To the Editor: The National Stroke Association
(NSA) guidelines on prevention of a first stroke address an important public
health problem.1 However, the statements
in the article regarding the value of carotid endarterectomy (CE) for patients
with asymptomatic stenosis are highly suspect.
The guidelines state that CE is useful in individuals with asymptomatic
carotid narrowing of greater than 60% if the surgery can be performed with
a morbidity and mortality rate of less than 3%. This claim is based on a single
study, the Asymptomatic Carotid Atherosclerosis Surgery (ACAS) trial, of dubious
generalizability.2 The ACAS enrolled only
select, low-risk patients. Twenty-five patients were screened clinically and
from ultrasound laboratories for every 1 patient entered in the study. In
addition, the surgeons in ACAS were vetted for excellence in their work: they
had to provide evidence of a recent complication rate of less than 3%. Indeed,
one third of the surgeons who applied were either rejected or did not complete
the certification process. Overall perioperative mortality in ACAS was 0.1%.
Perioperative mortality for the group of surgeons not given credentials by
ACAS was 2.2%, 22 times higher than that seen in the clinical trial results.
There are also performance data available suggesting that the surgical proficiency
observed in ACAS is not duplicated in clinical practice. In the recently completed
Aspirin and Carotid Endarterectomy Study, in which close to 1700 patients
were asymptomatic, the stroke and death rate in asymptomatic patients was
4.6%, higher than the NSA threshold of less than 3% (W. Taylor, PhD, written
communication September 1998).