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(Stroke. 1999;30:1286-1295.)
© 1999 American Heart Association, Inc.

Letters to the Editor

Standardization of Carotid Ultrasound

Merrill P. Spencer, MD

Institute of Applied Physiology and Medicine, Seattle, Washington

To the Editor:

The article by Ranke et al¹ in the February issue of Stroke represents an excellent advancement in Doppler grading of carotid artery stenosis. Since many surgeons now depend on Doppler ultrasound for decisions for carotid endarterectomy because of the costs and dangers of angiography and the cost and resolution problems of magnetic resonance imaging, it is of paramount importance that the accuracy of vascular laboratories be improved. Use of the continuity principle with Doppler ultrasound offers the greatest hope of correlating Doppler hemodynamics with angiographic morphology if velocities representative of the mean velocity can be consistently measured. The initial trial of this principle² was disappointing due to the problems with the unknown angle of continuous-wave Doppler and the limited resolution of then-current angiography. Also, without biplane angiography the shape of the stenotic lumen, which greatly affects the relationship of velocity ratios, was not known. Our analysis of the results of Ranke and coworkers¹ indicates a systematic asymmetry of the lumen exists, resulting in the intrastenotic/distal velocity ratio increasing the estimated severity by 18% over that expected if the stenosis in the lumen cross-section progressed in a symmetrical way.

To deal with the angle problem, we have found that handheld 2 megahertz pulse wave Doppler probes, interrogating the internal carotid artery stenosis and distal segment with a focal distance of 4 cm, agree well with velocity ratios from color Doppler imaging. Handheld pulse-wave Doppler ensures a consistent low angle and reaches the internal carotid artery well beyond turbulence. . . . [Full Text of this Article]

Carsten Ranke, MD Hans-Joachim Trappe, MD

Department of Cardiology and Angiology, University Hospital Herne, Ruhr-University Bochum, Herne, Germany

Andreas Creutzig, MD

Center of Internal Medicine, Department of Angiology

Hartmut Becker, MD

Center of Radiology, Department of Neuroradiology, Hannover Medical School, Hannover, Germany