title: Dynamic changes of P-wave duration and P-wave axis during head-up tilt test in patients with vasovagal syncope.
abstract: BACKGROUND
  The exact role of venous pooling in the pathogenesis of vasovagal syncope (VVS) is not fully elucidated. P-wave duration on an electrocardiogram can serve as a measure of atrial volume.
  
  
  METHODS
  Sixty-six patients (15 men, 51 women, mean age 32 years) with unexplained syncope were enrolled in the study.P-wave duration and the P-wave axis (PWA) were measured during passive head-up tilt test (HUT) in order to evaluate dynamic changes of atrial filling in patients with VVS.
  
  
  RESULTS
  HUT was positive in 40 patients (6 men, 34 women, mean age 32 +/- 9 years) and negative in 26 patients (9 men, 17 women, mean age 33 +/- 8 years). The P-wave duration was significantly reduced in HUT-positive patients at the onset of symptoms as compared to 5 minutes (88.8 +/- 11.9 vs 96.2 +/- 12.0 ms, P = 0.008), and baseline (88.8 +/- 11.9 vs 96.8 +/- 13.8 ms, P = 0.005). The P-wave duration was significantly shorter at the onset of presyncope in HUT-positive patients as compared to HUT-negative patients (88.8 +/- 11.9 vs 100.3 +/- 11.2 ms, P = 0.0002). In HUT-positive patients, a significant increase in PWA was found at the onset of symptoms when compared to baseline (67.7 +/- 22.1 degrees vs 47.9 +/- 14.9 degrees, P < 0.0001) and 5 minutes of HUT (67.7 +/- 22.1 degrees vs 54.4 +/- 14.9 degrees, P = 0.005). At the time of syncope, PWA was more inferior in HUT-positive patients than in HUT-negative patients (67.7 +/- 22.1 degrees vs 51.8 +/- 13.8 degrees, P = 0.015).
  
  
  CONCLUSIONS
  VVS is associated with the reduction in P-wave duration and the increase in PWA, which can be a result of exaggerated venous pooling and reduction in atrial volume.
authors.affiliation: Clinic of Internal Medicine III, Medical Faculty of P.J. Safarik University, Kosice, Slovakia. pmitro@lf.upjs.sk
authors.forename: Peter
authors.initials: P
authors.lastname: Mitro
authors.forename: Ján
authors.initials: J
authors.lastname: Spegár
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D004562:Electrocardiography; D004569:Electroencephalography; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D008297:Male; D019462:Syncope, Vasovagal / Q000503:physiopathology*; D018667:Tilt-Table Test