title: Digitized QT dispersion by the Valsalva maneuver in hypertensive patients.
abstract: BACKGROUND
  Hypertension is an important risk factor for sudden cardiac death, of which the incidence increases with increases in blood pressure. Prolonged QT dispersion has been identified to indicate increased risk of life-threatening ventricular arrhythmia and sudden cardiac death. In this study, QT dispersion was investigated in hypertensive patients during the strain phase of the Valsalva maneuver.
  
  
  METHODS
  The study population included 75 subjects: 25 with normal blood pressure (Control), 25 with stage I hypertension (Group A), and 25 with stage II hypertension (Group B). Electrocardiography for QT dispersion was recorded at 25 mm/sec paper speeds before and during the Valsalva maneuver.
  
  
  RESULTS
  The patients in Group B were significantly older than the controls (p<0.05). Differences in sex, smoking, diabetes, angina, and hyperlipidemia were not statistically significant between the three groups. The basal QT dispersion was 25.3 +/- 18.3 ms in the controls, 39.0 +/- 17.8 ms in Group A, and 36.8 +/- 18.8 ms in Group B. The QT dispersion was significantly higher in group A patients than the controls (p<0.05). In Group B only, a significant increase in QT dispersion was observed during the Valsalva maneuver, compared to conditions prior to the Valsalva maneuver (p<0.05).
  
  
  CONCLUSIONS
  The conditions that increase intrathoracic pressure may increase QT dispersion and severe hypertensive patients should avoid these conditions.
authors.affiliation: Division of Cardiology, Department of Internal Medicine, The Catholic University of Korea College of Medicine, Seoul, Korea.
authors.forename: Hee-Jeoung
authors.initials: HJ
authors.lastname: Yoon
authors.forename: Seung-Won
authors.initials: SW
authors.lastname: Jin
authors.forename: Jong-Min
authors.initials: JM
authors.lastname: Lee
authors.forename: Woo-Seung
authors.initials: WS
authors.lastname: Shin
authors.forename: Yong-Suk
authors.initials: YS
authors.lastname: Oh
authors.forename: Man-Young
authors.initials: MY
authors.lastname: Lee
authors.forename: Ki-Bae
authors.initials: KB
authors.lastname: Seung
authors.forename: Tai-Ho
authors.initials: TH
authors.lastname: Rho
authors.forename: Jae-Hyung
authors.initials: JH
authors.lastname: Kim
authors.forename: Soon-Jo
authors.initials: SJ
authors.lastname: Hong
authors.forename: Kyu-Bo
authors.initials: KB
authors.lastname: Choi
mesh_terms: D001794:Blood Pressure / Q000502:physiology; D004562:Electrocardiography; D005260:Female; D006801:Humans; D006973:Hypertension / Q000175:diagnosis / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012307:Risk Factors; D014636:Valsalva Maneuver / Q000502:physiology*