Extracranial carotid stenosis
1. Randomized trials on open versus endovascular procedures
The Asymptomatic Carotid Trial (ACT) I studied the outcome of carotid endarterectomy (CEA) and carotid artery stenting (CAS) in asymptomatic patients with severe carotid stenosis [1]. Between 2005 and 2013, 1,453 patients were enrolled in this randomized study, 1,089 in the CAS group, 364 in the CEA group. Endpoints of the trial were death, stroke or myocardial infarction at 30 days and 365 days post-procedure. Outcome: CAS was not inferior to CEA either in terms of the 30-day endpoint or after 1 year.
Another randomized study comparing CEA and CAS is the CREST Trial (Carotid Revascularization Endarterectomy versus Stenting Trial) [2]. The trial included 2502 patients with both asymptomatic and symptomatic carotid stenosis. Periprocedural strokes post-CAS were more frequent than following CEA (4.1% vs. 2.3%), while heart attacks, on the other hand, were significantly less common (1.1% vs. 2.3%). After 10 years, both groups did not differ significantly in the endpoint (stroke of any type, myocardial infarction or periprocedural death or ipsilateral stroke later), with 11.8% for CAS and 9.9% for CEA. In terms of symptoms (asymptomatic/symptomatic stenosis) no differences were seen between CAS and CEA. Nor were the differences in postoperative restenosis and revascularization significant: 12.2 % for CAS and 9.7 % for CEA.
The randomized International Carotid Stenting Study (ICSS) compared CEA and CAS in patients with recent symptomatic carotid stenosis [3]. A total of 853 patients were enrolled in the CAS group and 857 in the CEA group. The incidence of stroke, death, or heart attack within 120 days of surgery was significantly higher in the CAS group (8.5%) than in the CEA group (5.2%). After a median 4.2 years both groups did not differ in severe restenosis or occlusion, but the rate of stroke of any severity was still significantly higher in the CAS group (CAS 15.2%, CEA 9.4%).
2. Metaanalyses on open versus endovascular procedures
The efficacy and safety of CAS and CEA in 3,019 patients with asymptomatic carotid stenosis was studied in a systematic review with meta-analysis from 2017 [4]. The incidences of periprocedural stroke and death revealed a statistically marginally increased risk for CAS vs. CEA. Over the long term, clinically significant differences in the rates for stroke, death and myocardial infarction could not be excluded with certainty. It was concluded that unlike CAS, CEA appears to be the safer and more effective procedure in the treatment of asymptomatic carotid stenosis. Another meta-analysis from 2017 and a third analysis from 2018 arrived at similar results [5, 6].
While the previous analyses applied to patients with asymptomatic carotid stenosis, a meta-analysis from 2017 included 7,005 patients with asymptomatic and symptomatic stenosis [7]. In the study, CAS was associated with a significantly lower risk of myocardial infarction but with a higher risk of stroke and death compared to CEA. No significant difference was found between CAS and CEA regarding long-term mortality of any cause and restenosis rate. Based on the outcome, CEA was recommended as the treatment of choice in patients with carotid stenosis.
3. Registry data
3.1. CEA vs. CAS
Treatment of the US Medicare population by CEA and CAS between 1999 and 2014 was reported in 2017 [8]. 937,111 patients underwent CEA and 231,077 underwent CAS. During the period under review, the number of CEA cases decreased while the number of CAS cases increased. Regarding 30-day mortality, 30-day stroke, myocardial infarction or death and the risk of ischemic stroke after 1 year, outcomes improved despite increasing vascular risk factors. Interestingly enough, the number of procedures decreased over the review period, which was explained by optimized drug therapy and better health awareness.
Based on the Nationwide Inpatient Sample (NIS) from 2005 to 2011, the outcomes of CEA and CAS were studied in high-risk patients [9]. Data from 23,526 patients were included, 3,447 (14.7%) of whom underwent CAS, the remainder CEA. Asymptomatic stenosis was present in over 90% of cases. Inpatient mortality was 0.4%, with no difference between CAS (0.6%) and CEA (0.4%). However, in symptomatic patients, inpatient mortality was significantly higher in CAS than in CEA (4.7% vs. 2.0%). The rate of periprocedural stroke of 0.9% was significantly higher in CAS (1.4% vs. 0.9%). However, in symptomatic patients the rate did not differ. Over the review period, the number of procedures performed annually remained steady, while the number of high-risk patients treated increased slightly but significantly. As expected, the proportion of CAS increased over the review period while CEA decreased accordingly. The authors concluded that CAS was increasingly being performed in high-risk patients, but unlike in CEA, this increased the rate of periprocedural stroke in all high-risk patients and led to an additional increase in inpatient mortality in symptomatic patients.
