INFLUENCE OF HEART-RATE AND VASOACTIVE DRUGS ON BLOOD-FLOW PATTERNS AT THE CANINE ILIOFEMORAL BIFURCATION

Objective: The aim was to study the effects of altered heart rate and vasoactive drugs on the blood velocity patterns in the region of an ar terial bifurcation. Methods: Blood velocity profiles were measured in an exposed iliofemoral bifurcation of paced dogs using a pulsed Dopple r ultrasound velocimeter with high temporal and spatial resolution. Re sults: Decrease of the heart rate from 120 beats.min(-1) (2 Hz) to 60 beats.min(-1) (1 Hz) increased the peak forward velocity (30%), the pe ak reverse velocity (20%), and the duration of reverse flow (25%). Eac h drug caused qualitatively similar changes in velocity patterns at bo th heart rates. The systemic administration of angiotensin II reduced peak forward velocity (-26% at 2 Hz and -33% at 1 Hz) and forward flow duration (-15% at 1 Hz), the peak reverse velocity (-30% at 1 Hz), an d reverse how duration (-20% at 2 Hz and -28% at 1 Hz). Glyceryl trini trate also reduced the peak forward velocity (-19% at bath 2 and 1 Hz) but prolonged forward flow duration (28% at 2 Hz and 17% at 1 Hz) and that of reverse flow (45% at 2 Hz and 24% at 1 Hz), and also decrease d the degree of oscillation (-16% at 2 Hz). Barnidipine hydrochloride (a calcium channel antagonist) also increased the duration of forward flow (48% at 1 Hz) and of reverse flow (31% at 2 Hz) but reduced the p eak reverse velocity (-29% at 1 Hz) and flow oscillation (-22% at 2 Hz and 20% at 1 Hz). Conclusions: These dramatic changes in the pattern of blood flow, including alterations in the amplitudes and durations o f the different phases of the flow cycle, are expected to have importa nt consequences on the shear dependent responses of endothelial cells in the region of the bifurcation.