Objective: Effects of pacing-induced tachycardia on left ventricular f
unction have been studied extensively. However, little attention has b
een focused on aortic elastic properties during heart rate increments.
The aim was to determine the effects of right ventricular pacing on t
he 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 fiv
e 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 co
nstant of the pressure diameter (p-d) relation, derived from simultane
ous tip-micromanometer aortic pressure recordings and high-fidelity ul
trasonic intravascular aortic diameter recordings, were used as indice
s of aortic stiffness. Wave reflection was also studied. Results: Aort
ic pulse pressure and strain significantly decreased after pacing-indu
ced tachycardia (p<0.0001 and <0.05, respectively). During pacing, the
slope of the linear p-d relation as well as the stiffness constant we
re decreased, followed by increases at recovery (p<0.0001). The augmen
tation index and the aortoventricular coupling ratio were significantl
y decreased (p<0.0001). Conclusions: Pacing-induced increases in pulse
frequency may result in improved aortic distensibility and aortoventr
icular coupling. (C) 1998 Elsevier Science B.V. All rights reserved.