Images in vascular ultrasound. Stenosis of the innominate or left common carotid artery origin diagnosed on carotid ultrasound examination.

Abstract

Carotid ultrasound is quite accurate in identifying lesions of the carotid bifurcation. One of the criticisms of carotid duplex ultrasound is that it can miss lesions at the origin of the left common carotid or innominate artery. A common error encountered when performing a carotid duplex ultrasound examination is the failure to adequately image the proximal (right common carotid artery, innominate artery, left common carotid artery) arteries. While direct imaging of these vessels can determine with a high degree of certainty whether a signiŽ cant stenosis is present, there are other clues that should convince the ultrasonographer to search for a more proximal lesion. Panel A: Doppler spectral display found in the right distal common carotid artery (CCA). Note the appearance of a dampened, widened waveform with low peak systolic velocity of 21.6 cm=s. The systolic acceleration is slowed and the systolic peak is rounded as blood passing through a tight stenosis takes longer to reach peak systolic velocity. The maximum systolic velocity is low becauseblood  ow is reduced by the obstruction, and the diastolic  ow is increaseddue to dilatation of the capacitancevessels, thus decreasing peripheral resistance. Dampening is usually most evident in the CCA but may also be seen in the external carotid and internal carotid arterywaveforms. The recognitionof CCA dampening is important, as it may be the only ultrasonographic evidence of innominate artery or proximal left CCA stenosis. Panel B: The spectral waveformof this normal contralateralCCA is a combination of the low resistive waveform of the internal carotid artery (represents 80% of  ow) and a high resistivewaveform Panel A