Carotid endarterectomy operation

Motz and colleagues (2006) used their Raman probe in vivo approximately two years later. Spectra were taken from 14 femoral bypass and 6 carotid endarterectomy operations. The sites from which spectra were taken were... 

It is unknown whether carotid endarterectomy is of value when performed emergently after stroke, meaning within the first 24 hours after symptoms begin.9 It appears that patients with mild to moderate neurologic deficits, crescendo TIAs or stroke-in-evolution can be operated on safely within the first few hours after the onset of symptoms. Patients with more severe neurologic deficits should only be considered for carotid endarterectomy when the procedure can be performed within the first few hours after the onset of symptoms. It is not indicated for patients with permanent deficits from a moderate to severe completed stroke. 

The justification for randomized trials is not that no worthwhile observations can be made without them, but that important biases can occur in non-randomized comparisons which are particularly problematic if the benefits of treatment are, in reality, small or absent. For example, a non-randomized comparison of the effect of aspirin dosage on the operative risk of carotid endarterectomy (Table 18.2) reported a clinically and statistically significant lower operative risk in patients on high-dose aspirin (1300 mg) than taking low-dose aspirin (325 mg or less) (Barnett et al. 1998) however, a subsequent randomized trial (Taylor et al. 1999), performed to confirm this observation, showed that high-dose aspirin was, in fact, harmful (Table 18.1). It is likely that the non-randomized comparison had been biased by unmeasured differences between the patients in the low-dose and high-dose aspirin groups. 

The surgical removal of atheromatous plaque from within the carotid artery is termed carotid endarterectomy. The operation was first performed in an attempt to improve the flow of blood to the brain, although no systematic attempt was made to assess the risks and benefits of the procedure. Subsequently, randomized trials were performed in patients with a history of recent symptomatic stroke, and also in those with asymptomatic disease, to determine whether the operation was beneficial and, if so, what the predictors of benefit would be. As a result of these trials, carotid endarterectomy has been proven to be an effective treatment for the secondary prevention of stroke in selected patients. 

As a result of the large randomized controlled trials, it is now clear that endarterectomy of recently symptomatic severe carotid stenosis almost completely abolishes the high risk of ischemic stroke ipsiiaterai to the operated artery over the subsequent two or three years (see Ch. 27 for detailed discussion of the selection of patients for surgery). Moreover, this effect is durable over at least 10 years (European Carotid Surgery Trialists Collaborative Group 1991, 1998 Mayberg et al. 1991 North American Symptomatic Carotid Endarterectomy Trial Collaborators 1991 Barnett et al. 1998 Rothwell et al. 2003). Indeed, the ipsiiaterai stroke risk becomes so low that presumably both embolic and low-flow strokes are being prevented (Fig. 25.1). 

Riles TS, Kopelman I, Imparato AM (1979). Myocardial infarction following carotid endarterectomy. A review of 683 operations. Surgery 85 249-252... 

Winslow CM, Solomon DH, Chassin MR (1988). The appropriateness of carotid endarterectomy. New England Journal of Medicine 318 721-727 Wood JR (1857). Early history of the operation of ligature of the primitive carotid artery. New York Journal of Medicine July l-59... 

Table 27.2. A systematic review of the studies reporting the operative risks of stroke or death in carotid endarterectomy according to the nature of the presenting event and stratified according to year of publication ...

A systematic review of the associations between age and sex and the operative risks of carotid endarterectomy. Cerebrovascular Diseases 20 69-77... 

Fig. 28.2. The overall results of a meta-analysis of the operative risk of death (a) and stroke and death (b) from all studies published between 1990 and 2000 inclusive that reported risks from carotid endarterectomy for asymptomatic stenosis (Bond et ai. 2003a) compared with the same risks in the ACAS Trial (Executive Committee for the Asymptomatic Carotid Atherosclerosis Study 1995). Studies in the analysis of risk of stroke and death are...

In secondary prevention, carotid endarterectomy of an ulcerated and/or stenotic carotid artery is a very effective way to reduce stroke incidence and recurrence in appropriate patients and in centers where the operative morbidity and mortality are low. In fact, in ischemic stroke patients with 70% to 99% stenosis of an ipsilateral internal carotid artery, recurrent stroke risk can be reduced by up to 48% compared with medical therapy alone when combined with aspirin 325 mg daily. In patients in whom the risk of endarterectomy is thought to be excessive, carotid stenting may be effective in reducing recurrent stroke risk but is less invasive. Carotid stenting is still considered investigational, however, and issues remain regarding the optimal methods and patients for this procedure. 

Hertzer NR, Beven EG, O Hara PJ, Krajewski LP. A prospective study of vein patch angioplasty during carotid endarterectomy three-year results for 801 patients and 917 operations. Arm Surg 1987 206 628-35. 

Archie Jr IP. A fifteen-year experience with carotid endarterectomy after a formal operative protocol requiring highly frequent patch angioplasty. J Vase Surg 2000 31 724-35. 

Fig. 14.2. An external validation of the model detailed in Table 14.2 for the five-year risk of stroke on medical treatment in an independent randomized trial of endarterectomy versus medical treatment for symptomatic carotid stenosis (Rothwell et ai. 2005). Predicted risk of stroke on medical treatment is plotted against the observed risk of stroke in patients randomized to medical treatment in the trial (squares) and against the observed operative risk of stroke and death in patients randomized to surgical treatment (diamonds). Groups are quintiles of predicted risk.

How centers and clinicians were selected to participate in trials is seldom reported, but it can also have important implications for external validity. For example, the Asymptomatic Carotid Atherosclerosis Study (ACAS) trial of endarterectomy for asymptomatic carotid stenosis only accepted surgeons with an excellent safety record, rejecting 40% of applicants initially, and subsequently barring from further participation those who had adverse operative outcomes in the trial. The benefit from surgery in the trial was a result in major... 

External validity can also be affected if trials have protocols that differ from usual clinical practice. For example, prior to randomization in the trials of endarterectomy for symptomatic carotid stenosis patients had to be diagnosed by a neurologist and to have conventional arterial angiography, neither of which are routine in many centers. The trial intervention itself may also differ from that used in current practice, such as in the formulation and bioavailability of a drug, or the type of anesthetic used for an operation. The same can be true of the treatment in the control group in a trial, which may use a particularly low dose of the comparator drug or fall short of best current practice in some... 

The more pragmatic Medical Research Council Asymptomatic Carotid Surgery Trial (ACST) has probably produced more widely generalizable results (Halliday et al. 2004). Between 1993 and 2003, ACST randomized 3120 patients with > 60% mainly asymptomatic carotid stenosis (12% had symptoms at least six months previously) to immediate endarterectomy plus medical treatment versus medical treatment alone or until the operation became necessary. Surgeons were required to provide evidence of an operative risk of 6%... 

Fig, 28.3. The effect of endarterectomy for asymptomatic carotid stenosis on the risk of any stroke and operative death by sex (Rothwell 2004) in the /ksymptomatic Carotid Surgery Trial (ACST Halliday ef al. 2004) and the AC/ S Trial (Executive Committee for the Asymptomatic Carotid Atherosclerosis Study 1995). Cl, confidence interval. 

This concern extends to carotid artery stenting. Although carotid artery stenting in patients with asymptomatic CAS can be performed by experienced operators with a low complication rate, the procedure can be associated with high complication rate if performed by inexperienced operators, particularly in older patients with complex anatomy (24). In any case, institution-specific assessment of the risk of carotid intervention, endarterectomy, or stenting should be a prime consideration in clinical decision making regarding carotid revascularization in patients with asymptomatic CAS. 

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