Effectiveness of carotid endarterectomy for asymptomatic carotid stenosis: design of a clinical trial. Mayo Asymptomatic Carotid Endarterectomy Study Group

Drug Dosing in Patients Undergoing Therapeutic Plasma Exchange

Therapeutic plasma exchange (TPE) is an extracorporeal process in which a large volume of whole blood is taken from the patient's vein. Plasma is then separated from the other cellular components of the blood and discarded while the remaining blood components may then be returned to the patient. Replacement fluids such as albumin or fresh-frozen plasma may or may not be used. TPE has been used clinically for the removal of pathologic targets in the plasma in a variety of conditions, such as pathogenic antibodies in autoimmune disorders. TPE is becoming more common in the neurointensive care space as autoimmunity has been shown to play an etiological role in many acute neurological disorders. It is important to note that not only does TPE removes pathologic elements from the plasma, but may also remove drugs, which may be an intended or unintended consequence. The objective of the current review is to provide an up-to-date summary of the available evidence pertaining to drug removal via TPE and provide relevant clinical suggestions where applicable. This review also aims to provide an easy-to-follow clinical tool in order to determine the possibility of a drug removal via TPE given the procedure-specific and pharmacokinetic drug properties.

Carotid Endarterectomy in Patients with Renal Insufficiency: Should Selection Criteria be Different in Patients with Renal Insufficiency?

The objective of this study was to elucidate the relationship between outcomes from carotid endarterectomy (CEA) in patients with and without renal insufficiency.

Carotid endarterectomy is one of the most commonly performed vascular procedures. The role of cardiac comorbidity in carotid endarterectomy has been extensively studied. The relationship between renal failure and surgical outcomes has also been studied for both coronary artery bypass grafting and lower extremity occlusive disease. However, the role of renal insufficiency in relationship to decision making regarding surgical intervention for carotid stenosis is not well defined. The authors hypothesized that the outcomes from CEA were negatively influenced by renal dysfunction. A retrospective review was made of consecutive CEAs performed at their institution from 1990 to 1995. Patients were grouped into 2 categories according to their renal function. Group A, 448 patients (90%) with creatinine level 1.8 mg/dL or less, and group B, 49 patients (10%) with creatinine levels more than 1.8 mg/dL. Data from patients on dialysis are presented but were excluded for the purpose of analysis.

Included in the study were 497 patients with a mean age of 70 +8.9 and 74 +8.9 for groups A and B, respectively. Preoperative creatinine was 1.1 (±0.25) mg/dL for group A and 2.5 (+0.81) mg/dL for group B. Outcomes were as follows: perioperative cardiac events 5.4% vs 28.6%, stroke rates 2.7% vs 2.0%, and mortality rates 0.9% vs 8.2%, for groups A and B, respectively. At 60-month follow-up the stroke rates were 7.6% vs 6.1%, and the mortality rates 22.8% vs 59.2%, for groups A and B, respectively.

While patients with chronic renal insufficiency have no increased risk of perioperative or long-term neurologic events, perioperative and long-term mortality rates are significantly increased. This significant reduction in survival should prompt a more cautious application of CEA in patients with increased creatinine.

Clinical considerations in the management of asymptomatic carotid artery stenosis

Incidental findings pose considerable management dilemmas for the treating physician and psychological burden for the respective patient. With an aging population, more patients will be diagnosed with asymptomatic internal carotid artery stenosis. Patients will have to be counseled with regard to treatment options according to their individual risk profile and according to professionals' knowledge of evidence-based data derived from large randomized control trials. Treatment consensus has long been lacking for patients with asymptomatic carotid artery stenosis prior to any randomized controlled trials. Additionally, an individual's risk profile may be hard to assess according to knowledge gained from randomized controlled trials. Moreover, while earlier studies compared carotid endarterectomy and medical therapy, in the past years, a new therapeutic modality, carotid artery angioplasty and stenting, has emerged as a possible alternative. This has been evaluated in a recent randomized controlled trial, the Carotid Revascularization Endarterectomy versus Stenting Trial (CREST), which compared carotid endarterectomy with angioplasty and stenting in both symptomatic and asymptomatic patients. The following review summarizes current knowledge of the natural history, diagnosis, and treatment strategies to counsel patients with asymptomatic carotid artery stenosis.

Carotid endarterectomy and treatment options for carotid occlusive disease

BACKGROUND

Atherosclerotic stenosis of the extracranial internal carotid artery accounts for 15%-20% of ischemic strokes, depending on the population studied. Carotid endarterectomy (CEA) is the most frequently performed operation to prevent stroke.

