Overall, the results of the large randomized studies indicate that the differences between surgery and intervention were usually very small.
The Carotid Revascularization Endarterectomy vs. Stenting Trial (CREST) study started recruiting patients in 2000. Preliminary data from the introductory phase of the interventional arm of the study were published in 2004. The data so far indicate that the periprocedural risk increases significantly with increasing age. The stroke/death rate was 1.7% in the patient cohort under the age of 60; 1.3% in patients aged 60–69; 5.3% in those aged 70–79; and 12.1% in those aged 80 or over. The significant difference was independent of the patients’ neurological status, grade of stenosis, or use of embolic protection systems.
Studies for which recruitment has already started include the International Carotid Stenting Study (ICSS) and the Asymptomatic Carotid Stenosis, Stenting versus Endarterectomy Trial (ACT-1). Studies already in the planning stage that are expected to provide new findings on the success of treatments for asymptomatic stenoses—e.g., with regard to neurocognitive function—include the Transatlantic Asymptomatic Carotid Intervention Trial (TACIT) and the Asymptomatic Carotid Surgery Trial 2 (ACST-2).
The Carotid Revascularization Endarterectomy vs. Stenting Trial (CREST), including a total of 2502 recruited patients, is the largest randomized study so far carried out to compare carotid stent implantation with carotid surgery. Data from the lead-in phase of the interventional arm of the study were published in 2004 (Hobson et al. 2004). In that report, the rates of stroke/death in the patient cohort were 1.7% in those under the age of 60, 1.3% in those aged 60–69, 5.3% in those aged 70–79, and 12.1% in patients aged 80 or over. The significant difference was independent of the patients’ neurological status, the grade of stenosis, or the use of embolism protection systems. The full study results were published in 2010. No significant difference was seen between the two treatment methods with regard to the combined primary end point of periprocedural stroke, myocardial infarction or death, or ipsilateral stroke during the follow-up period. The event rates were 7.2% in the group of patients who were treated with stent implantation and 6.8% in the patients who underwent surgery (Brott et al. 2010). Studies still currently recruiting include the International Carotid Stenting Study (ICSS), the Asymptomatic Carotid Stenosis Stenting Versus Endarterectomy Trial (ACT-1), and the Asymptomatic Carotid Surgery Trial 2 (ACT-2).
An interim analysis of the ICSS study has been published for the first 120 days of follow-up. Patients with > 50% symptomatic carotid stenosis were randomly assigned either to endovascular or surgical treatment methods. It was not yet possible to analyze the study’s primary end point (the 3-year stroke rate). Instead, the results of the analysis focused on the 120-day rate of stroke, death, or procedure-related myocardial infarction. In a total of 1713 randomized patients, a significantly higher rate was seen after carotid stent implantation at 8.5%, in comparison with 5.2% after carotid surgery (Ederle et al. 2010).
Clinical results—vertebral artery stent implantation
Sundt et al. first reported successful treatment of the vertebrobasilar system using angioplasty in 1980 (Sundt et al. 1980). Since then, many clinical series have been published on vertebral artery angioplasty/stent implantation, with high rates of technical success (98–100%) (Malek et al. 1999; Piotin et al. 2000; Mukherjee et al. 2001). However, there is still a lack of data from large clinical series and from controlled randomized studies to allow more precise assessments of the complication and restenosis rates during long-term follow-up. A subanalysis of the CAVATAS study compared a small group of 16 patients with symptomatic vertebral artery stenosis who received either endovascular treatment (PTA or stent implantation) or conservative drug therapy. Two of the eight patients who received endovascular treatment suffered a periprocedural TIA. No cases of stroke in the vertebrobasilar flow area occurred in either treatment arm during the long-term follow-up (mean 4.7 years). Three patients each in the drug-treated arm of the study and also in the group with endovascular treatment died due to myocardial infarction or stroke in the carotid flow area (Coward et al. 2007). In the VAST study, currently still in progress, 180 patients with symptomatic vertebral artery stenosis > 50% have been randomly assigned to groups receiving either endovascular treatment (stent implantation) or conservative therapy. The planned follow-up period is one year (Compter et al. 2008).
Prospects
The rapid developments in interventional treatment for carotid and vertebral artery stenoses, such as new stents with greater flexibility and smaller diameters, improved embolic protection systems with secure apposition on the vascular wall, and other technical innovations, are anticipated to improve the results of carotid and vertebral artery stent implantation in the near future.
1.1.6.3 Surgical treatment
Surgical removal of atherosclerotic obstruction in the carotid artery is the most frequently conducted vascular operation worldwide. In terms of the criteria of evidence-based medicine, it is also the best-studied surgical intervention that exists, with tens of thousands of patients documented in international prospective, randomized studies. Carotid endarterectomy (CEA) was first reported by Eastcott and colleagues in the treatment of a patient who had had 33 transitory ischemic attacks (TIAs) (Eastcott et al. 1954). The operation is now carried out in Germany, for example, over 25,000 times per year (BQS-Bundesauswertung 2007).
Indications for surgery
CEA is able to reduce the risk of stroke sevenfold in patients with TIAs, and in patients with 60–90% asymptomatic stenoses of the internal carotid it can achieve an absolute risk reduction of 5% over 5 years (Biller et al. 1998). The highest incidence of perioperative stroke is associated with the presence of high-grade bilateral internal carotid artery stenosis.
On the basis of large prospective, randomized multicenter studies (Anon. 1995; Anon. 1998; Ferguson et al. 1999), the American Heart Association formulated the following generally accepted guidelines for establishing the indication for carotid endarterectomy in an interdisciplinary consensus taking into account the natural history without surgery and thus the maximum acceptable perioperative rates of stroke and mortality (Biller et al. 1998):
