title: Vagal cardiovascular reflexes in young persons with syncope.
abstract: 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.
authors: Laboratory of Clinical Neurophysiology, Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa.
authors: S A
authors: SA
authors: Barron
authors: Z
authors: Z
authors: Rogovski
authors: Y
authors: Y
authors: Hemli
mesh_terms: 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