Vagal cardiovascular reflexes in young persons with syncope.
OBJECTIVE
To study the neurocardiologic reflexes in young persons who have fainted under conditions of emotional stress.


METHODS
Case-control study.


METHODS
Clinical neurophysiology laboratory in Haifa, Israel.


METHODS
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.


METHODS
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.


CONCLUSIONS
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.
Barron
S A
SA
Laboratory of Clinical Neurophysiology, Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa.
Rogovski
Z
Z
Hemli
Y
Y
D000293:Adolescent; D002319:Cardiovascular System / Q000294:innervation*; D016022:Case-Control Studies; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D012018:Reflex / Q000502:physiology*; D012119:Respiration / Q000502:physiology; D013315:Stress, Psychological / Q000503:physiopathology; D013575:Syncope / Q000503:physiopathology* / Q000523:psychology; D014630:Vagus Nerve / Q000503:physiopathology*; D014636:Valsalva Maneuver / Q000502:physiology