title: Postural Heart Rate Changes in Young Patients With Vasovagal Syncope.
abstract: OBJECTIVE
  Recurrent postural vasovagal syncope (VVS) is caused by transient cerebral hypoperfusion from episodic hypotension and bradycardia; diagnosis is made by medical history. VVS contrasts with postural tachycardia syndrome (POTS), defined by chronic daily symptoms of orthostatic intolerance with excessive upright tachycardia without hypotension. POTS has recently been conflated with VVS when excessive tachycardia is succeeded by hypotension during tilt testing. We hypothesize that excessive tachycardia preceding hypotension and bradycardia is part of the vasovagal response during tilt testing of patients with VVS.
  
  
  METHODS
  We prospectively performed head-up tilt (HUT) testing on patients with recurrent VVS (n= 47, 17.9 ± 1.1 y), who fainted at least 3 times within the last year, and control subjects (n= 15, 17.1 ± 1.0 y), from age and BMI-matched volunteers and measured blood pressure, heart rate (HR), cardiac output, total peripheral resistance, and end tidal carbon dioxide.
  
  
  RESULTS
  Baseline parameters were the same in both groups. HR (supine versus 5 and 10 minutes HUT) significantly increased in control (65 ± 2.6 vs 83 ± 3.6 vs 85 ± 3.7,P< .001) and patients with VVS (69 ± 1.6 vs 103 ± 2.3 vs 109 ± 2.4,P< .001). HUT in controls maximally increased HR by 20.3 ± 2.9 beats per minute; the increase in patients with VVS of 39.8 ± 2.1 beats per minute was significantly greater (P< .001). An increase in HR of ≥40 beats per minute by 5 and 10 minutes or before faint with HUT, occurred in 26% and 44% of patients with VVS, respectively, but not in controls.
  
  
  CONCLUSIONS
  Orthostasis in VVS is accompanied by large increases in HR that should not be construed as POTS.
authors.affiliation: Departments of Pediatrics, and marvin_medow@nymc.edu.|Physiology, New York Medical College, Valhalla, New York.
authors.forename: Marvin S
authors.initials: MS
authors.lastname: Medow
authors.affiliation: Departments of Pediatrics, and.
authors.forename: Sana
authors.initials: S
authors.lastname: Merchant
authors.affiliation: Departments of Pediatrics, and.
authors.forename: Melissa
authors.initials: M
authors.lastname: Suggs
authors.affiliation: Departments of Pediatrics, and.
authors.forename: Courtney
authors.initials: C
authors.lastname: Terilli
authors.affiliation: Departments of Pediatrics, and.
authors.forename: Breige
authors.initials: B
authors.lastname: O'Donnell-Smith
authors.affiliation: Departments of Pediatrics, and.|Physiology, New York Medical College, Valhalla, New York.
authors.forename: Julian M
authors.initials: JM
authors.lastname: Stewart
mesh_terms: D000293:Adolescent; D001794:Blood Pressure / Q000502:physiology; D002648:Child; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D054971:Orthostatic Intolerance / Q000175:diagnosis*; D011446:Prospective Studies; D019462:Syncope, Vasovagal / Q000175:diagnosis*; D018667:Tilt-Table Test; D055815:Young Adult