In Vivo Measurement of Regional Large Artery Compliance by Intravascular Ultrasound Under Pentobarbital Anesthesia

Background: The presence of smooth muscle fibers on the wall of large arteries would suggest that arterial compliance might change in response to vasoactive substances. The purpose of this study is to determine the basal level of vasomotor tone in these arteries in a commonly used animal preparation and to learn whether the compliance of large conductance arteries can be altered in vivo by vasoactive agents.Methods: Proximal iliac arterial compliance was measured in 7 pentobarbital-anes thetized pigs, before and during local infusions of adenosine and norepinephrine. Luminal area was measured every forty milliseconds by means of a 30 MHz intravas cular ultrasound catheter and an automatic edge detection program. Simultaneous high- fidelity pressure measurements were obtained by means of a catheter-tipped pressure microtransducer positioned at the origin of the iliac artery. Linear regression analysis of the area/pressure relationship in two consecutive cardiac cycles (systolic phase only) was performed be...