Surgical Treatment of Asymptomatic Carotid Stenosis

John E. Castaldo; James F. Toole; Virginia J. Howard

doi:10.7326/0003-4819-125-6-199609150-00024

Letters |15 September 1996

Surgical Treatment of Asymptomatic Carotid Stenosis

John E. Castaldo, MD; James F. Toole, MD; Virginia J. Howard, MSPH

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TO THE EDITOR:

The article by Barnett and colleagues on the surgical treatment of asymptomatic carotid artery disease [1] deserves some clarification. First, the authors appear to misinterpret the failure to find statistically significant effects as implying the absence of an effect. The Asymptomatic Carotid Atherosclerosis Study (ACAS) was not designed to have good power to find differences in “disabling strokes” alone, to compare the treatments in women alone, or to evaluate differences in treatment effect between men and women.

Second, we agree with the authors that Doppler flow velocities reflect the cross-sectional area change of a vessel. It is precisely this measure, and not diameter, that is important for determining arterial pressure and flow. Nonetheless, Barnett and colleagues are wrong to imply that a “60% ACAS Doppler” stenosis is a measurement of area. All Doppler laboratories in the ACAS were validated to diameter measurements provided by arteriograms before being added to the study group. Thus, in the ACAS, 60%, 70%, and 80% Doppler stenoses are equivalent to 84%, 91%, and 96% cross-sectional area narrowing, respectively.

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Letters |15 September 1996

Surgical Treatment of Asymptomatic Carotid Stenosis

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Letters |15 September 1996

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