The arterial resistivity index (ARI) is a measure of pulsatile blood flow that indicates the resistance to blood flow through an artery. The ARI is a common way of characterizing the arterial waveform...

The arterial resistivity index (ARI) is a measure of pulsatile blood flow that indicates the resistance to blood flow through an artery. The ARI is a common way of characterizing the arterial waveform and is used in applications such as detection and monitoring of kidney disease, detection of pre-eclampsia during pregnancy and evaluation of the success of liver transplants. The equation for computing ARI is:where vsystole and vdiastole are the velocities of the blood flow during cardiac systole (i.e. contraction) and diastole (i.e. relaxation) respectively.