3.2. Impact of contralateral stenoses on CEA
The impact of contralateral stenosis and occlusion on the CEA outcome in 15,487 symptomatic and asymptomatic patients with carotid stenosis was studied based on the registry of the Vascular Study Group of New England (VSGNE) between 2003 and 2015 [10]. The study concluded that although in CEA contralateral carotid occlusion resulted in a slightly higher stroke/mortality rate, contralateral occlusion should not be considered a high-risk criterion, as the 30-day rates of stroke/death in both symptomatic and asymptomatic patients remained within the limits of the guidelines.
3.3. Impact of age and gender on CEA
Based on the German quality assurance database, the impact of age and gender on CEA outcomes was studied [11]. 142,074 procedures between 2009 and 2014 were analyzed. The patients were mostly male (68%) with a mean age of 71 years. The study found that increasing patient age, but not gender, was associated with a higher perioperative risk of stroke or death following CEA. While the mortality risk alone was significantly correlated with patient age, this was only partly true for the risk of stroke. Although perioperative neurologic complications were significantly more common in older patients, the numbers were so small in the end that age alone cannot be an exclusion criterion for CEA.
The impact of patient age on CEA outcome was also reviewed using the Society for Vascular Surgery Vascular Quality Initiative (VQI) database [12]. 7,390 patients aged 80 and 90 years were compared with 35,303 younger patients. Although perioperative neurologic complications were significantly more common in older patients, the numbers were so small that age alone cannot be an exclusion criterion for CEA. However, the one-year survival was significantly less favorable at 93.74% compared to 97.18% in younger patients.
3.4. Early carotid revascularization by CEA
A study from 2017 investigated the "best" time for CEA after the onset of neurologic symptoms due to carotid stenosis [13]. The database of the Vascular Study Group of New England (VSGNE) included 989 symptomatic patients with carotid stenosis who underwent CEA within one month of their neurologic event. If CEA was performed within 2 days of the onset of neurologic symptoms, the rate of post-operative stroke was 7.3%, compared to 4.0% in the group with surgery after 2-5 days and 2.1% after ≥ 6 days. The groups did not differ in their outcome after 1 year. The authors concluded that CEA for prevention of recurrent stroke should be performed as early as possible, but not in the first 2 days after the neurologic event. The recommendation was to intervene in the first week after the event.
An increased risk of CEA in the first 48 hours after the neurologic event was also identified in the Carotid Alarm Study [14].
3.5. CAS
The ACS NSQIP (American College of Surgeons National Surgical Quality Improvement Program) database identified approximately 450 patients who had undergone CAS in 2017 for carotid stenosis [15]. The rate of adverse postoperative events after 30 days was 7.1%. Postoperative stroke or death was observed in 3.6% of asymptomatic and in 2.8% of symptomatic patients. The authors concluded that while CAS can be performed in symptomatic patients, this is not true in asymptomatic patients, as these exceeded the defined limits for postoperative death and stroke. Older patients (> 80 years of age), women, patients of color, and those with more than one stent were at increased risk.
Another study reported on 13,086 CAS procedures between 2009 and 2014 recorded in the German quality assurance database [16]. Almost 64% of the procedures were performed on asymptomatic patients. Periprocedural stroke or death was recorded in 1.7% of asymptomatic and 3.7% of symptomatic patients. The use of embolism protection systems was associated with a significant reduction in death and stroke.
The correlation between postoperative outcome in CAS and the time interval between the onset of neurologic symptoms and surgery was studied in 4717 elective procedures from the German quality assurance database [17]. The study demonstrated that early CAS within the first 7 days after the neurologic event was associated with an increased risk of postinterventional stroke/death.