Asymptomatic carotid artery disease.

To the Editor:Dr. Mohr has provided a valuable review of asymptomatic carotid artery disease.'However, he misquotes the findings of Jonas and Hass. 2 Jonas and Hass concluded that after extracranial arterial surgery for TIA, a stroke complication rate of >2.9% is unacceptable if one wishes to have results that are significantly better than the results for the medical group in the Joint Study.The figure of 2.9% applies only to strokes, not to the combined morbidity-mortality rate as Dr. Mohr states.I have applied that same % 2 analysis used by Jonas and Hass to the total stroke and death rate reported for TIA patients in the Joint Study 3 (table).In the non-surgical group the total morbidity and mortality was 25.9%.In order to reach statistical superiority at the 5% level, the total morbidity and mortality in the surgical group would have to be no more than 16.8%.Subtracting the 15.4% long-term (42 month) morbidity and mortality rate yields an "acceptable" post-operative stroke or death rate of 1.4% or less.As non-surgical patients do not require arteriography, a combined morbidity-mortality rate of over 1.4% for arteriography, endarterectomy, and the post-operative period is unacceptable.It is unlikely that such a low morbidity-mortality rate could be achieved.