METHODS

Since the 1990s, several randomized controlled trials have been completed in which the authors analyzed the risks and benefits of the procedure for patients with symptomatic and asymptomatic stenosis of the internal carotid artery. Traditionally, CEA was compared with maximal medical therapy in its efficacy to prevent stroke and death; however, improvements in endovascular techniques have led to large studies in which the authors compared CEA with carotid angioplasty and stenting.

CONCLUSION

In this review, we will discuss our current knowledge of the role of CEA in the prevention of stroke in symptomatic and asymptomatic patients with carotid stenosis and compare its use to medical therapy and carotid angioplasty and stenting.

Carotid endarterectomy for asymptomatic carotid stenosis

BACKGROUND

Carotid endarterectomy (CEA) is of proven benefit in recently-symptomatic patients with severe carotid stenosis. Its role in asymptomatic stenosis is still debated. The Asymptomatic Carotid Surgery Trial (ACST) more than doubled the number of patients randomised to CEA trials. This revised review incorporates the recently published ACST results.

OBJECTIVES

Our objective was to determine the effects of CEA for patients with asymptomatic carotid stenosis.

SEARCH STRATEGY

We searched the Cochrane Stroke Group Trials Register (searched May 2004), MEDLINE (1966 to May 2004), EMBASE (1980 to June 2004), Current Contents (1995 to January 1997), and reference lists of relevant articles. We contacted researchers in the field to identify additional published and unpublished studies.

SELECTION CRITERIA

All completed randomised trials comparing CEA to medical treatment in patients with asymptomatic carotid stenosis.

DATA COLLECTION AND ANALYSIS

Two reviewers extracted data and assessed trial quality. Attempts were made to contact investigators to obtain missing information.

MAIN RESULTS

Three trials with a total of 5223 patients were included. In these trials, the overall net excess of operation-related perioperative stroke or death was 2.9%. For the primary outcome of perioperative stroke or death or any subsequent stroke, patients undergoing CEA fared better than those treated medically (relative risk (RR) 0.69, 95% confidence interval (CI) 0.57 to 0.83). Similarly, for the outcome of perioperative stroke or death or subsequent ipsilateral stroke, there was benefit for the surgical group (RR 0.71, 95% CI 0.55 to 0.90). For the outcome of any stroke or death, there was a non-significant trend towards fewer events in the surgical group (RR 0.92, 95% CI 0.83 to 1.02). Subgroup analyses were performed for the outcome of perioperative stroke or death or subsequent carotid stroke. CEA appeared more beneficial in men than in women and more beneficial in younger patients than in older patients although the data for age effect were inconclusive. There was no statistically significant difference between the treatment effect estimates in patients with different grades of stenosis but the data were insufficient.

AUTHORS' CONCLUSIONS

Despite about a 3% perioperative stroke or death rate, CEA for asymptomatic carotid stenosis reduces the risk of ipsilateral stroke, and any stroke, by approximately 30% over three years. However, the absolute risk reduction is small (approximately 1% per annum over the first few years of follow up in the two largest and most recent trials) but it could be higher with longer follow up.

The association of platelet-derived growth factor receptor expression, plaque morphology and histological features with symptoms in carotid atherosclerosis

Platelet-derived growth factor may influence smooth muscle cell migration and proliferation and, therefore, carotid plaque composition and stenosis. Platelet-derived growth factor receptor expression and histological features were compared in carotid plaques from symptomatic and asymptomatic patients. Immunocytochemistry and histology determined platelet-derived growth factor-alpha and -beta receptor expression, white blood cell infiltration, smooth muscle cell, elastin, cholesterol, collagen and intraplaque haemorrhage in carotid artery plaques removed at surgery or the post-mortem. Plaques with > 70% stenosis from asymptomatic (n = 10) and symptomatic patients (n = 27) had higher expression of platelet-derived growth factor and beta receptors and higher scores for macrophages and intraplaque haemorrhage than plaques with < 70% stenosis from asymptomatic patients (n = 33). Plaques with > 70% stenosis from symptomatic patients had significantly lower alpha receptor expression than plaques with > 70% stenosis from asymptomatic patients. The reduction of alpha receptor expression, which may inhibit smooth muscle cell migration, suggests that differential expression of platelet-derived growth factor receptor subunits in plaques may be related to symptoms.

Carotid endarterectomy for asymptomatic carotid stenosis

BACKGROUND

Whilst carotid endarterectomy (CEA) is of proven benefit in recently symptomatic patients with severe carotid stenosis, the role of carotid endarterectomy in preventing stroke in patients with asymptomatic carotid stenosis remains uncertain.

OBJECTIVES

The objective of this review therefore was to determine the effects of CEA for patients with asymptomatic carotid stenosis.

