1
3-2 Namiki, Tokorozawa
Saitama, Japan, 359-8513

Received: September 22, 1999
Accepted with revision: January 19, 2000