In this population-based study of 6553 asymptomatic patients undergoing CEA from 435 surgeons in 157 hospitals, we examined the potential impact of over 26 patient and clinical characteristics on risk of stroke or death within 30 days of CEA. The final multivariable model identified several sociodemographic, neurological severity and comorbidity factors independently associated with higher risk of perioperative complications.
Among sociodemographic factors, our finding that women had higher risk-adjusted odds of complications is consistent with prior studies.[30
] The higher risk in women may help explain why subgroup analyses of the RCTs and the meta-analyses found that asymptomatic women did not appear to benefit from CEA.[32
] If women have higher upfront rates of death or stroke due to the procedure, it will be harder for them to accrue the long term benefits. The higher perioperative risk among non-white patients has been reported in most studies of all-comers having CEA, though this has been attributed to higher rates of symptomatic disease among minorities[14
] Finding such a disparity among asymptomatic persons implies the differences are likely a function of a combination of patient, surgeon and hospital factors.[35
] Among the neurological severity variables, two markers of underlying prior cerebrovascular disease (severe disability and distant stroke or TIA) greatly increased the odds of adverse events as did ≥50% contralateral stenosis. These neurological severity variables have been found to increase risk in all-comer CEA populations.[9
] In the asymptomatic ACAS trial, both distant stroke and contralateral stenosis ≥60% were univariate predictors of 30 day death or stroke, though these analyses were not risk-adjusted.20
That the severity of ipsilateral stenosis was not related to short term
complications is consistent with the RCTs and meta-analyses which also found that long term
benefits from CEA in asymptomatic patients were similar in moderate and severe stenosis.[32
] The presence of major cardiovascular problems (congestive heart failure, coronary artery disease, and valvular heart disease) as risk factors is consistent with the literature.[8
] We have previously identified predictors of perioperative complications in all-comers in NYCAS (asymptomatic and symptomatic patients), this study focused on stratifying risk among the 6653 asymptomatic patients in the cohort. Both the all-comer and asymptomatic risk models included: Non-White, distant stroke or TIA, non-operated stensosis ≥50%, disability, and coronary artery disease as significant multivariables factors.24
The clinical prection rule version of the final risk models represents a new and practical contribution to the literature as it is the first risk score focused on asymptomatic patients. Prior risk scores in CEA were either for all-comers (symptomatic and asymptomatic)[22
] or the select patients and surgeons in the symptomatic ECST trial.[19
] While these other prediction rules were developed for different patient populations, our CEA-8 risk score shares in common with some of these other indices: female gender, prior cerebroavascular disease, contralateral stenosis, coronary artery disease, and congesetive heart failure (See Supplemental Table 5
The CEA-8 risk score can help referring physicians, surgeons, neurologists, and anesthesiologists calculate the short term risk of CEA in an individual patient. Because the absolute benefits of carotid revascularization among patients with with asymptomatic disease is very modest (reduction of about 1% lower risk of stroke per year), understanding the probability of upfront harm due to the procedure is critical to weighing its long term net benefit for a given patient.
The RCTs and national guidelines stress the importance of having CEA performed by a surgeon and hospital with ≤3% risk of death or stroke within 30 days. The good news from NYCAS was that the average 30 day death and stroke rate among asymptomatic patients having surgery in community practice was at the 3.0% benchmark. The cautionary news was that over one in four Medicare patients had a predicted probability of perioperative events >3%. We envision clinicians using the CEA-8 risk score in the following fashion. Patients with 0–2 points would be classified as low risk, safely below the 3% guideline threshold. Those with 3 points, with a predicted 4.7% death and stroke rate, would be moderate risk (slightly above 3% threshold). Those with 4 points (with a ≥7.5% risk of serious complications), are high risk and CEA would be unlikely to be beneficial for most patients with this profile. The seven factor “Patient-Friendly” CEA-7 risk score also clearly identifies low, moderate and high risk groups, and could be used by patients to help them make a shared, informed decision about surgery.
The study strengths should be viewed in the context of a few limitations. While NYCAS collected detailed data on potential risk factors and outcomes from medical records, it was based on documentation in real world practice. There was no prospective data collection or outcome examination as done in the RCTs. However, clinical events were reveiwed by two study investigators, and the richness of our data is much greater than most prior studies of CEA risk factors. NYCAS reflects practice in one state, albeit a large one, during 1998 and 1999. shows the perioperative outcomes and patient characteristics in NYCAS compared to the landmark a RCTs and two very recent large, observational cohort studies of CEA for asymptomatic disease. This shows that the outcome rates in NYCAS were comparable to those in RCTs[2
] and similar to those reported among Medicare beneficiaries during 2004–2005.[38
] It is worth noting, that a recent study by Woo et al of asymptomatic patients of all ages having CEA in the National Surgical Quality Improvement Program (NQSIP) registry reported lower absolute rates of perioperative death and stroke.[37
] These differences are likely due to to the fact that NYCAS Medicare patients were older and sicker than those in NSQIP and voluntary registries tend over-represent high performing institutions. The Woo et al study also excluded patients with a distant history of stroke and TIA, which represented 21.8% of asymptomatic patients in NYCAS—a risk factor that increased the risk-adjusted odds of death or stroke by 48%. However, the applicability of our results to non-Medicare populations merits further investigation, and future work should include validation of the prediction rule in an independent, more contemporary sample.
Comparison of Study Characteristics and Outcomes of CEA for Asymptomatic Patients
It is also worth acknowledging that a patient’s risk of surgical complications is a function of both their individual characteristics, as well as the skill and experience of surgeon and hospital team caring for them,[39
] so both elements of risk should be factored in an evidence-based decision about revascularization. Ultimately, the decision about revascularization needs to weigh both the short term risks of surgery against its long term benefits. More research is needed with regards to developing evidence-based estimates of the long term benefit of CEA for an individual asymptomatic patient.
In summary, though the rate of perioperative death and stroke after CEA in this population-based cohort were similar to those deemed optimal in the RCTs and national guidelines, the range of risk faced by asymptomatic patients undergoing surgery in community practice range from <1% to almost 10%. The new CEA-8 risk score we developed can help physicians counsel patients about the potential risks and benefits of CEA and help rationalize selection of appropriate candidates. Further prediction rules that could help asymptomatic patients individualize the long term benefits of CEA would be additionally valuable in improving overall decision making.