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(Circulation. 1995;92:2204-2209.)
© 1995 American Heart Association, Inc.

Articles

Abnormal Forearm Vascular Responses During Dynamic Leg Exercise in Patients With Vasovagal Syncope

Presented in part at the 67th Scientific Sessions of the American Heart Association, Dallas, Tex, November 1994.

Helen L. Thomson, MBBS; Suhas S. Lele, MD; John J. Atherton, FRACP; Karen N. Wright, BSC; Wayne Stafford, FRACP; Michael P. Frenneaux, MD

From the Department of Cardiology, Royal Brisbane Hospital, and University of Queensland, Brisbane, Queensland, Australia.

Correspondence to Prof Michael Frenneaux, Cardiology Department, Royal Brisbane Hospital, Brisbane 4029, Australia.

Background We have reported previously that in some patients with normal hearts who present with exercise syncope, abnormal forearm vasodilation is seen during leg exercise and tilt table tests are positive. This suggests that exercise syncope may be a variant of vasovagal syncope. In this study we tested the hypothesis that there is loss of the normal forearm vasoconstrictor response during dynamic leg exercise in an unselected population of patients with classic vasovagal syncope.

Methods and Results We evaluated forearm vascular responses during maximal semierect cycle exercise in 28 consecutive patients with vasovagal syncope and compared them with 30 age-matched control subjects. We also evaluated blood pressure responses during erect treadmill exercise (Bruce protocol). While forearm vascular resistance at rest was similar in the patients with vasovagal syncope and the control group, forearm vascular resistance was markedly lower in the patients than in control subjects at peak exercise (85±54 versus 149±94 units, P=.002). Forearm vascular resistance fell by 3±48% during exercise in patients versus an increase of 135±103% in control subjects (P<.0001). Systolic blood pressure during erect exercise was lower in patients versus control subjects (155±32 versus 188±17 mm Hg, P<.0001). Six of the vasovagal patients complained of exercise syncope or presyncope on specific inquiry, and 4 of these 6 exhibited exercise hypotension during erect treadmill exercise testing.

Conclusions Patients with vasovagal syncope exhibit a failure of the normal vasoconstrictor response in the forearm during dynamic leg exercise. Exercise syncope and presyncope are not uncommon in unselected patients with classic vasovagal syncope, as is exercise hypotension.

Key Words: syncope • exercise • vasoconstriction

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