Differentiation of embolic and thrombotic middle cerebral artery occlusion using ultrasonic carotid flow velocity analysis.

The purpose of this study was to determine the value of Duplex ultrasound of the carotid arteries in the differentiation of embolic from thrombotic middle cerebral artery (MCA) occlusion. We report here the results of carotid Duplex ultrasound study from 164 patients with acute ischemic stroke. Flow velocity and diameter were measured in bilateral common carotid arteries (CCA). The end-diastolic flow velocity (Ved) and the pulsatility index (PI) were calculated from Doppler waves. The PI is an index of peripheral vascular resistance. We compared the relationship between percent carotid stenosis and percent decrease in Ved. The patients studied could be classified into three groups using ultrasound parameters. Group I was characterized by > 30% decrease in Ved and < 80% carotid stenosis, group II by < 30% decrease in Ved and < 80% carotid stenosis, and group III by > 30% decrease in Ved and > 80% carotid stenosis. All 23 patients in group I had embolic MCA stem occlusion. 28 out of 115 patients in group II had thrombotic MCA stem occlusions. All 26 patients in group III had internal carotid artery occlusion or severe stenosis. Ved was markedly reduced in group I and group III compared to group II (p < 0.01). PI in the affected artery was increased in groups I and III (p < 0.01). Embolic occlusion was characterized by > 30% decrease in Ved in the absence of > 80% carotid stenosis, and an increase in PI. The results indicate that these two conditions can be differentiated using Duplex ultrasound in carotid arteries.