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Vagal Cardiovascular Reflexes in Young Persons with Syncope

Stephen A. Barron, MD; Ze'ev Rogovski, PhD; and Yeshiahu Hemli, MD
[+] Article and Author Information

From the Technion-Israel Institute of Technology and Rambam Medical Center, Haifa, Israel. Requests for Reprints: Stephen A. Barron, MD, Laboratory of Clinical Neurophysiology, Bruce Rappaport Faculty of Medicine, The Technion-Israel Institute of Technology, Efron Street, P.O. Box 9649, Haifa 31096, Israel. Grant Support: In part by the Lester Aronberg Foundation.


Copyright 2004 by the American College of Physicians


Ann Intern Med. 1993;118(12):943-946. doi:10.7326/0003-4819-118-12-199306150-00005
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Objective: To study the neurocardiologic reflexes in young persons who have fainted under conditions of emotional stress.

Design: Case-control study.

Setting: Clinical neurophysiology laboratory in Haifa, Israel.

Patients: Sixty persons (41 women and 19 men), 15 to 17 years old, who were referred for study because of syncope related to an emotionally distressing event. Forty aged-matched, healthy volunteers drawn from the same population served as controls.

Measurements: Resting electrocardiogram, inspiratory-expiratory difference in heart rate during deep breathing, heart rate response to the Valsalva maneuver, and blood pressure during motionless standing for 5 minutes.

Results: Although individual results were within widely accepted limits of normal, patients with syncope as a group had higher vagal autonomic tone than did controls. This manifested as a slower heart rate at rest (mean, 67.8 beats/min compared with 73.2 beats/min; P = 0.005), a higher inspiratory-expiratory difference in heart rate (mean, 44.1 beats/min compared with 37.9 beats/min; P = 0.001), and a higher Valsalva ratio (1.91 compared with 1.72; P < 0.0001). No significant difference was found in the PR and QTc (QT interval corrected for rate) intervals of the electrocardiogram or in the blood pressure response to standing.

Conclusion: Many young persons who faint under conditions of emotional distress do so because a relatively high vagal tone predisposes them to the cardioinhibitory component of the syncope. Age-related physiologic reduction in vagal cardiac responses may explain the lower incidence of this type of syncope with increasing age.

Figures

Grahic Jump Location
Figure 1.
Inspiratory-expiratory difference in heart rate in persons with syncope and in controls.
Grahic Jump Location
Grahic Jump Location
Figure 2.
The Valsalva ratio in persons with syncope and in controls.
Grahic Jump Location

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