Effect of downstream cross-sectional area of an arterial bed on the resistive index and the early systolic acceleration.
OBJECTIVE
To evaluate the effect of the increase in total cross-sectional area of arteries as they branch beyond the main trunks on the resistive index (RI) and early systolic acceleration (ESA).


METHODS
An essentially noncompliant in vitro model that used a pulsatile pump, blood-mimicking fluid, and a branching tubing network that could be configured to produce a downstream cross-sectional area one, two, four, or eight times that of the feeding vessel was used to investigate the relationship, if any, between arterial bed cross-sectional area and the RI and ESA.


RESULTS
The mean ESA in the branching network was inversely proportional to cross-sectional area, decreasing by approximately a factor of two for every doubling of the cross-sectional area. The mean RI in the branching network decreased with increasing cross-sectional area, but not as greatly as the ESA did; the mean RI in the bed with eight times the upstream cross-sectional area had an RI that was approximately three-fourths the upstream RI. These relationships are real, as the slopes of the plots (ESA vs cross-sectional area, P = .001; RI vs cross-sectional area, P < .02) are significantly different from zero.


CONCLUSIONS
RI and ESA decrease as a result of increasing downstream cross-sectional diameter of the arterial bed.
Bude
R O
RO
Department of Radiology, University of Michigan Medical Center, Ann Arbor 48109-0326, USA. ronbude@umich.edu
Rubin
J M
JM
D001158:Arteries / Q000502:physiology; D001783:Blood Flow Velocity / Q000502:physiology*; D006801:Humans; D008955:Models, Cardiovascular; D011673:Pulsatile Flow / Q000502:physiology; D013599:Systole / Q000502:physiology*; D018608:Ultrasonography, Doppler; D014655:Vascular Resistance / Q000502:physiology*