Health Dictionary
Reliable, easy-to-read patient information on common medical conditions — written in plain language, free of jargon, and grounded in current evidence. Browse the most frequent diagnoses, understand what they mean for everyday life, and learn which steps and questions help you have a focused conversation with your doctor.
Resistive index
Introduction
Overview
Overview
The arterial resistivity index (RI) is a measure of pulsatile blood flow that reflects the resistance to blood flow caused by microvascular bed distal to the site of measurement. A resistive index of 0 corresponds to continuous flow; a resistive index of 1 corresponds to systolic but no diastolic flow; and a resistive index greater than 1 corresponds to reversed diastolic flow.
Formula = (Peak systolic velocity – End diastolic velocity) / Peak systolic velocity
The RI is altered not by vascular resistance alone but by the combination of vascular resistance and vascular compliance.
References
References
Editor-In-Chief:
C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Aarti Narayan, M.B.B.S [2]