title: Effects of ventricular pacing-induced tachycardia on aortic mechanics in man.
abstract: OBJECTIVE
  Effects of pacing-induced tachycardia on left ventricular function have been studied extensively. However, little attention has been focused on aortic elastic properties during heart rate increments. The aim was to determine the effects of right ventricular pacing on the aortic elastic properties.
  
  
  METHODS
  We studied 14 normal subjects (baseline blood pressure, 129/84 +/- 10/6 mmHg; aortic diameter, 23.5/21.3 +/- 2.4/1.9 mm) at rest, during rapid right ventricular pacing (at five stepwise heart rate increases of 20 bpm every 2 min) and after 5 min recovery. Shifts as well as changes in the slope and the stiffness constant of the pressure diameter (p-d) relation, derived from simultaneous tip-micromanometer aortic pressure recordings and high-fidelity ultrasonic intravascular aortic diameter recordings, were used as indices of aortic stiffness. Wave reflection was also studied.
  
  
  RESULTS
  Aortic pulse pressure and strain significantly decreased after pacing-induced tachycardia (p < 0.0001 and < 0.05, respectively). During pacing, the slope of the linear p-d relation as well as the stiffness constant were decreased, followed by increases at recovery (p < 0.0001). The augmentation index and the aortoventricular coupling ratio were significantly decreased (p < 0.0001).
  
  
  CONCLUSIONS
  Pacing-induced increases in pulse frequency may result in improved aortic distensibility and aortoventricular coupling.
authors.affiliation: Hippokration Hospital, Department of Cardiology, University of Athens, Greece.
authors.forename: C
authors.initials: C
authors.lastname: Stefanadis
authors.forename: J
authors.initials: J
authors.lastname: Dernellis
authors.forename: M
authors.initials: M
authors.lastname: Vavuranakis
authors.forename: E
authors.initials: E
authors.lastname: Tsiamis
authors.forename: C
authors.initials: C
authors.lastname: Vlachopoulos
authors.forename: K
authors.initials: K
authors.lastname: Toutouzas
authors.forename: L
authors.initials: L
authors.lastname: Diamandopoulos
authors.forename: C
authors.initials: C
authors.lastname: Pitsavos
authors.forename: P
authors.initials: P
authors.lastname: Toutouzas
mesh_terms: D001011:Aorta / Q000502:physiology / Q000503:physiopathology*; D002304:Cardiac Pacing, Artificial; D004548:Elasticity; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D013610:Tachycardia / Q000503:physiopathology*