SEARCH STRATEGY

We searched the Cochrane Stroke Group Trials Register (June 1998), Medline (1966-Mar 1998), Current Contents (1995-Jan 1997), and reference lists of relevant articles. We contacted researchers in the field to identify additional published and unpublished studies.

SELECTION CRITERIA

All completed randomised trials comparing CEA to medical treatment in patients with asymptomatic carotid stenosis.

DATA COLLECTION AND ANALYSIS

Two reviewers extracted data and assessed trial quality. Attempts were made to contact investigators to obtain missing information.

MAIN RESULTS

Six trials were identified, but two were excluded on methodological grounds. Four trials with 2203 patients were included. In two trials aspirin was only given to patients in the medical group, and in two all patients received aspirin. The net excess "perioperative stroke or death" rate in the surgical group was 2.7% with relative risk 6.52 (95% confidence interval 2.66-15.96). The rates of "perioperative stroke or death or subsequent ipsilateral stroke" were 6.8% in the medical group vs 4.9% in the surgical group with RR 0.73 (0.52-1.02) favouring surgery. The rates of "any stroke or perioperative death" were 10.4% (medical) vs 8.1% (surgical) with RR 0.79 (0.60-1.02). The rates of "any stroke or death" were 23.2% (medical) vs 20.2% (surgical) with RR 0.89 (0.76-1.04). There were too few patients in CEA vs aspirin trials to determine whether aspirin had any confounding effect on outcome. An additional analysis including data from a fifth small unpublished trial altered slightly the risk ratios in favour of surgery and narrowed confidence intervals sufficiently to achieve statistical significance for each outcome. However, inclusion of these data had no appreciable effect on relative or absolute risk reduction.

REVIEWER'S CONCLUSIONS

There is some evidence favouring CEA for asymptomatic carotid stenosis, but the effect is at best barely significant, and extremely small in terms of absolute risk reduction.

Advances in Management of Carotid Atherosclerosis

Carotid artery stenosis is a common and potentially treatable cause of stroke. Stroke risk is increased as the degree of carotid stenosis increases, as well as in patients with neurological symptoms referable to the stenosed carotid artery. Carotid stenosis can be quantified by ultrasound imaging, magnetic resonance angiography, or conventional angiography. Medical treatment with platelet antiaggregants reduces stroke risk in some patients; other patients are best treated with carotid endarterectomy. Experimental treatments for carotid stenosis, including carotid angioplasty with or without stenting, are under investigation. We summarize the current literature and provide treatment recommendations for patients with atherosclerotic carotid artery disease.

Accurate measurement of carotid stenosis. Chaos in methodology

The methods used for measurement of carotid artery stenosis are not uniform. Witness the chaos that developed when the North American Symptomatic Carotid Endarterectomy Trial (NASCET) group changed its classification system from area to linear measurements only to discover that the European Carotid Stenosis Trial (ECST) used still another angiographic definition of degree of stenosis so that the data from the two studies were not comparable. Fortunately, this has been reconciled by recalculation of the data. In still other studies, using unvalidated ultrasound instruments has made it difficult or impossible to compare results. In part, these problems have been the result of misdirected attempts to amalgamate concepts from Doppler and duplex ultrasound with those of arteriography. The former is more precise and accurate than the latter, yet its methodology is harder to apply and has not been generally distributed. Even such anatomical terms as "carotid bulb" are not standard. Ultrasonographers consider it to be the distal common carotid artery, to vascular surgeons it is the carotid sinus, while still others consider it to be both or neither. The present authors advocate a uniform methodology utilizing duplex ultrasound and predict that it plus magnetic resonance angiography will become the standard by which extracranial carotid artery disease is evaluated in the future.

Stroke: the way things really are

BACKGROUND

To comply with governmental requirements regarding the validity of therapeutic modalities and for medico-legal purposes, it is important to distinguish between what has been scientifically proven and what is anecdotal in the prevention and management of stroke.

SUMMARY OF REVIEW

This review summarizes the evidence for many of the modalities used to prevent stroke in high-risk patients, including antiplatelet drugs, anticoagulants, and endarterectomy, and the limitations of each. Controversial therapeutic modalities for which no scientific proof exists, such as anticoagulation of progressing stroke, are also discussed. The term "standard of care" should apply to modalities proven to be effective by scientifically controlled studies, not because they are used by many physicians. Treatment of acute stroke is still disappointing despite the development of many promising pharmacological strategies in experimental animals. An important part of the reason may be that the window of therapeutic opportunity is much shorter than the usual entry time of patients in most clinical trials. This logistic problem merits serious attention.

CONCLUSIONS

Numerous controlled, randomized, multiple-center clinical trials have demonstrated that the efficacy or lack thereof of various therapies directed at preventing or treating stroke can be determined and that anecdotal data may be misleading and harmful. At the least we should be aware of what we know and what we do not.

