A low-resistance waveform is a pattern seen on spectral Doppler that demonstrates sustained forward flow during both systole and diastole, with relatively little difference between the peak and trough velocities. This pattern is characteristic of blood vessels that supply organs requiring constant perfusion, such as the brain (internal carotid artery), kidneys (renal artery), and the uterus during pregnancy. The resistive index in these vessels is typically low. Understanding waveform resistance patterns helps sonographers and physicians distinguish normal from abnormal blood flow. For instance, a previously low-resistance vessel that develops a high-resistance pattern may indicate downstream obstruction or rejection in a transplanted organ.
Sonography Term