(Stroke. 1996;27:266-269.)
© 1996 American Heart Association, Inc.
Articles |
From the Department of Clinical Neurosciences, Western General Hospital, Edinburgh, UK.
| Abstract |
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Methods We performed a systematic review comparing the risks of stroke and death due to carotid endarterectomy, performed by the same surgeons or in the same institutions, for symptomatic and asymptomatic stenosis in studies published since 1980.
Results Twenty-five studies fulfilled our criteria. Mortality within 30 days of endarterectomy was 1.31% for asymptomatic stenosis and 1.81% for symptomatic stenosis (odds ratio [OR], 0.69; 95% confidence interval [CI], 0.49 to 0.99). The risks of fatal stroke were 0.47% and 0.91%, respectively (OR, 0.57; 95% CI, 0.34 to 0.98). The overall risk of stroke and/or death was 3.35% for asymptomatic and 5.18% for symptomatic stenosis (OR, 0.61; 95% CI, 0.51 to 0.74).
Conclusions Mortality and the risk of stroke and/or death due to carotid endarterectomy are significantly lower for asymptomatic than symptomatic stenosis. These findings are consistent across virtually all studies and are likely to be widely generalizable.
Key Words: carotid endarterectomy carotid stenosis mortality
| Introduction |
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| Methods |
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Mortality and the risk of stroke and/or death were defined per operation. The CIs of the absolute risks of death, fatal stroke, and stroke and/or death were calculated using an extrabinomial method to account for any heterogeneity of risk among the individual studies.10 If there is heterogeneity of risk, standard methods of calculating CIs produce artificially narrow CIs. The overall ORs for death, fatal stroke, and stroke and/or death due to endarterectomy for asymptomatic versus symptomatic stenosis were calculated using the Mantel-Haenszel method.
| Results |
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There were 33 deaths (1.31%; 95% CI, 0.80 to 1.78) attributed to
endarterectomy for asymptomatic
stenosis and 172 deaths (1.81%; CI, 1.46 to 2.13) attributed
to surgery for symptomatic stenosis (OR, 0.69; CI,
0.49 to 0.99). The relative odds of death after surgery for
asymptomatic versus symptomatic
stenosis showed no statistically significant
heterogeneity between studies
(
2=12.6, df=20,
P=.90). Two
studies gave no information on the causes of
death.11 24
Among the remainder, the risk of nonstroke death was 0.81% (CI, 0.48
to 2.25) after surgery for asymptomatic
stenosis and 0.80% (CI, 0.60 to 0.99) after surgery for
symptomatic stenosis. The risk of fatal stroke was
0.47% (CI, 0.20 to 0.79) for asymptomatic
stenosis and 0.91% (CI, 0.51 to 1.14) for
symptomatic stenosis (OR, 0.57; CI, 0.38 to
0.98).
In no study was the risk of stroke and/or death due to
endarterectomy for asymptomatic
stenosis statistically significantly lower than the risk for
symptomatic stenosis. However, there was a trend
toward a lower risk for asymptomatic stenosis
in 24 of the 25 studies. The overall risks of stroke and/or death were
3.35% (CI, 2.38 to 4.31) for asymptomatic
stenosis and 5.18 (CI, 4.30 to 6.06) for
symptomatic stenosis (OR, 0.61; CI, 0.51 to 0.74;
Figure
). There was no significant heterogeneity between
studies in the relative odds of stroke and/or death after surgery for
asymptomatic versus symptomatic
stenosis (
2=13.6, df=24,
P=.96).
| Discussion |
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The risks of nonstroke death attributed to endarterectomy were almost identical for symptomatic and asymptomatic stenosis. The 40% difference in the overall odds of stroke and death was therefore accounted for by the significantly lower risks of fatal and nonfatal stroke associated with surgery for asymptomatic stenosis.
Why is surgery safer for asymptomatic stenosis than symptomatic stenosis? Symptomatic patients by definition have already suffered a stroke or transient ischemic attack in the distribution of the artery undergoing operation, and the same factors that caused the presenting symptoms, such as intraluminal thrombosis or poor collateral circulation, might also predispose to stroke at surgery. Additionally, clinical characteristics such as age, sex, or the proportion with coexisting cardiac disease may differ between symptomatic and asymptomatic patients. Only one of the 25 studies reviewed compared the characteristics of the two groups of patients.18 There were no differences. Similarly, the reported baseline characteristics of the patients randomized to surgery in the ACAS and VA asymptomatic trials3 8 are almost identical to those in the ECST and NASCET symptomatic studies.1 2 36 As far as we can tell, symptomatic and asymptomatic patients appear to have similar clinical characteristics.
The 3.35% overall risk of stroke and/or death due to endarterectomy for asymptomatic stenosis is similar to the 4.3% risk in the VA trial8 and is in keeping with the 3% limit set by the American Heart Association.37 It is, however, statistically significantly greater than the 1.5% risk in the ACAS trial.3 This difference is difficult to explain and casts doubt on the generalizability of the ACAS trial results to more routine surgical practice.
In conclusion, the mortality and risk of stroke and/or death due to carotid endarterectomy performed by the same surgeons or in the same institutions are approximately 40% lower for asymptomatic stenosis than symptomatic stenosis. This finding is very consistent and is likely to be widely generalizable.
| Selected Abbreviations and Acronyms |
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| Acknowledgments |
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| Footnotes |
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Received October 3, 1995; revision received November 14, 1995; accepted November 14, 1995.
| References |
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