The prevention of cardiovascular disease. Emphasis on secondary prevention

Atherosclerosis is a progressive disease affecting all major arteries. Clinical evidence of atherosclerosis increases the risk of subsequent morbid and mortal events fivefold to sevenfold over the next 5 to 10 years. The same risk factors contribute to the initial development of CVD events as to their recurrence. Both coronary and noncoronary events, such as stroke or PAD, reflect the severity of the underlying atherosclerotic process and strongly predict future excess CVD morbidity and mortality. Short-term and long-term survival depends on modifying the risk factors that contribute to CVD events. Although absolute proof of benefit for secondary prevention does not exist for all risk factors, the data from primary prevention trials and the secondary prevention trials that have been done argue strongly for aggressive intervention. Benefit has been demonstrated for smoking cessation, cholesterol reduction, and blood pressure control. Selected patients may benefit from additional medical, procedural, or surgical interventions to prolong life, such as beta-blocking agents, aspirin, or carotid endarterectomy. Many secondary prevention measures are a cost-effective way to reduce the substantial morbidity and mortality due to CVD. Contrary to primary prevention, even modest treatment effects from secondary prevention efforts can benefit large numbers of patients. Finally, secondary prevention may be more successful because patients with clinical evidence of CVD may be more highly motivated than their healthy counterparts to make and maintain lifestyle changes.

Carotid endarterectomy: trials and tribulations

Since its introduction 40 years ago, the value of carotid endarterectomy has been controversial. In the early 1980s, several clinical trials were initiated to determine the efficacy of this operation in patients with carotid stenoses who were either symptomatic or asymptomatic for retinal or hemispheric ischemia. In 1991, interim results were published for the North American Symptomatic Carotid Endarterectomy Trial (NASCET) and the European Carotid Surgery Trial (ECST), both reporting efficacy for surgery in patients with symptomatic carotid artery stenosis of greater than 70%. Subgroup analyses revealed variable risk groups. The Veterans Administration (VA) Symptomatic Trial (Cooperative Studies Program 309 of the Department of Veterans Affairs) terminated early because of these results and its findings were consistent with the results of the larger trials. NASCET and ECST continue for symptomatic patients with carotid stenoses between 30% and 69%. The results of three trials in asymptomatic patients, the Mayo asymptomatic trial, the Carotid Artery Stenosis with Asymptomatic Narrowing: Operation Versus Aspirin trial, and the VA Asymptomatic Trial (Cooperative Studies Protocol 167 of the Department of Veterans Affairs), have been reported. None showed a statistically significant benefit for surgery in the prevention of stroke or death. However, none was sufficiently large to exclude such a benefit. The large Asymptomatic Carotid Atherosclerosis Study is in progress. Differences in the results and design of these trials are discussed as are restrictions in the applicability of their results.

Results of a randomized controlled trial of carotid endarterectomy for asymptomatic carotid stenosis. Mayo Asymptomatic Carotid Endarterectomy Study Group

We undertook a randomized controlled trial designed to compare the effects of carotid endarterectomy with medical treatment using low-dose aspirin in patients with asymptomatic carotid stenosis. During 30 months of recruitment, 71 randomized and 87 eligible nonrandomized patients participated in a follow-up protocol. The total ipsilateral perioperative stroke and death rate was 0% among randomized patients and 3% among nonrandomized patients, and the major stroke and death rate was 0% for both groups. Too few cerebral ischemic events occurred to judge the comparative effectiveness of carotid endarterectomy versus low-dose aspirin for asymptomatic carotid stenosis. The trial was terminated early because of a significantly higher number of myocardial infarctions and transient cerebral ischemic events in the surgical group than in the medical group. Most of the events were not temporally related to the surgical procedure, but there was evidence that these events could have related to the absence of aspirin use in the surgical group. These observations reinforce the appropriateness of the use of aspirin throughout the perioperative period and beyond (unless contraindications exist) in patients with asymptomatic carotid stenosis who undergo carotid endarterectomy.

Ischemic stroke. How to keep the first one from happening

The prevention of stroke has undenied merit. Recognition of stroke-inducing conditions (eg, cardiac diseases associated with embolism, polycythemia) provides opportunities for specific prevention strategies. For a larger number of patients, however, risk factors for degenerative vascular disease should be addressed. The evidence for efficacy is strongest for treatment of hypertension, and smoking cessation also reduces the risk of stroke. The value of treatment of hyperlipidemia in reducing the incidence of a first stroke remains to be demonstrated. Optimal management of carotid bruit and asymptomatic stenosis will be clarified by results of ongoing clinical trials. On the basis of available data, use of aspirin by healthy persons without risk factors cannot be recommended as a method for preventing a first ischemic stroke.